Phone: +91 44 27480203 Address: Scientist-D
Biofouling and Biofilm Processes Section, Water and Steam Chemistry Division, Bhabha Atomic Research Centre Facilities,
Kalpakkam. 603102. IN
Aim: Among cell surface proteins, biofilm-associated protein promotes biofilm development in Stap... more Aim: Among cell surface proteins, biofilm-associated protein promotes biofilm development in Staphylococcus aureus strains. Aim of this study was to investigate proteinase-mediated biofilm dispersion in different isolates of S. aureus. Methods and Results: Microtitre plate based biofilm assay showed that 2 7 μg/mL proteinase K significantly inhibited biofilm development in bap-positive S. aureus V329 as well as other S. aureus strains, i.e. SA7, SA10, SA33, SA352 and but not in bap-mutant M556 and SA392 (a weak biofilm producing strain). However, proteinase K treatment on S. aureus planktonic cells showed that there was no inhibition of planktonic growth at any concentration of proteinase K when tested up to 32 μg/mL. This observation ruled out the possibility of S. aureus biofilm inhibition by altering the cell viability. Proteinase K treatment upon 24 h old preformed biofilms showed an enhanced dispersion of bap-positive V329 and SA7, SA10, SA33 and SA352 biofilms, however, protei...
ABSTRACT Biofilm forming marine bacterium Paenibacillus lautus NE3B01 was isolated from water sam... more ABSTRACT Biofilm forming marine bacterium Paenibacillus lautus NE3B01 was isolated from water sample collected from Bhitarkanika mangrove forest. From the biofilm growth study, Paenibacillus lautus NE3B01 showed many steps of biofilm formation and detachment. Biofilm formation begins with initial attachment of planktonic cells to the substratum, followed by cell division, growth, maturation and detachment of cells from the community. The detached cells can again form a new biofilm after coming in contact with substratum. From the biofilm growth studies, Paenibacillus lautus NE3B01 established mature biofilm with in 6h of growth followed by further formation and disintegration stages. Microscopy studies of Paenibacillus lautus NE3B01 biofilm on glass surface,growing colony on solid media and swarming pattern revealed the competing sibling phenotypes. Paenibacillus lautus NE3B01 survive overcrowding by switching between motile rods and immotile cocci, two distinct vegetative phenotypes. The current finding is of indication that the bacteria adapt to changing environmental conditions by inducible and reversible phenotypic switching.
ABSTRACT Biofilm forming marine bacterium Paenibacillus lautus NE3B01 was isolated from water sam... more ABSTRACT Biofilm forming marine bacterium Paenibacillus lautus NE3B01 was isolated from water sample collected from Bhitarkanika mangrove forest. From the biofilm growth study, Paenibacillus lautus NE3B01 showed many steps of biofilm formation and detachment. Biofilm formation begins with initial attachment of planktonic cells to the substratum, followed by cell division, growth, maturation and detachment of cells from the community. The detached cells can again form a new biofilm after coming in contact with substratum. From the biofilm growth studies, Paenibacillus lautus NE3B01 established mature biofilm with in 6h of growth followed by further formation and disintegration stages. Microscopy studies of Paenibacillus lautus NE3B01 biofilm on glass surface,growing colony on solid media and swarming pattern revealed the competing sibling phenotypes. Paenibacillus lautus NE3B01 survive overcrowding by switching between motile rods and immotile cocci, two distinct vegetative phenotypes. The current finding is of indication that the bacteria adapt to changing environmental conditions by inducible and reversible phenotypic switching.
Marine bacterial biofilms were studied under different physicochemical conditions for enhanced bi... more Marine bacterial biofilms were studied under different physicochemical conditions for enhanced bioremediation of polycyclic aromatic hydrocarbons (PAHs). Molecular characterization of ten environmental isolates was done by 16S rRNA gene sequencing. The effect of different physicochemical parameters, such as pH, salt concentration, temperature, carbon source on their biofilm production capability was monitored. Various topological parameters of the biofilms such as total biomass (EPS and cells content), thickness, roughness coefficient, diffusion distance and surface to biovolume ratio were studied using a confocal scanning laser microscope (CSLM). Among the various strains studied, the total biomass was maximum for P. aeruginosa N6P6 (106.64 mm 3 mm À2) followed by S. acidaminiphila NCW702 (26.92 mm 3 mm À2) indicating the formation of dense biofilm. Significant negative correlation (P < 0.05) was observed between the roughness coefficient of the biofilm and PAH degradation, whereas a significant positive correlation (P < 0.05) was observed between PAH (phenanthrene and pyrene) degradation and total biomass, thickness and diffusion distance of the biofilms. PAH degradation was studied both in planktonic and biofilm modes of growth. Biofilm facilitated degradation of the two PAHs was higher than the planktonic cells. This work demonstrates that the attached phenotypes of the marine bacteria showed noticeable variation in biofilm architecture and, in turn, biodegradation of PAHs.
Studies on the effect of calcium on Bap-mediated inhibition and modulation of Staphylococcus aure... more Studies on the effect of calcium on Bap-mediated inhibition and modulation of Staphylococcus aureus biofilm was the motivation behind this study. In this study, the effect of calcium on modulation of Staphylococcus aureus biofilm has been studied. Four S. aureus bovine mastitis isolates viz. SA7, SA10, SA33 and bap-positive S. aureus V329 (positive control) along with a bap-isogenic mutant M556 (negative control) were used in this study. PCR was used for detection of bap, biofilm assays were done in microtitre plates and confocal laser scanning microscopy (CLSM) was used to study the biofilm architecture. PCR mediated detection identified SA7, SA10 and SA33 as bap-negative strains. Biofilm assay showed that Ca 2+ inhibited the biofilm growth of SA10 and SAV329 in a dose dependent manner whereas SA7 and SA33 did not show any inhibition. Strain M556 was found to be a weak biofilm former and showed no significant change in the presence of Ca 2+. The planktonic growth study results showed that Ca 2+ did not influence planktonic growth in any of the S. aureus strains except SA10 where ≥ 5 mM Ca 2+ had an inhibitory effect. Interaction of Bap and Ca 2+ was found to be specific, since studies with Mg 2+ did not show any inhibitory effect on V329 biofilm formation. CLSM images of V329, SA7 and SA10 biofilms showed reduction in biofilm thickness as well as altered biofilm topography. The inhibition effect of Ca 2+ on V329 and SA10 biofilms disappeared in the presence of chelating agent EDTA at a sub-minimum inhibitory concentration (0.15 mM). The paper elaborates the role of Ca 2+ in the biofilm architecture of S. aureus.
Microbial granules are more effective than monoculture bacteria in the bioremediation process of ... more Microbial granules are more effective than monoculture bacteria in the bioremediation process of environmental contaminants. Among various types of microbial granules phototrophic granules are relatively advantageous in bioremediation than heterotrophic granules since they are self-sustaining. [Co(III)–EDTA] À generated during nuclear waste management is difficult to remove from the radioactive waste due to its high solubility and stability. In this study, phototrophic granules generated from a freshwater source were used for the reduction of [Co(III)–EDTA] À under anoxic conditions. The results of the study showed that the phototrophic granules efficiently reduced the highly soluble [Co(III)–EDTA] À to a lesser soluble form, [Co(II)–EDTA] 2– up to a concentration of 20 mM. The rate of [Co(III)–EDTA] À reduction was found to be relatively high when the process was performed with acclimatized phototrophic granules when compared to non-acclimatized granules. Specific studies using antibiotics to kill the heterotrophic bacterial population of the phototrophic granules showed that [Co(III)–EDTA] À reduction was carried out predominantly by the phototrophs. Investigations were also carried out to test the robustness of phototrophic granules to perform [Co(III)–EDTA] À reduction after gamma irradiation. The phototrophic granules showed substantial radio-tolerance and could reduce [Co(III)–EDTA] À without any significant loss in the activity, when irradiated up to 2 kGy. The study suggests that phototrophic granules have potential application in bioremediation of moderate level nuclear waste.
The corrosion inhibition efficiency of 3-(4-chlorobenzoylmethyl) benzimidazoliumbromide in water ... more The corrosion inhibition efficiency of 3-(4-chlorobenzoylmethyl) benzimidazoliumbromide in water medium has been evaluated using electrochemical and other techniques. The mixed type inhibitive behavior of the inhibitor was evaluated by potentiodynamic polarization study. The inhibition efficiency increased with increasing pH up to 7.0 and showed a decrease with rise in temperature of the medium. Charge transfer resistance (R ct) values confirmed the formation of a protective layer by the adsorption of the inhibitor on the carbon steel surface. The adsorption degree of 3-(4-chlorobenzoylmethyl) benzimidazoliumbromide on the metal substrate obeyed Langmuir adsorption isotherms. Surface characterization of the carbon steel in the absence and presence of inhibitor has been monitored by atomic force (AFM) and scanning electron microscopy (SEM) with energy dispersive X-Ray spectroscopy (EDX). Quantum chemical analysis (QCA) data supported the adsorption efficiency of the inhibitor. The results obtained from electrochemical noise analysis (ENA) were in good agreement with other studies.
A precise quantification of Co(II)EDTA complex is required to develop bioremediation approaches f... more A precise quantification of Co(II)EDTA complex is required to develop bioremediation approaches for Co(III)EDTA complex that is generated in various industrial processes. It is cumbersome to quantify Co(II)EDTA in a mixture of Co(II)EDTA and Co(III)EDTA by normal UV-visible spectrophotometric methods as both the complexes absorb significantly at 490 nm, which is the λ max of Co(II)EDTA. Whereas other sophisticated techniques such as gas chromatography, atomic absorption spectrophotometer, inductively coupled plasma-atomic emission spectroscopy can measure individual species of Co(II)EDTA or Co(III)EDTA when present alone but are ineffective to measure the Co(II)EDTA precisely when it is mixed with Co(III)EDTA. Hence, an attempt has been made to develop a spectrophotometric method for its quantification. This paper describes the development of a simple and economic dual wavelength spectrophotometric method for the determination of Co(II)EDTA in a mixture of Co(II)EDTA and Co(III)EDTA complexes. The wavelength pair, 490-580 nm was optimized for the measurement of absorbance for this dual wavelength method of determination of Co(II)EDTA in the presence of Co(III)EDTA.
Naturally stressed habitats are known to be repositories for novel microorganisms with potential ... more Naturally stressed habitats are known to be repositories for novel microorganisms with potential bioremediation applications. In this study, we isolated a [Co(III)-EDTA]− educing bacterium Bacillus licheniformis SPB-2 from a solar salt pan that is exposed to constant cycles of hydration and desiccation in nature. [Co(III)-EDTA]− rted during nuclear waste management process is difficult to remove from the waste due to its high stability and solubility. It's reduced form i.e. [Co(II)-EDTA]2− is less stable though it is toxic. This study showed that B. licheniformis SPB-2 reduced 1 mM [Co(III)-EDTA]− in 14 days when grown in a batch mode. However, subsequent cycles showed an increase in the reduction activity, which was observed up to four cycles. Interestingly, the present study also showed that [Co(III)-EDTA]− acted as an inducer for B. licheniformis SPB-2 spore germination. Vegetative cells germinated from the spores were found to be involved in [Co(III)-EDTA]− reduction. More detailed investigations showed that after [Co(III)-EDTA]− reduction, i.e. [Co(II)-EDTA]2− complex was removed by B. licheniformis SPB-2 from the bulk liquid by adsorption phenomenon. The bacterium showed a D10 value (radiation dose required to kill 90% cells) of ∼250 Gray (Gy), which signifies the potential use of B. licheniformis SPB-2 for bioremediation of moderately active nuclear waste.
AimBiofilm formation and polycyclic aromatic hydrocarbons (PAHs) degradation by a marine bacteriu... more AimBiofilm formation and polycyclic aromatic hydrocarbons (PAHs) degradation by a marine bacterium Stenotrophomonas acidaminihila NCW-702 was investigated.Biofilm formation and polycyclic aromatic hydrocarbons (PAHs) degradation by a marine bacterium Stenotrophomonas acidaminihila NCW-702 was investigated.Methods and resultsThe biofilm structure was studied by confocal laser scanning microscopy (CLSM). Both planktonic and biofilm cultures were used for PAHs (phenanthrene and pyrene) degradation. In 7 days, S. acidaminiphila biofilm culture efficiently degraded 71.1 ±3.1% and 40.2 ±2.4% of phenanthrene and pyrene respectively. Whereas, 38.7 ±2.5% of phenanthrene and 29.7 ±1% of pyrene degradation was observed in planktonic culture. The presence of phenolic intermediates in the culture supernatant during degradation process was evaluated by Folin-Ciocalteau reagent. The average thickness and diffusion distance of S. acidaminiphila NCW-702 biofilm was found to be 23.94 ± 2.62 μm and 2.68 ± 0.7 μm respectively. Bacterial biofilms have numerous metabolic features that aid in the degradation of hydrophobic organic pollutants.The biofilm structure was studied by confocal laser scanning microscopy (CLSM). Both planktonic and biofilm cultures were used for PAHs (phenanthrene and pyrene) degradation. In 7 days, S. acidaminiphila biofilm culture efficiently degraded 71.1 ±3.1% and 40.2 ±2.4% of phenanthrene and pyrene respectively. Whereas, 38.7 ±2.5% of phenanthrene and 29.7 ±1% of pyrene degradation was observed in planktonic culture. The presence of phenolic intermediates in the culture supernatant during degradation process was evaluated by Folin-Ciocalteau reagent. The average thickness and diffusion distance of S. acidaminiphila NCW-702 biofilm was found to be 23.94 ± 2.62 μm and 2.68 ± 0.7 μm respectively. Bacterial biofilms have numerous metabolic features that aid in the degradation of hydrophobic organic pollutants.ConclusionBiofilm of S. acidaminiphila NCW-702 was able to degrade PAHs more efficiently as compared to planktonic cells. The findings support the efficacy of biofilms over planktonic culture in bioremediation applications.Biofilm of S. acidaminiphila NCW-702 was able to degrade PAHs more efficiently as compared to planktonic cells. The findings support the efficacy of biofilms over planktonic culture in bioremediation applications.Significance and Impact of the StudyThe study provides a constructive application of bacterial biofilms for the bioremediation of hydrophobic organic contaminants. The biofilm mode remediation process has the advantage of reusability of bacterial biomass and is also a low cost process as compare to cell immobilization techniques.This article is protected by copyright. All rights reserved.The study provides a constructive application of bacterial biofilms for the bioremediation of hydrophobic organic contaminants. The biofilm mode remediation process has the advantage of reusability of bacterial biomass and is also a low cost process as compare to cell immobilization techniques.This article is protected by copyright. All rights reserved.
Biofilm-forming marine bacterium Paenibacillus lautus NE3B01 was isolated from a mangrove ecosyst... more Biofilm-forming marine bacterium Paenibacillus lautus NE3B01 was isolated from a mangrove ecosystem, Odisha, India. This isolate formed a swarming type of colony pattern on the solid culture medium with 0.5–2 % agar. Phase contrast microscopy study of a growing colony of P. lautus on solid media and swarming pattern revealed the existence of two phenotypically distinct cells (i.e. cocci and rods) across the colonies. However, in actively growing planktonic culture, only rod-shaped cells were observed. Biofilm growth studies (crystal violet assay) with the isolate showed significant biofilm formation by 6 h, and the detachment phase was observed after 18 h. Biofilm parameters (such as total biomass, roughness coefficient, biofilm thickness, etc.) of 24-h-old P. lautus biofilm were studied by confocal scanning laser microscopy (CSLM). The CSLM study showed that P. lautus formed a biofilm with an average thickness of 14.8 ± 2.6 μm, a high roughness coefficient (0.379 ± 0.103) and surface to bio-volume ratio (4.59 ± 1.12 μm2/μm3), indicating a highly uneven topography of the biofilm. This also indicates that the 24-h-old biofilm is in dispersal phase. Scanning electron microphotographs of P. lautus also supported the existence of two distinct phenotypes of P. lautus. The current findings suggest that P. lautus has two vegetative phenotypes and to decongest the overcrowded biofilm the bacterium can switch over to motile rods from nonmotile cocci and vice versa.
A potential biofilm forming and phenanthrene utilizing marine bacterium Pseudomonas mendocina NR8... more A potential biofilm forming and phenanthrene utilizing marine bacterium Pseudomonas mendocina NR802 was isolated from Rushukulya, Odisha, East Coast of India. The effect of Ca2+ and Mg2+ on biofilm growth and phenanthrene degradation was evaluated. Among the various tested concentrations, 20 mM of Ca2+ and Mg2+ showed a significant enhancement in biofilm production by the bacterium. The SEM-EDAX study showed that the elemental composition of the biofilm varied significantly when grown in the presence of Ca2+ and Mg2+. The CSLM analysis of biofilms grown in the presence of 20 mM Ca2+ and Mg2+ reveal the critical role of these ions on biofilm architectural parameters such as total biomass, biofilm thickness, roughness coefficient and surface to biovolume ratio. Ca2+ was found to enhance the extracellular polymeric substances (EPS) production and phenanthrene degradation. Ca2+ enhanced the biofilm growth in a dose dependent manner, whereas Mg2+ significantly increased the cell growth in biofilm. More than 15% increase in phenanthrene degradation was observed when biofilm was grown in the presence of an additional 20 mM Ca2+. This study also supports the fundamental role of Ca2+ in biofilm growth, architecture as well as biofilm-mediated pollutant degradation.
In this study, a promising bioremediation approach was developed to remove [Co(III)-EDTA]− comple... more In this study, a promising bioremediation approach was developed to remove [Co(III)-EDTA]− complex that is generated during the waste management process. Though several studies have been reported on bioremediation of cobalt, the removal of [Co(III)-EDTA]− complex has not been tested. A [Co(III)-EDTA]− resistant bacterium, Pseudomonas aeruginosa SPB-1 was isolated from the solar-salt-pan and physical parameters were optimized for its growth. The various studies showed that the removal of [Co(III)-EDTA]− from the bulk liquid was due to the adsorption of the complex by the biomass. Using absorption/desorption isotherm over a range of pH (1–8), the maximum adsorption of [Co(III)-EDTA]− was found to be at pH 7.0 and maximum desorption from the biomass occurred at pH 1.0, thus rendering an ion exchange property to P. aeruginosa SPB-1 biomass. P. aeruginosa SPB-1 biomass could be used as bio-resin that showed 80.4 ± 3.27% adsorption capacity up to fourth cycle and the biomass was viable till the ninth cycle with 10.5 ± 7.3% adsorption. Radiation tolerance potential i.e. D10 value for the strain was found to be ∼300 Gy, which suggests the potential use of the bacterium in bioremediation of moderately active nuclear waste.
Deinococcus radiodurans R1 is a highly radio-tolerant bacterium. Depending on the nutrient availa... more Deinococcus radiodurans R1 is a highly radio-tolerant bacterium. Depending on the nutrient availability D. radiodurans R1 exists in three morphologies viz. monococcal, diplococcal and tetracoccal. In this study, we examined whether nutrition-induced morphotypes of D. radiodurans showed similar DNA damage upon gamma radiation exposure. Total DNA damage after radiation exposure was estimated by comparing percent double-strand breaks (DSBs) in genomic DNA. It was found that all three morphotypes exhibited different radiation tolerances which were also dependent on the radiation dose given. Monococcal forms were found to be most radio-tolerant at most of the tested radiation doses. Results showed that these nutrient-starved-condition induced morphotypes show lesser DNA DSBs upon irradiation, hence show higher radio-tolerance.
The dominant role of biofilm-associated protein (Bap) in Staphylococcus aureus biofilm developmen... more The dominant role of biofilm-associated protein (Bap) in Staphylococcus aureus biofilm development prompted us to investigate Bap as a potential target for proteinase-mediated biofilm dispersion. Biofilm assay in microtitre plates showed that proteinase K hampered the early adhesion of cells as well as biofilm development. Proteinase K treatment of 24- and 48-h-old biofilms showed enhanced dispersion of bap-positive S. aureus biofilm; however, proteinase K did not affect the bap-negative S. aureus biofilm. When antibiotics were used in combination with proteinase K, significant enhancement in antibiotic action was noticed against bap-positive S. aureus biofilm. This study establishes that antibiotics in combination with proteinase K can be used for controlling S. aureus biofilms in whose development Bap surface protein has a major role. We propose that Bap protein could be a potential target for therapeutic control of S. aureus infections (for example, bovine mastitis).
Bacterial adhesion is a threshold event in the formation of biofilms. Several studies on molecula... more Bacterial adhesion is a threshold event in the formation of biofilms. Several studies on molecular and biochemical aspects have highlighted that the protein matrix of the biofilm is of interest in developing strategies to combat biofouling. The prevalent role of biofilm associated protein (Bap) of Staphylococcus aureus in early adhesion and the putative presence of Ca2+ binding EF hand motif in Bap was the motivation for this study. Biofilm assays (S. aureus strains V329 and M556) were done in micro-titer plates and confocal laser scanning microscopy (CLSM) was used to study the biofilm architecture. The results showed that Ca2+ did not influence planktonic growth of the cultures; however, it modulated the biofilm architecture of S. aureus V329 in a dose dependent manner. Strain M556 was found to be a weak biofilm former and showed no significant change in the presence of Ca2+. When tested with increasing NaCl concentration, there was no reversal of the Bap-dependent Ca2+ inhibition of S. aureus V329 biofilm. This indicates that the interaction of Bap and Ca2+ is not mere electrostatic. CLSM images of V329 biofilm showed reduction in biofilm thickness as well as altered biofilm topography with varying Ca2+ concentrations. The inhibition effect of Ca2+ on strain V329 biofilm disappeared in the presence of chelating agent EDTA at a non-inhibiting concentration (0.15 mM). The paper elaborates the role of Ca2+ in biofilm architecture of S. aureus.
Aim: Among cell surface proteins, biofilm-associated protein promotes biofilm development in Stap... more Aim: Among cell surface proteins, biofilm-associated protein promotes biofilm development in Staphylococcus aureus strains. Aim of this study was to investigate proteinase-mediated biofilm dispersion in different isolates of S. aureus. Methods and Results: Microtitre plate based biofilm assay showed that 2 7 μg/mL proteinase K significantly inhibited biofilm development in bap-positive S. aureus V329 as well as other S. aureus strains, i.e. SA7, SA10, SA33, SA352 and but not in bap-mutant M556 and SA392 (a weak biofilm producing strain). However, proteinase K treatment on S. aureus planktonic cells showed that there was no inhibition of planktonic growth at any concentration of proteinase K when tested up to 32 μg/mL. This observation ruled out the possibility of S. aureus biofilm inhibition by altering the cell viability. Proteinase K treatment upon 24 h old preformed biofilms showed an enhanced dispersion of bap-positive V329 and SA7, SA10, SA33 and SA352 biofilms, however, protei...
ABSTRACT Biofilm forming marine bacterium Paenibacillus lautus NE3B01 was isolated from water sam... more ABSTRACT Biofilm forming marine bacterium Paenibacillus lautus NE3B01 was isolated from water sample collected from Bhitarkanika mangrove forest. From the biofilm growth study, Paenibacillus lautus NE3B01 showed many steps of biofilm formation and detachment. Biofilm formation begins with initial attachment of planktonic cells to the substratum, followed by cell division, growth, maturation and detachment of cells from the community. The detached cells can again form a new biofilm after coming in contact with substratum. From the biofilm growth studies, Paenibacillus lautus NE3B01 established mature biofilm with in 6h of growth followed by further formation and disintegration stages. Microscopy studies of Paenibacillus lautus NE3B01 biofilm on glass surface,growing colony on solid media and swarming pattern revealed the competing sibling phenotypes. Paenibacillus lautus NE3B01 survive overcrowding by switching between motile rods and immotile cocci, two distinct vegetative phenotypes. The current finding is of indication that the bacteria adapt to changing environmental conditions by inducible and reversible phenotypic switching.
ABSTRACT Biofilm forming marine bacterium Paenibacillus lautus NE3B01 was isolated from water sam... more ABSTRACT Biofilm forming marine bacterium Paenibacillus lautus NE3B01 was isolated from water sample collected from Bhitarkanika mangrove forest. From the biofilm growth study, Paenibacillus lautus NE3B01 showed many steps of biofilm formation and detachment. Biofilm formation begins with initial attachment of planktonic cells to the substratum, followed by cell division, growth, maturation and detachment of cells from the community. The detached cells can again form a new biofilm after coming in contact with substratum. From the biofilm growth studies, Paenibacillus lautus NE3B01 established mature biofilm with in 6h of growth followed by further formation and disintegration stages. Microscopy studies of Paenibacillus lautus NE3B01 biofilm on glass surface,growing colony on solid media and swarming pattern revealed the competing sibling phenotypes. Paenibacillus lautus NE3B01 survive overcrowding by switching between motile rods and immotile cocci, two distinct vegetative phenotypes. The current finding is of indication that the bacteria adapt to changing environmental conditions by inducible and reversible phenotypic switching.
Marine bacterial biofilms were studied under different physicochemical conditions for enhanced bi... more Marine bacterial biofilms were studied under different physicochemical conditions for enhanced bioremediation of polycyclic aromatic hydrocarbons (PAHs). Molecular characterization of ten environmental isolates was done by 16S rRNA gene sequencing. The effect of different physicochemical parameters, such as pH, salt concentration, temperature, carbon source on their biofilm production capability was monitored. Various topological parameters of the biofilms such as total biomass (EPS and cells content), thickness, roughness coefficient, diffusion distance and surface to biovolume ratio were studied using a confocal scanning laser microscope (CSLM). Among the various strains studied, the total biomass was maximum for P. aeruginosa N6P6 (106.64 mm 3 mm À2) followed by S. acidaminiphila NCW702 (26.92 mm 3 mm À2) indicating the formation of dense biofilm. Significant negative correlation (P < 0.05) was observed between the roughness coefficient of the biofilm and PAH degradation, whereas a significant positive correlation (P < 0.05) was observed between PAH (phenanthrene and pyrene) degradation and total biomass, thickness and diffusion distance of the biofilms. PAH degradation was studied both in planktonic and biofilm modes of growth. Biofilm facilitated degradation of the two PAHs was higher than the planktonic cells. This work demonstrates that the attached phenotypes of the marine bacteria showed noticeable variation in biofilm architecture and, in turn, biodegradation of PAHs.
Studies on the effect of calcium on Bap-mediated inhibition and modulation of Staphylococcus aure... more Studies on the effect of calcium on Bap-mediated inhibition and modulation of Staphylococcus aureus biofilm was the motivation behind this study. In this study, the effect of calcium on modulation of Staphylococcus aureus biofilm has been studied. Four S. aureus bovine mastitis isolates viz. SA7, SA10, SA33 and bap-positive S. aureus V329 (positive control) along with a bap-isogenic mutant M556 (negative control) were used in this study. PCR was used for detection of bap, biofilm assays were done in microtitre plates and confocal laser scanning microscopy (CLSM) was used to study the biofilm architecture. PCR mediated detection identified SA7, SA10 and SA33 as bap-negative strains. Biofilm assay showed that Ca 2+ inhibited the biofilm growth of SA10 and SAV329 in a dose dependent manner whereas SA7 and SA33 did not show any inhibition. Strain M556 was found to be a weak biofilm former and showed no significant change in the presence of Ca 2+. The planktonic growth study results showed that Ca 2+ did not influence planktonic growth in any of the S. aureus strains except SA10 where ≥ 5 mM Ca 2+ had an inhibitory effect. Interaction of Bap and Ca 2+ was found to be specific, since studies with Mg 2+ did not show any inhibitory effect on V329 biofilm formation. CLSM images of V329, SA7 and SA10 biofilms showed reduction in biofilm thickness as well as altered biofilm topography. The inhibition effect of Ca 2+ on V329 and SA10 biofilms disappeared in the presence of chelating agent EDTA at a sub-minimum inhibitory concentration (0.15 mM). The paper elaborates the role of Ca 2+ in the biofilm architecture of S. aureus.
Microbial granules are more effective than monoculture bacteria in the bioremediation process of ... more Microbial granules are more effective than monoculture bacteria in the bioremediation process of environmental contaminants. Among various types of microbial granules phototrophic granules are relatively advantageous in bioremediation than heterotrophic granules since they are self-sustaining. [Co(III)–EDTA] À generated during nuclear waste management is difficult to remove from the radioactive waste due to its high solubility and stability. In this study, phototrophic granules generated from a freshwater source were used for the reduction of [Co(III)–EDTA] À under anoxic conditions. The results of the study showed that the phototrophic granules efficiently reduced the highly soluble [Co(III)–EDTA] À to a lesser soluble form, [Co(II)–EDTA] 2– up to a concentration of 20 mM. The rate of [Co(III)–EDTA] À reduction was found to be relatively high when the process was performed with acclimatized phototrophic granules when compared to non-acclimatized granules. Specific studies using antibiotics to kill the heterotrophic bacterial population of the phototrophic granules showed that [Co(III)–EDTA] À reduction was carried out predominantly by the phototrophs. Investigations were also carried out to test the robustness of phototrophic granules to perform [Co(III)–EDTA] À reduction after gamma irradiation. The phototrophic granules showed substantial radio-tolerance and could reduce [Co(III)–EDTA] À without any significant loss in the activity, when irradiated up to 2 kGy. The study suggests that phototrophic granules have potential application in bioremediation of moderate level nuclear waste.
The corrosion inhibition efficiency of 3-(4-chlorobenzoylmethyl) benzimidazoliumbromide in water ... more The corrosion inhibition efficiency of 3-(4-chlorobenzoylmethyl) benzimidazoliumbromide in water medium has been evaluated using electrochemical and other techniques. The mixed type inhibitive behavior of the inhibitor was evaluated by potentiodynamic polarization study. The inhibition efficiency increased with increasing pH up to 7.0 and showed a decrease with rise in temperature of the medium. Charge transfer resistance (R ct) values confirmed the formation of a protective layer by the adsorption of the inhibitor on the carbon steel surface. The adsorption degree of 3-(4-chlorobenzoylmethyl) benzimidazoliumbromide on the metal substrate obeyed Langmuir adsorption isotherms. Surface characterization of the carbon steel in the absence and presence of inhibitor has been monitored by atomic force (AFM) and scanning electron microscopy (SEM) with energy dispersive X-Ray spectroscopy (EDX). Quantum chemical analysis (QCA) data supported the adsorption efficiency of the inhibitor. The results obtained from electrochemical noise analysis (ENA) were in good agreement with other studies.
A precise quantification of Co(II)EDTA complex is required to develop bioremediation approaches f... more A precise quantification of Co(II)EDTA complex is required to develop bioremediation approaches for Co(III)EDTA complex that is generated in various industrial processes. It is cumbersome to quantify Co(II)EDTA in a mixture of Co(II)EDTA and Co(III)EDTA by normal UV-visible spectrophotometric methods as both the complexes absorb significantly at 490 nm, which is the λ max of Co(II)EDTA. Whereas other sophisticated techniques such as gas chromatography, atomic absorption spectrophotometer, inductively coupled plasma-atomic emission spectroscopy can measure individual species of Co(II)EDTA or Co(III)EDTA when present alone but are ineffective to measure the Co(II)EDTA precisely when it is mixed with Co(III)EDTA. Hence, an attempt has been made to develop a spectrophotometric method for its quantification. This paper describes the development of a simple and economic dual wavelength spectrophotometric method for the determination of Co(II)EDTA in a mixture of Co(II)EDTA and Co(III)EDTA complexes. The wavelength pair, 490-580 nm was optimized for the measurement of absorbance for this dual wavelength method of determination of Co(II)EDTA in the presence of Co(III)EDTA.
Naturally stressed habitats are known to be repositories for novel microorganisms with potential ... more Naturally stressed habitats are known to be repositories for novel microorganisms with potential bioremediation applications. In this study, we isolated a [Co(III)-EDTA]− educing bacterium Bacillus licheniformis SPB-2 from a solar salt pan that is exposed to constant cycles of hydration and desiccation in nature. [Co(III)-EDTA]− rted during nuclear waste management process is difficult to remove from the waste due to its high stability and solubility. It's reduced form i.e. [Co(II)-EDTA]2− is less stable though it is toxic. This study showed that B. licheniformis SPB-2 reduced 1 mM [Co(III)-EDTA]− in 14 days when grown in a batch mode. However, subsequent cycles showed an increase in the reduction activity, which was observed up to four cycles. Interestingly, the present study also showed that [Co(III)-EDTA]− acted as an inducer for B. licheniformis SPB-2 spore germination. Vegetative cells germinated from the spores were found to be involved in [Co(III)-EDTA]− reduction. More detailed investigations showed that after [Co(III)-EDTA]− reduction, i.e. [Co(II)-EDTA]2− complex was removed by B. licheniformis SPB-2 from the bulk liquid by adsorption phenomenon. The bacterium showed a D10 value (radiation dose required to kill 90% cells) of ∼250 Gray (Gy), which signifies the potential use of B. licheniformis SPB-2 for bioremediation of moderately active nuclear waste.
AimBiofilm formation and polycyclic aromatic hydrocarbons (PAHs) degradation by a marine bacteriu... more AimBiofilm formation and polycyclic aromatic hydrocarbons (PAHs) degradation by a marine bacterium Stenotrophomonas acidaminihila NCW-702 was investigated.Biofilm formation and polycyclic aromatic hydrocarbons (PAHs) degradation by a marine bacterium Stenotrophomonas acidaminihila NCW-702 was investigated.Methods and resultsThe biofilm structure was studied by confocal laser scanning microscopy (CLSM). Both planktonic and biofilm cultures were used for PAHs (phenanthrene and pyrene) degradation. In 7 days, S. acidaminiphila biofilm culture efficiently degraded 71.1 ±3.1% and 40.2 ±2.4% of phenanthrene and pyrene respectively. Whereas, 38.7 ±2.5% of phenanthrene and 29.7 ±1% of pyrene degradation was observed in planktonic culture. The presence of phenolic intermediates in the culture supernatant during degradation process was evaluated by Folin-Ciocalteau reagent. The average thickness and diffusion distance of S. acidaminiphila NCW-702 biofilm was found to be 23.94 ± 2.62 μm and 2.68 ± 0.7 μm respectively. Bacterial biofilms have numerous metabolic features that aid in the degradation of hydrophobic organic pollutants.The biofilm structure was studied by confocal laser scanning microscopy (CLSM). Both planktonic and biofilm cultures were used for PAHs (phenanthrene and pyrene) degradation. In 7 days, S. acidaminiphila biofilm culture efficiently degraded 71.1 ±3.1% and 40.2 ±2.4% of phenanthrene and pyrene respectively. Whereas, 38.7 ±2.5% of phenanthrene and 29.7 ±1% of pyrene degradation was observed in planktonic culture. The presence of phenolic intermediates in the culture supernatant during degradation process was evaluated by Folin-Ciocalteau reagent. The average thickness and diffusion distance of S. acidaminiphila NCW-702 biofilm was found to be 23.94 ± 2.62 μm and 2.68 ± 0.7 μm respectively. Bacterial biofilms have numerous metabolic features that aid in the degradation of hydrophobic organic pollutants.ConclusionBiofilm of S. acidaminiphila NCW-702 was able to degrade PAHs more efficiently as compared to planktonic cells. The findings support the efficacy of biofilms over planktonic culture in bioremediation applications.Biofilm of S. acidaminiphila NCW-702 was able to degrade PAHs more efficiently as compared to planktonic cells. The findings support the efficacy of biofilms over planktonic culture in bioremediation applications.Significance and Impact of the StudyThe study provides a constructive application of bacterial biofilms for the bioremediation of hydrophobic organic contaminants. The biofilm mode remediation process has the advantage of reusability of bacterial biomass and is also a low cost process as compare to cell immobilization techniques.This article is protected by copyright. All rights reserved.The study provides a constructive application of bacterial biofilms for the bioremediation of hydrophobic organic contaminants. The biofilm mode remediation process has the advantage of reusability of bacterial biomass and is also a low cost process as compare to cell immobilization techniques.This article is protected by copyright. All rights reserved.
Biofilm-forming marine bacterium Paenibacillus lautus NE3B01 was isolated from a mangrove ecosyst... more Biofilm-forming marine bacterium Paenibacillus lautus NE3B01 was isolated from a mangrove ecosystem, Odisha, India. This isolate formed a swarming type of colony pattern on the solid culture medium with 0.5–2 % agar. Phase contrast microscopy study of a growing colony of P. lautus on solid media and swarming pattern revealed the existence of two phenotypically distinct cells (i.e. cocci and rods) across the colonies. However, in actively growing planktonic culture, only rod-shaped cells were observed. Biofilm growth studies (crystal violet assay) with the isolate showed significant biofilm formation by 6 h, and the detachment phase was observed after 18 h. Biofilm parameters (such as total biomass, roughness coefficient, biofilm thickness, etc.) of 24-h-old P. lautus biofilm were studied by confocal scanning laser microscopy (CSLM). The CSLM study showed that P. lautus formed a biofilm with an average thickness of 14.8 ± 2.6 μm, a high roughness coefficient (0.379 ± 0.103) and surface to bio-volume ratio (4.59 ± 1.12 μm2/μm3), indicating a highly uneven topography of the biofilm. This also indicates that the 24-h-old biofilm is in dispersal phase. Scanning electron microphotographs of P. lautus also supported the existence of two distinct phenotypes of P. lautus. The current findings suggest that P. lautus has two vegetative phenotypes and to decongest the overcrowded biofilm the bacterium can switch over to motile rods from nonmotile cocci and vice versa.
A potential biofilm forming and phenanthrene utilizing marine bacterium Pseudomonas mendocina NR8... more A potential biofilm forming and phenanthrene utilizing marine bacterium Pseudomonas mendocina NR802 was isolated from Rushukulya, Odisha, East Coast of India. The effect of Ca2+ and Mg2+ on biofilm growth and phenanthrene degradation was evaluated. Among the various tested concentrations, 20 mM of Ca2+ and Mg2+ showed a significant enhancement in biofilm production by the bacterium. The SEM-EDAX study showed that the elemental composition of the biofilm varied significantly when grown in the presence of Ca2+ and Mg2+. The CSLM analysis of biofilms grown in the presence of 20 mM Ca2+ and Mg2+ reveal the critical role of these ions on biofilm architectural parameters such as total biomass, biofilm thickness, roughness coefficient and surface to biovolume ratio. Ca2+ was found to enhance the extracellular polymeric substances (EPS) production and phenanthrene degradation. Ca2+ enhanced the biofilm growth in a dose dependent manner, whereas Mg2+ significantly increased the cell growth in biofilm. More than 15% increase in phenanthrene degradation was observed when biofilm was grown in the presence of an additional 20 mM Ca2+. This study also supports the fundamental role of Ca2+ in biofilm growth, architecture as well as biofilm-mediated pollutant degradation.
In this study, a promising bioremediation approach was developed to remove [Co(III)-EDTA]− comple... more In this study, a promising bioremediation approach was developed to remove [Co(III)-EDTA]− complex that is generated during the waste management process. Though several studies have been reported on bioremediation of cobalt, the removal of [Co(III)-EDTA]− complex has not been tested. A [Co(III)-EDTA]− resistant bacterium, Pseudomonas aeruginosa SPB-1 was isolated from the solar-salt-pan and physical parameters were optimized for its growth. The various studies showed that the removal of [Co(III)-EDTA]− from the bulk liquid was due to the adsorption of the complex by the biomass. Using absorption/desorption isotherm over a range of pH (1–8), the maximum adsorption of [Co(III)-EDTA]− was found to be at pH 7.0 and maximum desorption from the biomass occurred at pH 1.0, thus rendering an ion exchange property to P. aeruginosa SPB-1 biomass. P. aeruginosa SPB-1 biomass could be used as bio-resin that showed 80.4 ± 3.27% adsorption capacity up to fourth cycle and the biomass was viable till the ninth cycle with 10.5 ± 7.3% adsorption. Radiation tolerance potential i.e. D10 value for the strain was found to be ∼300 Gy, which suggests the potential use of the bacterium in bioremediation of moderately active nuclear waste.
Deinococcus radiodurans R1 is a highly radio-tolerant bacterium. Depending on the nutrient availa... more Deinococcus radiodurans R1 is a highly radio-tolerant bacterium. Depending on the nutrient availability D. radiodurans R1 exists in three morphologies viz. monococcal, diplococcal and tetracoccal. In this study, we examined whether nutrition-induced morphotypes of D. radiodurans showed similar DNA damage upon gamma radiation exposure. Total DNA damage after radiation exposure was estimated by comparing percent double-strand breaks (DSBs) in genomic DNA. It was found that all three morphotypes exhibited different radiation tolerances which were also dependent on the radiation dose given. Monococcal forms were found to be most radio-tolerant at most of the tested radiation doses. Results showed that these nutrient-starved-condition induced morphotypes show lesser DNA DSBs upon irradiation, hence show higher radio-tolerance.
The dominant role of biofilm-associated protein (Bap) in Staphylococcus aureus biofilm developmen... more The dominant role of biofilm-associated protein (Bap) in Staphylococcus aureus biofilm development prompted us to investigate Bap as a potential target for proteinase-mediated biofilm dispersion. Biofilm assay in microtitre plates showed that proteinase K hampered the early adhesion of cells as well as biofilm development. Proteinase K treatment of 24- and 48-h-old biofilms showed enhanced dispersion of bap-positive S. aureus biofilm; however, proteinase K did not affect the bap-negative S. aureus biofilm. When antibiotics were used in combination with proteinase K, significant enhancement in antibiotic action was noticed against bap-positive S. aureus biofilm. This study establishes that antibiotics in combination with proteinase K can be used for controlling S. aureus biofilms in whose development Bap surface protein has a major role. We propose that Bap protein could be a potential target for therapeutic control of S. aureus infections (for example, bovine mastitis).
Bacterial adhesion is a threshold event in the formation of biofilms. Several studies on molecula... more Bacterial adhesion is a threshold event in the formation of biofilms. Several studies on molecular and biochemical aspects have highlighted that the protein matrix of the biofilm is of interest in developing strategies to combat biofouling. The prevalent role of biofilm associated protein (Bap) of Staphylococcus aureus in early adhesion and the putative presence of Ca2+ binding EF hand motif in Bap was the motivation for this study. Biofilm assays (S. aureus strains V329 and M556) were done in micro-titer plates and confocal laser scanning microscopy (CLSM) was used to study the biofilm architecture. The results showed that Ca2+ did not influence planktonic growth of the cultures; however, it modulated the biofilm architecture of S. aureus V329 in a dose dependent manner. Strain M556 was found to be a weak biofilm former and showed no significant change in the presence of Ca2+. When tested with increasing NaCl concentration, there was no reversal of the Bap-dependent Ca2+ inhibition of S. aureus V329 biofilm. This indicates that the interaction of Bap and Ca2+ is not mere electrostatic. CLSM images of V329 biofilm showed reduction in biofilm thickness as well as altered biofilm topography with varying Ca2+ concentrations. The inhibition effect of Ca2+ on strain V329 biofilm disappeared in the presence of chelating agent EDTA at a non-inhibiting concentration (0.15 mM). The paper elaborates the role of Ca2+ in biofilm architecture of S. aureus.
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Papers by Sudhir K Shukla