Bacterial growth

Objectives: Time-kill studies are commonly used in investigations of new antimicrobial agents. However, they typically provide descriptive information on pharmacodynamics. We developed a mathe- matical model to capture the relationship between microbial burden and antimicrobial agent concentrations. Methods: Time-kill studies were performed with 108 cfu/mL of Pseudomonas aeruginosa at baseline. Meropenem at 0, 0.25, 1, 4, 16 and 64 3

The HOBAS aeration system was tested to compare changes in environmental and bacteriological parameters in ponds growing Penaeus monodon during a single production cycle. The stocking density in the aerated pond was doubled to 12 post-larvae (PL) m − 2 in contrast to the non-aerated pond with 6 (PL) m − 2. Microbial abundance in the ponds ranged between 105 − 6 cells ml − 1. Among the physiological groups of bacteria enumerated, the heterotrophs dominated with an abundance of 104 CFU ml − 1. Of the nitrogen and sulfur cycle bacteria, the nitrifiers flourished in the aerated pond and could maintain ammonia-N concentration within permissible levels. Bacterial activity also maintained sulfide concentrations at  − 1. Non-aerated conditions promoted denitrification maintaining nitrate concentration between 0.32 and 0.98 μM NO3  − -N l − 1. However, a marked increase in ammonium content was observed in the non-aerated pond at the end of the culture period. Thus in high-density ponds, the aerators served to stimulate bacterial growth and activity which consequently maintained the quality of the water to match that of low-density ponds. Accordingly, these aerators could be effectively used to sustain higher yields. The effluent from the aerated pond is less likely to alter the redox balance of the receiving waters.

We have shown previously that in the presence of inducer Bacillus cereus 183, significant increases in bacteriocin production and bactericidal activity of B. thuringiensis occur when the latter is cultivated at pH 7.2, 28°C, and 180 rpm. Here we show that this activity can be further improved when B. thuringiensis is induced with B. cereus 183 and then cultivated with modification of pH, temperature, and agitation. Five native strains of B. thuringiensis, LBIT 269, LBIT 287, LBIT 404, LBIT 420, and LBIT 524 which synthesize, respectively, morricin 269, kurstacin 287, kenyacin 404, entomocin 420, and tolworthcin 524, were cultivated in four different fermentation media. Of these, fermentation in tryptic soy broth (TSB) yielded the highest level of bacteriocin activity (~100–133 FU). Bacteria grown in TSB were induced with B. cereus 183 and cultivated at different pH (6.0, 7.2, 8.0), temperature (26, 28, 30°C), and agitation (150, 180, 210 rpm). Full factorial design was performed and results were analyzed with analysis of variance (ANOVA) and Tukey multiple comparison tests at significant level of α ≤ 0.05 to study the influence of the three variables on bacterial growth and bacteriocin production. Our data show that the highest bacteriocin activity was found with LBIT 269 and LBIT 404 with an increase of ~95–100% compared with induced B. thuringiensis strains cultivated under fixed conditions (pH 7.2, 28°C, 180 rpm), for which the data were set at 0%. The optimal conditions for morricin 269 and kenyacin 404 production were, respectively, pH 8, 30°C, 210 rpm and pH 7.2, 26°C, 210 rpm.

JACOB, J. C. F.; JESUS, V. L. T. de; BARBOSA, H. P.; ZIMMERMAN, M. F.; SILVA, A. G. da; MELO, C. M.; Antimicrobic susceptibility of uterine and clitoral swabs of mares with endometritis. Rev. Univ. Rural, Sér. Ciên. da Vida, V.22 n2, 2002 (Suplemento), p. 109-114. 15 uterine swabs and 15 clitoral fossa swabs were examinated from Mangalarga Marchador mares

The potential eco-toxicity of nanosized titanium dioxide (TiO2), silicon dioxide (SiO2), and zinc oxide (ZnO) water suspensions was investigated using Gram-positive Bacillus subtilis and Gram-negative Escherichia coli as test organisms. These three photosensitive nanomaterials were harmful to varying degrees, with antibacterial activity increasing with particle concentration. Antibacterial activity generally increased from SiO2 to TiO2 to ZnO, and B. subtilis was most susceptible to their effects. Advertised nanoparticle size did not correspond to true particle size. Apparently, aggregation produced similarly sized particles that had similar antibacterial activity at a given concentration. The presence of light was a significant factor under most conditions tested, presumably due to its role in promoting generation of reactive oxygen species (ROS). However, bacterial growth inhibition was also observed under dark conditions, indicating that undetermined mechanisms additional to photocatalytic ROS production were responsible for toxicity. These results highlight the need for caution during the use and disposal of such manufactured nanomaterials to prevent unintended environmental impacts, as well as the importance of further research on the mechanisms and factors that increase toxicity to enhance risk management.

Efficient host exploitation by parasites is frequently likely to depend on cooperative behaviour. Under these conditions, mixed-strain infections are predicted to show lower virulence (host mortality) than are single-clone infections, due to competition favouring non-contributing social 'cheats' whose presence will reduce within-host growth. We tested this hypothesis using the cooperative production of iron-scavenging siderophores by the pathogenic bacterium Pseudomonas aeruginosa in an insect host. We found that infection by siderophore-producing bacteria (cooperators) results in more rapid host death than does infection by non-producers (cheats), and that mixtures of both result in intermediate levels of virulence. Within-host bacterial growth rates exhibited the same pattern. Crucially, cheats were more successful in mixed infections compared with single-clone infections, while the opposite was true of cooperators. These data demonstrate that mixed clone infections can fa...

Feasibility for bacterial leaching of two different copper ores from Pakistan was investigated with locally isolated, acidophilic thiobacilli in shake flask culture at 28±2°C. After a lag period of 16 d,Thiobacillus thiooxidans solubilized up to 19% of copper present in chalcopyrite ore in 14 d before entering stationary phase. In oxidized copper ore amended with chalcopyrite ore and supplemented with

Current theatre practice and protocol involves the use of pressure sore prevention pads in the positioning and support of all patients undergoing orthopaedic surgery. Microbiological swabs were taken from those pads placed adjacent to the operative field immediately before implant surgery. Eleven out of the 13 pads sampled yielded bacterial growth capable of causing deep-seated infection. The transfer of these pads between the designated orthopaedic theatres and the rest of the theatre complex was also noted. We recommend that the use of these pads should be closely reviewed. They should either be used with stricter guidelines for decontamination between use or disposable ‘clean’ alternatives sought.

Proteus mirabilis colonies exhibit striking geometric regularity. Basic microbiological methods and imaging techniques were used to measure periodic macroscopic events in swarm colony morphogenesis. We distinguished three initial phases (lag phase, first swarming phase, and first consolidation phase) followed by repeating cycles of subsequent swarming plus consolidation phases. Each Proteus swarm colony terrace corresponds to one swarming-plus-consolidation cycle. The duration of the lag phase was dependent upon inoculation density in a way that indicated the operation of both cooperative and inhibitory multicellular effects. On our standard medium, the second and subsequent swarm phases displayed structure in the form of internal waves visible with reflected and dark-field illumination. These internal waves resulted from organization of the migrating bacteria into successively thicker cohorts of swarmer cells. Bacterial growth and motility were independently modified by altering th...

Water-column mixing is known to have a decisive impact on plankton communities. The underlying mechanisms depend on the size and depth of the water body, nutrient status and the plankton community structure, and they are well understood for shallow polymictic and deep stratified lakes. Two consecutive mixing events of similar intensity under different levels of herbivory were performed in enclosures in a shallow, but periodically stratified, eutrophic lake, in order to investigate the effects of water-column mixing on bacteria abundance, phytoplankton abundance and diversity, and rotifer abundance and fecundity. When herbivory by filter-feeding zooplankton was low, water-column mixing that provoked a substantial nutrient input into the euphotic zone led to a strong net increase of bacteria and phytoplankton biomass. Phytoplankton diversity was lower in the mixed enclosures than in the undisturbed ones because of the greater contribution of a few fast-growing species. After the second mixing event, at a high biomass of filter-feeding crustaceans, the increase of phytoplankton biomass was lower than after the first mixing, and diversity remained unchanged because enhanced growth of small fast-growing phytoplankton was prevented by zooplankton grazing. Bacterial abundance did not increase after the second mixing, when cladoceran biomass was high. Changes in rotifer fecundity indicated a transmission of the phytoplankton response to the next trophic level. Our results suggest that water-column mixing in shallow eutrophic lakes with periodic stratification has a strong effect on the plankton community via enhanced nutrient availability rather than resuspension or reduced light availability. This fuels the basis of the classic and microbial food chain via enhanced phytoplankton and bacterial growth, but the effects on biomass may be damped by high levels of herbivory.

In a joint venture between Agricultural Research Organization, Volcani Center and StePac L.A Ltd. (Tefen, Israel), a series of plastic films have been developed (commercial name Xtend®) with higher permeability to water vapor than most commercially available MAP products. Using hydrophilic Xtend® films manufactured from various proprietary blends of polyamides with other polymeric and non- polymeric compounds allowed achieving in-pack

Metal pollution is a serious problem for environmental safety and programmes of monitoring and bioremediation are needed. Among the processes of bioremediation, the use of microbes to remove and degrade contaminants is considered a biotechnological approach to clean up polluted environments. The aim of this study was to evaluate the ability of Serratia marcescens in Pb, Cd and Cr removal and the potential use of these bacteria in toxic metal bioremediation from polluted environments. A short-term study (120 min) was carried out to study the bacterial growth in the presence of sub-inhibitory concentrations of each metal analysed and the kinetics of metal biosorption in S. marcescens strain. In addition, metal influence on the biosynthesis of the red pigment 'prodigiosina' by S. marcescens was monitored. The results obtained in this study show metals biosorption by S. marcescens (range: 0.0133-0.213 μg/g for Pb; 0.097-0.1853 μg/g for Cd; and 0.105-0.176 μg/g for Cr) and confirm the possible use of this bacterium to realize bioremediation processes, especially for Pb removal, and as a bioindicator of metal pollution.

Passerine birds that reuse nest sites face an increased parasite and pathogen load. They also are more likely to use fresh green vegetation during nest construction. The present results demonstrate that at least one passerine, the European Starling: (a) selects a small subset of available plant species for inclusion in nest material; and (b) chooses plants whose volatiles are more likely to inhibit arthropod hatching and bacterial growth relative to a random subset of available vegetation. The results also show that preferred plants possess greater numbers of mono- and sesqueter-penes at higher concentrations relative to a random subset of available plants. These findings strongly suggest that starlings use chemicals in fresh vegetation as fumigants against parasites and pathogens.