Molecular Microbiology

In December 2019, the emergence of SARS-CoV-2 virus in China led to a pandemic. Since both Influenza Like Illness (ILI) and COVID-19 case definitions overlap, we re-investigated the ILI cases using PCR for the presence of SARS-CoV-2 in 739 nasopharyngeal swabs collected from November 2019 to March 2020. SARS-CoV-2 RNA was found in 37 samples (5%) collected mostly during February 2020. It was followed by confirmation of evolutionary and spatial relationships using next generation sequencing (NGS). We observed that the overall incidence of ILI cases during 2019–2020 influenza season was considerably higher than previous years and was gradually replaced with SARS-CoV-2, which indicated a silent transmission among ambulatory patients. Sequencing of representative isolates confirmed independent introductions and silent transmission earlier than previously thought. Evolutionary and spatial analyses revealed clustering in the GH clade, characterized by three amino acid substitutions in spi...

The competency of microbiology professionals is obtained through the theoretical knowledge gained in the class and the practical skills and applications that lead to the better understanding and interpretations the subject matter. This laboratory manual is designed to guide the student through basic microbiology laboratory techniques, procedures and experiments. It provides students good techniques in practical investigations to ensure and proceed safely and to successfully achieve the required educational and research aims. The main portion of this manual involves the identification of unknown microbial agents. The manual can also be used as a reference material and guideline protocol for basic microbiological practices and research experiments.

This laboratory manual encompasses the basic laboratory techniques which start with description about basic laboratory safety rule, cleaning and sterilization methods, bacterial staining techniques, bacterial culturing methods, primary identification and secondary biochemical tests and antibiotic sensitivity tests. It also includes commonly used serological tests, mycological and viral culture and identification technique. Each of these technique are written detail accordingly and the steps in each tests includes principles of the test, objectives of the test, materials and reagents used, methods and/or procedures and their possible results and subsequent interpretations.

High standards of laboratory safety and containment that will ensure healthy working conditions for student, laboratory staff and protection of the environment must be of the greatest priority. They can only be achieved by careful study of the principles involved followed by practical application to premises, facilities, operating procedures and hygiene. Orientations or short term training must be given to all students and laboratory personnel before they are entirely allowed to use the laboratory.

Analysis of the transcriptome of slyA mutant Salmonella enterica serovar Typhimurium revealed that many SlyA-dependent genes, including pagC, pagD, ugtL, mig-14, virK, phoN, pgtE, pipB2, sopD2, pagJ and pagK, are also controlled by the PhoP/PhoQ regulatory system. Many SlyA- and PhoP/PhoQ-co-regulated genes have functions associated with the bacterial envelope, and some have been directly implicated in virulence and resistance to antimicrobial peptides. Purified His-tagged SlyA binds to the pagC and mig-14 promoters in regions homologous to a previously proposed ‘SlyA-box’. The pagC promoter lacks a consensus PhoP binding site and does not bind PhoP in vitro, suggesting that the effect of PhoP on pagC transcription is indirect. Stimulation of pagC expression by PhoP requires SlyA. Levels of SlyA protein and mRNA are not significantly changed under low-magnesium PhoP-inducing conditions in which pagC expression is profoundly elevated, however, indicating that the PhoP/PhoQ system does not activate pagC expression by altering SlyA protein concentration. Models are proposed in which PhoP may control SlyA activity via a soluble ligand or SlyA may function as an anti-repressor to allow PhoP activation. The absence of almost all SlyA-activated genes from the Escherichia coli K12 genome suggests that the functional linkage between the SlyA and PhoP/PhoQ regulatory systems arose as Salmonella evolved its distinctive pathogenic lifestyle.

One limiting factor in studies of tuberculosis and leprosy is the difficulty of genetic analysis and manipulation of mycobacteria. Two approaches were adopted for the construction of vectors, based on different Escherichia coli plasmids and using Mycobacterium smegmatis as the host. In both cases we found that the original E. coli plasmid is capable of being replicated in M. smegmatis, yielding chloramphenicol-resistant colonies. One such plasmid has been recovered from a M. smegmatis transformant and used to re-transform both M. smegmatis and E. coli to chloramphenicol resistance. This plasmid is indistinguishable from the original plasmid by restriction analysis, and can be used as a shuttle vector for the genetic manipulation of mycobacterial species.

Bacteriophage lambda has an archetypal immunity system, which prevents superinfection of its E. coli lysogens. It is now known that superinfection at high frequency can occur with toxigenic lambda-like phages, and here we demonstrate that superinfection of a lambda lysogen can lead to acquisition of additional lambda genomes, confirmed by Southern hybridisation and quantitative PCR. As many as 8 integration events were observed, but at very low frequency (6.4 x 10(-4)) and always as multiple insertions at the established primary integration site in E. coli. Sequence analysis of the complete immunity region demonstrated that these multiply infected lysogens were not immunity mutants. In conclusion, although lambda superinfection immunity can be confounded, it is a rare event.

In vivo and in vitro analyses indicate that transcription of the argO gene coding for an arginine exporter is regulated by the global transcriptional regulator Lrp, an effect that went by unnoticed in previous genome-scale screenings of the Lrp regulatory network in Escherichia coli. Lrp activates the argO promoter fourfold; exogenous leucine antagonizes, but does not completely eliminate this effect. Activation by Lrp interferes with the previously demonstrated activation of the argO promoter by ArgP. This interference results from the mutual inhibitory binding of the two activators to overlapping targets. As a consequence, each regulator acts more potently in the absence of the other. Dimeric Lrp binds cooperatively to at least three regularly spaced semi-palindromic binding sites. Leucine reduces complex formation approximately twofold but concomitantly enhances the cooperativity of the binding. Footprinting data suggest a severe Lrp-induced deformation of the argO control region. Combined, the effector modulated activation of argO transcription by ArgP and Lrp must ensure an adapted and fine-tuned synthesis of the transporter in response to environmental conditions. The repertoire of bacterial transcription regulation mechanisms is vast, but the competitive activation of a single promoter by two activator proteins as described here appears to be rare.

Two actin genes, actA from the hemibiotrophic anthracnose fungus, Colletotrichum gloeosporioides (Penz.) Penz. & Sacc. f. sp. malvae, and act1 from its host, Malva pusilla (Sm.) were cloned from a cDNA library developed from infected host tissue. The actin gene, actA, of C. gloeosporioides f. sp. malvae, which is similar to that of other euascomycetes, appears to be expressed constitutively. The actin gene of M. pusilla is most similar to one of the actin genes of Arabidopsis thaliana that is unique in being responsive to environmental stimuli such as wounding. Expression of actA was used to follow the growth of the fungus in the plant tissue. Low actA expression occurred until 72–96 h after inoculation and then increased rapidly, corresponding with the timing of the shift from slower biotrophic fungal growth to much more rapid necrotrophic growth. In contrast, expression of act1 approximately doubled during the biotrophic phase and then rapidly declined during the necrotrophic phase. Increased host actin expression could be due to host cytoskeleton rearrangement in response to biotrophic infection, and the subsequent decrease in host actin expression could be due to host cell disruption resulting from tissue maceration during necrosis. This is the first report of a host actin gene that can increase in expression during a compatible plant-pathogen interaction.

Glutamate racemase (MurI) has been proposed as a target for anti-tuberculosis drug development based on the inability of ΔmurI mutants of Mycobacterium smegmatis to grow in the absence of d-glutamate. In this communication, we identify ΔmurI suppressor mutants that are detected during prolonged incubation. Whole genome sequencing of these ΔmurI suppressor mutants identified the presence of a SNP, located in the promoter region of MSMEG_5795. RT-qPCR and transcriptional fusion analyses revealed that the ΔmurI suppressor mutant overexpressed MSMEG_5795 14-fold compared to the isogenic wild-type. MSMEG_5795, which is annotated as 4-amino-4-deoxychorismate lyase (ADCL) but which also has homology to d-amino acid transaminase (d-AAT), was expressed, purified and found to have d-AAT activity and to be capable of producing d-glutamate from d-alanine. Consistent with its d-amino acid transaminase function, overexpressed MSMEG_5795 is able to complement both ΔmurI deletion mutants and alanin...

Soupene et al. [J. Bacteriol. (2003) 185 5611–5626] made the unexpected observation that the presence of a mutation, in the gene for the N-acetylglucosamine repressor, nagC, increased the growth rate of Escherichia coli MG1655 on galactose, an unrelated sugar. We have found that NagC, binds to a single, high-affinity site overlapping the promoter of galP (galactose permease) gene and that expression of galP is repressed by a combination of NagC, GalR and GalS. In addition to the previously identified galOE operator, other gal operators further upstream are required for full repression. GalS has a specific role, as it binds with higher affinity to one of the upstream operators but its effect in vivo is only observed in the presence of GalR. Regulation of galP by three specific repressors, NagC, GalR and GalS is unusual in that it involves multiple, specific regulators from two different areas of metabolism. This novel regulation seems to be particular for E. coli and its nearest neighbour, Shigella. Other bacteria with galP orthologues, although retaining the metK-galP gene order, do not have the NagC site. Although quantitative effects were strain specific, nagC mutations increased the growth rate on galactose of all E. coli strains tested.

Bacillus subtilis spo0K mutants are blocked at the first step in sporulation. The spo0K strain was found to contain two mutations: one was linked to the trpS locus, and the other was elsewhere on the chromosome. The mutation linked to trpS was responsible for the sporulation defect (spo-). The unlinked mutation enhanced this sporulation deficiency but had no phenotype on its own. The spo- mutation was located in an operon of five genes highly homologous to the oligopeptide transport (Opp) system of Gram-negative species. Studies with toxic peptide analogues showed that this operon does indeed encode a peptide-transport system. However, unlike the Opp system of Salmonella typhimurium, one of the two ATP-binding proteins, OppF, was not required for peptide transport or for sporulation. The OppA peptide-binding protein, which is periplasmically located in Gram-negative species, has a signal sequence characteristic of lipo-proteins with an amino-terminal lipo-amino acid anchor. Cellular location studies revealed that OppA was associated with the cell during exponential growth, but was released into the medium in stationary phase. A major role of the Opp system in Gram-negative bacteria is the recycling of cell-wall peptides as they are released from the growing peptidoglycan. We postulate that the accumulation of such peptides may play a signaling role in the initiation of sporulation, and that the sporulation defect in opp mutants results from an inability to transport these peptides.

Cytochromes of the c-type function on the outer side of the cytoplasmic membrane in bacteria where they also are assembled from apo-cytochrome polypeptide and haem. Two distinctly different systems for cytochrome c maturation are found in bacteria. System I present in Escherichia coli has eight to nine different Ccm proteins. System II is found in Bacillus subtilis and comprises four proteins: CcdA, ResA, ResB and ResC. ResB and ResC are poorly understood polytopic membrane proteins required for cytochrome c synthesis. We have analysed these two B. subtilis proteins produced in E. coli and in the native organism. ResB is shown to bind protohaem IX and haem is found covalently bound to residue Cys-138. Results in B. subtilis suggest that also ResC can bind haem. Our results complement recent findings made with Helicobacter CcsBA supporting the hypothesis that ResBC as a complex translocates haem by attaching it to ResB on the cytoplasmic side of the membrane and then transferring it to an extra-cytoplasmic location in ResC, from where it is made available to the apo-cytochromes.

Microorganisms are key-role player for stabilization of landfill sites. In order to evaluate the availability of T-RFLP(Terminal Restriction Fragment Length Polymorphism) for monitoring microbial community variations during stabilization of landfill sites, the phylogenic diversity of microbial community in the leachate from 4 different full-scale landfills was characterized by T-RFLP based on bacterial 16S rDNA. Main population of microbial community analyzed by T-RFLP was significantly similar with that of microbial community analyzed by clone library analysis. The results of T-RFLP analysis for main population of microbial community in the leachate from landfills with different landfill structures, waste types and landfill ages showed apparently different microbial diversity and structures. Therefore, long-term monitoring of microbial community in leachate from landfill sites by using T-RFLP is expected to be available for evaluation of landfill stability.

Background: Diarrheagenic Escherichia coli (DEC) is regarded as a great public health concern all around the world causing diarrhoea which can be transmitted through food chain. Aims: This study aimed to determine the contamination level and exact distribution rate of DEC in food products consumed by human. Methods: Seven hundred and twenty samples of food from animal origin and fishes were analysed by conventional and molecular method for the presence of E. coli and two multiplex polymerase chain reaction (mPCR) for detection of DEC. Results: Two hundred and eighty-three E. coli isolates were detected. The classification of DEC by two multiplex PCR assay yielded 84 DEC pathotypes. Enterotoxigenic E. coli (ETEC) was detected at high rates (75%) followed by shiga-toxigenic E. coli (STEC) and enterohemorrhagic E. coli (EHEC) (each of 9.5%), enteroaggregative E. coli (EAEC) (3.5%) and atypical enteropathogenic E. coli (aEPEC) (about 2.3%). The highest number of DEC (n=26; 21.6%) was observed from beef carcasses in abattoir while the lowest number (n=7; 5.8%) was noticed from burger samples (P<0.01). Enterotoxigenic E. coli was widespread in local raw ground meat and fish surface swabs (P<0.001), EAEC (P<0.01), and EHEC (P<0.001) were only in beef carcasses swabs, STEC was more prevalent in both imported and local raw burger (P<0.01), while the isolates of aEPEC were from imported chicken carcasses (P>0.05). Conclusion: High DEC contamination rate that was observed is attributed to the poor hygienic practices during food processing. Therefore, a superior hygienic application is required.

Resumen: En la Argentina el sector avícola ha incrementado la producción gracias a las transformaciones tecnológicas y a la mejora en la eficiencia productiva. El aumento del consumo generó interés en comercios de diferentes rubros a comercializar pollo entero y subproductos, sin el correcto cumplimiento de las Buenas Prácticas de Manufactura (BPM) en muchos de los casos, acarrea consecuencias a nivel poblacional a través de las Enfermedades Transmisibles por Alimentos (ETA). El objetivo general de este trabajo fue realizar una evaluación microbiológica sobre patógenos causantes de ETA en 30 muestras de carne aviar, provenientes de 6 establecimientos expendedores de aves y carnes de la ciudad de Tandil, específicamente detectar la presencia de Salmonella spp. y Staphylococcus aureus coagulasa positivo a través de técnicas de cultivo in vitro, y detectar y confirmar presencia de Escherichia coli O157 shiga toxigénica por PCR real time. No existieron diferencias estadísticamente significativas en cuanto a la presencia de Salmonella spp. y Staphylococcus aureus coagulasa positivo. Si se expusieron diferencias proporcionales entre los establecimientos en cuanto a la contaminación con Escherichia coli y Escherichia coli O157, presentes en las muestras provenientes de carnicerías junto con la detección del gen que codifica la producción de la toxina Stx2. La información obtenida a partir de este trabajo remarca la importancia de divulgar y capacitar a la comunidad en general y a los manipuladores en particular, aportando estrategias de prevención y control con el fin de evitar el desarrollo de las ETA.

We have initiated a project to sequence the 3Mbp genome of the thermoacidophilic archaebacterium Sulfolobus solfataricus P2. Cosmids were selected from a provisional set of minimally overlapping clones, subcloned in pUC18, and sequenced using a hybrid (random plus directed) strategy to give two blocks of contiguous unique sequence, respectively, 100389 and 56105bp. These two contigs contain a total of 163 open reading frames (ORFs) in 26–29 putative operons; 56 ORFs could be identified with reasonable certainty. Clusters of ORFs potentially encode proteins of glycogen biosynthesis, oxidative decarboxylation of pyruvate, ATP-dependent transport across membranes, isoprenoid biosynthesis, protein synthesis, and ribosomes. Putative promoters occur upstream of most ORFs. Thirty per cent of the predicted strong and medium-strength promoters can initiate transcription at the start codon or within 10 nucleotides upstream, indicating a process of initial mRNA-ribosome contact unlike that of most eubacterial genes. A novel termination motif is proposed to account for 15 additional terminations. The two contigs differ in densities of ORFs, insertion elements and repeated sequences; together they contain two copies of the previously reported insertion sequence ISC 1217, five additional IS elements representing four novel types, four classes of long non-IS repeated sequences, and numerous short, perfect repeats.

Biodiesel, as an alternative fuel, is gradually receiving more popularity for use in internal combustion engines. However questions continue to arise with regard to its compatibility with elastomeric materials. The present work aims to investigate the comparative degradation of physical properties for different elastomers [e.g. ethylene propylene diene monomer (EPDM), silicone rubber (SR), polychloroprene (CR), polytetrafluroethylene (PTFE) and nitrile rubber (NBR)] upon exposure to diesel and palm biodiesel. Static immersion tests in B0(diesel), B10 (10% biodiesel in diesel), B20, B50 and B100(biodiesel) were carried out at room temperature (25 °C) for 1000 h. Different physical properties like, changes in weight and volume, hardness and tensile strength were measured at every 250 h of immersion time. Compositional changes in biodiesel due to exposure of different elastomers were investigated by Gas chromatography mass spectroscopy (GCMS). The overall sequence of compatible elastomers in palm biodiesel is found to be PTFE > SR > NBR > EPDM > CR.

http://www.sciencedirect.com/science/article/pii/S0360544210007139

Naturally occurring polysaccharide pectin, the meth ylated ester of polygalacturonic acid, is very impo rtance in both scientific and commercial world due to its biodegradability. A lar ge group of pectinase enzymes causing breakdown of pectin polysaccharides of plants and fruit are used in industrial sector t o increase the yield and clarity of fruit juices. In this study, two bacterial strains were isolated using dilutions of 10 -4 and 10 -6 of rotten oranges. Isolated organisms were identif ied based on staining and biochemical tests. The pectinolytic activity was de termined using pectin containing minimal essential medium. The methodology applied was Kirby Bauer agar well diffusion method at the temperature is 35 ± 2 0 C. Based on Gram staining, spore staining and biochemical tests, two bacterial strains L ( Staphylococcus aureus ) and M ( Bacillus cereus ) were isolated and identified. Both strains showed different pectinolytic zones dependi ng on the concentration of inoculum...

The study reports the prevalence of multiple antibiotic resistance (MAR) and molecular chacterization of resistance (BlaCTX and GyrA) genes in Salmonella recovered from stool samples of diarrhoeal patients in Ile-Ife, Osun state, Nigeria. Salmonella was cultured on molten Salmonella and Shigella agar (Oxoid, Ltd, Bashingstoke, Hampshire, England) plate at 37 0 C. Susceptibility of isolates to antibiotics was done on Mueller Hinton (Himedia lab Ltd, Vadhani) by disk diffusion technique. Detection of plasmid DNA in multiple antibiotic resistant isolates was carried out by alkali lysis (TENS) method and resistance genes (BlaCTX and GyrA) were detected by the polymerase chain reaction. A total of 69 Salmonella (S.Typhimurium(82.6 %), S.Typhi(10.1 %) and S.ParatyphiA (7.3 %)) were cultured from 187 diarrhoeal stool samples analysed. Resistance was mostly to nitrofurantoin (100%), ceftriazone (97.2 %), and gentamicin (94.2 %) among others. Sixty seven (97.1 %) of the Salmonella isolates were resistant to at least two different classes of antibiotics with 32 antibiotypes. Multiple plasmids of molecular weights (1.46-23.13 kbp) and resistance genes (GyrA-282 bp, blaCTX-480 bp) were detected in the representative MAR isolates. The prevalence of MAR Salmonella in diarrhoeal patients' stool samples is high in the study area with attendant public health and economic loss consequences.

Pharmaceutical Microbiology: Essentials for Quality Assurance and Quality Control presents that latest information on protecting pharmaceutical and healthcare products from spoilage by microorganisms, and protecting patients and consumers. With both sterile and non-sterile products, the effects can range from discoloration to the potential for fatality.

The book provides an overview of the function of the pharmaceutical microbiologist and what they need to know, from regulatory filing and GMP, to laboratory design and management, and compendia tests and risk assessment tools and techniques. These key aspects are discussed through a series of dedicated chapters, with topics covering auditing, validation, data analysis, bioburden, toxins, microbial identification, culture media, and contamination control.

Hematopoiesis is the process in which all Blood lineages are produced from Hematopoietic Stem cells. Through series of Progenitor cells, Hematopoietic stem cells produce a large number of Adult Stem cells. Hematopoietic Stem cells have the ability of self-renewal and self-division This Divisional event results in the Differentiation of Hematopoietic Stem cells into-Lymphocytes, Granulocytes, Monocytes, etc. Progenitor cells also contain cells that act as our body's Defense mechanism. This Always active defense mechanism consists of T cells, B cells, and Natural Killer cells. These cells work together to fight against any viruses or any pathogen and destroy them or exclude them out of the body. By understanding the Hematopoietic process and Defense mechanism, development has been done in the formation of new therapies for curing specific diseases. The basic concept of Stem cell production and its classification are defined here. This paper includes the concept of the production of Progenitor cell lineages which are classified as Lymphoid Progenitor cells and Myeloid Progenitor cells. Here we discuss the Embryonic development and classification of each blood lineages.

La preparación del vino a partir de la vid (vitis vinifera) es, sin duda una práctica milenaria en la Historia de la humanidad, toda vez que se tienen registros arqueológicos de su existencia, desde hace poco más de 3,000 años, en la antigua Mesopotamia y casi en paralelo en Egipto, donde se le conocía como Shedeh, bebida -que afirmaban los egipcios de la época faraónica- que había sido inventada, nada menos que por el mismo Osiris (Historia del vino, 2017) y  (Vinoselección, 2020). En la Grecia clásica (700 A.C.) y después en el Imperio Romano (300 A.C.) la ingesta de vino estaba vinculada a ritos religiosos, funerarios y populares. En el Panteón de la mitología griega, el vino se asoció a la deidad antropomórfica y pagana de Dionisio, a quien los romanos renombraron como Baco y en ambas civilizaciones mediterráneas, esa deidad representaba el placer del trabajo, la fertilidad de la tierra (por asociación la fecundidad del ser humano) y por supuesto el éxtasis del espíritu  (Enciclopedia Británica, 2020).

In this spoken discourse, P.R. Sarkar (1922-1990) first proposed the revolutionary scientific concept of microvita. These mysterious living creatures, “smaller or subtler than atoms, or electrons or protons” are, in his view, the carriers of life and creators of minds throughout the universe. There are three broad categories of microvita. The crudest microvita can be seen in powerful microscopes and can cause diseases said to be of virus origin. Subtler microvita are known indirectly through their actions and through conceptions reflected into perceptions. Microvita are creations in the “returning phase” of the cosmic cycle of creation—the phase where individual minds evolve. Microvita travel through physical media or through ideas. According to P.R. Sarkar, research on microvita through physico-psycho-spiritual efforts must be started “immediately without any further delay.” Human beings need to develop control over these microvita if many problems of modern society are to be solved “in a nice way”.  P.R. Sarkar, also known as Shrii Shrii Anandamurti, was the founder and president of the global movement Renaissance Universal (RU) and the Renaissance Artists and Writers Association (RAWA) of spiritually-oriented and socially-minded intellectuals, artists and writers, and the founder of the global spiritual movement Ananda Marga (“Path of Bliss”). He was a spiritual guru and social philosopher.

Rapid microbiological method technologies aim to provide more sensitive, accurate, precise, and reproducible test results when compared with conventional, growth-based methods. Rapid methods normally involve some form of automation and the methods often capture data electronically. With several different technologies available on the marketplace, the microbiologist has a difficult, and sometimes expensive, choice to make in selecting the optimal method. This article outlines some of the considerations that need to be considered for their selection.

As described in previous work, the use of synthetic chemical ingredients in modern cosmetics is postulated to be a cause of damage to the skin microbiome. The discovery that biodiversity on the human skin is currently the only reliable indicator of skin health, meant that for the first time, a mechanism to test for healthy skin was possible. Using this mechanism and in collaboration with The Medical University of Graz, who carried out the independent study, this work aimed to help answer whether modern day synthetic cosmetics are a main cause of long-term damage to the skin microbiome. Thirty-two human participants tested three different face washes for their effect on the skin's microbial diversity, along with skin pH, moisture and TEWL (trans-epidermal water loss), washing twice-a-day for four weeks. The upper volar forearm of the volunteers was swabbed at the beginning, two weeks in and at the end of the four weeks. 16S rRNA sequencing was used. One leading 'natural' brand full of synthetic ingredients, a leading synthetic brand and a 100% natural face wash were used. Results give the first indications of a link between synthetic ingredients in a cosmetics product and its effect on skin microbiome biodiversity. It paves the way for future studies on the topic with a larger sample group, longer test period and standardised methodology to create a universal standard for testing the health of skin using benchmark diversity values. This can be used in the future to test the effectiveness of cosmetics or ingredients on skin health, leading to the restriction in cosmetics of products proven to harm the skin's natural environment. Keywords: skin microbiome; skin microbiome biodiversity; biodiversity; skin ecosystem; skin allergy epidemic; benchmark skin health values; effect of synthetic cosmetics on skin; 21st century skin ailments; measure skin health; healthy skin ecosystem; healthy skin bacteria; damaged skin bacteria

We report the presence of long stretches of tandem repeats in the genome of the halophilic Archaea Haloferax mediterranei and Haloferax volcanii. A 30 bp sequence with dyad symmetry (including 5 bp inverted repeats) was repeated in tandem, interspersed with 33-39 bp unique sequences. This structure extends for long stretches--1.4 kb at one location in H. mediterranei chromosome and about 3 kb in the H. volcanii chromosome. The tandem repeats (designated TREPs) show a similar distribution in both organisms, appearing once or twice in the H. volcanii and H. mediterranei chromosomes, and once in the largest, probably essential megaplasmid of each organism but not in the smaller replicons. Sequencing of the structures in both H. volcanii replicons revealed an extremely high sequence conservation in both replicons within the species, as well as in the different organisms. Homologous sequences have also been found in other more distantly related halophilic members of the Archaea. Transformation of H. volcanii with a recombinant plasmid containing a 1.1 kb fragment of the TREPs produced significant alterations in the host cells, particularly in terms of cell viability. The introduction of extra copies of TREPs within the vector significantly alters the distribution of the genome among the daughter cells, as observed by DAPI staining. Although the precise biological role cannot be completely ascertained, all the data conform with the tandem repeats being involved in replicon partitioning in halobacteria.

Dans le cadre de la préparation de la licence en Techniques du Laboratoire et au sein de l’Institut Nationale des Professions Infirmières et Techniques de Santé, l’institut a offert un stage académique du 17/02/2020 jusqu’à 30/04/2020 au sein des Laboratoires de Microbiologie d’Oujda.
C’est pourquoi l’objectif de notre stage est focalisé sur le savoir-faire des analyses microbiologiques.