Identification of Lactobacillus reuteri genes specifically induced in the mouse gastrointestinal tract. - Related Documents




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44601.0000Identification of Lactobacillus reuteri genes specifically induced in the mouse gastrointestinal tract. Lactobacilli are common inhabitants of the gastrointestinal tracts of mammals and have received considerable attention due to their putative health-promoting properties. Little is known about the traits that enhance the ability of these bacteria to inhabit the gastrointestinal tract. In this paper we describe the development and application of a strategy based on in vivo expression technology (IVET) that enables detection of Lactobacillus reuteri genes specifically induced in the murine gut. A plasmid-based system was constructed containing 'ermGT (which confers lincomycin resistance) as the primary reporter gene for selection of promoters active in the gastrointestinal tract of mice treated with lincomycin. A second reporter gene, 'bglM (beta-glucanase), allowed differentiation between constitutive and in vivo inducible promoters. The system was successfully tested in vitro and in vivo by using a constitutive promoter. Application of the IVET system with chromosomal DNA of L. reuteri 100-23 and reconstituted lactobacillus-free mice revealed three genes induced specifically during colonization. Two of the sequences showed homology to genes encoding xylose isomerase (xylA) and peptide methionine sulfoxide reductase (msrB), which are involved in nutrient acquisition and stress responses, respectively. The third locus showed homology to the gene encoding a protein whose function is not known. Our IVET system has the potential to identify genes of lactobacilli that have not previously been functionally characterized but which may be essential for growth of these bacteria in the gastrointestinal ecosystem.200312676681
44510.9997Selection of Shigella flexneri candidate virulence genes specifically induced in bacteria resident in host cell cytoplasm. We describe an in vivo expression technology (IVET)-like approach, which uses antibiotic resistance for selection, to identify Shigella flexneri genes specifically activated in bacteria resident in host cell cytoplasm. This procedure required construction of a promoter-trap vector containing a synthetic operon between the promoterless chloramphenicol acetyl transferase (cat) and lacZ genes and construction of a library of plasmids carrying transcriptional fusions between S. flexneri genomic fragments and the cat-lacZ operon. Clones exhibiting low levels (<10 micro g ml-1) of chloramphenicol (Cm) resistance on laboratory media were analysed for their ability to induce a cytophatic effect--plaque--on a cell monolayer, in the presence of Cm. These clones were assumed to carry a plasmid in which the cloned fragment acted as a promoter/gene which is poorly expressed under laboratory conditions. Therefore, only strains harbouring fusion-plasmids in which the cloned promoter was specifically activated within host cytoplasm could survive within the cell monolayer in the presence of Cm and give a positive result in the plaque assay. Pai (plaque assay induced) clones, selected following this procedure, were analysed for intracellular (i) beta-galactosidase activity, (ii) proliferation in the presence of Cm, and (iii) Cm resistance. Sequence analysis of Pai plasmids revealed genes encoding proteins of three functional classes: external layer recycling, adaptation to microaerophilic environment and gene regulation. Sequences encoding unknown functions were also trapped and selected by this new IVET-based protocol.200212390353
845620.9997Identification of genes required by Bacillus thuringiensis for survival in soil by transposon-directed insertion site sequencing. Transposon-directed insertion site sequencing was used to identify genes required by Bacillus thuringiensis to survive in non-axenic plant/soil microcosms. A total of 516 genetic loci fulfilled the criteria as conferring survival characteristics. Of these, 127 (24.6 %) were associated with uptake and transport systems; 227 loci (44.0 %) coded for enzymatic properties; 49 (9.5 %) were gene regulation or sensory loci; 40 (7.8 %) were structural proteins found in the cell envelope or had enzymatic activities related to it and 24 (4.7 %) were involved in the production of antibiotics or resistance to them. Eighty-three (16.1 %) encoded hypothetical proteins or those of unknown function. The ability to form spores was a key survival characteristic in the microcosms: bacteria, inoculated in either spore or vegetative form, were able to multiply and colonise the soil, whereas a sporulation-deficient mutant was not. The presence of grass seedlings was critical to colonisation. Bacteria labelled with green fluorescent protein were observed to adhere to plant roots. The sporulation-specific promoter of spo0A, the key regulator of sporulation, was strongly activated in the rhizosphere. In contrast, the vegetative-specific promoters of spo0A and PlcR, a pleiotropic regulator of genes with diverse activities, were only very weakly activated.201424310935
26230.9996Genome scanning in Haemophilus influenzae for identification of essential genes. We have developed a method for identifying essential genes by using an in vitro transposition system, with a small (975 bp) insertional element containing an antibiotic resistance cassette, and mapping these inserts relative to the deduced open reading frames of Haemophilus influenzae by PCR and Southern analysis. Putative essential genes are identified by two methods: mutation exclusion or zero time analysis. Mutation exclusion consists of growing an insertional library and identifying open reading frames that do not contain insertional elements: in a growing population of bacteria, insertions in essential genes are excluded. Zero time analysis consists of monitoring the fate of individual insertions after transformation in a growing culture: the loss of inserts in essential genes is observed over time. Both methods of analysis permit the identification of genes required for bacterial survival. Details of the mutant library construction and the mapping strategy, examples of mutant exclusion, and zero time analysis are presented.199910438768
26340.9996Selection and characterization of a promoter for expression of single-copy recombinant genes in Gram-positive bacteria. BACKGROUND: In the past ten years there has been a growing interest in engineering Gram-positive bacteria for biotechnological applications, including vaccine delivery and production of recombinant proteins. Usually, bacteria are manipulated using plasmid expression vectors. The major limitation of this approach is due to the fact that recombinant plasmids are often lost from the bacterial culture upon removal of antibiotic selection. We have developed a genetic system based on suicide vectors on conjugative transposons allowing stable integration of recombinant DNA into the chromosome of transformable and non-transformable Gram-positive bacteria. RESULTS: The aim of this work was to select a strong chromosomal promoter from Streptococcus gordonii to improve this genetic system making it suitable for expression of single-copy recombinant genes. To achieve this task, a promoterless gene encoding a chloramphenicol acetyltransferase (cat), was randomly integrated into the S. gordonii chromosome and transformants were selected for chloramphenicol resistance. Three out of eighteen chloramphenicol resistant transformants selected exhibited 100% stability of the phenotype and only one of them, GP215, carried the cat gene integrated as a single copy. A DNA fragment of 600 base pairs exhibiting promoter activity was isolated from GP215 and sequenced. The 5' end of its corresponding mRNA was determined by primer extention analysis and the putative -10 and a -35 regions were identified. To study the possibility of using this promoter (PP) for single copy heterologous gene expression, we created transcriptional fusions of PP with genes encoding surface recombinant proteins in a vector capable of integrating into the conjugative transposon Tn916. Surface recombinant proteins whose expression was controlled by the PP promoter were detected in Tn916-containing strains of S. gordonii and Bacillus subtilis after single copy chromosomal integration of the recombinant insertion vectors into the resident Tn916. The surface recombinant protein synthesized under the control of PP was also detected in Enterococcus faecalis after conjugal transfer of a recombinant Tn916 containing the transcriptional fusion. CONCLUSION: We isolated and characterized a S. gordonii chromosomal promoter. We demonstrated that this promoter can be used to direct expression of heterologous genes in different Gram-positive bacteria, when integrated in a single copy into the chromosome.200515651989
838850.9996Essential genes from Arctic bacteria used to construct stable, temperature-sensitive bacterial vaccines. All bacteria share a set of evolutionarily conserved essential genes that encode products that are required for viability. The great diversity of environments that bacteria inhabit, including environments at extreme temperatures, place adaptive pressure on essential genes. We sought to use this evolutionary diversity of essential genes to engineer bacterial pathogens to be stably temperature-sensitive, and thus useful as live vaccines. We isolated essential genes from bacteria found in the Arctic and substituted them for their counterparts into pathogens of mammals. We found that substitution of nine different essential genes from psychrophilic (cold-loving) bacteria into mammalian pathogenic bacteria resulted in strains that died below their normal-temperature growth limits. Substitution of three different psychrophilic gene orthologs of ligA, which encode NAD-dependent DNA ligase, resulted in bacterial strains that died at 33, 35, and 37 degrees C. One ligA gene was shown to render Francisella tularensis, Salmonella enterica, and Mycobacterium smegmatis temperature-sensitive, demonstrating that this gene functions in both Gram-negative and Gram-positive lineage bacteria. Three temperature-sensitive F. tularensis strains were shown to induce protective immunity after vaccination at a cool body site. About half of the genes that could be tested were unable to mutate to temperature-resistant forms at detectable levels. These results show that psychrophilic essential genes can be used to create a unique class of bacterial temperature-sensitive vaccines for important human pathogens, such as S. enterica and Mycobacterium tuberculosis.201020624965
631460.9996Identification of genes involved in the resistance of mycobacteria to killing by macrophages. The survival of M. leprae and M. tuberculosis in the human host is dependent upon their ability to produce gene products that counteract the bactericidal activities of macrophages. To identify such mycobacterial genes and gene products, recombinant DNA libraries of mycobacterial DNA in E. coli were passed through macrophages to enrich for clones carrying genes that endow the normally susceptible E. coli bacteria with an enhanced ability to survive within macrophages. Following three cycles of enrichment, 15 independent clones were isolated. Three recombinants were characterized in detail, and each confers significantly enhanced survival on E. coli cells carrying them. Two of the cloned genetic elements also confer enhanced survival onto M. smegmatis cells. Further characterization of these genes and gene products should provide insights into the survival of mycobacteria within macrophages and may identify new approaches of targets for combatting these important pathogens.19948080180
15770.9996Analysis of proteins responsive to acetic acid in Acetobacter: molecular mechanisms conferring acetic acid resistance in acetic acid bacteria. Acetic acid bacteria are used for industrial vinegar production because of their remarkable ability to oxidize ethanol and high resistance to acetic acid. Although several molecular machineries responsible for acetic acid resistance in acetic acid bacteria have been reported, the entire mechanism that confers acetic acid resistance has not been completely understood. One of the promising methods to elucidate the entire mechanism is global analysis of proteins responsive to acetic acid by two-dimensional gel electrophoresis. Recently, two proteins whose production was greatly enhanced by acetic acid in Acetobacter aceti were identified to be aconitase and a putative ABC-transporter, respectively; furthermore, overexpression or disruption of the genes encoding these proteins affected acetic acid resistance in A. aceti, indicating that these proteins are involved in acetic acid resistance. Overexpression of each gene increased acetic acid resistance in Acetobacter, which resulted in an improvement in the productivity of acetic acid fermentation. Taken together, the results of the proteomic analysis and those of previous studies indicate that acetic acid resistance in acetic acid bacteria is conferred by several mechanisms. These findings also provide a clue to breed a strain having high resistance to acetic acid for vinegar fermentation.200817920150
633980.9996Novel acid resistance genes from the metagenome of the Tinto River, an extremely acidic environment. Microorganisms that thrive in acidic environments are endowed with specialized molecular mechanisms to survive under this extremely harsh condition. In this work, we performed functional screening of six metagenomic libraries from planktonic and rhizosphere microbial communities of the Tinto River, an extremely acidic environment, to identify genes involved in acid resistance. This approach has revealed 15 different genes conferring acid resistance to Escherichia coli, most of which encoding putative proteins of unknown function or previously described proteins not known to be related to acid resistance. Moreover, we were able to assign function to one unknown and three hypothetical proteins. Among the recovered genes were the ClpXP protease, the transcriptional repressor LexA and nucleic acid-binding proteins such as an RNA-binding protein, HU and Dps. Furthermore, nine of the retrieved genes were cloned and expressed in Pseudomonas putida and Bacillus subtilis and, remarkably, most of them were able to expand the capability of these bacteria to survive under severe acid stress. From this set of genes, four presented a broad-host range as they enhance the acid resistance of the three different organisms tested. These results expand our knowledge about the different strategies used by microorganisms to survive under extremely acid conditions.201323145860
630590.9996Antimicrobial genes from Allium sativum and Pinellia ternata revealed by a Bacillus subtilis expression system. Antimicrobial genes are found in all classes of life. To efficiently isolate these genes, we used Bacillus subtilis and Escherichia coli as target indicator bacteria and transformed them with cDNA libraries. Among thousands of expressed proteins, candidate proteins played antimicrobial roles from the inside of the indicator bacteria (internal effect), contributing to the sensitivity (much more sensitivity than the external effect from antimicrobial proteins working from outside of the cells) and the high throughput ability of screening. We found that B. subtilis is more efficient and reliable than E. coli. Using the B. subtilis expression system, we identified 19 novel, broad-spectrum antimicrobial genes. Proteins expressed by these genes were extracted and tested, exhibiting strong external antibacterial, antifungal and nematicidal activities. Furthermore, these newly isolated proteins could control plant diseases. Application of these proteins secreted by engineered B. subtilis in soil could inhibit the growth of pathogenic bacteria. These proteins are thermally stable and suitable for clinical medicine, as they exhibited no haemolytic activity. Based on our findings, we speculated that plant, animal and human pathogenic bacteria, fungi or even cancer cells might be taken as the indicator target cells for screening specific resistance genes.201830266995
6312100.9996D-serine deaminase is a stringent selective marker in genetic crosses. The presence of the locus for D-serine deaminase (dsd) renders bacteria resistant to growth inhibition by D-serine and enables them to grow with D-serine as the sole nitrogen source. The two properties permit stringent selection in genetic crosses and make the D-serine deaminase gene an excellent marker, especially in the construction of strains for which the use of antibiotic resistance genes as selective markers is not allowed.19957814336
6324110.9996Genetic and biochemical basis of tetracycline resistance. Properties of several, well characterized, tetracycline resistance determinants were compared. The determinants in Tn1721 and Tn10 (both from Gram-negative bacteria) each contain two genes; one encodes a repressor that regulates both its own transcription and that of a membrane protein that confers resistance by promoting efflux of the drug. Determinants from Gram-positive bacteria also encode efflux proteins, but expression of resistance is probably regulated by translational attenuation. The likely tetracycline binding site (a common dipeptide) in each efflux protein was predicted. The presence of the common binding site is consistent with the ability of an efflux protein originating in Bacillus species to be expressed in Escherichia coli.19863542941
6313120.9996A Novel Nonantibiotic, lgt-Based Selection System for Stable Maintenance of Expression Vectors in Escherichia coli and Vibrio cholerae. Antibiotic selection for the maintenance of expression plasmids is discouraged in the production of recombinant proteins for pharmaceutical or other human uses due to the risks of antibiotic residue contamination of the final products and the release of DNA encoding antibiotic resistance into the environment. We describe the construction of expression plasmids that are instead maintained by complementation of the lgt gene encoding a (pro)lipoprotein glyceryl transferase essential for the biosynthesis of bacterial lipoprotein. Mutations in lgt are lethal in Escherichia coli and other Gram-negative organisms. The lgt gene was deleted from E. coli and complemented by the Vibrio cholerae-derived gene provided in trans on a temperature-sensitive plasmid, allowing cells to grow at 30°C but not at 37°C. A temperature-insensitive expression vector carrying the V. cholerae-derived lgt gene was constructed, whereby transformants were selected by growth at 39°C. The vector was successfully used to express two recombinant proteins, one soluble and one forming insoluble inclusion bodies. Reciprocal construction was done by deleting the lgt gene from V. cholerae and complementing the lesion with the corresponding gene from E. coli The resulting strain was used to produce the secreted recombinant cholera toxin B subunit (CTB) protein, a component of licensed as well as newly developed oral cholera vaccines. Overall, the lgt system described here confers extreme stability on expression plasmids, and this strategy can be easily transferred to other Gram-negative species using the E. coli-derived lgt gene for complementation.IMPORTANCE Many recombinant proteins are produced in bacteria from genes carried on autonomously replicating DNA elements called plasmids. These plasmids are usually inherently unstable and rapidly lost. This can be prevented by using genes encoding antibiotic resistance. Plasmids are thus maintained by allowing only plasmid-containing cells to survive when the bacteria are grown in medium supplemented with antibiotics. In the described antibiotic-free system for the production of recombinant proteins, an essential gene is deleted from the bacterial chromosome and instead provided on a plasmid. The loss of the plasmid becomes lethal for the bacteria. Such plasmids can be used for the expression of recombinant proteins. This broadly applicable system removes the need for antibiotics in recombinant protein production, thereby contributing to reducing the spread of genes encoding antibiotic resistance, reducing the release of antibiotics into the environment, and freeing the final products (often used in pharmaceuticals) from contamination with potentially harmful antibiotic residues.201829222103
292130.9996Mechanisms underlying expression of Tn10 encoded tetracycline resistance. Tetracycline-resistance determinants encoding active efflux of the drug are widely distributed in gram-negative bacteria and unique with respect to genetic organization and regulation of expression. Each determinant consists of two genes called tetA and tetR, which are oriented with divergent polarity, and between them is a central regulatory region with overlapping promoters and operators. The amino acid sequences of the encoded proteins are 43-78% identical. The resistance protein TetA is a tetracycline/metal-proton antiporter located in the cytoplasmic membrane, while the regulatory protein TetR is a tetracycline inducible repressor. TetR binds via a helix-turn-helix motif to the two tet operators, resulting in repression of both genes. A detailed model of the repressor-operator complex has been proposed on the basis of biochemical and genetic data. The tet genes are differentially regulated so that repressor synthesis can occur before the resistance protein is expressed. This has been demonstrated for the Tn10-encoded tet genes and may be a common property of all tet determinants, as suggested by the similar locations of operators with respect to promoters. Induction is mediated by a tetracycline-metal complex and requires only nanomolar concentrations of the drug. This is the most sensitive effector-inducible system of transcriptional regulation known to date. The crystal structure of the TetR-tetracycline/metal complex shows the Tet repressor in the induced, non-DNA binding conformation. The structural interpretation of many noninducible TetR mutants has offered insight into the conformational changes associated with the switch between inducing and repressing structures of TetR. Tc is buried in the core of TetR, where it is held in place by multiple contacts to the protein.19947826010
260140.9996Improved antibiotic resistance gene cassette for marker exchange mutagenesis in Ralstonia solanacearum and Burkholderia species. Marker exchange mutagenesis is a fundamental approach to understanding gene function at a molecular level in bacteria. New plasmids carrying a kanamycin resistance gene or a trimethoprim resistance gene were constructed to provide antibiotic resistance cassettes for marker exchange mutagenesis in Ralstonia solanacearum and many antibiotic-resistant Burkholderia spp. Insertion sequences present in the flanking sequences of the antibiotic resistance cassette were removed to prevent aberrant gene replacement and polar mutation during mutagenesis in wild-type bacteria. Plasmids provided in this study would be convenient for use in gene cassettes for gene replacement in other Gram-negative bacteria.201121538255
261150.9996Suicide vectors for antibiotic marker exchange and rapid generation of multiple knockout mutants by allelic exchange in Gram-negative bacteria. Allelic exchange is frequently used in bacteria to generate knockout mutants in genes of interest, to carry out phenotypic analysis and learn about their function. Frequently, understanding of gene function in complex processes such as pathogenesis requires the generation of multiple mutant strains. In Pseudomonads and other non-Enterobacteriaceae, this is a time-consuming and laborious process based on the use of suicide vectors and allelic exchange of the appropriate mutant version of each gene, disrupted by a different antibiotic marker. This often implies the generation of a series of mutants for each gene, each disrupted by a different antibiotic marker, in order to obtain all possible double or multiple mutant combinations. In this work, we have modified this method by developing a set of 3 plasmid derivatives from the previously described suicide vector for allelic exchange, pKAS32, to make antibiotic marker exchange easier and thus accelerate the entire process. Briefly, the construction of each single gene knockout mutant is carried out by allelic exchange of the chromosomal gene with a mutant allele disrupted by the insertion of a kanamycin resistance cassette. When a double mutant strain is required, antibiotic marker exchange is performed in either one of the single mutants, using any of the three plasmid derivatives that carry the kanamycin resistance gene disrupted by either a chloramphenicol, gentamycin, or streptomycin resistance cassette. The single mutant strain, carrying now an antibiotic resistance marker other than kanamycin, can be used to introduce a second mutation using the original plasmid constructs, to generate a double mutant. The process can be repeated sequentially to generate multiple mutants. We have validated this method by generating strains carrying different combinations of mutations in genes encoding different transcriptional regulators of the Hrp type III secretion system in Pseudomonas syringae. We have also tested the genetic organisation and stability of the resulting mutant strains during growth in laboratory conditions as well as in planta.200616750581
268160.9996Amplification of bacitracin transporter genes in the bacitracin producing Bacillus licheniformis. We have amplified the previously cloned and sequenced genes of the bacitracin exporter (bcr), a member of the ATP-binding transport protein family, within the chromosome of the bacitracin producing Bacillus licheniformis. Amplification of the transporter genes was followed by greatly increased bacitracin resistance. Antibiotic production was enhanced at a low level of bcr genes amplification. An enlarged increase in the copy number of the bcr genes negatively affects the overall growth of bacteria.19979418256
6327170.9996The Response of Enterococcus faecalis V583 to Chloramphenicol Treatment. Many Enterococcus faecalis strains display tolerance or resistance to many antibiotics, but genes that contribute to the resistance cannot be specified. The multiresistant E. faecalis V583, for which the complete genome sequence is available, survives and grows in media containing relatively high levels of chloramphenicol. No specific genes coding for chloramphenicol resistance has been recognized in V583. We used microarrays to identify genes and mechanisms behind the tolerance to chloramphenicol in V583, by comparison of cells treated with subinhibitory concentrations of chloramphenicol and untreated V583 cells. During a time course experiment, more than 600 genes were significantly differentially transcribed. Since chloramphenicol affects protein synthesis in bacteria, many genes involved in protein synthesis, for example, genes for ribosomal proteins, were induced. Genes involved in amino acid biosynthesis, for example, genes for tRNA synthetases and energy metabolism were downregulated, mainly. Among the upregulated genes were EF1732 and EF1733, which code for potential chloramphenicol transporters. Efflux of drug out of the cells may be one mechanism used by V583 to overcome the effect of chloramphenicol.201020628561
6311180.9996Development of an antibiotic marker-free platform for heterologous protein production in Streptomyces. BACKGROUND: The industrial use of enzymes produced by microorganisms is continuously growing due to the need for sustainable solutions. Nevertheless, many of the plasmids used for recombinant production of proteins in bacteria are based on the use of antibiotic resistance genes as selection markers. The safety concerns and legal requirements surrounding the increased use of antibiotic resistance genes have made the development of new antibiotic-free approaches essential. RESULTS: In this work, a system completely free of antibiotic resistance genes and useful for the production of high yields of proteins in Streptomyces is described. This system is based on the separation of the two components of the yefM/yoeBsl (antitoxin/toxin) operon; the toxin (yoeBsl) gene, responsible for host death, is integrated into the genome and the antitoxin gene (yefMsl), which inactivates the toxin, is located in the expression plasmid. To develop this system, the toxin gene was integrated into the genome of a strain lacking the complete operon, and the antibiotic resistance gene integrated along with the toxin was eliminated by Cre recombinase to generate a final host strain free of any antibiotic resistance marker. In the same way, the antibiotic resistance gene from the final expression plasmid was removed by Dre recombinase. The usefulness of this system was analysed by checking the production of two hydrolases from different Streptomyces. Production of both proteins, with potential industrial use, was high and stable over time after strain storage and after serial subcultures. These results support the robustness and stability of the positive selection system developed. CONCLUSIONS: The total absence of antibiotic resistance genes makes this system a powerful tool for using Streptomyces as a host to produce proteins at the industrial level. This work is the first Streptomyces antibiotic marker-free system to be described. Graphical abstract Antibiotic marker-free platform for protein expression in Streptomyces. The antitoxin gene present in the expression plasmid counteracts the effect of the toxin gene in the genome. In absence of the expression plasmid, the toxin causes cell death ensuring that only plasmid-containing cells persist.201728950904
6217190.9996Identification of the sigmaB regulon of Bacillus cereus and conservation of sigmaB-regulated genes in low-GC-content gram-positive bacteria. The alternative sigma factor sigma(B) has an important role in the acquisition of stress resistance in many gram-positive bacteria, including the food-borne pathogen Bacillus cereus. Here, we describe the identification of the set of sigma(B)-regulated genes in B. cereus by DNA microarray analysis of the transcriptome upon a mild heat shock. Twenty-four genes could be identified as being sigma(B) dependent as witnessed by (i) significantly lower expression levels of these genes in mutants with a deletion of sigB and rsbY (which encode the alternative sigma factor sigma(B) and a crucial positive regulator of sigma(B) activity, respectively) than in the parental strain B. cereus ATCC 14579 and (ii) increased expression of these genes upon a heat shock. Newly identified sigma(B)-dependent genes in B. cereus include a histidine kinase and two genes that have predicted functions in spore germination. This study shows that the sigma(B) regulon of B. cereus is considerably smaller than that of other gram-positive bacteria. This appears to be in line with phylogenetic analyses where sigma(B) of the B. cereus group was placed close to the ancestral form of sigma(B) in gram-positive bacteria. The data described in this study and previous studies in which the complete sigma(B) regulon of the gram-positive bacteria Bacillus subtilis, Listeria monocytogenes, and Staphylococcus aureus were determined enabled a comparison of the sets of sigma(B)-regulated genes in the different gram-positive bacteria. This showed that only three genes (rsbV, rsbW, and sigB) are conserved in their sigma(B) dependency in all four bacteria, suggesting that the sigma(B) regulon of the different gram-positive bacteria has evolved to perform niche-specific functions.200717416654