The
group includes several
species with closely related phylogeny. The most well-studied members of the group,
,
, and
, are known for their pathogenic potential. Here, we present the historical ...rationale for speciation and discuss shared and unique features of these bacteria. Aspects of cell morphology and physiology, and genome sequence similarity and gene synteny support close evolutionary relationships for these three species. For many strains, distinct differences in virulence factor synthesis provide facile means for species assignment.
is the causative agent of anthrax. Some
strains are commonly recognized as food poisoning agents, but strains can also cause localized wound and eye infections as well as systemic disease. Certain
strains are entomopathogens and have been commercialized for use as biopesticides, while some strains have been reported to cause infection in immunocompromised individuals. In this article we compare and contrast
,
, and
, including ecology, cell structure and development, virulence attributes, gene regulation and genetic exchange systems, and experimental models of disease.
The
group comprises numerous closely related species, including bioterrorism agent
, foodborne pathogen
, and biopesticide
Differentiating organisms capable of causing illness or death from those ...used in industry is essential for risk assessment and outbreak preparedness. However, current species definitions facilitate species-phenotype incongruences, particularly when horizontally acquired genes are responsible for a phenotype. Using all publicly available
group genomes (
= 2,231), we show that current species definitions lead to overlapping genomospecies clusters, in which 66.2% of genomes belong to multiple genomospecies at a conventional 95 average nucleotide identity (ANI) genomospecies threshold. A genomospecies threshold of ≈92.5 ANI is shown to reflect a natural gap in genome similarity for the
group, and medoid genomes identified at this threshold are shown to yield resolvable genomospecies clusters with minimal overlap (six of 2,231 genomes assigned to multiple genomospecies; 0.269%). We thus propose a nomenclatural framework for the
group which accounts for (i) genomospecies using resolvable genomospecies clusters obtained at ≈92.5 ANI, (ii) established lineages of medical importance using a formal collection of subspecies names, and (iii) heterogeneity of clinically and industrially important phenotypes using a formalized and extended collection of biovar terms. We anticipate that the proposed nomenclature will remain interpretable to clinicians, without sacrificing genomic species definitions, which can in turn aid in pathogen surveillance; early detection of emerging, high-risk genotypes; and outbreak preparedness.
Historical species definitions for many prokaryotes, including pathogens, have relied on phenotypic characteristics that are inconsistent with genome evolution. This scenario forces microbiologists and clinicians to face a tradeoff between taxonomic rigor and clinical interpretability. Using the
group as a model, a conceptual framework for the taxonomic delineation of prokaryotes which reconciles genomic definitions of species with clinically and industrially relevant phenotypes is presented. The nomenclatural framework outlined here serves as a model for genomics-based bacterial taxonomy that moves beyond arbitrarily set genomospecies thresholds while maintaining congruence with phenotypes and historically important species names.
The Bacillus genus includes species such as Bacillus cereus, Bacillus licheniformis and Bacillus subtilis, some of which may be pathogenic or causative agents in the spoilage of food products. The ...main goal of this work was to apply matrix-assisted laser desorption ionisation-time of flight (MALDI-TOF) mass fingerprinting to the classification of these Bacillus species. Genetic analyses were also compared to phyloproteomic analyses. A collection of 57 Bacillus strains isolated from fresh and processed food and from culture collections were studied and their mass spectra compiled. The resulting mass fingerprints were compared and characteristic peaks at the strain and species levels were assigned. The results showed that MALDI-TOF was a good complementary approach to 16S rRNA sequencing and even a more powerful tool in the accurate classification of Bacillus species, especially for differentiating B. subtilis and B. cereus from Bacillus amyloliquefaciens and Bacillus thuringiensis, respectively. MALDI-TOF was also found to provide valuable information at both intra- and interspecies levels in the Bacillus species studied.
► MALDI-TOF was compared to genetic analysis for the identification of Bacillus spp. ► MALDI-TOF allowed a better differentiation of Bacillus subtilis from Bacillus amyloliquefaciens. ► MALDI-TOF allowed a better differentiation of Bacillus cereus from Bacillus thuringiensis. ► Genetic analysis of Bacillus spp is complemented with MALDI-TOF fingerprinting.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Tungrymbai and bekang are naturally fermented soybean foods commonly consumed in Meghalaya and Mizoram states of India. A total of 39 samples of tungrymbai and 43 samples of bekang were collected ...from different villages and markets of Meghalaya and Mizoram, respectively and were analysed for microbial load. In both tungrymbai and bekang, the average population of Bacillus spp. was 8.2±0.1logcfu/g. A total of 428 isolates of Bacillus were isolated from tungrymbai (211) and bekang (217) for detailed identification. On the basis of a combination of phenotypic and molecular characterisation using ARDRA, ITS-PCR and RAPD-PCR techniques, species of Bacillus isolated from tungrymbai were identified as Bacillus licheniformis (25.5%), Bacillus pumilus (19.5%) and Bacillus subtilis (55%), and species of Bacillus from bekang were Bacillus brevis (2%), Bacillus circulans (7.5%), Bacillus coagulans (6.5%), B. licheniformis (16.5%), B. pumilus (9.1%), Bacillus sphaericus (4.6%), B. subtilis (51.8%), and Lysinibacillus fusiformis (2%). The most dominant bacterium in both products was B. subtilis.
•We isolated Bacillus species from tungrymbai and bekang, naturally fermented soybean foods of India.•Based on molecular characterisations using ARDRA, ITS-PCR and RAPD-PCR techniques, species of Bacillus were identified as Bacillus brevis, B. cereus, B. circulans, B. coagulans, B. licheniformis, B. pumilus, B. subtilis and Lysinibacillus fusiformis.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The soil-related Bacillus and Paenibacillus species have increasingly been implicated in various human diseases. Nevertheless, their identification still poses problems in the clinical microbiology ...laboratory and, with the exception of Bacillus anthracis and Bacillus cereus, little is known on their pathogenicity for humans. In this study, we evaluated the use of matrix-assisted laser desorption-ionization time of flight mass spectrometry (MALDI-TOF MS) in the identification of clinical isolates of these genera and conducted genotypic and phenotypic analyses to highlight specific virulence properties. Seventy-five clinical isolates were subjected to biochemical and MALDI-TOF MS identification. 16S rDNA sequencing and supplemental tests were used to solve any discrepancies or failures in the identification results. MALDI-TOF MS significantly outperformed classical biochemical testing for correct species identification and no misidentification was obtained. One third of the collected strains belonged to the B. cereus species, but also Bacillus pumilus and Bacillus subtilis were isolated at high rate. Antimicrobial susceptibility testing showed that all the B. cereus, B. licheniformis, B. simplex, B. mycoides, Paenibacillus glucanolyticus and Paenibacillus lautus isolates are resistant to penicillin. The evaluation of toxin/enzyme secretion, toxin-encoding genes, motility, and biofilm formation revealed that B. cereus displays the highest virulence potential. However, although generally considered nonpathogenic, most of the other species were shown to swim, swarm, produce biofilms, and secrete proteases that can have a role in bacterial virulence. In conclusion, MALDI-TOF MS appears useful for fast and accurate identification of Bacillus and Paenibacillus strains whose virulence properties make them of increasing clinical relevance.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Bacillus strains produce non-ribosomal lipopeptides that can be grouped into three families: surfactins or lichenysins, iturins and fengycins or plispastatins. These biosurfactants show a broad ...spectrum of biological activities. To detect strains able to produce these lipopeptides, a new polymerase chain reaction screening approach was developed using degenerated primers based on the intraoperon alignment of adenylation and thiolation nucleic acid domains of all enzymes implicated in the biosynthesis of each lipopeptide family. The comparative bioinformatics analyses of each operon led to the design of four primer pairs for the three families taking into account the differences between open reading frames of each synthetase gene. Tested on different Bacillus sp. strains, this technique was used successfully to detect not only the expected genes in the lipopeptide producing strains but also the presence of a plispastatin gene in Bacillus subtilis ATCC 21332 and a gene showing a high similarity with the polyketide synthase type I gene in the B. subtilis ATCC 6633 genome. It also led to the discovery of the presence of non-ribosomal peptide synthetase genes in Bacillus thuringiensis serovar berliner 1915 and in Bacillus cereus LMG 2098. In addition, this work highlighted the differences between the fengycin and plipastatin operon at DNA level.
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CEKLJ, DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
MocR/GabR family proteins are widely distributed prokaryotic transcriptional regulators containing pyridoxal 5'-phosphate (PLP), a coenzyme form of vitamin B6. The Bacillus subtilisGabR, probably the ...most extensively studied MocR/GabR family protein, consists of an N-terminal DNA-binding domain and a PLP-binding C-terminal domain that has a structure homologous to aminotransferases. GabR suppresses transcription of gabR and activates transcription of gabT and gabD, which encode gamma -aminobutyrate (G alpha beta alpha ) aminotransferase and succinate semialdehyde dehydrogenase, respectively, in the presence of PLP and GABA. In this study, we examined the mechanism underlying GabR-mediated gabTD transcription with spectroscopic, crystallographic and thermodynamic studies, focusing on the function of the aminotransferase domain. Spectroscopic studies revealed that GABA forms an external aldimine with the PLP in the aminotransferase domain. Isothermal calorimetry demonstrated that two GabR molecules bind to the 51-bp DNA fragment that contains the GabR-binding region. GABA minimally affected Delta Gbinding upon binding of GabR to the DNA fragment but greatly affected the contributions of Delta H and Delta S to Delta Gbinding. GABA forms an external aldimine with PLP and causes a conformational change in the aminotransferase domain, and this change likely rearranges GabR binding to the promoter and thus activates gabTD transcription.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Emerging B. cereus strains that cause anthrax-like disease have been isolated in Cameroon (CA strain) and Côte d'Ivoire (CI strain). These strains are unusual, because their genomic characterisation ...shows that they belong to the B. cereus species, although they harbour two plasmids, pBCXO1 and pBCXO2, that are highly similar to the pXO1 and pXO2 plasmids of B. anthracis that encode the toxins and the polyglutamate capsule respectively. The virulence factors implicated in the pathogenicity of these B. cereus bv anthracis strains remain to be characterised. We tested their virulence by cutaneous and intranasal delivery in mice and guinea pigs; they were as virulent as wild-type B. anthracis. Unlike as described for pXO2-cured B. anthracis, the CA strain cured of the pBCXO2 plasmid was still highly virulent, showing the existence of other virulence factors. Indeed, these strains concomitantly expressed a hyaluronic acid (HA) capsule and the B. anthracis polyglutamate (PDGA) capsule. The HA capsule was encoded by the hasACB operon on pBCXO1, and its expression was regulated by the global transcription regulator AtxA, which controls anthrax toxins and PDGA capsule in B. anthracis. Thus, the HA and PDGA capsules and toxins were co-regulated by AtxA. We explored the respective effect of the virulence factors on colonisation and dissemination of CA within its host by constructing bioluminescent mutants. Expression of the HA capsule by itself led to local multiplication and, during intranasal infection, to local dissemination to the adjacent brain tissue. Co-expression of either toxins or PDGA capsule with HA capsule enabled systemic dissemination, thus providing a clear evolutionary advantage. Protection against infection by B. cereus bv anthracis required the same vaccination formulation as that used against B. anthracis. Thus, these strains, at the frontier between B. anthracis and B. cereus, provide insight into how the monomorphic B. anthracis may have emerged.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Biofilm formation by 102 Bacillus cereus and B. thuringiensis strains was determined. Strains isolated from soil or involved in digestive tract infections were efficient biofilm formers, whereas ...strains isolated from other diseases were poor biofilm formers. Cell surface hydrophobicity, the presence of an S layer, and adhesion to epithelial cells were also examined.
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