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Bacillus anthracis, Bacillus cereus, and Bacillus thuringiensis--one species on the basis of genetic evidence.

Bacillus anthracis, Bacillus cereus, and Bacillus thuringiensis are members of the Bacillus cereus group of bacteria, demonstrating widely different phenotypes and pathological effects. B. anthracis causes the acute fatal disease anthrax and is a potential biological weapon due to its high toxicity. B. thuringiensis produces intracellular protein crystals toxic to a wide number of insect larvae and is the most commonly used biological pesticide worldwide. B. cereus is a probably ubiquitous soil bacterium and an opportunistic pathogen that is a common cause of food poisoning. In contrast to the differences in phenotypes, we show by multilocus enzyme electrophoresis and by sequence analysis of nine chromosomal genes that B. anthracis should be considered a lineage of B. cereus. This determination is not only a formal matter of taxonomy but may also have consequences with respect to virulence and the potential of horizontal gene transfer within the B. cereus group.

Bacillus↗

Genome differences that distinguish Bacillus anthracis from Bacillus cereus and Bacillus thuringiensis.

The three species of the group 1 bacilli, Bacillus anthracis, B. cereus, and B. thuringiensis, are genetically very closely related. All inhabit soil habitats but exhibit different phenotypes. B. anthracis is the causative agent of anthrax and is phylogenetically monomorphic, while B. cereus and B. thuringiensis are genetically more diverse. An amplified fragment length polymorphism analysis described here demonstrates genetic diversity among a collection of non-anthrax-causing Bacillus species, some of which show significant similarity to B. anthracis. Suppression subtractive hybridization was then used to characterize the genomic differences that distinguish three of the non-anthrax-causing bacilli from B. anthracis Ames. Ninety-three DNA sequences that were present in B. anthracis but absent from the non-anthrax-causing Bacillus genomes were isolated. Furthermore, 28 of these sequences were not found in a collection of 10 non-anthrax-causing Bacillus species but were present in all members of a representative collection of B. anthracis strains. These sequences map to distinct loci on the B. anthracis genome and can be assayed simultaneously in multiplex PCR assays for rapid and highly specific DNA-based detection of B. anthracis.

Bacillus↗

Sporosarcina aquimarina sp. nov., a bacterium isolated from seawater in Korea, and transfer of Bacillus globisporus (Larkin and Stokes 1967), Bacillus psychrophilus (Nakamura 1984) and Bacillus pasteurii (Chester 1898) to the genus Sporosarcina as Sporosarcina globispora comb. nov., Sporosarcina psychrophila comb. nov. and Sporosarcina pasteurii comb. nov., and emended description of th.

A light-orange-coloured, facultatively anaerobic, rod-shaped bacterium (strain SW28T), which was isolated from seawater in Korea, was taxonomically studied by a polyphasic approach. This organism formed round terminal endospores in swollen sporangia. The peptidoglycan type is A4alpha, based on L-Lys-L-Ala-D-Asp. The predominant menaquinone is MK-7 and the major fatty acid is ante-C15:0. The G+C content of the DNA is 40 mol%. Phylogenetic analysis based on 16S rDNA sequences showed that strain SW28T falls within the radiation of a cluster comprising the rRNA group 2 bacilli and non-Bacillus-type organisms. Strain SW28T showed the highest degree of relatedness to the type strain of Sporosarcina ureae, sharing 96.8% 16S rDNA similarity. Levels of DNA-DNA relatedness between strain SW28T and S. ureae DSM 2281T and the type strains of some Bacillus species forming a coherent phylogenetic cluster are less than 12.5%. On the basis of phenotypic and chemotaxonomic characteristics, 16S rDNA sequence analysis and DNA-DNA relatedness data, it is proposed that strain SW28T should be placed in the genus Sporosarcina as a new species, Sporosarcina aquimarina sp. nov. The type strain is SW28T (= KCCM 41039T = JCM 10887T). From the results of the taxonomic re-evaluation, it is also proposed that Bacillus globisporus, Bacillus psychrophilus and Bacillus pasteurii be transferred to the genus Sporosarcina as Sporosarcina globispora, Sporosarcina psychrophila and Sporosarcina pasteurii, respectively.

Bacillaceae↗

Fatty acid composition and primer specificity of de novo fatty acid synthetase in Bacillus globispores, Bacillus insolitus, and Bacillus psychrophilus.

The fatty acid compositions of three psychrophilic species of Bacillus were determined by gas--liquid chromatography. The proportions of straight-chain fatty acids, branched-chain fatty acids, and unsaturated fatty acids were found to be 13.3, 86.7, and 26.1% of the total cellular fatty acids for Bacillus globispores, 36.6, 63.4, and 25.1% for Bacillus insolitus, and 6.9, 93.1, and 18.4% for Bacillus psychrophilus, respectively. In all three organisms the de novo fatty acid synthetase specificity towards acyl-CoA primers was butyryl-CoA greater than propionyl-CoA much greater than acetyl-CoA. This shows that B. insolitus, which has an unusually large proportion of straight-chain fatty acids for Bacillus, does not possess a different de novo fatty acid synthetase than the other two organisms. Therefore, the greater proportion of straight-chain fatty acids in B. insolitus may be explained by a large supply of straight-chain primer.

Acyl Coenzyme A↗

Expression of a Bacillus thuringiensisdelta-endotoxin cry1Ab gene in Bacillus subtilis and Bacillus licheniformis strains that naturally colonize the phylloplane of tomato plants (Lycopersicon esculentum, Mills).

AIMS: To introduce a cry gene into microorganisms that naturally colonize the phylloplane of tomato plants to improve the persistence of the Cry proteins for controlling a South American tomato moth (Tuta absoluta, Meyrick, 1917). METHODS AND RESULTS: A cry1Ab gene isolated from a native Bacillus thuringiensis strain (LM-466), showing a relevant activity against T. absoluta larvae, was cloned into the shuttle vector pHT315 (Arantes and Lereclus 1991). The construct was introduced by electroporation into native Bacillus subtilis and Bacillus licheniformis strains, both natural inhabitants of the tomato phylloplane. Western analysis and toxicity assays against the target larvae proved that the successful expression of the gene was accomplished in host bacteria. Recombinant toxin displayed a similar LC50 value in comparison to native donor strain LM-466. Both transformed Bacillus survived for at least 45 days on the tomato leaf surface. CONCLUSIONS: Plant-associated microorganisms that naturally colonize the phylloplane could be useful as recombinant microbial delivery systems of toxin genes of B. thuringiensis. SIGNIFICANCE AND IMPACT OF THE STUDY: Modified microorganisms capable of surviving on leaf surfaces for several weeks with insecticidal activity should allow for a reduction in pesticide application.

Animals↗

Proteomic profiling and identification of immunodominant spore antigens of Bacillus anthracis, Bacillus cereus, and Bacillus thuringiensis.

Differentially expressed and immunogenic spore proteins of the Bacillus cereus group of bacteria, which includes Bacillus anthracis, Bacillus cereus, and Bacillus thuringiensis, were identified. Comparative proteomic profiling of their spore proteins distinguished the three species from each other as well as the virulent from the avirulent strains. A total of 458 proteins encoded by 232 open reading frames were identified by matrix-assisted laser desorption ionization-time-of-flight mass spectrometry analysis for all the species. A number of highly expressed proteins, including elongation factor Tu (EF-Tu), elongation factor G, 60-kDa chaperonin, enolase, pyruvate dehydrogenase complex, and others exist as charge variants on two-dimensional gels. These charge variants have similar masses but different isoelectric points. The majority of identified proteins have cellular roles associated with energy production, carbohydrate transport and metabolism, amino acid transport and metabolism, posttranslational modifications, and translation. Novel vaccine candidate proteins were identified using B. anthracis polyclonal antisera from humans postinfected with cutaneous anthrax. Fifteen immunoreactive proteins were identified in B. anthracis spores, whereas 7, 14, and 7 immunoreactive proteins were identified for B. cereus and in the virulent and avirulent strains of B. thuringiensis spores, respectively. Some of the immunodominant antigens include charge variants of EF-Tu, glyceraldehyde-3-phosphate dehydrogenase, dihydrolipoamide acetyltransferase, Delta-1-pyrroline-5-carboxylate dehydrogenase, and a dihydrolipoamide dehydrogenase. Alanine racemase and neutral protease were uniquely immunogenic to B. anthracis. Comparative analysis of the spore immunome will be of significance for further nucleic acid- and immuno-based detection systems as well as next-generation vaccine development.

Antigens, Bacterial↗

Fluorescent amplified fragment length polymorphism analysis of Bacillus anthracis, Bacillus cereus, and Bacillus thuringiensis isolates.

DNA from over 300 Bacillus thuringiensis, Bacillus cereus, and Bacillus anthracis isolates was analyzed by fluorescent amplified fragment length polymorphism (AFLP). B. thuringiensis and B. cereus isolates were from diverse sources and locations, including soil, clinical isolates and food products causing diarrheal and emetic outbreaks, and type strains from the American Type Culture Collection, and over 200 B. thuringiensis isolates representing 36 serovars or subspecies were from the U.S. Department of Agriculture collection. Twenty-four diverse B. anthracis isolates were also included. Phylogenetic analysis of AFLP data revealed extensive diversity within B. thuringiensis and B. cereus compared to the monomorphic nature of B. anthracis. All of the B. anthracis strains were more closely related to each other than to any other Bacillus isolate, while B. cereus and B. thuringiensis strains populated the entire tree. Ten distinct branches were defined, with many branches containing both B. cereus and B. thuringiensis isolates. A single branch contained all the B. anthracis isolates plus an unusual B. thuringiensis isolate that is pathogenic in mice. In contrast, B. thuringiensis subsp. kurstaki (ATCC 33679) and other isolates used to prepare insecticides mapped distal to the B. anthracis isolates. The interspersion of B. cereus and B. thuringiensis isolates within the phylogenetic tree suggests that phenotypic traits used to distinguish between these two species do not reflect the genomic content of the different isolates and that horizontal gene transfer plays an important role in establishing the phenotype of each of these microbes. B. thuringiensis isolates of a particular subspecies tended to cluster together.

Animals↗

Fatty acids in Bacillus larvae, Bacillus lentimorbus, and Bacillus popilliae.

The types of fatty acids produced by two strains each of Bacillus larvae, B. lentimorbus, and B. popilliae, and their distribution patterns, were studied by gas-liquid chromatography. All six organisms produced eight major fatty acids: six branched (iso-C(14), -C(15), -C(16), and -C(17), and anteiso-C(15) and -C(17)), two normal (n-C(14) and -C(16)), and two minor (n-C(15) and monounsaturated n-C(16)). In addition, some other trace acids were produced. Branched-chain fatty acids accounted for 54 to 85% of the total fatty acids. These compositions are similar to those previously found with 26 strains of 12 species of the genus Bacillus. Thus, an abundance of branched-chain fatty acids seems to be a characteristic of the biochemical nature of the genus Bacillus. It is noteworthy that marked differences between the nutritional requirements of the three insect pathogens used in the present study and those of the other 12 species of the genus Bacillus studied previously are not significantly reflected in their fatty acid composition.

Animals↗

Cloning of the maltose phosphorylase gene from Bacillus sp. strain RK-1 and efficient production of the cloned gene and the trehalose phosphorylase gene from Bacillus stearothermophilus SK-1 in Bacillus subtilis.

The maltose phosphorylase (MPase) gene of Bacillus sp. strain RK-1 was cloned by PCR with oligonucleotide primers designed on the basis of a partial N-terminal amino acid sequence of the purified enzyme. The MPase gene consisted of 2,655 bp encoding a theoretical protein with a Mr of 88,460, and had no secretion signal sequence, although most of the MPase activity was detected in the culture supernatant of RK-1. This cloned MPase gene and the trehalose phosphorylase (TPase) gene from Bacillus stearothermophilus SK-1 were efficiently expressed intracellularly under the control of the Bacillus amyloliquefaciens alpha-amylase promoter in Bacillus subtilis. The production yields were estimated to be more than 2 g of enzyme per liter of medium, about 250 times the production of the original strains, in a simple shake flask. About 60% of maltose was converted into trehalose by the simultaneous action of both enzymes produced in B. subtilis.

Amino Acid Sequence↗

A comparative study of Bacillus cereus, Bacillus thuringiensis and Bacillus anthracis extracellular proteomes.

Bacillus cereus, Bacillus thuringiensis and Bacillus anthracis are closely related species that share a similar genetic background but occupy different ecological niches. Virulence plasmids bearing genes coding for toxins, may explain, at least partly, this specialization. We have compared by 2-DE in the early stationary phase of growth the extracellular proteomes of three strains of these species that have lost their virulence plasmids. Proteins expected to be secreted or to belong to the cell wall or to the cytosol were found in the three proteomes. For the cell wall and cytosolic proteins located in the extracellular space, the three proteomes were similar. Cytosolic proteins included enolase, GroEL, PdhB, PdhD, SodA and others. Cell surface proteins were mainly autolysins, proteases, nucleotidases and OppAs. In contrast, the secreted proteins profiles of B. cereus and B. thuringiensis were quite different from that of B. anthracis. B. cereus and B. thuringiensis extracellular proteomes both contained large amounts of secreted degradative enzymes and toxins, including nine proteases, three phospholipases, two haemolysins and several enterotoxins. Most of the genes encoding these enzymes and toxins are controlled by the transcriptional activator PlcR. The extracellular proteome of the pXO1-, pXO2- B. anthracis 9131 strain contained only one secreted protein: the metalloprotease InhA1, also found in the proteomes of the two other strains and possibly involved in antibacterial peptide degradation.

Amino Acid Sequence↗

Siderophores of Bacillus anthracis, Bacillus cereus, and Bacillus thuringiensis.

Three Bacillus anthracis Sterne strains (USAMRIID, 7702, and 34F2) and Bacillus cereus ATCC 14579 excrete two catecholate siderophores, petrobactin (which contains 3,4-dihydroxybenzoyl moieties) and bacillibactin (which contains 2,3-dihydroxybenzoyl moieties). However, the insecticidal organism Bacillus thuringiensis ATCC 33679 makes only bacillibactin. Analyses of siderophore production by previously isolated [Cendrowski et al., Mol. Microbiol. 52 (2004) 407-417] B. anthracis mutant strains revealed that the B. anthracis bacACEBF operon codes for bacillibactin production and the asbAB gene region is required for petrobactin assembly. The two catecholate moieties also were synthesized by separate routes. PCR amplification identified both asbA and asbB genes in the petrobactin producing strains whereas B. thuringiensis ATCC 33679 retained only asbA. Petrobactin synthesis is not limited to the cluster of B. anthracis strains within the B. cereus sensu lato group (in which B. cereus, B. anthracis, and B. thuringiensis are classified), although petrobactin might be prevalent in strains with pathogenic potential for vertebrates.

Bacillus anthracis↗

Bacillus cereus, Bacillus thuringiensis and Bacillus mycoides differentiation using a PCR-RE technique.

A method was developed to differentiate between Bacillus cereus, Bacillus mycoides and Bacillus thuringiensis using the polymerase chain reaction combined with a restriction endonuclease (PCR-RE) technique. This fast and simple protocol, applied to pure culture strains, was developed using the gyrB DNA sequence, as previously proposed by other authors. Strains from international collections were used to optimize the method which was then applied to the identification of strains isolated from food samples. Amplifications were specific for the B. cereus group. Only Staphylococcus aureus gave the same size PCR product, but it was easily differentiated from strains in the B. cereus group by using restriction analysis, based on digestion with the RsaI, Sau3AI and EcoRI endonucleases. Specific amplifications and good differentiations were obtained using pure strains, suggesting the possibility of using the method described to identify the B. cereus group directly in food samples.

Bacillus↗

Diversity and differential distribution of IS231, IS232 and IS240 among Bacillus cereus, Bacillus thuringiensis and Bacillus mycoides.

Bacillus cereus, Bacillus thuringiensis and Bacillus mycoides are very closely related bacteria, generally considered as subspecies of B. cereus sensu lato. Different transposable elements have been isolated from B. thuringiensis, including IS231, IS232 and IS240 and their variants. The distribution of these three insertion sequences (IS) within the B. cereus group has been investigated in 90 strains of B. thuringiensis (representing 61 serovars), in 30 reference strains of B. cereus and in 33 strains of B. mycoides. Since these IS elements are delimited by well-conserved and specific inverted repeats, the use of primers corresponding to these ends allowed their amplification by PCR. The results showed that IS231 is the most abundant element in the three taxa, whereas IS232 is apparently exclusively associated with B. thuringiensis. Hybridization and Dral RFLP analysis of the PCR products confirmed and extended knowledge of the heterogeneity previously observed among iso-IS231 elements. Moreover, a similar diversity was observed among iso-IS240 elements. This contrasted with the relative homogeneity displayed by iso-IS232 elements. No specific association appeared to exist between any particular iso-element and a specific strain or serotype.

Bacillus↗

Inactivation of spores of Bacillus anthracis Sterne, Bacillus cereus, and Bacillus thuringiensis subsp. israelensis by chlorination.

Three species of Bacillus were evaluated as potential surrogates for Bacillus anthracis for determining the sporicidal activity of chlorination as commonly used in drinking water treatment. Spores of Bacillus thuringiensis subsp. israelensis were found to be an appropriate surrogate for spores of B. anthracis for use in chlorine inactivation studies.

Bacillus anthracis↗

Methionine regeneration and aminotransferases in Bacillus subtilis, Bacillus cereus, and Bacillus anthracis.

The conversion of ketomethiobutyrate to methionine has been previously examined in a number of organisms, wherein the aminotransferases responsible for the reaction have been found to be members of the Ia subfamily (L. C. Berger, J. Wilson, P. Wood, and B. J. Berger, J. Bacteriol. 183:4421-4434, 2001). The genome of Bacillus subtilis has been found to contain no subfamily Ia aminotransferase sequences. Instead, the analogous enzymes in B. subtilis were found to be members of the If subfamily. These putative aspartate aminotransferases, the yugH, ywfG, ykrV, aspB, and patA gene products, have been cloned, expressed, and characterized for methionine regeneration activity. Only YkrV was able to convert ketomethiobutyrate to methionine, and it catalyzed the reaction only when glutamine was used as amino donor. In contrast, subcellular homogenates of B. subtilis and Bacillus cereus utilized leucine, isoleucine, valine, alanine, phenylalanine, and tyrosine as effective amino donors. The two putative branched-chain aminotransferase genes in B. subtilis, ybgE and ywaA, were also cloned, expressed, and characterized. Both gene products effectively transaminated branched-chain amino acids and ketoglutarate, but only YbgE converted ketomethiobutyrate to methionine. The amino donor preference for methionine regeneration by YbgE was found to be leucine, isoleucine, valine, phenylalanine, and tyrosine. The B. subtilis ybgE gene is a member of the family III of aminotransferases and falls in a subfamily designated here IIIa. Examination of B. cereus and Bacillus anthracis genome data found that there were no subfamily IIIa homologues in these organisms. In both B. cereus and B. anthracis, two putative branched-chain aminotransferases and two putative D-amino acid aminotransferases were discovered as members of subfamily IIIb. These four sequences were cloned from B. cereus, expressed, and characterized. Only the gene product from the sequence designated Bc-BCAT2 was found to convert ketomethiobutyrate to methionine, with an amino donor preference of leucine, isoleucine, valine, phenylalanine, and tyrosine. The B. anthracis homologue of Bc-BCAT2 was also cloned, expressed, and characterized and was found to be identical in activity. The aminooxy compound canaline was found to be an uncompetitive inhibitor of B. subtilis YbgE and also inhibited growth of B. subtilis and B. cereus in culture.

Amino Acid Sequence↗

Pathogenomic sequence analysis of Bacillus cereus and Bacillus thuringiensis isolates closely related to Bacillus anthracis.

Bacillus anthracis, Bacillus cereus, and Bacillus thuringiensis are closely related gram-positive, spore-forming bacteria of the B. cereus sensu lato group. While independently derived strains of B. anthracis reveal conspicuous sequence homogeneity, environmental isolates of B. cereus and B. thuringiensis exhibit extensive genetic diversity. Here we report the sequencing and comparative analysis of the genomes of two members of the B. cereus group, B. thuringiensis 97-27 subsp. konkukian serotype H34, isolated from a necrotic human wound, and B. cereus E33L, which was isolated from a swab of a zebra carcass in Namibia. These two strains, when analyzed by amplified fragment length polymorphism within a collection of over 300 of B. cereus, B. thuringiensis, and B. anthracis isolates, appear closely related to B. anthracis. The B. cereus E33L isolate appears to be the nearest relative to B. anthracis identified thus far. Whole-genome sequencing of B. thuringiensis 97-27and B. cereus E33L was undertaken to identify shared and unique genes among these isolates in comparison to the genomes of pathogenic strains B. anthracis Ames and B. cereus G9241 and nonpathogenic strains B. cereus ATCC 10987 and B. cereus ATCC 14579. Comparison of these genomes revealed differences in terms of virulence, metabolic competence, structural components, and regulatory mechanisms.

Amino Acids↗

A selective chromogenic agar that distinguishes Bacillus anthracis from Bacillus cereus and Bacillus thuringiensis.

A selective and differential plating medium, R & F anthracis chromogenic agar (ACA), has been developed for isolating and identifying presumptive colonies of Bacillus anthracis. ACA contains the chromogenic substrate 5-bromo-4-chloro-3-indoxyl-choline phosphate that upon hydrolysis yields teal (blue green) colonies indicating the presence of phosphatidylcholine-specific phospholipase C (PC-PLC) activity. Among seven Bacillus species tested on ACA, only members of the Bacillus cereus group (B. anthracis, B. cereus, and B. thuringiensis) produced teal colonies (PC-PLC positive) having cream rings. Examination of colony morphology in 18 pure culture strains of B. anthracis (15 ATCC strains plus AMES-1-RIID, ANR-1, and AMED-RIID), with one exception, required 48 h at 35 to 37 degrees C for significant color production, whereas only 24 h was required for B. cereus and B. thuringiensis. This differential rate of PC-PLC synthesis in B. anthracis (due to the truncated plcR gene and PlcR regulator in B. anthracis) allowed for the rapid differentiation on ACA of presumptive colonies of B. anthracis from B. cereus and B. thuringiensis in both pure and mixed cultures. Effective recovery of B. anthracis from a variety of matrices having both high (soil and sewage) and low microbial backgrounds (cloth, paper, and blood) spiked with B. anthracis ANR-1 spores suggests the probable utility of ACA plating for B. anthracis recovery in a diversity of applications.

Agar↗