Bacillus anthracis diverges from related clades of the Bacillus cereus group in 16S-23S ribosomal DNA intergenic transcribed spacers containing tRNA genes.
Mung bean nuclease treatment of 16S-23S ribosomal DNA intergenic transcribed spacers (ITS) amplified from several strains of the six species of the Bacillus cereus group showed that B. anthracis Davis TE702 and B. mycoides G2 have other intermediate fragments in addition to the 220- and 550-bp homoduplex fragments typical of the B. cereus group. Long and intermediate homoduplex ITS fragments from strains Davis TE702 and G2 and from another 19 strains of the six species were sequenced. Two main types of ITS were found, either with two tRNA genes (tRNA(Ile) and tRNA(Ala)) or without any at all. Strain Davis TE702 harbors an additional ITS with a single tRNA gene, a hybrid between the tRNA(Ile) and tRNA(Ala) genes, suggesting that a recombination event rather than a deletion generated the single tDNA-containing ITS. Strain G2 showed an additional ITS of intermediate length with no tDNA and no similarity to other known sequences. Neighbor-joining analysis of tDNA-containing long ITS indicated that B. cereus and B. thuringiensis represent a single clade. Three signature sequences discriminated B. anthracis from B. cereus and B. thuringiensis, indicating that the anthrax agent started evolving separately from the related clades of the B. cereus group. B. mycoides and B. weienstephanensis were very closely related, while B. pseudomycoides appeared the most distant species.
Cherif
Ameur
A
Dipartimento di Scienze e Tecnologie Alimentari e Microbiologiche, Università degli Studi di Milano, 20133 Milan, Italy.
Borin
Sara
S
Rizzi
Aurora
A
Ouzari
Hadda
H
Boudabous
Abdellatif
A
Daffonchio
Daniele
D
D001408:Bacillus anthracis / Q000145:classification* / Q000235:genetics; D001409:Bacillus cereus / Q000145:classification* / Q000235:genetics; D001483:Base Sequence; D021903:DNA, Ribosomal Spacer / Q000032:analysis / Q000235:genetics*; D014644:Genetic Variation; D008969:Molecular Sequence Data; D010802:Phylogeny; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D012338:RNA, Ribosomal, 23S / Q000235:genetics; D012344:RNA, Transfer, Ala / Q000235:genetics*; D012355:RNA, Transfer, Ile / Q000235:genetics*; D017422:Sequence Analysis, DNA
D021903:DNA, Ribosomal Spacer; D012336:RNA, Ribosomal, 16S; D012338:RNA, Ribosomal, 23S; D012344:RNA, Transfer, Ala; D012355:RNA, Transfer, Ile