Draft Genome Sequence of Bacillus cereus LA2007, a Human-Pathogenic Isolate Harboring Anthrax-Like Plasmids

GENOME ANNOUNCEMENT

Bacillus cereus strains containing genetic determinants that confer pathogenic capabilities similar to those found on Bacillus anthracis have been recently described (1–5). In B. anthracis, virulence determinants are carried on two large plasmids, pXO1 and pXO2, including the genes necessary to produce the anthrax toxin (lef, cya, and pagA) and a d-polyglutamic acid capsule (capBCADE) allowing the pathogen to evade host immune response. Plasmids similar to pXO1 and pXO2 have been found in a number of previously sequenced B. cereus sensu lato strains causing anthrax-like diseases (1–5). It has not been determined whether or not lateral transfer has occurred between members of B. cereus and B. anthracis, the direction of such a transfer, or the phylogenetic relationships of the strains based on the plasmid sequences. To gain deeper insights into the evolution of B. cereus strains causing anthrax-like diseases, we present the draft genome sequence of LA2007, a bacterial pathogen isolated from a fatal pneumonia case in a female welder from Louisiana.

DNA was extracted from overnight culture on Trypticase soy agar with 5% sheep blood using the Maxwell 16 Promega instrument, and sequencing was performed on an Illumina GAIIx platform. Read quality control, assembly, and annotation were performed as described by Tsementzi et al. (6).

The assembled genome of LA2007 consisted of 67 contigs, with a G+C content of 35% and a total genome size of 5,224,740 bp. The estimated percent completeness and contamination were 99.15% and 0.28%, respectively. The genome was predicted to contain a total of 5,777 putative protein-coding sequences, 15 rRNA operons, and 57 tRNA genes. The calculated average nucleotide identity (ANI) (7) of LA2007 was 94.76% against B. anthracis Ames while it was 99.99%; against similar B. cereus strains, i.e., strains G9241 (2), 03BB87 (3), and BcFL2013 (1), previously associated with severe pneumonia and cutaneous infections.

Characterization of plasmid gene content showed that the genome of B. cereus LA2007 contains a pXO1-like plasmid assembled in eight contigs, each one of them showing at least 99.70% ANI and 80% gene coverage with B. anthracis Ames pXO1. The results with B. anthracis Ames pXO1 suggest that LA2007 (or its ancestors) might have horizontally acquired the pXO1 plasmid from B. anthracis (since the ANI of the plasmid is higher than that of the main chromosome), although detailed phylogenetic analysis will be required to robustly test this finding. A comparison with plasmid pBCXO1 from strains G9241, 03BB87, and BcFL2013 revealed an ANI of ≥99.99% in all three cases, similar to the chromosomes mentioned above. A plasmid homologous to pBc210 reported in B. cereus G9241 was also identified in LA2007. The plasmid in LA2007 was assembled in nine contigs and showed 99.98% ANI compared to the plasmid of G9241. Anthrax toxin genes and complete genes for the production of hyaluronic acid synthases (hasACB) and exopolysaccharides (bpsHGFEDCBAX) were also identified in LA2007 suggesting its ability to produce protective capsules.