Complete Genome Sequence of the Highly Hemolytic Strain Bacillus cereus F837/76

Abstract

Highly hemolytic strain Bacillus cereus F837/76 was isolated in 1976 from a contaminated prostate wound. The complete nucleotide sequence of this strain reported here counts nearly 36,500 single-nucleotide differences from the closest sequenced strain, Bacillus thuringiensis Al Hakam. F827/76 also contains a 10-kb plasmid that was not detected in the Al Hakam strain.

GENOME ANNOUNCEMENT

In addition to notorious food poisoning problems and anthrax, some strains of the Bacillus cereus group have been isolated as the cause of clinical infections, including fatal pneumonia resembling anthrax (4, 7, 8). The strain B. cereus F837/76 was isolated from a prostate wound (13). This strain was shown to be an efficient producer of hemolytic and nonhemolytic enterotoxins (3, 11, 14). Phylogenetically, it appeared to cluster with the clinical strains and the strains prone to acquire anthrax toxin and capsule plasmids (6, 7), although only two such cases were detailed (1, 7, 8).

The complete genome sequence of B. cereus F837/76 was determined by a whole-genome shotgun approach using dideoxy Sanger technology. Two plasmid libraries were constructed with mean insert sizes of 3 and 10 kb. Assembling of 80,000 reads resulted in 168 contigs. Finishing was accomplished by an additional 1,514 reads using primer walking over the multiplex combinatorial PCR products (12). The genome of F837/76, with an average G+C content of 35.4%, consists of one circular chromosome (5,122,907 bp) and two circular extrachromosomal elements: pF837_10kb (10,288 bp; G+C content, 31.1%) and pF837_55kb (55,304 bp; G+C content, 36.2%).

Prediction of protein-encoding genes (coding sequences [CDS]) and assignment of functions were done using the RAST annotation suite (2). The genome of F837/76 contains 5,373 of the predicted CDS and two plasmids, pF837_55kb and pF837_10kb, containing 84 and 11 CDS, respectively. The plasmid pF837_55kb shares 99.5% nucleotide identity over 85% of the length with the plasmid pALH1 of Bacillus thuringiensis Al Hakam (5). The genome of Al Hakam is the closest to that of F837/76. Alignment of the two genomes using MUMmer (9) detected about 36,500 single-nucleotide differences. A counterpart of pF837_10kb was not reported for Al Hakam (5). The F837/76 genome encodes 105 tRNAs and includes 12 rRNA operons. Putatively inducible prophages were not detected in the chromosome by using the Prophinder tool of the database ACLAME (10), although pF837_55kb could be a nonintegrated prophage since it contains multiple phage-related genes, encoding a terminase subunit, endolysin, a tape measure protein, and others. The availability of the F837/76 genome should facilitate the understanding of evolution of virulence in clinical nonanthrax strains of the B. cereus group.

Nucleotide sequence accession numbers.

The complete genome of B. cereus F837/76 has been deposited in GenBank under accession numbers CP003187 (chromosome), CP003188 (pF837_55kb), and CP003189 (pF837_10kb).