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J Bacteriol. Aug 2011; 193(16): 4274–4275.
PMCID: PMC3147672

Genome of Ochrobactrum anthropi ATCC 49188T, a Versatile Opportunistic Pathogen and Symbiont of Several Eukaryotic Hosts[down-pointing small open triangle]

Abstract

Ochrobactrum anthropi is a common soil alphaproteobacterium that colonizes a wide spectrum of organisms and is being increasingly recognized as an opportunistic human pathogen. Potentially life-threatening infections, such as endocarditis, are included in the list of reported O. anthropi infections. These reports, together with the scant number of studies and the organism's phylogenetic proximity to the highly pathogenic brucellae, make O. anthropi an attractive model of bacterial pathogenicity. Here we report the genome sequence of the type strain O. anthropi ATCC 49188, which revealed the presence of two chromosomes and four plasmids.

GENOME ANNOUNCEMENT

Ochrobactrum anthropi is a common soil alphaproteobacterium (7) that can interact with or colonize many eukaryotic organisms, leading to different outcomes, such as disease or even growth of some plants (references 4 and 13 and references therein). O. anthropi, a close relative of brucellae, has not garnered much attention (5, 8) but is becoming increasingly recognized as a potentially problematic opportunistic and nosocomial pathogen (13). A rising number of reported cases includes some potentially life-threatening infections, such as endocarditis (6, 9, 14). These reports, together with the organism's intrinsic multiresistance to antibiotics (13), could lead to a situation resembling that of an Acinetobacter sp., whose importance as a highly problematic nosocomial pathogen skyrocketed in the past few years (12). The increasing relevance of O. anthropi to human health, together with its phylogenetic proximity to the highly pathogenic brucellae (a USDA Select Agent), prompted us to determine the genomic sequence of the type strain O. anthropi ATCC 49188.

O. anthropi ATCC 49188T was draft sequenced to >15-fold coverage, consisting of 91,706 Sanger sequencing reads. Gaps, repeats, and regions of poor quality were resolved using an additional 1,900 finishing reads, resulting in a genome of finished quality (3). Similar to other Rhizobiales, the 4.8-Mb genome of O. anthropi consists of multiple circular chromosomes, a 2,887,297-bp replicon with the prototypical bacterial chromosome origin of replication, and a 1,895,911-bp replicon with a repABC origin commonly found in other secondary chromosomes and plasmids of the Rhizobiaceae (18). Both chromosomes have an average G+C content of 56% and together comprise 4,424 protein-coding genes (~87% coding), along with 31 pseudogenes and 73 structural RNAs (rRNA, tRNA, and small RNA). Both chromosomes are highly similar to and colinear with the two chromosomes of Brucella spp.; however, the 1.5-Mb difference in size can be attributed to the acquisition of novel islands in O. anthropi and the degradation of a genome for the brucellae, as has been previously described (17).

In addition, the O. anthropi genome contains four plasmids, of which pOAN01, pOAN02, and pOAN03 have the characteristics expected of alphaproteobacterial plasmids, while pOAN04 is more puzzling, lacking known replication, partition, and conjugative systems. Plasmids pOAN01 (170,351 bp), pOAN02 (101,491 bp), and pOAN03 (93,589 bp) harbor one or more RepABC and/or RepC replication or replication-partition systems (2, 16). Genes known to be related to stabilization factors have also been found among these three plasmids, including genes encoding ParB-like, PilT-type, and toxin-antitoxin plasmid addiction systems. All three RepABC plasmids include a large number of genes encoding transposases and integrases from different families, but pOAN04 lacks such genes. Plasmid pOAN01 includes a complete set of type IV secretion system genes that suggest it is self-transmissible, and pOAN02 is the only other plasmid with homologs that suggest it is mobilizable (coding for antirestriction and mobilization proteins). All four plasmids may contribute to the fitness of O. anthropi, as they harbor several transporters, though metabolic genes are found only in pOAN01, pOAN03, and pOAN04.

A comparison of the genomics of O. anthropi to that of other pathogenic alphaproteobacteria will permit us to understand its mechanisms of virulence and take appropriate measures to prevent it from developing into a dangerous pathogen.

Acknowledgments

This work was partially supported by a grant from the California State University Program for Education and Research in Biotechnology (CSUPERB) and a minigrant from the CSU State Fund. The genome sequencing work conducted by the U.S. Department of Energy Joint Genome Institute is supported by the Office of Science of the U.S. Department of Energy under contract number DE-AC02-05CH11231.

Footnotes

[down-pointing small open triangle]Published ahead of print on 17 June 2011.

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