MOLECULAR BIOLOGY AND GENOMICS OF FOODBORNE PATHOGENS
Location: Produce Safety and Microbiology Research
Title: The complete genome sequence and analysis of the human pathogen Campylobacter lari.
Submitted to: Foodborne Pathogens and Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 21, 2008
Publication Date: August 19, 2008
Citation: Miller, W.G., Wang, G., Binnewies, T.T., Parker, C. 2008. The complete genome sequence and analysis of the human pathogen Campylobacter lari. Foodborne Pathogens and Disease. 5(4):371-386.
Interpretive Summary: Although food-borne pathogens like Campylobacter jejuni are major causal agents of gastroenteritis world-wide, other less well-characterized food-borne organisms have been implicated increasingly in human disease. One of these organisms is Campylobacter lari. Campylobacter lari, a close relative of C. jejuni, is a marine Campylobacter, is found often on shellfish (i.e. mussels and oysters), is naturally resistant to the class of antibiotics that includes ciprofloxacin, and causes the same clinical disease symptoms as C. jejuni. However, little is known about this organism. Therefore, to characterize C. lari, the complete chromosomal DNA sequence was determined for a human clinical isolate of this species. A noteworthy feature of this organism is the absence of several key genes in multiple metabolic pathways, including those pathways related to the synthesis of amino acids and energy production. The absence of these genes is mirrored in another closely-related Campylobacter, Campylobacter insulaenigrae, an organism also isolated often from marine environments, specifically from marine mammals such as seals and dolphins. This suggests that genomic reduction in C. lari may influence or have been influenced by its presence in the marine ecosystem.
Campylobacter lari is a member of the epsilon subdivision of the Proteobacteria and is part of the thermotolerant Campylobacter group, a clade that includes the human pathogen Campylobacter jejuni. Here we present the complete genome sequence of the human clinical isolate, C. lari RM2100. The genome of strain RM2100 is ~1.53 Mb and includes the 46 kb megaplasmid pCL2100. Also present within the strain RM2100 genome is a 36 kb putative prophage, termed CLIE1, which is similar to CJIE4, a putative prophage present within the C. jejuni RM1221 genome. Nearly all (90%) of the gene content in strain RM2100 is similar to genes present in the genomes of other characterized thermotolerant campylobacters. However, several genes involved in amino-acid biosynthesis and energy metabolism, identified previously in other Campylobacter genomes, are absent from the C. lari RM2100 genome. Therefore, C. lari RM2100 is predicted to be multiply auxotrophic, unable to synthesize eight different amino acids, acetyl-coA and pantothenate. Additionally, strain RM2100 does not contain a complete TCA cycle and is missing the CydAB terminal oxidase of the respiratory chain. Defects in the amino-acid biosynthetic pathways in this organism could be potentially compensated by the large number of encoded peptidases. Nevertheless, the apparent absence of certain key enzymatic functions in strain RM2100 would be expected to have an impact on C. lari biology. It is also possible that the reduction in the C. lari metabolic machinery is related to its environmental range and host preference.