Intimate interactions between bacteria and eukaryotes have influenced the course of organismal evolution and ecological distribution. While ubiquitous, there is generally little understanding of the physiological basis of such associations, particularly when they are nonpathogenic in nature (symbiotic). Earthworms of the family Lumbricidae harbor novel symbiotic betaproteobacteria within their nephridia (excretory organ). Few symbiotic betaprotebacteria have been reported, and no other beneficial bacteria are described that specifically colonize the excretory organs of animals. To better understand the physiological and evolutionary dimensions of this symbiosis, JGI will sequence the genome of the isolated Acidovorax symbiont, and the genomes of two additional species within the genus: the plant pathogen A. avenae subsp. citrulli, and the nitroaromatic compound-degrader Acidovorax sp. JS42. Comparison of genomes from representatives of this single phylogenetic group will provide a genomic perspective on genetic and metabolic features that characterize these very divergent lifestyles–symbiotic, pathogenic, and free living. In addition to contributing to our understanding of the earthworm symbiosis, this information should extend general understanding of the adaptive radiation of microorganisms and be of benefit to several scientific fields of economic and environmental importance.
The availability of genomes from three Acidovorax species will provide an important comparative framework. The sequence of A. avenae subsp. citrulli should provide information about the character of the division between closely related symbiotic and pathogenic bacteria. The sequencing of Acidovorax sp. JS42 will provide information about the gene content of a free-living species with a catabolic capacity relevant to bioremediation of nitroaromatic-contaminated soils. Thus, the genome sequence data will be of interest to a broad group of investigators, immediately drawing together a diverse and interdisciplinary group of researchers that have explored different physiological and ecological dimensions of this genus, as well as those interested in the features of host/microbe interactions in general.
CSP project participants: David A. Stahl (proposer), Seana K. Davidson, and Nicolás Pinel (Univ. of Washington).