Interactions of alpha-proteobacteria with eukaryotic cells

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The long-term objective of our research program is to understand the molecular basis of the interactions between alpha-proteobacteria and eukaryotic cells. This group of bacteria comprises animal and human pathogens (Bartonella, Brucella, Ochrobactrum), plant pathogens (Agrobacterium) and plant symbionts (Mesorhizobium, Rhizobium, Sinorhizobium) as well as free-living bacteria. The genomic sequences of many alpha-proteobacteria became available in recent years. Based on this wealth of information, post-genomic studies are now possible that are aimed at understanding the different survival strategies of this group of bacteria. We have chosen the genus Ochrobactrum for our research program as its different species reflect a broad spectrum of life styles from free-living soil bacteria to plant symbionts and opportunistic human pathogens. The principal model for our work during the next funding period will be the opportunistic pathogen Ochrobactrum anthropi. This organism lives in soil, but the number of reports on its isolation from immuno-suppressed patients in hospitals has been increasing, suggesting that it has significant pathogenic potential. As the pathogenicity for humans is modest, O. anthropi can be studied under biosafety level 2 conditions, which is an important pre-requisite for our long-term research plans. In the next funding period, we will characterize the intracellular trafficking of O. anthropi and the regulation of its virulence genes. This work will set the stage for a comprehensive systems approach, which will use fusions to genes regulated during intracellular growth to characterize the metabolic responses of the pathogen. In the context of our long-term research program we will extend our research to plant symbiotic and free-living members of the genus Ochrobactrum. This analysis will provide fascinating novel insights into the different survival strategies that enable closely related bacteria to live in very different environments.