Phage Resistance of a Marine Bacterium, Roseobacter denitrificans OCh114, as Revealed by Comparative Proteomics
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Roseobacter is a dominant lineage in the marine environment. This group of bacteria is diverse in terms of both their phylogenetic composition and their physiological potential. Roseobacter denitrificans OCh114 is one of the most studied bacteria of the Roseobacter lineage. Recently, a lytic phage (RDJLΦ1) that infects this bacterium was isolated and a mutant strain (M1) of OCh114 that is resistant to RDJLΦ1 was also obtained. Here, we investigate the mechanisms supporting phage resistance of M1. Our results excluded the possibilities of several phage resistance mechanisms, including abortive infection, lysogeny, and the clustered regularly interspaced short palindromic repeats (CRISPRs) related mechanism. Adsorption kinetics assays revealed that adsorption inhibition might be a potential cause for the phage resistance of M1. Comparative proteomic analysis of M1 and OCh114 revealed significant changes in the membrane protein compliment of these bacteria. Five membrane proteins with important biological functions were significantly down-regulated in the phage-resistant M1. Meanwhile, several outer membrane porins with different modifications and an OmpA family domain protein were markedly up-regulated. We hypothesize that the down-regulated membrane proteins in M1 may serve as the potential phage receptors, whose absence prevented the adsorption of phage RDJLΦ1 to host cells and subsequent infection.
KeywordsAdsorption Inhibition Aerobic Anoxygenic Phototrophic Bacterium Outer Membrane Porin Phage Resistance Abortive Infection
We are grateful to Prof. Steven W. Wilhelm (University of Tennessee, USA) for his constructive comments during the review process. This study was supported by the MOST project (2007CB815904), NSFC projects (40632013 and 40806052), and SOA project (200805068). Yongyu Zhang was supported by the MEL Young Scientist Visiting Fellowship (MELRS0931) and the Key Science and Technology Project of Fujian Province, China (No. 2009Y0044).
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