AUTHOR=Pang Maoda , Lin Xiaoqin , Liu Jin , Guo Changming , Gao Shanshan , Du Hechao , Lu Chengping , Liu Yongjie 

TITLE=Identification of Aeromonas hydrophila Genes Preferentially Expressed after Phagocytosis by Tetrahymena and Involvement of Methionine Sulfoxide Reductases

JOURNAL=Frontiers in Cellular and Infection Microbiology

VOLUME=6

YEAR=2016

URL=https://www.frontiersin.org/journals/cellular-and-infection-microbiology/articles/10.3389/fcimb.2016.00199

DOI=10.3389/fcimb.2016.00199

ISSN=2235-2988

ABSTRACT=<p>Free-living protozoa affect the survival and virulence evolution of pathogens in the environment. In this study, we explored the fate of <italic>Aeromonas hydrophila</italic> when co-cultured with the bacteriovorous ciliate <italic>Tetrahymena thermophila</italic> and investigated bacterial gene expression associated with the co-culture. Virulent <italic>A. hydrophila</italic> strains were found to have ability to evade digestion in the vacuoles of this protozoan. In <italic>A. hydrophila</italic>, a total of 116 genes were identified as up-regulated following co-culture with <italic>T. thermophila</italic> by selective capture of transcribed sequences (SCOTS) and comparative dot-blot analysis. A large proportion of these genes (42/116) play a role in metabolism, and some of the genes have previously been characterized as required for bacterial survival and replication within macrophages. Then, we inactivated the genes encoding methionine sulfoxide reductases, <italic>msrA</italic>, and <italic>msrB</italic>, in <italic>A. hydrophila</italic>. Compared to the wild-type, the mutants Δ<italic>msrA</italic> and Δ<italic>msrAB</italic> displayed significantly reduced resistance to predation by <italic>T. thermophila</italic>, and 50% lethal dose (LD<sub>50</sub>) determinations in zebrafish demonstrated that both mutants were highly attenuated. This study forms a solid foundation for the study of mechanisms and implications of bacterial defenses.</p>