New Multidrug Efflux Systems in a Microcystin-Degrading Bacterium and Its Genomic Feature.

A microcystin-degrading bacterial strain, T2, was isolated from the culture of a microalgae . The strain T2 is Gram-stain-negative, non-motile, aerobic, non-spore-forming and phototrophic. The cells of T2 are able to grow in ranges of temperature from 15 to 37 °C, with a pH of 6 to 8 and a salinity of 0 to 1% NaCl. Here, we sequenced the complete genome of T2, aiming to better understand the evolutionary biology and the function of the genus at the molecular level. The complete genome of . T2 contained a circular chromosome (3,977,381 bp) with 64.3% GC content and a sizable plasmid (145.829 bp) with 60.7% GC content which comprises about 3.5% of the total genetic content. A total of 3842 coding genes, including 46 tRNAs and 6 rRNAs, were predicted in the genome. The genome contains genes for glycolysis, citric acid cycle, Entner-Doudoroff pathways, photoreaction center and bacteriochlorophyll synthesis. A 7.9 K gene cluster containing , , and of microcystin-degrading enzymes was identified. Notably, eight different efflux pumps categorized into RND, ABC and MFS types have been identified in the genome of strain T2. Our findings should provide new insights of the alternative reaction pathway as well as the enzymes which mediated the degradation of microcystin by bacteria, as well as the evolution, architectures, chemical mechanisms and physiological roles of the new bacterial multidrug efflux system.