Comparative Genome Analysis And Expression Of Agarases Of Catenovulum Agarivorans YM01~T

Marine microbes play significant roles in accelerating the marine carbon cycle feedback through respiration. Catenovulum agarivorans YMO1T, being identified as a novel genus and species, demonstrated significant carbohydrate degrading activities and produced highly thermostable agarases. The genome of this bacterium had been sequenced previously and 15 putative agarases-coding genes were found. In this study, more extensive genomic analysis and comparisons were performed to identify the agarases and explore the potential roles of YM01T in marine carbon cycle.The whole genome of YM01T is composed of a single chromosome of 5,025,099 base pairs containing 4215 open reading frames. Compared with other agar-degrading strains, YM01T contains more specific genes assigned to carbohydrate transport and metabolism as well as signal transduction mechanisms. The identification of carbohydrate-active enzymes unveiled that Catenovulum strains YM01T and DS2 harbored more proportion of CAZymes (10.70% and 17.12%, respectively) in their genomes and demonstrated significant genetic advantages in the utilization of starch, cellulose, gellan, agarose, xylogulan and pectin. Among the 15 putative agarase genes,10 agarase genes of YM01T had been cloned and expressed, and three of which were confirmed agarolytic activity in vitro. The GH50 agarase YM01-5 was purified and characterized, whose molecule weight is 91.6kDa and isoelectric point is 5.31. YM01-5 showed maximum activity at 37℃ and pH 9.0. The Km and Vmax value of YM01-5 was 222.2 mg/mg and 20.8U/mg, respectively. SDS, Ni2+ inhibited the agarolytic activity of YM01-5, while Mg2+ and Fe3+ promoted its activity. YM01-5 showed exo-hydrolytic activity and produced neoagarobiose as final product. In addition, genome analysis demonstrated that YM01T harbored 63 chemotaxis genes involved in signal recognition and transduction, excitation, adaptation and signal removal, reflecting a strong demand of YM01T to detect sensory stimuli in the marine environment.The genome of YM01T demonstrated evident genetic advantages in carbohydrates utilization and chemotaxis, indicating the metabolic flexibility of YM01T to acquire energy from variety carbon sources and accelerate the carbon cycle feedback in marine environment. The identification of agarases in YM01T provides a better understanding of its agarolytic system and also shows an extensive application prospect of it.