Genome Sequence of Microbulbifer thermotolerans HB226069 Reveals Its Versatility to Degrade Multiple Polysaccharides and Determination of the Alginate Lyases

Abstract

Polysaccharide-degrading bacteria are key participants in the global carbon cycle and algal biomass recycling. Herein, a polysaccharide lyase-producing strain HB226069 was isolated from Sargassum sp. from QingGe Port, Hainan, China. Results of the phylogenetic of 16S rRNA gene and genotypic analysis clearly indicate that the isolate should be classified as Microbulbifer thermotolerans. The whole genome is a 4,021,337 bp circular chromosome with the G + C content of 56.5%. Analysis of the predicted genes indicates that strain HB226069 encodes 161 CAZymes, and abundant putative enzymes involved in polysaccharide degradation were predicted, including alginate lyase, fucosidase, agarase, xylanase, cellulase, pectate lyase, amylase, and chitinase. Three of the putative polysaccharide lyases from PL7 and PL17 families were involved in alginate degradation. The alginate lyases of strain HB226069 showed the maximum activity 117.4 U/mL at 50°C, pH 7.0 and 0.05 M FeCl3, while exhibited the best stability at 30°C and pH 7.0. The thin layer chromatography (TLC) and Electrospray Ionization Mass Spectrometry (ESI-MS) analysis indicated that the alginate oligosaccharide degraded by the partially purified alginate lyases contained oligosaccharides of DP2-DP5 and monosaccharide while reacting for 36 h. The complete genome of M. thermotolerans HB226069 enriches our understanding of the mechanism of polysaccharide lyase production and provides support for its potential application in polysaccharide degradation.