Microbial Communities Associated with the White Sea Red Algae as a Source of Xylanolytic Microorganisms

Abstract: Microorganisms associated with algae and able to utilize complex substrates (e.g., plant heteropolysaccharides) may be important producers of hydrolytic enzymes. The microbial communities of the red algae Corallina sp. and Phyllophora sp. sampled in the Kandalaksha Gulf basin of the White Sea were analyzed using high-throughput sequencing of the V4-variable region of the 16S rRNA gene. The dominant phyla in microbiomes of both samples were Pseudomonadota and Bacteroidota (GTDB classification, https://gtdb.ecogenomic.org/). For the Corallina sp. sample, dominance of the Vibrio, Agarivorans, and Photobacterium genera was shown, while Granulosicoccus and Aliivibrio dominated in the Phyllophora sp. sample. The analyzed red macroalgae with associated microbiota were used as an inocula to obtain microbial enrichment cultures growing on β-1,4-xylan or β-1,3-glucan (curdlan). It was shown that, similar to environmental samples Pseudomonadota and Bacteroidota phyla representatives were prevalent in all enrichment cultures. However, unlike the environmental samples, in the enrichment cultures the dominant genera were Marinomonas, Reinekea, Polaribacter, and Pseudoalteromonas. The latter, as well as the representatives of Vibrio sp., were isolated in pure cultures for which the xylanolytic activity was shown.