Bacterial community dynamics during polysaccharide degradation at contrasting sites in the S outhern and A tlantic O ceans

Abstract

Summary The bacterial degradation of polysaccharides is central to marine carbon cycling, but little is known about the bacterial taxa that degrade specific marine polysaccharides. Here, bacterial growth and community dynamics were studied during the degradation of the polysaccharides chitin, alginate and agarose in microcosm experiments at four contrasting locations in the S outhern and A tlantic O ceans. At the Southern polar front, chitin‐supplemented microcosms were characterized by higher fractions of actively growing cells and a community shift from A lphaproteobacteria to G ammaproteobacteria and B acteroidetes . At the A ntarctic ice shelf, chitin degradation was associated with growth of B acteroidetes , with 24% higher cell numbers compared with the control. At the P atagonian continental shelf, alginate and agarose degradation covaried with growth of different A lteromonadaceae populations, each with specific temporal growth patterns. At the M auritanian upwelling, only the alginate hydrolysis product guluronate was consumed, coincident with increasing abundances of A lteromonadaceae and possibly cross‐feeding SAR 11. 16 S rRNA gene amplicon libraries indicated that growth of the B acteroidetes ‐affiliated genus R eichenbachiella was stimulated by chitin at all cold and temperate water stations, suggesting comparable ecological roles over wide geographical scales. Overall, the predominance of location‐specific patterns showed that bacterial communities from contrasting oceanic biomes have members with different potentials to hydrolyse polysaccharides.

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