title: Response of bacterial communities from California coastal waters to alginate particles and an alginolytic Alteromonas macleodii strain.
abstract: Alginate is a major cell wall polysaccharide from marine macroalgae and nutrient source for heterotrophic bacteria. Alginate can form gel particles in contact with divalent cations as found in seawater. Here, we tested the hypothesis that alginate gel particles serve as carbon source and microhabitat for marine bacteria by adding sterile alginate particles to microcosms with seawater from coastal California, a habitat rich in alginate-containing macroalgae. Alginate particles were rapidly colonized and degraded, with three- to eightfold higher bacterial abundances and production among alginate particle-associated (PA) bacteria. 16S rRNA gene amplicon sequencing showed that alginate PA bacteria were enriched in OTUs related to Cryomorphaceae, Saprospiraceae (Bacteroidetes) and Phaeobacter (Alphaproteobacteria) towards the end of the experiment. In microcosms amended with alginate particles and the proficient alginolytic bacterium Alteromonas macleodii strain 83-1, this strain dominated the community and outcompeted Cryomorphaceae, Saprospiraceae and Phaeobacter, and PA hydrolytic activities were over 50% higher. Thus, alginolytic activity by strain 83-1 did not benefit non-alginolytic strains by cross-feeding on alginate hydrolysis or other metabolic products. Considering the global distribution and extensive biomass of alginate-containing macroalgae, the observed bacterial dynamics associated with the utilization and remineralization of alginate microhabitats promote the understanding of carbon cycling in macroalgae-rich waters worldwide.
authors.affiliation: Institute for Chemistry and Biology of the Marine Environment, University of Oldenburg, 26129 Oldenburg, Germany.
authors.forename: Maximilian
authors.initials: M
authors.lastname: Mitulla
authors.affiliation: Marine Biology Research Division, Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA, 92037, USA.|Laboratoire d'Oceanographie Microbienne (LOMIC), Observatoire Océanologique de Banyuls sur mer, Sorbonne Universités, UPMC, France.
authors.forename: Julie
authors.initials: J
authors.lastname: Dinasquet
authors.affiliation: Marine Biology Research Division, Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA, 92037, USA.
authors.forename: Ryan
authors.initials: R
authors.lastname: Guillemette
authors.affiliation: Institute for Chemistry and Biology of the Marine Environment, University of Oldenburg, 26129 Oldenburg, Germany.
authors.forename: Meinhard
authors.initials: M
authors.lastname: Simon
authors.affiliation: Marine Biology Research Division, Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA, 92037, USA.
authors.forename: Farooq
authors.initials: F
authors.lastname: Azam
authors.affiliation: Institute for Chemistry and Biology of the Marine Environment, University of Oldenburg, 26129 Oldenburg, Germany.
authors.forename: Matthias
authors.initials: M
authors.lastname: Wietz
mesh_terms: D000464:Alginates / Q000378:metabolism*; D020591:Alteromonas / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D001419:Bacteria / Q000145:classification / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D002140:California; D017753:Ecosystem; D020723:Glucuronic Acid / Q000378:metabolism; D006603:Hexuronic Acids / Q000378:metabolism; D010802:Phylogeny; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D012623:Seawater / Q000382:microbiology*
chemical_list: D000464:Alginates; D006603:Hexuronic Acids; D012336:RNA, Ribosomal, 16S; D020723:Glucuronic Acid