title: Molecular Characterisation and Co-cultivation of Bacterial Biofilm Communities Associated with the Mat-Forming Diatom Didymosphenia geminata.
abstract: Didymosphenia geminata (Lyngbye) M. Schmidt is a stalked freshwater diatom that is expanding its range globally. In some rivers, D. geminata forms thick and expansive polysaccharide-dominated mats. Like other stalked diatoms, D. geminata cells attach to the substratum with a pad of adhesive extracellular polymeric substance. Research on D. geminata and other diatoms suggests that bacterial biofilm composition may contribute to successful attachment. The aim of this study was to investigate the composition and role of bacterial biofilm communities in D. geminata attachment and survival. Bacterial biofilms were collected at four sites in the main stem of a river (containing D. geminata) and in four tributaries (free of D. geminata). Samples were characterised using automated rRNA intergenic spacer analysis and high-throughput sequencing (HTS). Mat-associated bacteria were isolated and their effect on the early establishment of D. geminata cells assessed using co-culturing experiments. ARISA and HTS data showed differences in bacterial communities between samples with and without D. geminata at two of the four sites. Samples with D. geminata had a higher relative abundance of Sphingobacteria (p < 0.01) and variability in community composition was reduced. Analysis of the 76 bacteria isolated from the mat revealed 12 different strains representing 8 genera. Co-culturing of a Carnobacterium sp. with D. geminata reduced survival (p < 0.001) and attachment (p < 0.001) of D. geminata. Attachment was enhanced by Micrococcus sp. and Pseudomonas sp. (p < 0.001 and p < 0.01, respectively). These data provide evidence that bacteria play a role in the initial attachment and on-going survival of D. geminata, and may partly explain observed distribution patterns.
authors.affiliation: Cawthron Institute, Private Bag 2, Nelson, 7001, New Zealand.|Department of Biology, University of Konstanz, 78457, Konstanz, Germany.
authors.forename: Josephin
authors.initials: J
authors.lastname: Brandes
authors.affiliation: Cawthron Institute, Private Bag 2, Nelson, 7001, New Zealand.
authors.forename: Jeanne M
authors.initials: JM
authors.lastname: Kuhajek
authors.affiliation: Cawthron Institute, Private Bag 2, Nelson, 7001, New Zealand.
authors.forename: Eric
authors.initials: E
authors.lastname: Goodwin
authors.affiliation: Cawthron Institute, Private Bag 2, Nelson, 7001, New Zealand. susie.wood@cawthron.org.nz.|Environmental Research Institute, University of Waikato, Private Bag 3105, Hamilton, 3240, New Zealand. susie.wood@cawthron.org.nz.
authors.forename: Susanna A
authors.initials: SA
authors.lastname: Wood
mesh_terms: D001419:Bacteria / Q000145:classification / Q000235:genetics* / Q000254:growth & development / Q000302:isolation & purification; D018407:Bacterial Physiological Phenomena / Q000235:genetics; D001483:Base Sequence; D018441:Biofilms; D056573:Carnobacterium / Q000254:growth & development; D002448:Cell Adhesion; D018920:Coculture Techniques; D004269:DNA, Bacterial; D017377:Diatoms / Q000235:genetics* / Q000254:growth & development / Q000382:microbiology* / Q000502:physiology; D005618:Fresh Water / Q000382:microbiology*; D059014:High-Throughput Nucleotide Sequencing; D009520:New Zealand; D010802:Phylogeny; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D045483:Rivers / Q000382:microbiology; D045249:Sphingobacterium; D014871:Water Microbiology
chemical_list: D004269:DNA, Bacterial; D012336:RNA, Ribosomal, 16S
keywords: 16S rRNA gene sequences; Automated rRNA intergenic spacer analysis; High-throughput sequencing; Rivers