title: An efficient screening method for the isolation of heterotrophic bacteria influencing growth of diatoms under photoautotrophic conditions.
abstract: Interactions between photoautotrophic diatoms and heterotrophic bacteria are important for the biogeochemical C-cycle in the oceans. Additionally, biofilms formed by diatoms and bacteria are the initiating step of biofouling processes, which causes high costs in shipping. Despite this ecological and economical importance, the knowledge about biochemical and molecular mechanisms underlying these interkingdom interactions is relatively small. For analyzing these mechanisms, laboratory model systems are required. In this study, an efficient screening method for isolating bacteria influencing photoautotrophic diatom growth was established. First, diatom cultures of Phaeodactylum tricornutum and Thalassiosira pseudonana were made axenic by applying β-lactam antibiotics. Second, a non-invasive method for measuring growth of multiple parallel diatom cultures by chlorophyll fluorescence was established. This method allowed semi-quantitative chlorophyll determination of cultures with up to 3 μg (chlorophyll) ml(-1). Axenic diatom cultures were then used for enriching bacteria and led to the isolation of 24 strains influencing growth of both diatom strains in various ways. For example, Rheinheimera sp. strain Tn16 inhibited growth of T. pseudonana, while it stimulated growth and cell aggregation of P. tricornutum. Thus, this screening method is appropriate for isolating heterotrophic bacteria showing different interactions with different diatom species ranging from synergistic to antagonistic. In consecutive applications, this method will be useful to screen for bacterial mutants with altered phenotypes regarding the influence on diatom growth.
authors.affiliation: Westfälische Wilhelms-Universität Münster, Institut für Molekulare Mikrobiologie und Biotechnologie, Corrensstr. 3, 48149 Münster, Germany.
authors.forename: Karsten
authors.initials: K
authors.lastname: Zecher
authors.affiliation: Westfälische Wilhelms-Universität Münster, Institut für Molekulare Mikrobiologie und Biotechnologie, Corrensstr. 3, 48149 Münster, Germany.
authors.forename: Nina
authors.initials: N
authors.lastname: Jagmann
authors.affiliation: Institut für Werkstoffsystemtechnik, Thurgau an der Hochschule Konstanz (WITg), Konstanzer Straße 19, CH - 8274 Tägerwilen.
authors.forename: Philipp
authors.initials: P
authors.lastname: Seemann
authors.affiliation: Westfälische Wilhelms-Universität Münster, Institut für Molekulare Mikrobiologie und Biotechnologie, Corrensstr. 3, 48149 Münster, Germany. Electronic address: bodo.philipp@uni-muenster.de.
authors.forename: Bodo
authors.initials: B
authors.lastname: Philipp
mesh_terms: D052818:Autotrophic Processes / Q000528:radiation effects; D001419:Bacteria / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism / Q000528:radiation effects; D002734:Chlorophyll / Q000378:metabolism; D017377:Diatoms / Q000737:chemistry / Q000254:growth & development* / Q000378:metabolism / Q000382:microbiology*; D005470:Fluorometry / Q000379:methods*; D052836:Heterotrophic Processes / Q000528:radiation effects; D008027:Light
chemical_list: D002734:Chlorophyll
keywords: Bacteria–diatom interaction; Biofilm; Biofouling; Chlorophyll fluorescence quantification; Marine heterotrophic bacteria; Microbial co-culture