title: A bacterial culture-independent method to investigate chemically mediated control of bacterial epibiosis in marine invertebrates by using TRFLP analysis and natural bacterial populations.
abstract: It has been postulated that a variety of physically undefended marine invertebrates have evolved strategies to control microbial epibiosis chemically. Ecologically meaningful experiments that demonstrate chemically mediated antibacterial effects are difficult due to the small number of cultivable bacteria. Based on the example of three sponges, this study introduces a culture-independent methodology to investigate chemically mediated control of bacterial epibiosis by analyzing the natural bacterial consortia. Organic extracts of sponges were immobilized in hydrogels at tissue level concentrations and exposed to the same source of natural seawater for bacterial colonization. Terminal restriction fragment length polymorphism analysis of polymerase chain reaction-amplified bacterial community DNA obtained from these gels was shown to be a useful tool to study bacterial community shifts in response to sponge metabolites by comparing bacterial ribotypes obtained from the gel surfaces. Several terminal restriction fragments were absent relative to the control suggesting that settlement of specific bacteria was prevented. On the other hand, additional fragments occurred in some treatments, coinciding with higher bacterial abundance evidenced by DAPI counts of bacterial cells, indicating the bacterial utilization of sponge extract components. The advantages of this method are (1) a culture-independent approach, i.e. the assessment of antimicrobial activities against natural bacterial communities, (2) no restriction to particular modes of microbial colonization, i.e. antibiotic and repellant, and (3) the in situ assessment of antimicrobial compounds under flow conditions.
authors.affiliation: Institute for Chemistry and Biology of the Marine Environment, Carl von Ossietzky University, Oldenburg, Germany.
authors.forename: Tilmann
authors.initials: T
authors.lastname: Harder
authors.forename: Stanley Chun Kwan
authors.initials: SC
authors.lastname: Lau
authors.forename: Wai-Yee
authors.initials: WY
authors.lastname: Tam
authors.forename: Pei-Yuan
authors.initials: PY
authors.lastname: Qian
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001419:Bacteria / Q000145:classification / Q000235:genetics / Q000254:growth & development / Q000302:isolation & purification; D001422:Bacterial Adhesion; D018914:Cells, Immobilized; D017753:Ecosystem; D020100:Hydrogels; D007448:Invertebrates / Q000737:chemistry / Q000382:microbiology; D008386:Marine Biology; D008826:Microbial Sensitivity Tests; D016133:Polymerase Chain Reaction; D012150:Polymorphism, Restriction Fragment Length; D011161:Porifera / Q000737:chemistry* / Q000382:microbiology*
chemical_list: D000900:Anti-Bacterial Agents; D020100:Hydrogels