Abstract
Our understanding of microbial natural environments combines in situ experimentation with studies of specific interactions in laboratory-based setups. The purpose of this work was to develop, build and demonstrate the use of a microbial culture chamber enabling both in situ and laboratory-based studies. The design uses an enclosed chamber surrounded by two porous membranes that enables the comparison of growth of two separate microbial populations but allowing free exchange of small molecules. Initially, we tested if the presence of the macroalga Fucus vesiculosus inside the chamber affected colonization of the outer membranes by marine bacteria. The alga did indeed enrich the total population of colonizing bacteria by more than a factor of four. These findings lead us to investigate the effect of the presence of the coccolithophoric alga Emiliania huxleyi on attachment and biofilm formation of the marine bacterium Phaeobacter inhibens DSM17395. These organisms co-exist in the marine environment and have a well-characterized interdependence on secondary metabolites. P. inhibens attached in significantly higher numbers when having access to E. huxleyi as compared to when exposed to sterile media. The experiment was carried out using a wild type (wt) strain as well as a TDA-deficient strain of P. inhibens. The ability of the bacterium to produce the antibacterial compound, tropodithietic acid (TDA) influenced its attachment since the P. inhibens DSM17395 wt strain attached in higher numbers to a surface within the first 48 h of incubation with E. huxleyi as compared to a TDA-negative mutant. Whilst the attachment of the bacterium to a surface was facilitated by presence of the alga, however, we cannot conclude if this was directly affected by the algae or whether biofilm formation was dependent on the production of TDA by P. inhibens, which has been implied by previous studies. In the light of these results, other applications of immersed culture chambers are suggested.
Highlights
Communities of marine bacteria are known to live in association with and colonize the surface of macro algae
Biofilm Formation Enriched by the Presence of Fucus vesiculosus
Enrichment of the biofilm was observed on the open, experimental membrane relative to the outer surface of the PAO membrane without a connection to the central chamber
Summary
Communities of marine bacteria are known to live in association with and colonize the surface of macro algae. Some algae such as Fucus vesiculosus, produce a range of chemical compound to attract a specific mixed bacterial community (Wahl, 1989; Lachnit et al, 2010, 2013; Saha et al, 2011). Over the past decade, studied the interactions between the marine bacterium, Phaeobacter inhibens and other bacteria, especially those that are fish pathogenic (Prol et al, 2009; D’Alvise et al, 2012; Prol García et al, 2014; Grotkjær et al, 2016; Porsby and Gram, 2016). P. inhibens is a common part of the microbiota in marine aquaculture and has potential as a fish probiotic due to production of a small antibacterial compound, tropodithietic acid (TDA)
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