Abstract
The discovery of secondary metabolites from marine microorganisms is beset by numerous challenges including difficulties cultivating and subsequently eliciting expression of biosynthetic genes from marine microbes in the laboratory. In this paper, we describe a method of culturing three species from the marine bacterial genus Pseudoalteromonas using cotton scaffold supplemented liquid media. This simple cultivation method was designed to mimic the natural behavior of some members of the genus wherein they form epibiotic/symbiotic associations with higher organisms such as sponges and corals or attach to solid structures as a biofilm. Our scaffolded cultivation is highly effective at stimulating an attachment/biofilm phenotype and causes large changes to metabolite profiles for the microbes investigated. Metabolite changes include alteration to the production levels of known molecules such as violacein, thiomarinol A, and the alterochromide and prodiginine families of molecules. Finally and critically, our technique stimulates the production of unknown compounds that will serve as leads for future natural product discovery. These results suggest our cultivation approach could potentially be used as a general strategy for the activation of silent gene clusters in marine microbes to facilitate access to their full natural product biosynthetic capacity.
Highlights
Mining of microbes for bioactive natural products has resulted in the discovery of a plethora of valuable pharmaceutically relevant compounds (Newman & Cragg, 2016)
To obtain greater access to the encoded secondary metabolites of marine bacteria such as Pseudoalteromonas luteoviolacea, we sought to grow bacteria in conditions resembling those in their native habitat by making a simple modification to laboratory culturing conditions
We have found that addition of a cotton scaffold to standard marine bacterial growth media is an effective technique to promote attachment and biofilm formation
Summary
Mining of microbes for bioactive natural products has resulted in the discovery of a plethora of valuable pharmaceutically relevant compounds (Newman & Cragg, 2016). Marine microorganisms are obligate symbionts with other marine organisms or form biofilms when settled on surfaces Species adapted to these modes of life can be challenging to culture in vitro, and they may differentially express natural product biosynthetic gene clusters under standard laboratory conditions (Berrue, Withers, Haltli, Withers, & Kerr, 2011; Stewart, 2012). We detail the effect of cultivation with a cotton scaffold on biofilm formation and the production of the known metabolites violacein, thiomarinol A, the alterochromides, and the prodiginines (Figure 1) by three bacterial species, Pseudoalteromonas luteoviolacea 2ta (Maansson et al, 2016; Yang, Xiong, Lee, Qi, & Qian, 2007), P. piscicida JCM 20779 We describe global changes in metabolite profiles for the microbes investigated
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