Abstract
Phaeobacter inhibens 2.10 is an effective biofilm former and colonizer of marine surfaces and has the ability to outcompete other microbiota. During biofilm dispersal P. inhibens 2.10 produces heritable phenotypic variants, including those that have a reduced ability to inhibit the co-occurring bacterium Pseudoalteromonas tunicata. However, the genetic changes that underpin the phenotypic variation and what the ecological consequences are for variants within the population are unclear. To answer these questions we sequenced the genomes of strain NCV12a1, a biofilm variant of P. inhibens 2.10 with reduced inhibitory activity and the P. inhibens 2.10 WT parental strain. Genome wide analysis revealed point mutations in genes involved in synthesis of the antibacterial compound tropodithietic acid (TDA) and indirectly in extracellular polymeric substances (EPS) production. However, confocal laser scanning microscopy analyses found little differences in biofilm growth between P. inhibens 2.10 WT (parental) and NCV12a1. P. inhibens NCV12a1 was also not outcompeted in co-cultured biofilms with P. tunicata, despite its reduced inhibitory activity, rather these biofilms were thicker than those produced when the WT strain was co-cultured with P. tunicata. Notably, dispersal populations from biofilms of P. inhibens NCV12a1 had a higher proportion of WT-like morphotypes when co-cultured with P. tunicata. These observations may explain why the otherwise non-inhibiting variant persists in the presence of a natural competitor, adding to our understanding of the relative importance of genetic diversification in microbial biofilms.
Highlights
Natural microbial biofilms are complex, highly structured communities enclosed within a selfproduced matrix and are ubiquitous on all surfaces within aqueous environments (Davey and O’Toole, 2000; Dang et al, 2008)
Phenotypic Variation in Phaeobacter inhibens Biofilms from parental cells. This phenomenon of dispersal variation has been observed for a number of bacterial taxa, including Pseudomonas aeruginosa (Webb et al, 2004; Kirisits et al, 2005; Luján et al, 2011), Pseudomonas fluorescens (SanchezContreras et al, 2002; Sauer et al, 2002), Pseudomonas putida (Hansen et al, 2007), Serratia marcescens (Koh et al, 2007), Pseudoalteromonas tunicata (Mai-Prochnow et al, 2006), Vibrio cholerae (Matz et al, 2005), and Phaeobacter inhibens 2.10 (Lutz et al, 2016), where characteristics such as competitive fitness, colony morphology, colonization ability, and growth vary between individuals of the dispersing population
One of the mutations was in a region of the genome related to tropodithietic acid (TDA) synthesis and the second was in a gene related to cell wall recycling and linked to extracellular polymeric substances (EPS) production (Table 1), suggesting these functions are directly or indirectly related to the decrease in competitive fitness previously reported for this strain (Lutz et al, 2016)
Summary
Natural microbial biofilms are complex, highly structured communities enclosed within a selfproduced matrix and are ubiquitous on all surfaces within aqueous environments (Davey and O’Toole, 2000; Dang et al, 2008). Genome sequencing and comparative analysis was performed to identify the underlying genetic changes associated with the P. inhibens NCV12a1 variant strain.
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