Extracellular Polymeric Substance Architecture Influences Natural Genetic Transformation of Acinetobacter baylyi in Biofilms

Abstract

Genetic exchange by natural transformation is an important mechanism of horizontal gene transfer in biofilms. Thirty-two biofilm metrics were quantified in a heavily encapsulated Acinetobacter baylyi strain and a miniencapsulated mutant strain, accounting for cellular architecture, extracellular polymeric substances (EPS) architecture, and their combined biofilm architecture. In general, transformation location, abundance, and frequency were more closely correlated to EPS architecture than to cellular or combined architecture. Transformation frequency and transformant location had the greatest correlation with the EPS metric surface area-to-biovolume ratio. Transformation frequency peaked when EPS surface area-to-biovolume ratio was greater than 3 m 2 /m 3 and less than 5 m 2 /m 3 . Transformant location shifted toward the biofilm-bulk fluid interface as the EPS surface area-to-biovolume ratio increased. Transformant biovolume was most closely correlated with EPS biovolume and peaked when transformation occurred in close proximity to the substratum. This study demonstrates that biofilm architecture influences A. baylyi transformation frequency and transformant location and abundance. The major role of EPS may be to facilitate the binding and stabilization of plasmid DNA for cellular uptake.

Extracellular DNA in natural environments: features, relevance and applications

“…Merod and Wuertz 2014; Wang et al 2002) and was found to occur frequently, as biofilms are hotspots, i.e. offer ideal conditions for HGT including high cell density, increased genetic competence and an accumulation of exDNA.…”

Helicobacter pylori Biofilm Formation and Its Potential Role in Pathogenesis

“…In addition to antibiotic tolerance, biofilms often represent a reservoir of genetic diversity by promoting genetic exchange between different subpopulations. Several studies have documented the increased dissemination of antibiotic resistance genes in biofilms through horizontal gene transfer, integrative conjugative elements, and natural transformation (102)(103)(104). Additionally, bacterial cells within biofilms undergo several stressful conditions, including major nutrient starvation, which could increase the mutation frequency and the emergence of antibiotic-resistant mutant strains (8,69,105,106).…”

The Social Life of Aeromonas through Biofilm and Quorum Sensing Systems

“…The analysis of “transformability” and “donatability” between Aeromonas strains showed that transformation of groups was constrained to phylogroups (Huddleston et al, 2013), consistent with some population studies that have highlighted HGT between close relatives in the genus Aeromonas (Silver et al, 2011; Roger et al, 2012b). The high concentration of extracellular DNA within a biofilm may facilitate the transformation of Aeromonas , as in other bacteria capable of natural transformation (Merod and Wuertz, 2014). …”