Bacteriocins and the assembly of natural Pseudomonas fluorescens populations

Abstract

When competing for space and resources, bacteria produce toxins known as bacteriocins to gain an advantage over competitors. Recent studies in the laboratory have confirmed theoretical predictions that bacteriocin production can determine coexistence, by eradicating sensitive competitors or driving the emergence of resistant genotypes. However, there is currently limited evidence that bacteriocin-mediated competition influences the coexistence and distribution of genotypes in natural environments, and what factors drive interactions towards inhibition remain unclear. Using natural soil populations of Pseudomonas fluorescens, we assessed the ability of the isolates to inhibit one another with respect to spatial proximity in the field, genetic similarity and niche overlap. The majority of isolates were found to produce bacteriocins; however, widespread resistance between coexisting isolates meant relatively few interactions resulted in inhibition. When inhibition did occur, it occurred more frequently between ecologically similar isolates. However, in contrast with results from other natural populations, we found no relationship between the frequency of inhibition and the genetic similarity of competitors. Our results suggest that bacteriocin production plays an important role in mediating competition over resources in natural settings and, by selecting for isolates resistant to local bacteriocin production, can influence the assembly of natural populations of P. fluorescens.

Environmental determinants of pyoverdine production, exploitation and competition in natural Pseudomonas communities

“…Observation (c), meanwhile, could be the result of ponds being more open systems, where strain mixing is conceivably high due to the more diffusive and less structured environment, and where new strains can easily be introduced from the surrounding (terrestrial) habitats. Contrary to soils, where local adaptation has been observed (Bruce et al ., ), increased strain mixing and the potential source‐sink dynamics between soil and pond habitats might even out local variation in community composition in ponds.…”

Sources and survival ofListeria monocytogeneson fresh, leafy produce

“…This effect could be due to competition for nutrients and space combined with inhibitory bacteriocins which are produced by soil bacteria to kill or inhibit the growth of competitors (Bruce et al . ), meaning that a large inoculum is not sustainable in the soil. Survival has been shown to be dependent on soil type and abiotic factors such as soil texture (especially clay content), pH and basic cation saturation ratio appear to be significant drivers of L. monocytogenes survival in soil (Locatelli et al .…”

Probiotic potential of thermotolerant lactic acid bacteria isolated from “Gari “a cassava-based African fermented food

“…This suggests that L. plantarum SB1 and L. acidophilus SB4 can be used not only against intestinal or foodborne pathogenic microorganisms but also against food spoilage bacteria such as Listeria monocytogenes. The inhibitory activity of probiotic bacteria against pathogenic is associated to the production of organic acid or mostly the production of antimicrobial proteins called bacteriocins [18][19][20][21][22][23][24]. For the isolates selected in this study, further studies need to be done in order to characterize and identify the nature of their antimicrobials molecules released during growth.…”