Benefits of plasticity in biofilm production revealed
Researchers from Princeton University decode the advantages of flexible biofilm production strategies in a new study published in The ISME Journal
- Bacterial strains have evolved to specialize in biofilm formation or planktonic growth, or can transition between these states
- The ability to disperse biofilm biomass is crucial for effective transitioning between the biofilm and planktonic growth modes
- Bacteria possessing flexible biofilm production strategies are able to outcompete specialists under environmental conditions with high variation
The ability of bacteria to switch between biofilm and planktonic models of growth is well known, but the conditions favoring flexible versus fixed biofilm production are not fully understood. In a new study published in the ISME Journal, researchers from Princeton University investigated three strains of Vibrio cholerae with varying capacities for biofilm matrix production under different environmental conditions. The authors show that a fluctuating environment selects the wild-type strain with plastic biofilm production strategy over strains specialized in either biofilm or planktonic states. These results are consistent with the habitat conditions known to be important for V. chloreae in its natural state, for example during infection in the intestine.
Bacteria can grow in a free-swimming state, as planktonic cells, or in surface-attached communities, termed biofilms. The planktonic and biofilm growth modes differ dramatically with respect to spatial constraints, nutrient access, population density and cell–cell interactions. Fitness trade-offs underlie how successfully bacteria compete in each of these environments. Accordingly, some bacteria have evolved to be specialists in biofilm formation, while others specialize in planktonic growth. There are species, however, that possess flexible strategies: they can transition between the molecular programs required for biofilm formation and for planktonic growth. Such flexible strategies often sacrifice competitive ability against specialists in a given habitat. There is little exploration of the ecological conditions favoring the evolution of the flexible biofilm production strategy for bacteria in competition with specialist biofilm producers or specialist non-producers. Here, we study the human pathogen Vibrio cholerae, a flexible biofilm-former, as well as constitutive biofilm-producing and non-producing mutants. We assess the fitness of these strains under biofilm conditions, planktonic conditions and conditions that demand the ability to transition between the two growth modes. We show that, relative to the specialists, the wild type is superior at dispersal from biofilms to the planktonic phase; however, this capability comes at the expense of reduced competitive fitness against constitutive biofilm producers on surfaces. Wild-type V. cholerae can outcompete the constitutive biofilm producers and non-producers if habitat turnover is sufficiently frequent. Thus, selection for phenotypic flexibility in biofilm production depends on the frequency of environmental fluctuations encountered by bacteria.
Environmental fluctuation governs selection for plasticity in biofilm production. Jing Yan, Carey D Nadell and Bonnie L Bassler. The ISME Journal, 24 March 2017