Project description:Biofilms are well organized, cooperating communities of microorganisms encased in a self-produced extracellular matrix, providing resilience against external stress such as antimicrobial agents and host defenses. A hallmark of biofilms is their phenotypic heterogeneity, which enhances the overall growth and survival of the community. In this study, we demonstrate that removing the genes encoding the key molecular chaperones DnaK and trigger factor disrupts protein homeostasis in Bacillus subtilis and leads to the formation of extremely mucoid biofilms with aberrant architecture, compromised structural integrity, and altered phenotypic heterogeneity. These changes include a drastic reduction in the motile subpopulation and an overrepresentation of matrix producers and endospores. Overproduction of poly-γ-glutamic acid contributed crucially to the mucoid phenotype and aberrant biofilm architecture. Elevated temperatures led to protein homeostasis impairment resulting in mucoid and aberrant biofilm phenotypes. Our findings suggest that disruption of protein homeostasis, whether due to the absence of molecular chaperones or environmental factors, constrain biofilm formation.
Project description:Interactions occurring in microbial communities can affect the fitness and adaptability of their individual members when facing changing environmental conditions. This study investigated the impact of interspecies interactions in selecting Bacillus thuringiensis variants emerging in biofilm and planktonic environments. During evolution experiments, a B. thuringiensis distinct phenotypic variant of B. thuringiensis frequently occurred, despite the presence of other species or culture setup. Remarkably, selection of this variant was significantly favored over its ancestor in biofilm settings and when coexisting with other species co-isolated from a wastewater facility, namely Pseudomonas defluvii and Pseudomonas brenneri. Interestingly, the evolved phenotype did not show higher biofilm productivity than its ancestor under any condition, while it was indeed reduced in mixed-species biofilms. Such observation aligned with the reduced abundance of TasA, a major biofilm matrix component in Bacillus species, and SpoVG, a regulator of sporulation, as revealed by matrix proteomics analysis. Furthermore, the variant showed shorter generation time and a lack of sporulation compared to its ancestor, consistent with mutations in key genes for regulating sporulation. Our results indicate that interspecies interactions within biofilms promote B. thuringiensis diversification and alter traits such as biofilm matrix production. Although sporulation is a survival mechanism, this study provides evidence that sporulation does not confer a fitness advantage in in vitro biofilm setting, even within mixed cultures, in the absence of severe stress.
Project description:The objective of the current study was to understand the glutaraldehyde resistance mechanisms in P. fluorescens and P. aeruginosa biofilms. Glutaraldehyde is a common biocide used in various industries to control the microbial growth. Recent reports of emergence of glutaraldehyde resistance in several bacterial species motivated this study to understand the genetic factors responsible got glutaraldehyde resistance. Using a combination of phenotypic assays, chemical genetic assays and RNA-seq, we demonstrate that novel efflux pump, polyamine biosynthesis, lipid biosynthesis and phosphonate degradation play significant role in glutaraldehyde resistance and post-glutaraldehyde recovery of Psudomonad biofilms.
Project description:Stenotrophomonas maltophilia K279a diverges into subpopulations with distinct but reversible phenotypes of small and big colonies when challenged with ampicillin. This observation is consistent with the formation of long cell chains during exponential growth phase and the occurrence of mainly coccoid– or rod-shaped cells in liquid media. Further, scanning electron micrographs of SMK279a revealed that cells formed gigantic outer membrane vesicles in response to β-lactam treatment. RNA-seq analysis of small vs. big colonies unveiled that cells regulate at least seven genes differentially among colony morphotypes. Among those were the blaL1 and blaL2 genes the most strongly regulated ones with an eleven- and six-fold increased transcription, respectively. Further studies with promoter fusions of blaL1 and blaL2 genes implied that expression of both genes is also subject to high levels of phenotypic heterogeneous expression on a single cell level. Additional RNA-seq analysis of this homogenously versus heterogeneously blaL2 expressing cells identified comE homologue as differentially expressed, in which by the expression of extra copies of comE in S. maltophilia K279a reduced the level of those cells that were in a blaL2-ON model to 1% or lower. Together with genome-wide sequence analysis of cells from the different colony morphotypes, the data presented here suggests that phenotypic heterogeneity in S. maltophilia K279a is a result of non-genetic variations within isogenic populations and also polymorphisms in this strain do not influence β-lactamase resistance phenotype.
Project description:Biofilms are closely packed cells held and shielded by extracellular matrix composed of structural proteins and exopolysaccharides (EPS). As matrix components are costly to produce and shared within the population, EPS-deficient cells can act as cheaters by gaining benefits from the cooperative nature of EPS producers. Remarkably, genetically programmed EPS producers can also exhibit phenotypic heterogeneity at single-cell level. Previous studies have shown that spatial structure of biofilms limits the spread of cheaters, but the long-term influence of cheating on biofilm evolution is not well understood. Here, we examine the influence of EPS nonproducers on evolution of matrix production within the populations of EPS producers in a model biofilm-forming bacterium, Bacillus subtilis. We discovered that general adaptation to biofilm lifestyle leads to an increase in phenotypical heterogeneity of eps expression. However, prolonged exposure to EPS-deficient cheaters may result in different adaptive strategy, where eps expression increases uniformly within the population. We propose a molecular mechanism behind such adaptive strategy and demonstrate how it can benefit the EPS producers in the presence of cheaters. This study provides additional insights on how biofilms adapt and respond to stress caused by exploitation in long-term scenario.
Project description:Transcription profile of Escherichia coli cells in biofilms under static batch culture was compared to that of E. coli cells in planktonic cultures. Both E. coli biofilm and planktonic cultures were cultivated for 18 h in 10% Luria-Bertani broth at room temperature (20 degree Celsius). Biofilms were grown in static batch culture in petri dishes. Both planktonic culture and biofilms were homogenized and run through a separated protocol.