Date Published: April 18, 2019
Publisher: Public Library of Science
Author(s): Mahtab Waseem, Jason Q. L. Williams, Arumugam Thangavel, Patrick C. Still, Patrick Ymele-Leki, Meghan Scobee Blackledge.
Phosphoenolpyruvate-carbohydrate phosphotransferase system (PTS) is a highly conserved, multistep chemical process which uses phosphate transfer to regulate the intake and use of sugars and other carbohydrates by bacteria. In addition to controlling sugar uptake, the PTS regulates several bacterial cellular functions such as chemotaxis, glycogen metabolism, catabolite repression and biofilm formation. Previous studies have shown that the phosphoenolpyruvate (PEP) to pyruvate ratio is a critical determinant of PTS functions. This study shows that 2-oxo-4-phenyl-2,5-dihydro-3-furancarbonitrile (MW01), a compound with structural similarity to known natural products, induces Vibrio cholerae to grow preferentially in the biofilm mode in a mechanism that involves interaction with pyruvate. Spectrophotometric assays were used to monitor bacterial growth kinetics in microtiter plates and quantitatively evaluate biofilm formation in borosilicate glass tubes. Evidence of MW01 and pyruvate interactions was determined by nuclear magnetic resonance spectroscopy. Given the established connection between PTS activity and biofilm formation, this study also highlights the potential impact that small-molecule modulators of the PTS may have in the development of innovative approaches to manage desired and undesired microbial cultures in clinical, industrial and environmental settings.
Antimicrobial resistance against effective antibiotics is a global issue with societal, environmental, and economic repercussions [1, 2]. This global challenge is exacerbated by the ability of most bacteria to grow within structured microbial communities called biofilms. Made of single- or multi-species communities, biofilms enable microorganisms to withstand antibiotic dosages of up to 100–1000 times higher than they could resist as free-floating cells and to more rapidly develop resistance to antimicrobial mechanisms [3–8]. However, owing to the natural complexity of biological ecosystems, non-pathogenic biofilms are the mode of subsistence of select bacterial organisms in the environment–as is the case for Vibrio cholerae.
Biofilm formation by V. cholerae is primarily dependent on two factors: presence of environmental calcium ions in concentrations comparable to those found in seawater, or production of V. cholerae exopolysaccharide (VPS) [17, 30, 31]. A paradigm for the control of biofilm formation by V. cholerae relies on control of the expression of the vps operon, which itself transcriptionally regulates the production of VPS polysaccharides by the phosphoenolpyruvate phosphotransferase system (PTS) [12, 17, 18, 32]. The PTS is highly conserved among bacterial organisms. It is a multicomponent signal transduction cascade that regulates chemotaxis, glycogen catabolism, detection of quorum sensing molecules, and bacteria biofilm formation, through multiple independent pathways [12–18]. In the lesser understood pathway, two components of the PTSNtr secondary system, EIIANtr1 and EIIANtr2, inhibit vps expression and V. cholerae biofilm formation [12, 18]. In a second pathway, glucose-specific PTS components in rich medium, EIIAGlc and EIIBCGlc may respectively activate and inhibit vps transcription under the influence of the transcriptional repressor Mlc [12, 18]. In a third pathway observed in minimal or rich growth media, phosphoenolpyruvate (PEP)-dependent, phosphorylated HPr or FPr inhibits vps expression and consequently inhibits biofilm formation by V. cholerae [12, 18].