Vibrio cholerae Combines Individual and Collective Sensing to Trigger Biofilm Dispersal

Abstract

SummaryBacteria can generate benefits for themselves and their kin by living in multicellular, matrix-enclosed communities, termed biofilms, which are fundamental to microbial ecology and the impact bacteria have on the environment, infections, and industry [1, 2, 3, 4, 5, 6]. The advantages of the biofilm mode of life include increased stress resistance and access to concentrated nutrient sources [3, 7, 8]. However, there are also costs associated with biofilm growth, including the metabolic burden of biofilm matrix production, increased resource competition, and limited mobility inside the community [9, 10, 11]. The decision-making strategies used by bacteria to weigh the costs between remaining in a biofilm or actively dispersing are largely unclear, even though the dispersal transition is a central aspect of the biofilm life cycle and critical for infection transmission [12, 13, 14]. Using a combination of genetic and novel single-cell imaging approaches, we show that Vibrio cholerae integrates dual sensory inputs to control the dispersal response: cells use the general stress response, which can be induced via starvation, and they also integrate information about the local cell density and molecular transport conditions in the environment via the quorum sensing apparatus. By combining information from individual (stress response) and collective (quorum sensing) avenues of sensory input, biofilm-dwelling bacteria can make robust decisions to disperse from large biofilms under distress, while preventing premature dispersal when biofilm populations are small. These insights into triggers and regulators of biofilm dispersal are a key step toward actively inducing biofilm dispersal for technological and medical applications, and for environmental control of biofilms.

Evolutionary dynamics of phage resistance in bacterial biofilms

“…Prior work from our groups and others have shown that phages can be immobilized within the biofilm matrix, where they are blocked from gaining access to otherwise susceptible cells (17,18). Our observations here indicate that whenever phage movement is limited within biofilms, it is likely that the extracellular matrix (which is modeled implicitly here as the factor controlling phage diffusion) contains phages which are blocked from host access but not necessarily inert; they remain a threat to susceptible cells after the dispersion of biofilms due to mechanical disturbance or induced by bacteria themselves after depleting local nutrient supplies (53,54). The implications of this prediction are a subject for future work.…”

The intra-genus and inter-species quorum-sensing autoinducers exert distinct control overVibrio choleraebiofilm formation and dispersal

“…DNA fragments that were not native to V. 513 cholerae were synthesized as g-blocks (IDT) or were purchased as plasmids (mNG was licensed 514 from Allele Biotech) [44,45]. HapR was fused to mNG as previously described [9]. 515…”

“…While 42 these findings show an overarching role for QS in repressing biofilm formation at HCD, they are 43 incomplete because they were obtained from V. cholerae mutants locked in the LCD or HCD QS 44 mode that are thus unable to progress through the normal QS program. Furthermore, how V. 45 cholerae cells disperse from biofilms and the role played by QS in dispersal have only recently 46 begun to be addressed [9]. Here, we establish a simple microscopy-based assay with wildtype 47 (WT) V. cholerae that allows us to examine the full biofilm lifecycle and assess the role of QS in 48 both biofilm formation and biofilm dispersal.…”

“…In V. cholerae biofilm studies to date, researchers have overwhelmingly employed either 99 hyper-biofilm forming V. cholerae strains that are locked at LCD and incapable of QS and biofilm 100 dispersal, or they have used fluid flow to wash autoinducers away from growing WT biofilms, in 101 effect locking the V. cholerae cells at LCD [9,[31][32][33][34]. While these strategies have accelerated 102 studies of early V. cholerae biofilm formation and enabled identification and characterization of 103 biofilm matrix components, QS, which is known to control the process, has not been 104 systematically examined in a WT V. cholerae strain capable of naturally transitioning between 105 LCD and HCD behavior as biofilms form and disperse.…”

“…LuxO is dephosphorylated, AphA 69 production is terminated, and HapR production is activated [26]. In this situation, HCD behaviors 70 are enacted, and, germane to this work, virulence and biofilm formation are repressed, and V. 71 cholerae disperses from existing biofilms (Fig 1A, right) [9,27]. It has long been puzzling why the 72 autoinducer signals are processed via the identical, shared pathway in V. cholerae as this system 73 architecture is not obviously conducive to gleaning specific information from each autoinducer.…”