Flagella and Pili-Mediated Near-Surface Single-Cell Motility Mechanisms in P. aeruginosa

Abstract

Bacterial biofilms are structured multicellular communities that are responsible for a broad range of infections. Knowing how free-swimming bacteria adapt their motility mechanisms near a surface is crucial for understanding the transition from the planktonic to the biofilm phenotype. By translating microscopy movies into searchable databases of bacterial behavior and developing image-based search engines, we were able to identify fundamental appendage-specific mechanisms for the surface motility of Pseudomonas aeruginosa. Type IV pili mediate two surface motility mechanisms: horizontally oriented crawling, by which the bacterium moves lengthwise with high directional persistence, and vertically oriented walking, by which the bacterium moves with low directional persistence and high instantaneous velocity, allowing it to rapidly explore microenvironments. The flagellum mediates two additional motility mechanisms: near-surface swimming and surface-anchored spinning, which often precedes detachment from a surface. Flagella and pili interact cooperatively in a launch sequence whereby bacteria change orientation from horizontal to vertical and then detach. Vertical orientation facilitates detachment from surfaces and thereby influences biofilm morphology.

Contrasted coevolutionary dynamics between a bacterial pathogen and its bacteriophages

“…We hypothesize that the relative use of LPS and pili as primary receptors contributed to the range of coevolutionary dynamics observed for our phage isolates. First, under our experimental conditions (agitated liquid culture and rapid bacterial growth), bacteria likely produce few pili (58) and/or retract them infrequently (59). This sparsity of pili can reduce adsorption by pili-dependent phages and thereby lessen selection for resistance relative to phages using LPS as primary receptors.…”

Combinatorial discovery of polymers resistant to bacterial attachment

“…This may be a consequence of the individual cells sensing the nature of the polymer surface by their cell envelope-associated sensory proteins or by specific surface structures such as flagella and pili involved in near-surface movement 39 . It is also possible that the bacterial population collectively responds to the polymer through quorum sensing (bacterial cell-to-cell communication) mechanisms 40 , such that the lack of bacterial attachment occurs through this population-dependent decision-making process.…”

Effects of null mutation of the heat-shock gene htpG on the production of virulence factors by Pseudomonas aeruginosa

“…Motility is an important virulence determinant of P. aeruginosa [34,36]. Besides swimming, P. aeruginosa cells can also move by swarming and twitching [23,37]. Twitching is dependent on pilus retraction and independent of the presence of flagella.…”