Role of Type IV Pili in Predation by Bdellovibrio bacteriovorus

Abstract

Bdellovibrio bacteriovorus, as an obligate predator of Gram-negative bacteria, requires contact with the surface of a prey cell in order to initiate the life cycle. After attachment, the predator penetrates the prey cell outer membrane and enters the periplasmic space. Attack phase cells of B. bacteriovorus have polar Type IV pili that are required for predation. In other bacteria, these pili have the ability to extend and retract via the PilT protein. B. bacteriovorus has two pilT genes, pilT1 and pilT2, that have been implicated in the invasion process. Markerless in-frame deletion mutants were constructed in a prey-independent mutant to assess the role of PilT1 and PilT2 in the life cycle. When predation was assessed using liquid cocultures, all mutants produced bdelloplasts of Escherichia coli. These results demonstrated that PilT1 and PilT2 are not required for invasion of prey cells. Predation of the mutants on biofilms of E. coli was also assessed. Wild type B. bacteriovorus 109JA and the pilT1 mutant decreased the mass of the biofilm to 35.4% and 27.9% respectively. The pilT1pilT2 mutant was able to prey on the biofilm, albeit less efficiently with 50.2% of the biofilm remaining. The pilT2 mutant was unable to disrupt the biofilm, leaving 92.5% of the original biofilm after predation. The lack of PilT2 function may impede the ability of B. bacteriovorus to move in the extracellular polymeric matrix and find a prey cell. The role of Type IV pili in the life cycle of B. bacteriovorus is thus for initial recognition of and attachment to a prey cell in liquid cocultures, and possibly for movement within the matrix of a biofilm.

Microbial Surface Colonization and Biofilm Development in Marine Environments

“…BALOs may employ chemotaxis to respond to chemoattractants and to track prey bacteria (691) and employ gliding motility to "scout" for prey on surfaces (692). Bdellovibrio bacteriovorus predation requires the type IV pili (693), which may play an important role in initial attachment to a prey bacterium in aquatic environments and possibly in movement for locating prey bacteria within the matrix of biofilms (694). BALOs are phylogenetically and environmentally diverse in the ocean (695)(696)(697), and they display niche separation, different predation strategies, and prey selectivity such that some BALOs are more specific for particular prey organisms, while others are more prey generic (696,(698)(699)(700).…”

Predatory Bacteria Attenuate Klebsiella pneumoniae Burden in Rat Lungs

“…B. bacteriovorus randomly moves through the environment via the use of a single, polar flagellum and invades across the prey outer cell membrane into the periplasmic space of the Gram-negative prey, establishing a bdelloplast. The mechanism by which B. bacteriovorus bacteria invade their prey is not completely elucidated, but type IV pili have been implicated as essential in the process (5–7). Once inside, B. bacteriovorus grows in a filamentous manner by digesting the prey cell from within, divides into a number of progeny, and then lyses the bdelloplast to continue looking for more prey to invade.…”

Comparative Analyses of Transport Proteins Encoded within the Genomes of Bdellovibrio bacteriovorus HD100 and Bdellovibrio exovorus JSS

“…These results indicate that a direct interaction between type IV pili and the prey cell is required for successful predation. Chanyi and Koval [2014] suggested that the role of type IV pili in the life cycle of Bba is for the initial recognition of and attachment to a prey cell, and possibly also for movement within the matrix of a biofilm. It is noteworthy that Bex lacks such structures.…”