Characterizing the flagellar filament and the role of motility in bacterial prey‐penetration by Bdellovibrio bacteriovorus

Abstract

SummaryThe predatory bacterium Bdellovibrio bacteriovorus swims rapidly by rotation of a single, polar flagellum comprised of a helical filament of flagellin monomers, contained within a membrane sheath and powered by a basal motor complex. Bdellovibrio collides with, enters and replicates within bacterial prey, a process previously suggested to firstly require flagellar motility and then flagellar shedding upon prey entry. Here we show that flagella are not always shed upon prey entry and we study the six fliC flagellin genes of B. bacteriovorus , finding them all conserved and expressed in genome strain HD100 and the widely studied lab strain 109J. Individual inactivation of five of the fliC genes gave mutant Bdellovibrio that still made flagella, and which were motile and predatory. Inactivation of the sixth fliC gene abolished normal flagellar synthesis and motility, but a disordered flagellar sheath was still seen. We find that this nonmotile mutant was still able to predate when directly applied to lawns of YFP-labelled prey bacteria, showing that flagellar motility is not essential for prey entry but important for efficient encounters with prey in liquid environments.

The Bdellovibrio bacteriovorus twin-arginine transport system has roles in predatory and prey-independent growth

“…5a) were seen, by microscopy, to attach to and invade prey and form bdelloplasts at the same rate; a finding confirmed by the use of the luminescent predation assay (Lambert et al, 2003(Lambert et al, , 2006 which showed that the initial prey death was equal for both the wild-type and tatA1 Bd mutant B. bacteriovorus strains (data not shown). The wildtype B. bacteriovorus lysed the bdelloplasts after 4 h in synchronous cultures (Fig.…”

“…Furthermore, it is likely that there are some TatBCA2-specific substrates that are essential for B. bacteriovorus viability in both growth modes. The very slow axenic growth phenotype of a single tatA/E homologue is unprecedented, even more so given the high levels of gene redundancy seen in other dual orthologous gene systems in B. bacteriovorus (Lambert et al, 2006;Rendulic et al, 2004).…”

“…RT-PCR was used to determine which of the tat system and substrate genes were expressed in the predatory life cycle and whether expression patterns differed in the tatA1 mutant. RNA was isolated as described previously (Evans et al, 2007;Lambert et al, 2006) from both wild-type B. bacteriovorus HD100 and the tatA1 mutant strain and from HID2, an HI derivative of B. bacteriovorus HD100 (Evans et al, 2007). RT-PCR with 25 amplification cycles (allowing a semiquantitative view of expression levels) was carried out as described previously (Evans et al, 2007) using the primers listed in Supplementary Table S2 (available with the online version of this paper).…”

“…The plasmids were conjugated into B. bacteriovorus HD100 as described previously (Evans et al, 2007;Lambert et al, 2006;Lambert & Sockett, 2008). Subsequent HD and HI B. bacteriovorus strains were tested by culture and colony PCR for evidence of a secondary crossover event (Evans et al, 2007); putative deletion mutants were confirmed by Southern blotting (Southern, 1975) and sequencing (MWG Biotech) to confirm for Bd1802 the deletion of the gene and the loss of the suicide vector, and for tatA1 the insertion of the kanamycin cassette at the correct site, the lack of a wild-type gene and also for the loss of the suicide vector.…”

Bacterial predator–prey dynamics in microscale patchy landscapes

“…We studied the bacterial predator Bdellovibrio bacteriovorus preying upon Escherichia coli. Bdellovibrio bacteriovorus is a small (0.4 Â 1 mm) and highly motile (it can swim over 160 mm s 21 , or 160 body lengths per second [22]) predator of Gramnegative bacteria, that occurs, for example, in soil, in the human gut and in water [23]. To complete its life cycle, B. bacteriovorus inserts itself into the periplasmic space of its prey and converts it into a round-shaped 'bdelloplast' [24].…”