Figure 7 Transcriptional expression patterns of the three Bdellovibrio chaperonin genes during axenic Host-Independent growth. RT-PCR with transcript specific

primers was carried out on matched concentrations of RNA (matched by Nanodrop spectrophotometer readings) from axenically grown Host-Independent Bdellovibrio. Three independently isolated strains of each sigma factor mutant and each host-independent (HI) wild-type were used to account for HI strain-to strain variation. L- NEB 100 bp ladder –ve – no template negative control + ve- HD100 genomic DNA positive control. Conclusions We have shown that of three B. bacteriovorus HD100 sigma factor genes with at least partial rpoE homology, one- bd3314, Rabusertib is likely essential for Bdellovibrio cell life and cannot be deleted. bd0881 and bd0743 can be deleted with the Bdellovibrio retaining the ability to grow predatorily or prey-independently. In the case of ΔBd0881 the predatory efficiency was reduced,

despite the flagellar motility of the mutant being slightly increased, (despite a slight but statistically significant shortening of ROCK inhibitor flagellar filament length) thus the change in predation efficiency may not be due to motility changes but regulation of other predatory genes. The bd0881 gene has an expression pattern across the predatory cycle that is ML323 similar to that of the flagellin genes whose expression is required for Bdellovibrio

motility. That bd0881 expression is turned off and then resumes at a similar time to flagellin gene expression, during the predatory cycle, implies stiripentol that Bd0881 may have a role associated with pre-septation developmental maturation of Bdellovibrio around the time that flagella are being built in newly dividing cells. However the Bd0881 sigma factor does not directly regulate the expression of fliC flagellin or mot flagellar motor genes themselves. Surprisingly, predatory efficiency was not affected in our cultures by the slower swimming speed of the ΔBd0743 sigma factor mutant; this is probably indicative of sufficient mixing of predator and prey at close quarters in lab conditions. The slight increase in flagellar length in ΔBd0743 mutants is likely to have come with the incorporation of a higher percentage of a less rigid flagellin in the flagella causing a less efficient “bow wave” and this may account for the slower swimming. In both the ΔBd0743 and ΔBd0881 mutants, small but significant changes in swimming speed were paradoxically associated with changes apparently in the wrong direction in flagellar length. This shows that it is not simply flagellar length that governs the thrust produced by flagellar propellers.