Mutations affecting predation ability of the soil bacterium Myxococcus xanthus

Abstract

Myxococcus xanthus genetic mutants with characterized phenotypes were analysed for the ability to prey on susceptible bacteria. Quantification of predatory ability was scored by a newly developed method under conditions in which prey bacteria provided the only source of nutrients. These results were corroborated by data derived using a previously published protocol that measures predation in the presence of limited external nutrients. First, early developmental regulatory mutants were examined, because their likely functions in assessing the local nutrient status were predicted to be also important for predation. The results showed that predation efficiency is reduced by 64-80 % for mutants of three A-signalling components, AsgA, AsgC and AsgE, but not for AsgB. This suggests that an Asg regulon function that is separate from A-signal production is needed for predation. Besides the Asg components, mutations in the early developmental genes sdeK and csgA were also consistently observed to reduce predatory efficacy by 36 and 33 %, respectively. In contrast, later developmental components, such as DevRS, 4406 and PhoP4, did not appear to play significant roles in predation. The predatory abilities of mutants defective for motility were also tested. The data showed that adventurous, but not social, motility is required for predation in the assay. Also, mutants for components in the chemotaxis-like Frz system were found to be reduced in predation efficiency by between 62 and 85 %. In sum, it was demonstrated here that defects in development and development-related processes affect the ability of M. xanthus to prey on other bacteria.

The predatory life cycle of Myxococcus xanthus

“…In addition, Myx. xanthus strains deficient in proteins controlling A-motility also showed predatory deficiencies (Pham et al, 2005), suggesting that these cell-to-cell interactions may also impact predation. Other predators, such as Bdellovibrio, have also been observed to utilize A-motility homologues for predation (Lambert et al, 2011).…”

“…Additionally, csgA, sdeK and three asg genes (essential for various aspects of fruiting-body formation under starvation conditions) are needed for predation (Pham et al, 2005;. The involvement of csgA in predation is peculiar as it is not expressed when cells are grown in high-nutrient liquid broth (Kim & Kaiser, 1990).…”

Predatory activity of Myxococcus xanthus outer-membrane vesicles and properties of their hydrolase cargo

“…In the environment, prey killing by M. xanthus may involve both mxOMVs and secreted factors, potentially with different prey organisms exhibiting different susceptibilities to mxOMVs and soluble factors. Individual myxobacterial strains have different prey ranges (Morgan et al, 2010;Pham et al, 2005), and it would be interesting to determine whether prey specificity is a consequence of selective targeting by mxOMVs, or differential resistance/susceptibility to mxOMV cargo.…”

Phosphate Acquisition Components of the Myxococcus xanthus Pho Regulon Are Regulated by both Phosphate Availability and Development

“…Cessation of growth required the concentration of P to be reduced below 10 M and was unaffected by previous incubation in different media, whether the medium was rich or minimal (DCY medium or A1W) (unpublished data). M. xanthus is able to grow with other microorganisms as sole nutrient sources (16). We therefore tested a range of P-containing biomolecules that might be expected to be released by lysis of prey to determine their abilities to act as sole P sources.…”

“…Phosphate levels in media were determined using the method of Itaya and Ui (9). The M. xanthus strains used in this study were wild-type strain DK1622 (10) and phoP4 mutant VP963 (16). VP963 carries an unmarked in-frame deletion of phoP4 engineered in a DK1622 background.…”