The interrelationship of nutrient sources and basal medium had a strong impact on swarming motility.

Rapid swarming was observed using several carbon learn more sources on M8 medium, but only succinate and CAA supported swarming on FW based medium. The transport of glucose (and some other sugars) is limited by low levels of phosphate in FW medium. When FW medium is amended with phosphate, swarming is restored, along with higher growth yields in vitro (not shown). Even in the presence of phosphate, however, swarming is more robust on succinate than glucose. This result contrasts with results from P. aeruginosa [23]. However, the minimal media used in these experiments are different, and this comparison merits further study. It remains to be determined what other factors might be involved in reduced swarming rates on glucose when phosphate is not limiting. The most striking carbon source based difference was in response to maltose, where the rate of swarming and the structure of the swarm differed sharply with observations on other carbon sources. Comparison of the swarm edge on maltose (Fig 7C) with the swarm edge on succinate inhibited by CR and humidified (Fig 3O, P), is suggestive of the possibility that the lack of wetting agent may be partially responsible for this phenotype. The results with CAA, along with previous work on swarming in P. aeruginosa led us to wonder about

amino acids as sole nitrogen sources in the context of swarming. Several of the amino acids tested were able to support robust growth and swarming with succinate as a carbon source, while others were conducive to GSK872 less robust swarming. We did not identify any amino acids that supported growth but not swarming. Obviously, however, our testing was not exhaustive, and future work will examine the remaining amino acid substrates. Our results show substantially different response patterns to those seen previously in P. aeruginosa PAO1 [22]. With the exceptions of LY2874455 solubility dmso histidine and glycine, which were conducive to swarming in both organisms, all of the amino acids which we tested did not support P. aeruginosa

PAO1 swarming. It should be noted here that in this instance the same basal medium (M8) was used, although we tested an additional basal formulation. next This may relate to the differences in the ecological niches for these organisms, and the predominance of amino acids in plant root exudates. The specific composition of the organic material in the source soil for V. paradoxus EPS has not been determined. The presence of very thin tendrils beyond the edge of the swarm is discernable by phase contrast microscopy on several amino acid nitrogen sources (Fig 6, arrows). This extruded substance does not appear to correlate with swarming rate, and is distinct from the wetting agent that we see macroscopically. Based on time-lapse video microscopy using wild-type and mutant V.