The requirement of both rhl gene clusters for normal swarming motility supports this model (see below). The presence of a transposase of the mutator family in close proximity of one of the gene clusters (BTH_II1082) can also be indicative that a past duplication of an original single copy occurred and positive selection throughout evolution of some bacterial lineages conserved the paralogs. Long chain rhamnolipids from Burkholderia: effects on the CMC Considering

the length of the carbon chains of the fatty acid moiety Chk inhibitor of rhamnolipids produced by Burkholderia species, it was compelling to determine their effect on lowering the surface tension of water. A total rhamnolipid extract from B. thailandensis lowers the surface tension to 42 mN/m, with a CMC value of 225 mg/L. These values are higher than those traditionally reported for rhamnolipids produced by Pseudomonas species (typically around 30 mN/m and CMC

in the order of 20 to 200 mg/L) [36]; however, it is only recently that HAAs have been discovered, as well as their efficacious surface tension-lowering potential [16]. Thus, we assume that results pertaining to surface tension properties of Emricasan concentration rhamnolipids published prior to this report could have been biased by a contamination with easily co-purified HAAs. For the purpose of the present study, we compared our results with those we have published for purified rhamnolipids and HAAs produced by P. check details aeruginosa PG201 [16]. The purified rhamnolipids from this strain lower surface tension to 40 mN/m with a CMC value of approximately Rebamipide 600 mg/L, while the HAA mixtures displays values of 29 mN/m with a CMC of approximately 800 mg/L. Consequently, it is clear that the longer chain rhamnolipids produced by B. thailandensis

start forming micelles at a much lower concentration than P. aeruginosa rhamnolipids, 225 mg/L versus 600 mg/L. These values can be compared as the rhamnolipid mixture from B. thailandensis used for our tests contained only traces of HAAs. The effect of alkyl ester chain length of sophorolipids, a class of biosurfactants produced by Candida bombicola, has been studied with regards to micellization. The study reported a direct effect of carbon chain length on decreasing the CMC. Additional CH2 groups render the molecule more hydrophobic and thus facilitate micelle formation [37]. This might explain the lower CMC value obtained with the longer chain rhamnolipids produced by B. thailandensis in comparison to those obtained by P. aeruginosa. Both rhlA alleles are necessary for normal swarming motility Swarming motility always involves biosurfactants. For example, serrawettin W2, a wetting agent produced by Serratia liquefaciens, is required for swarming motility in a nonflagellated mutant [38, 39]. In regards to P.