The processes underlying the loss of motility of the ΔluxS Hp mutant were manifested by fewer and shorter flagella that presumably derived from the altered flagella protein production and the modulated
expression of a number of genes linked with flagella assembly and function. Previous studies have shown that mutations of luxS Hp in H. pylori diminished motility on soft agar. The altered motility phenotype was restored completely by genetic complementation with luxS Hp or significantly restored selleck kinase inhibitor by metabolic complementation with wild-type CFS [18–20]. In contrast to our study, in Osaki et al. and Rader et al.’s studies complementation of luxS Hp was performed by placing luxS Hp at a second site in the chromosome rather than at the original locus [19, 20]. Like these previous reports, our study shows that abolished motility of J99 ΔluxS Hp mutation was restored entirely by complementation with the luxS Hp gene and significantly by in vitro synthesised
AI-2. The previous studies, with complete complementation of motility with luxS Hp through insertion at a new chromosomal locus, argue against polar effects of luxS Hp mutagenesis on other genes which influence motility. Our study, with complementation with luxS Hp through creating a revertant results in similar levels of AZD1480 research buy LuxSHp to wild-type and thus better shows that the phenotypes attributed to the mutant were not due Luminespib purchase to secondary mutations elsewhere in the chromosome. Furthermore, having demonstrated that MccAHp and MccBHp function
consecutively to convert the product of LuxSHp (homocysteine) into cysteine as part of the RTSP , we reasoned Meloxicam that inactivation of any of these three enzymes would have a similar influence upon cysteine biosynthesis, whilst only the ΔluxS Hp mutant would be devoid of AI-2. Thus, if the reduced motility of the ΔluxS Hp mutant derived from disrupted cysteine biosynthesis, mutants in mccA Hp and mccB Hp would have a similar motility defect. Therefore, we performed an experiment to exclude the possibility that the effect on motility was due to non-specific secondary metabolic effects of LuxSHp. To do this, wild-type, ΔluxS Hp, ΔmccA Hp and ΔmccB Hp strains were inoculated on the same motility plate, allowing the production of AI-2 and the biosynthesis of cysteine to be isolated from each other. As expected, only the ΔluxS Hp mutant was non-motile. This, for the first time, suggests that motility of H. pylori cannot be affected by disrupting the cysteine provision pathway, but can be blocked by the loss of luxS Hp itself. By using a chemically defined medium, we confirmed the provision of cysteine had no effect on motility of H. pylori. Earlier publications have suggested that AI-2 may not act as a signal in some bacteria but instead may simply be a by-product of the important AMC pathway .