| Summary: | <p>Abstract</p> <p>Background</p> <p>Heme is typically a major iron source for bacteria, but little is known about how bacteria of the <it>Leptospira </it>genus, composed of both saprophytic and pathogenic species, access heme.</p> <p>Results</p> <p>In this study, we analysed a two-component system of the saprophyte <it>Leptospira biflexa</it>. <it>In vitro </it>phosphorylation and site-directed mutagenesis assays showed that Hklep is a histidine kinase which, after autophosphorylation of a conserved histidine, transfers the phosphate to an essential aspartate of the response regulator Rrlep. Hklep/Rrlep two-component system mutants were generated in <it>L. biflexa</it>. The mutants could only grow in medium supplemented with hemin or δ-aminolevulinic acid (ALA). In the pathogen <it>L. interrogans</it>, the <it>hklep </it>and <it>rrlep </it>orthologous genes are located between <it>hemE </it>and <it>hemL </it>genes, which encode proteins involved in heme biosynthesis. The <it>L. biflexa hklep </it>mutant could be complemented with a replicative plasmid harbouring the <it>L. interrogans </it>orthologous gene, suggesting that these two-component systems are functionally similar. By real-time quantitative reverse transcription-PCR, we also observed that this two-component system might influence the expression of heme biosynthetic genes.</p> <p>Conclusion</p> <p>These findings demonstrate that the Hklep/Rrlep regulatory system is critical for the <it>in vitro </it>growth of <it>L. biflexa</it>, and suggest that this two-component system is involved in a complex mechanism that regulates the heme biosynthetic pathway.</p>
|
|---|
