Functional analysis of hydrogenases and their effects on cell growth and magnetosome synthesis in Magnetospirillum gryphiswaldense

This study addressed the effect of hydrogen metabolism on cell growth and magnetosome synthesis in Magnetospirillum gryphiswaldense strain MSR-1. Two deletion mutants were generated: L206, with single deletion of the hupL gene encoding H2-uptake [NiFe] hydrogenase; and B206, with double deletion of the hyaB gene encoding H2-producing [NiFe] hydrogenase and the hupL gene. The wild-type and mutant strains were compared in terms of hydrogen uptake capability, hydrogen yield, growth rate, and iron uptake, and observed by transmission electron microscopy. Results indicate that HupSL protein is a specific H2-uptake hydrogenase while HyaAB protein is a specific H2-producing hydrogenase. In comparison to wild-type and B206, L206 released a greater quantity of H2 under conditions that induce magnetosomes synthesis, and showed higher rates of growth and iron uptake. M. gryphiswaldense appears to regulate reducing power in vivo, via H2-uptake hydrogenase and H2-producing hydrogenase, to promote iron absorption and magnetosome synthesis.