The phylogeny of uptake hydrogenases in Frankia
Résumé
Uptake hydrogenase is an enzyme that is beneficial for nitrogen fixation in bacteria. Recent studies have shown that Frankia sp. has two sets of uptake hydrogenase genes, organized in synton 1 and synton 2. In the present study, phylogenetic analysis of the structural subunits of hydrogenase syntons 1 and 2 showed a distinct clustering pattern between the proteins of Frankia strains that were isolated from different host plants and non-Frankia organisms. The structural subunits of hydrogenase synton 1 of Frankia sp. Cp11, Frankia alni ACN14a, and F. alni AvC11 were grouped together while those of Frankia spp. Cc13, KB5, UGL140104, and UGL011102 formed another group. The structural subunits of hydrogenase synton 2 of F. alni ACN14a and Frankia spp. Cc13 and BCU110501 grouped together, but those of Frankia spp. KB5 and Cp11, F.alni Ar13, and F. alni AvC11 comprised a separate group. The structural subunits of hydrogenase syntons 1 and 2 of Frankia sp. EAN1pec were more closely related to those of non-Frankia bacteria, i.e., Streptomyces avermitilis and Anaeromyxobacter sp., respectively, than to those of other Frankia strains, suggesting the occurrence of lateral gene transfer between these organisms. In addition, the accessory Hyp proteins of hydrogenase syntons 1 and 2 of F. alni ACN14a and Frankia sp. Cc13 were shown to be phylogenetically more related to each other than to those of Frankia EAN1 pec.