Intra- and interspecies transfer and expression of Rhizobium japonicum hydrogen uptake genes and autotrophic growth capability

Abstract
Cosmids containing hydrogen uptake genes were previously isolated. Four new cosmids that contain additional hup gene(s) were identified by congual transfer of a R. japonicum 122DES gene bank into a Tn5-generated Hup- mutant and screening for the acquisition of Hup activity. The newly isolated cosmids, pHU50-pHU53, contain part of the previously isolated pHU1 but extend as far as 20 kilobases beyond its border. pHU52 complements 5 of 6 Hup- mutants and confers activity on several Hup- wild-type R. japonicum strains in the free-living state and where tested in nodules. Transconjugants obtained from interspecies transfer of pHU52 to R. meliloti 102F28, 102F32, and 102F51 and R. leguminosarum 128C53 showed hydrogen-dependent methyleneblue reduction, performed the oxyhydrogen reaction, and showed hydrogen-dependent autotrophic growth by virtue of the introduced genes. The identity of the presumptive transconjugants was confirmed by antibiotic-resistance profiles and by plant nodulation tests.