Open AccessFerric iron‐reducing Shewanella putrefaciens and N 2 ‐fixing Bradyrhizobium japonicum with uptake hydrogenase are unable to oxidize atmospheric H 2
Author(s) -
Klüber Hans Detlef,
Conrad Ralf
Publication year - 1993
Publication title -
fems microbiology letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.899
H-Index - 151
eISSN - 1574-6968
pISSN - 0378-1097
DOI - 10.1111/j.1574-6968.1993.tb06408.x
Subject(s) - shewanella putrefaciens , bradyrhizobium japonicum , hydrogenase , bradyrhizobium , chemistry , electron acceptor , shewanella , hydrogen , bacteria , leghemoglobin , nuclear chemistry , biology , biochemistry , rhizobiaceae , nitrogen fixation , nitrogen , organic chemistry , root nodule , genetics , symbiosis
Bradyrhizobium japonicum and Shewanella putrefaciens were unable to oxidize hydrogen at atmospheric concentrations (0.55 ppmv), neither in suspension nor when added to sterile soil. The K m ‐value of S. putrefaciens for H 2 (39 ppmv in gas phase, 0.22 μM in aqueous phase), using Fe(III) as electron acceptor, showed a 4–5‐fold higher affinity for H 2 than that of B. japonicum (1200 ppmv; 0.84 μM) or other hydrogen‐oxidizing bacteria. However, the V max (4.54 fmol H 2 h −1 cell −1 ) and threshold (> 0.5 ppmv; 0.35 nM) of S. putrefaciens and the V max (7.19 fmol H 2 h −1 cell −1 ) and threshold (> 0.5 ppmv; 0.35 nM) of B. japonicum were in the same order of magnitude as data for Knallgas bacteria from relevant literature. To enable hydrogen oxidation in soil the soil‐samples with S. putrefaciens even had to be supplemented with Fe(III). Fresh soil, on the other hand, oxidized hydrogen very efficiently below atmospheric mixing ratios, demonstrating that there must be other oxidation activities in soil.