LAUSR

Abstract Hydrogen formed during nitrogen fixation in legumes can enter the surrounding soil and confer multiple benefits to crops. Here, we used Sinorhizobium meliloti 1021, whose genome was sequenced in 2001, as a model bacterium to study the relationship between the bacterium and legume. We investigated the effects of hydrogen on the gene expression in S. meliloti using RNA-sequencing technology. We identified 43 genes whose expression was altered by hydrogen treatment; among these, 39 were downregulated, and 4 were upregulated. These genes accounted for 1.5% of the total 2941 annotated genes of the S. meliloti genome. Gene ontology and pathway analyses revealed that the hydrogen-regulated genes were associated with catalytic activity and binding. Further, these genes were primarily involved in arginine, proline, and β-alanine metabolism. Real-time PCR revealed that the transcription levels of SMc02983, cyoB, cyoC, and cyoD were reduced after hydrogen treatment. These results provide a theoretical framework for exploring new metabolic pathways of S. meliloti.