Screening of Nitrogenase-Like Genes and Characterization of Their Functional Diversity
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Date
2024-05
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The Ohio State University
Abstract
Under anaerobic, sulfate-limiting conditions some organisms turn to volatile organic sulfur compounds (VOSCs) in the environment for their sulfur needs. Recently, a previously unidentified relative of nitrogenase was discovered to perform sulfur acquisition from VOSCs. These enzymes, methyl-thio alkane reductases (MARs) reduce VOSCs into hydrocarbons and methanethiol (CH3-SH) for methionine synthesis. For example, dimethylsulfide is converted to the potent greenhouse gas, methane, and (2-methylthio)ethanol to the key plant regulatory hormone and industrial feedstock, ethylene. Initially, methylthio-alkane reductases were discovered in the photosynthetic bacterium, Rhodospirillum rubrum. However, upon further phylogenetic analysis, gene homologs were identified in numerous additional bacteria. To explore the diversity of bacteria with methylthio-alkane reductase activity and the role it may play in each organism’s respective environment, a gene synthesis and complementation approach was carried out in R. rubrum. As a result, functional MAR sequences were localized to one clade of nitrogen-fixation like (NFL) sequences. Subsequently, to understand the diversity of substrates for MAR, growth experiments were conducted with R. rubrum in the presence of possible MAR substrates. Commercially relevant chemicals including propane, butane, and isobutane were discovered as MAR reaction products from VOSC cleavage. Moving forward, identified MAR sequences with high activity for hydrocarbon production may be further employed in bioengineering efforts to produce large yields of these industrially important commodity chemicals.