biostudies-literatureLu ZOffice of Extramural Research, National Institutes of HealthNIGMS NIH HHSE3266-E3275https://www.ebi.ac.uk/biostudies/studies/S-EPMC5889672biostudies-literatureUnknown115(14)It has been unclear whether superoxide and/or hydrogen peroxide play important roles in the phenomenon of obligate anaerobiosis. This question was explored using <i>Bacteroides thetaiotaomicron</i>, a major fermentative bacterium in the human gastrointestinal tract. Aeration inactivated two enzyme families-[4Fe-4S] dehydratases and nonredox mononuclear iron enzymes-whose homologs, in contrast, remain active in aerobic <i>Escherichia coli</i> Inactivation-rate measurements of one such enzyme, <i>B. thetaiotaomicron</i> fumarase, showed that it is no more intrinsically sensitive to oxidants than is an <i>E. coli</i> fumarase. Indeed, when the <i>E. coli</i> enzymes were expressed in <i>B. thetaiotaomicron</i>, they no longer could tolerate aeration; conversely, the <i>B. thetaiotaomicron</i>Proceedings of the National Academy of Sciences of the United States of AmericaEndogenous superoxide is a key effector of the oxygen sensitivity of a model obligate anaerobe.PMC5889672GM049640R37 GM049640R01 GM049640Imlay JASethu RLu ZfalseEndogenous superoxide is a key effector of the oxygen sensitivity of a model obligate anaerobe.It has been unclear whether superoxide and/or hydrogen peroxide play important roles in the phenomenon of obligate anaerobiosis. This question was explored using <i>Bacteroides thetaiotaomicron</i>, a major fermentative bacterium in the human gastrointestinal tract. Aeration inactivated two enzyme families-[4Fe-4S] dehydratases and nonredox mononuclear iron enzymes-whose homologs, in contrast, remain active in aerobic <i>Escherichia coli</i> Inactivation-rate measurements of one such enzyme, <i>B. thetaiotaomicron</i> fumarase, showed that it is no more intrinsically sensitive to oxidants than is an <i>E. coli</i> fumarase. Indeed, when the <i>E. coli</i> enzymes were expressed in <i>B. thetaiotaomicron</i>, they no longer could tolerate aeration; conversely, the <i>B. thetaiotaomicron</i>2018-01-01T00:00:00Z2018 Apr2025-04-26T18:12:50.112Z2019-03-26T23:58:08ZS-EPMC58896722955953410.1073/pnas.1800120115