Stress Response of Mesosutterella multiformis Mediated by Nitrate Reduction

Bacterial stress responses are closely associated with the survival and colonization of anaerobes in the human gut. Mesosutterella multiformis JCM 32464^T is a novel member of the family Sutterellaceae, an asaccharolytic bacterium. We previously demonstrated energy generation via heme biosynthesis, which is coupled with nitrate reductase. Here, physiological and morphological changes in M. multiformis induced by exposure to nitrate were investigated. The ability of M. multiformis to reduce nitrate was determined using a colorimetric assay. A unique morphology was observed during nitrate reduction under anaerobic conditions. The association between nitrate concentration and cell size or cellular fatty acid composition was evaluated. Nitrate-induced responses of M. multiformis were compared to those of related species. An increase in cellular filamentation and the ratio of saturated: unsaturated fatty acids was mediated specifically by nitrate. This indicates a decrease in cell fluidity and low leakage. Furthermore, a similar response was not observed in other related species cultured in the presence of nitrate. Hence, the nitrate-induced stress response in new anaerobes such as M. multiformis was demonstrated. The response could also be involved in the conservation of menaquinones and the maximization of nitrate reduction.