Clostridium acetobutylicum bacterial membrane responses to carbon ion beam irradiation perturbations

Abstract

Background Clostridium acetobutylicum is an important strain during acetone-butanol-ethanol (ABE) fermentation. However, butanol has toxic effects on cells, limiting the application of ABE fermentation. Accordingly, in this study, we aimed to elucidate the metabolic mechanisms through which Clostridium adapts to butanol stress to facilitate the industrial utilization of Clostridium. Results First, using cell morphology, cell membrane permeability and membrane potential, cell surface hydrophobicity, and cell membrane fatty acid composition analyses in wild-type (ATCC 824) and butanol-tolerant (Y217) strains under butanol stress, we explored the responses in the cell membrane to evaluate the damage caused by butanol poisoning. After 2.0% (v/v) butanol treatment, the extracellular conductivity of ATCC 824 increased, intracellular proteins and nucleotides were released in large quantities, the fluorescein diacetate staining rate decreased, the membrane potential decreased, and the cell membrane permeability increased. Under butanol shock, the cell surface of Y217 cells remained intact, and its butanol tolerance mechanism increased the integrity of cell membrane and reduced leakage of cell contents caused by changed in cell membrane permeability, thereby preventing butanol damage to the cell membrane. When stimulated with butanol, Y217 cells showed reduced surface hydrophobicity, thereby improving cellular tolerance to butanol. A comparison of differences in fatty acid compositions between ATCC 824 and Y217 cell membranes under butanol stress further demonstrated that maintenance of the normal physiological characteristics of cell membranes played important roles in resisting the impact of organic solvents. Conclusions Our findings clarified the changes in physiological and biochemical characteristics of the mutant Y217 cell membrane stimulated with butanol to enhance its tolerance. These results may provide important theoretical guidance for further accelerating the acquisition of bacteria with high butanol tolerance and promoting butanol production. Moreover, our study provided a scientific basis for improving the industrial and environmental adaptability of Clostridium.