Advances in research progress on acid tolerance mechanism of Gram- negative bacteria mediated by molecular chaperone protein / 中国药科大学学报

@#The tolerance of microorganism under acid stress is of significant importance to the growth and industrial production of bacterial strain. When the bacterial cells are exposed to the external acid environment, proteins in periplasmic space are under higher acid stress and are thusmore susceptible to severe damage from acid than the intracellular protein, and these are also more susceptible to severe damage from acid than the intracellular protein. During the acid-resisting process of Gram-negative bacteria, in addition to the intracellular decarboxylase system, the molecular chaperone can also participate in the identification and protection of the space structure of protein as an important "correcting" mechanism. This paper, reviews the current researches on the function, structure, acid-resisting mechanism of variousmolecular chaperones, including HdeA, HdeB, DnaK and GroEL. Finally, the research progress of the acid-resisting mechanism among Gram-negative bacteria is summarized. Through in-depth investigation and analysis of the physiological adaptation strategy of molecular chaperone to the acid stress environment, this study can help to conduct physiological property modification of target strain and improve their viability and tolerance in acid stress environment, which has its important theoretical and practical significance.

Mechanical characteristics of the spirochete flagella in 2D micro-periplasmic space / 医用生物力学

Objective To investigate mechanical characteristics of the spirochete flagella with tight-fitting ribbon configuration in micro-periplasmic space. Methods The 2D model of two parallel plates was used to simplify the periplasmic space, and the effects of flagellum spacing and eccentricity on force and torque acted on the spirochete flagella, and wall shear stress acted on the spirochete protoplasmic cylinder were studied by using numerical simulation method. Results (1) The relationship between the flagellum horizontal force and eccentricity was presented as a parabolic curve, and the peak value of the flagellum horizontal force was mainly caused by the gradual increase of pressure difference at two sides of the cylinder and the resistance viscous force as well. Flagellum spacing had no significant influence on flagellum horizontal force. (2) The relationship between the flagellum torque and eccentricity was presented as an exponential curve, and smaller flagella spacing would cause bigger flagella torque. (3) Flagellum spacing had no significant effect on wall shear stress of the protoplasmic cylinder, but it would be increased with the number of flagella and the eccentricity increasing. Conclusions Numerical simulation results in this study can qualitatively reflect mechanical characteristics of the spirochete flagella, and also provide references for further understanding the morphology of spirochete as well as its kinematic mechanism and pathogenic characteristics.