Bacterial structural features responding to environmental stress

Bacterial membranous structures have been reported to function as cell-to-cell communication and stress responses to alleviate a stimulated environment. Recently, the electron microscope was used to detect the membrane ultrastructure through pre-isolation of the exposed bacteria and the subsequent static observation, and the light microscopy resolved microscopic membrane dynamics without ultrastructural information. However, the insights of formation and morphologies of bacterial structural features at the nanoscale in native state was still lacked. Here, we developed a workflow of liquid-phase TEM imaging to investigate the bacteria membrane-structural changes in response to environmental stresses in magnetospirillum magneticum (AMB-1 strain). We found that the bacterial survive for a short period under the harsh environment, during which the bacterial changing its structure and morphology to defense against the external stress. The formation of outer membrane projections including outer membrane tubes (OMTs) and outer membrane vesicles (OMVs) are associated with stress conditions under electron irradiation. Our study suggested the notion that both of OMTs and OMVs are the stress inducing factors before the diderm bacterial lysed, and the bacterial stress response to environmental stimuli is one complex process with multiple reactions. We hope the developed TEM imaging under environmental conditions will be helpful in the growing field of studying bacterial membrane structures.