Serratia spp. are widely distributed in nature. Serratia marcescens is the most common Serratia sp. associated with human disease, followed by strains of the S. liquefaciens complex: S. liquefaciens, S. grimesii and S. proteamaculans. The clinical significance of these species is largely unknown, because most clinical data refer to the S. liquefaciens group and do not differentiate the species therein. Macrophages play key roles in host defense by recognizing, engulfing, and killing microorganisms. We used several in vitro assays to investigate the interaction between Serratia and macrophages. The picture shows a Confocal Laser Scanning Micrograph (CLSM) of human peripheral blood monocytes differentiated to macrophages, and infected with a red fluorescent Serratia liquefaciens. A macrophage try to capture bacteria by means of a long pseudopod. Bacteria seem to walk along this structure.
After fixation, cells were permeabilized with Triton X-100. Atto-488 phalloidin (Sigma Aldrich), which binds polymerized F-actin, was used to identify actin filaments and fibers. Preparations were mounted in Fluoroshield- mounting medium containing DAPI (Sigma Aldrich). Series of optical sections were obtained with a NIKON A1R confocal scanning laser microscope equipped with a Nikon A1 digital camera, and a 403nm, 488nm, 561nm lasers. Original Magnification: ×600.
Credit: Ramos Vivas Jose
Sigma-Aldrich microbiology photography competition