Surface location of SseB variants under in vitro culture conditions. S. Typhimurium wild type (WT), the sseB strain, or the sseB strain harboring psseB for expression of WT sseB, or plasmids for the expression of various mutant alleles of sseB (psseB Δx) were grown in vitro under conditions that induced the synthesis and secretion of SseB. At 8 h of culture, the bacteria were fixed on chitosan-pretreated cover slips. The bacterial cells were stained with rabbit anti-Salmonella O-1,4,5,12,27 antiserum conjugated with DyLight 547 NHS ester (red). SseB was immuno-stained using rabbit polyclonal antibody against recombinant SseB as primary antibody and anti rabbit Alexa488 was used as secondary antibody (green). A) Presence of SseB within the bacterial cytoplasm was investigated by immunofluorescence labeling of SseB after lysozyme permeabilization of the bacteria. B) For analyses of SseB secretion and surface location, the lysozyme treatment was omitted.