SUMMARY: In aerobic static broth cultures grown at 37°, salmonellas of genotype Fim(1), i.e. bearing type-1 (mannose-sensitive, haemagglutinating) fimbriae, formed a surface pellicle consisting of densely packed bacteria shortly after the cessation of logarithmic growth at about 6 hr, and then, during the next 24 hr, underwent a large secondary phase of growth. Salmonellas of genotype Fim(2), i.e. bearing type-2 (non-haemagglutinating) fimbriae, and most Fim (non-fimbriate) salmonellas did not form a pellicle and gave only slight post-logarithmic growth; after 24–72 hr the amount of their growth, i.e. bacterial concentration estimated turbidimetrically, was only one-third to one-half that of comparable type-1 fimbriate bacteria. Fim strains of differed from most other Fim salmonellas by forming a pellicle and undergoing an associated secondary phase of growth, but they gave these effects 24–48 hr later than did the Fim(1) strains. A pellicle was not formed by any organism either in static cultures incubated anaerobically or in cultures aerated by continuous shaking, and in these two sets of conditions the course and amount of growth were the same for the Fim(1) as for the Fim bacteria. It is concluded that the large secondary phase of growth shown by the Fim(1) bacteria in aerobic static broth results from the free availability of atmospheric oxygen to the bacteria growing in the pellicle.

The presence of 0.2% (w/v) of the haemagglutination-inhibiting sugar, α-methylmannoside, which was not utilized within 6 days, delayed by more than 24 hr the formation of a pellicle and the onset of the secondary phase of growth in aerobic static cultures of the Fim(1) strain LT2 of Another haemagglutination-inhibiting sugar, D-mannose, was utilized within 12 hr and delayed pellicle formation by only 2–3 hr in cultures of strain LT2, but it caused a prolonged (> 24 hr) delay in pellicle formation in cultures of two non-mannose-utilizing mutants of strain LT2. D-glucose and L-sorbose, which do not inhibit haemagglutination, did not delay pellicle formation. These findings, together with the failure of Fim(2) bacteria to form a pellicle, suggest that the property of type-1 fimbriae that promotes early pellicle formation is the same as that responsible for the mannose-sensitive haemagglutinating activity.


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