Fimbriation, Pellicle Formation and the Amount of Growth of Salmonellas in Broth

Abstract

In aerobic static broth cultures grown at 37", salmonellas of genotype Fim( I)+, i.e. bearing type-I (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(a)+, 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. Fimstrains of Salmonella typhimurium 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( I)+ 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)f as for the Fim-bacteria. It is concluded that the large secondary phase of growth shown by the Fim(I)+ 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 yo (w/v) of the haemagglutination-inhibiting sugar, a-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(z)+ strain LT2 of Salmonella typhimurium. Another haemagglutination-inhibiting sugar, D-mannose, was utilized within 12 hr and delayed pellicle formation by only 2-3 hr in cultures of strain L T~, but it caused a prolonged (> 24 hr) delay in pellicle formation in cultures of two non-mannose-utilizing mutants of strain L T~. 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 hbriae that promotes early pellicle formation is the same as that responsible for the mannose-sensitive haemagglutinating activity.

Thin, aggregative fimbriae mediate binding of Salmonella enteritidis to fibronectin

“…S. enteritidis and S. typhimurium also bind collagen V via type 3 fimbriae (34). Thus other enteric bacteria also promote pellicle production when cells are grown in static broth (25,33), but our data indicate that these type 1 fimbriae are not the only appendages which promote pellicle production. In addition, repeated subculturing of bacterial pathogens often results in the loss of fimbria production and the associated aggregative phenotype (5).…”

Type 1 Pili Enhance the Invasion of Salmonella braenderup and Salmonella typhimurium to HeLa Cells

“…It is known that the non-piliated variants become dominant with serial aerobic cultivation on nutrient agar plates (3,16). Such phase variation has been reported in Salmonella serovars (9,15,19). In this report we obtained a type 1 pili-defective mutant (strain 303 or 503) by the transposon-insertion mutagenesis.…”

Environmental regulation of the fim switch controlling type 1 fimbrial phase variation in Escherichia coli K-12: effects of temperature and media

“…It has long been known that growth conditions can affect the proportion of fimbriate bacteria (8,12,29,35,36). Growth in poorly aerated static liquid medium enriches for fimbriate bacteria, whereas growth in well-aerated liquid medium, or on agar, favors the afimbriate phase.…”

“…It has been known for many years that certain growth conditions favor the isolation of fimbriate bacteria (growth in static broth, anaerobic growth), whereas other conditions favor afimbriate bacteria (exponential growth in well-aerated broth, growth on agar) (12,29,35,36). It is also clear that strong selective pressures operate under these conditions (14,35,36). Whether these observations reflect selective outgrowth, regulation, or a combination of these factors is unclear.…”