SUMMARY: Treatment with 60% hydrofluoric acid (HF) removed most of the phosphorus and small amounts of mannan, glucan and protein from walls of two non-flocculent strains (366 and 1004) and two flocculent strains (1005 and 1063) of . Organisms of all strains showed increased flocculating ability following HF treatment. Flocculation of untreated organisms of 1005 and 1063, and of HF-treated organisms of all four strains, declined appreciably when they were washed in deionized water, with or without EDTA, and the flocculation was measured in deionized water instead of in 0·05 -sodium acetate containing Ca. Treatment with 1,2-epoxypropane also caused a decrease in the flocculating ability of these organisms. Extracting the lipids from organisms of strains 366 and 1004 had no effect on their flocculating ability, but decreased the flocculating ability of organisms of strains 1005 and 1063. pH–electrophoretic mobility curves of untreated and HF-treated organisms confirmed the loss of wall phosphate by HF treatment, and indicated that HF treatment had little effect on the content of protein carboxyl groups in the outer wall layers. Mannose at 0·22 completely prevented floc formation by organisms of strain 1063; but, even at 0·33 , it had very little effect on floc formation by HF-treated organisms of strains 366 and 1063. Organisms of all four strains bound fluorescein-conjugated concanavalin A to the same extent after treatment with HF as before, but this treatment led to a greatly diminished binding of fluorescein-conjugated antiserum raised against organisms of strain 366. The results indicate that phosphodiester linkages in yeast-wall mannan are not involved in bridge formation through Ca during floc formation and that this arises principally through carboxyl groups.


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