Fluoride Action Network


AIMS: To investigate effects of fluoride ion (F ) on, and kinetics of its movement into and out of, spores and growing cells of Bacillus species.

METHODS AND RESULTS: Effects of F on Bacillus cell growth, spore germination and outgrowth and heat resistance were investigated, as well as F movement into and out of spores using 19 F-NMR. F inhibited Bacillus subtilis spore germination and outgrowth, and YhdU, now named FluC, was crucial to prevent F accumulation in growing cells and to minimize F inhibition of spore germination. Dormant wild-type, yhdU and coat defective B. subtilis spores, and Bacillus cereus spores incubated in 40 mmol l-1 NaF for 48 h accumulated 2-2·6 mol l-1  F and its movement into Bacillus spores was highest at low pH. Bacillus subtilis spores lacking Ca-dipicolinic acid accumulated higher F levels than wild-type spores.

CONCLUSIONS: These results are consistent with F incorporation into the dormant spore core, and as HF and/or NaF, but not CaF2 . YhdU played no significant role in F uptake or efflux in dormant spores, but assisted in F export early in spore germination.

SIGNIFICANCE AND IMPACT OF STUDY: This knowledge provides new insight into effects of F on Bacillus cells and spores and how this anion moves into, and out of spores.