Fluoride movement into and out of Bacillus spores and growing cells and effects of fluoride accumulation on spore properties.

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. B. 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 either 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. This article is protected by copyright. All rights reserved.