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Fluoride movement into and out of Bacillus spores and growing cells and effects of fluoride accumulation on spore properties
- Dong, W., Setlow, P.
- Journal of applied microbiology 2019 v.126 no.2 pp. 503-515
- Bacillus cereus, Bacillus subtilis, cell growth, heat tolerance, pH, sodium fluoride, spore germination, spores
- 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 ¹⁹F‐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.