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Abstract
SUMMARY: Germination of the endospores of the thermophilic actinomycete Thermoactinomyces vulgaris (isolate CUB337) was observed by means of phase-contrast and electron microscopy. The first cytological change was the appearance of four fibrillar regions in the core. During germination the core became granular in texture and swollen, the cortex became laminated and later uniformly reduced to a thin layer. At this late stage of germination and before outgrowth, layers external to the cortex also showed signs of breakdown. The endospores were induced to germinate by 10 mM solutions of L-leucine, L-β-phenylalanine, L-alanine, L-α-amino butyric acid, L-valine, L-methionine, L-cystine, L-β-asparagine, inosine, adenosine and by 1 mM-N-dodecylamine. The effect of heat treatment in general decreased germination but a period of storage increased germination. Outgrowth was inhibited by nisin but was less sensitive to novobiocin than was outgrowth in Bacillus coagulans.
The response of isolate CUB337 to germinant compounds resembled that of Bacillus cereus but when endospores of nine other Thermoactinomyces vulgaris isolates were tested, considerable strain variation was observed.
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