Authors: S.V. Kazakov
Affilation: Pace University, United States
Pages: 274 - 277
Keywords: bacillus spores, ionic reservoirs, multi-layered structure, multi-steps kinetics of pH-equilibration, proton diffusivities
A dormant bacterial spore is regarded as a natural ionic reservoir, i.e. a system capable of changing the external pH or ionic strength by accumulating or releasing ions. In this work, we introduce a method of time-resolved micro-potentiometry for probing the kinetics of proton uptake by dormant Bacillus subtilis spores, which has never been studied prior this work. It was shown that the plurality of steps comprising the uptake of protons may be attributed to the nanometer scaled compartments of the multi-layered spore structure. The important conclusion derived from the time constants systematically presented for the spore structural layers is that the effective diffusion coefficient for hydrogen ions within the spore core was significantly lower than the one within coats and cortex. The finding that the difference between proton diffusivities in the spore cortex and the spore core depends on the concentration of spores and initial concentration of protons is striking, since it may have a physiological importance as a physico-chemical precursor of spore’s quorum sensing mechanism. The concentrations of free hydrogen ions inside the spore were found to be up to 3 orders of magnitude higher than that outside the spore, whereas the concentrations of co-ions (chloride ions) were reversal on both sides of a spore surface. In the practical point of view, regulation of the spore internal pH may be the way of its metabolic dormancy control, since the internal pH may be a contributing factor to enzymatic activity within the dormant spore.