In this paper, water distribution and variation were investigated in lactic acid bacteria using low field nuclear magnetic resonance (LF-NMR). Three different water fractions in bacterial cells, bounding water (T21), semi-combined water (T22) and free water (T23) were represented respectively, according to the information of water distribution provided by transverse relaxation time (T2), T21, corresponding to water particles bound to cell wall, was less than 10 ms, T22, corresponding to the water particles bound to proteins and other macromolecules in the cytoplasm and representing intracellular water, is in the range of the 10 ms to 100 ms, T23, corresponding to water particles which have a high degree of freedom and representing extracellular water, is larger than 100 ms. Osmotic shock can change water distribution in lactic acid bacteria cells and increase the degree of water freedom. The multigelation can lead to formation of ice crystals from the intracellular water, which further influence the cell structure, and then cause the loss of intracellular water, resulting in cell collapse and rupture finally. LF-NMR analysis could provide the quantitative information of water distribution information in lactic acid bacteria cells precisely, and prove water distribution in the cells is closely related to cell damage further.
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