SUMMARY: ATCC 6872 was grown aerobically in minimal defined glucose media of different osmolalities induced either by NaCl, other eletrolytes or non-electrolytes. Growth rate was slightly affected by elevation of medium osmolality up to 1 M-NaCl, but severely decreased at 1.5 M; however even at 2 M-NaCl, slow growth still occurred. Glycine betaine (or its precursor choline) did not stimulate growth in high osmotic media, although it accumulated intracellularly and was not metabolized. An organic solute which increased substantially in concentration during osmotic treatment with various osmolytes, was isolated and identified as pipecolic acid. No accumulation of this imino acid was observed when the medium concentration was raised by adding the permeant glycerol or when the culture medium was supplemented with glycine betaine (1 mM). While this non-proteic cyclic amino acid may play an important role in bacterial adaptation to environmental stress, it did not accumulate to a high level. Preliminary data suggest that the biosynthesis of pipecolic acid from lysine is strongly regulated by external osmolality.


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