MOISTURE REQUIREMENTS OF BACTERIA

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Abstract
As water activity (aw) was lowered with KC1 from a favorable level, lag phase and generation time of A. aerogenes were progressively lengthened at any 1 temperature, until growth was prevented. As temperature was decreased below the optimal for rate of growth (37[degree]C), the lower limit of aw for growth was raised progressively. The apparent lag phase and the generation time were also proportionately longer at low aw values than would normally be expected for a drop in temperature. At acid pH values the tolerance of the organism to low aw was less than within the optimal pH range; but at alkaline pH values tolerances to low aw were greater than at pH 7.0, lag phases were shorter and generation times longer. When both pH and temperature were made unfavorable, lower limits of aw for growth were higher, and lag phases and generation times were longer, than if only 1 factor was made adverse. A. aerogenes needed less water for growth in the presence of malate than in its absence.