THE NUMBERS AND GROWTH RATES OF THE BACTERIA IN HEVEA LATEX, AMMONIATED FIELD LATEX AND AMMONIATED LATEX CONCENTRATE

SUMMARY: The rates of growth of bacteria on Hevea latex systems in the presence and absence of ammonia have been derived from colony count data obtained on a modified Kligler's iron agar medium. For fresh latex, ammoniated field latex, and ammoniated latex concentrate, variations in the bacterial populations encountered are given for a period of about one year's testing, with some data on commercial samples of latex concentrate. Field latex at routine collection contained about 8 × 10 6 bacteria/ml. This could be reduced by 62% by the use of sterile tapping cups. In the routine latex, the mixed population grew logarithmically after a lag phase of 2·1/2–3 hr. In clean latex the lag phase was extended to 4 hr. On ammoniation to 0.3% (w/w), the population was reduced over about 2 hr, but subsequently logarithmic growth recurred, without a lag phase. On concentration and further ammoniation to 0·7% (w/w), the count dropped still further, levels of 10/ml or less being achieved in clean conditions, but very slow logarithmic growth again occurred with a lag phase preceding it.