EFFECT OF MALATHION AND TRICHLORFON ON GROWTH1 AND MORPHOLOGY OF LACTIC CULTURE ORGANISMS

Abstract

Addition of 100 ppm of malathion or trichlorfon had little effect on lactic acid production in reconstituted non-fat dry milk by Streptococus diacetilactis or Streptococus thermophilus. Variation in cell size of Streptococus cremoris 3, Streptococcus lactis W 8 and several strains of S. thermophilus occurred following repeated transfers in litmus milk to which 100 ppm of malathion or 500 ppm trichlorfon had been added. The Lactobacillus bulgaricus A culture, after 15 serial transfers in litmus milk containing 500 ppm of trichlorfon, exhibited increased frequency of chain formation and cell structure 30 to 50 μ long with few visible cross walls. A similar effect was observed with L. bulgaricus A and L. bulgaricus GA after repeated transfers in litmus milk which contained 100 ppm malathion. One of five strains of L. casei studied showed similar changes in morphology after repeated transfers in litmus milk which contained 100 ppm malathion. Adding 500 ppm trichlorfon produced a lesser effect. Changes in morphology of this strain of L. casei were not permanent since cells resumed their usual appearance following three to five transfers in plain litmus milk.