Bacterial lysis by lysozyme.

Observations were made on cultures obtained from three different sources: one (C) maintained for many years in this laboratory, another (4698) received from the American Type Culture Collection, and a third (F) received recently from Dr. Fleming. To our knowledge all derive from the original organism isolated by Fleming (1922). For purposes of convenience each will be designated as a separate "strain." All three, with a few minor variations, exhibited the same cultural characteristics and could not be distinguished on the basis of the usual laboratory tests. Immunologically, however, there was a significant difference between the C and 4698 strains on the one hand, and the F on the other. The organism, a gram-positive micrococcus, grows well on ordinary media within a range of pH 7.0 to 7.6 and at an optimum temperature of 37 C. The colonies in undifferentiated cultures are characteristicaly yelow, convex, opaque, smooth, and glistening. The F strain when received produced a definitely lighter pigment than the other two, and this difference is still apparent after repeated transfer. In broth all cultures usually remain clear, with a sediment which becomes more and more viscid on aging. Better growth is obtained in shallow layers or with aeration. In agar shakes growth occurs on or very near the surface. Reactions in the usual biochemical tests are generally negative. Gelatin is not liquefied. Nitrates are not reduced. Litmus milk becomes slightly alkaline with no other changes. Glucose, lactose, maltose, saccharose, mannitol, and salicin are not fermented. Indole and H2S are not produced. Starch is not hydrolyzed. The 4698 strain was used in experiments to develop a synthetic medium which would support the growth of M. lysodeikticus. A basal medium containing vitamin-free acid hydrolyzate of casein (General Biochemicals), 0.5 per cent; cystine, 0.01 per cent; tryptophane, 0.01 per cent; salts A and B (according to Snell and Wright, 1941); and adenine, 5 ppm; resulted in visible but poor growth. None of the following substances when added to the basal medium proved to have a stimulatory effect: thiamine, niacin, pyridoxine, pantothenic acid, riboflavin,