THYMINELESS INDUCTION OF BACTERIOPHAGE IN BACILLUS MEGATERIUM

Abstract

Bacillus megaterium was obtained by lysogenizing a previously characterized thymine auxotroph of strain KM (KM:T-) with a phage suspension from B. m?egaterium 899a. When strain KM:T-(L) is de

Effects of Mitomycin C and Thymidine Deprivation on Lysogenic and Sensitive Strains of Bacillus megaterium

“…This observation might argue in favor of the presence of other inducible elements (prophage or probacteriocins) in sensitive strains of KM. However, it should be emphasized that cell lysis can be detected only 60 to 120 min after the initiation of exponential death (6,20). In addition, attempts to detect either infectious phage, killing particles, bacteriocins, or morphologically identifiable phage components in sensitive strains of KM, or to obtain cured strains, have been unsuccessful (Maisch and Wachsman, unpublished data).…”

“…The techniques used for the measurement of turbidity, as well as those for the determination of cell ribonucleic acid (RNA), deoxyribonucleic acid (DNA), and protein have been described in detail (21). Viable-cell counts and freephage titers were determined as described previously (6), by use of the soft-agar overlay technique with tryptose-yeast extract-agar.…”

Characteristics of φT, the Temperate Bacteriophage Carried by Bacillus megaterium 899a

“…Bacterial strains and cultivation. B. megaterium 899a was kindly sent to us by J. T. Wachsman along with B. megaterium KM (T Tr U),-which was used as a XT indicator strain (11). An asporogenous strain B. megaterium 899a Sp--1, which was blocked early in sporulation, was readily selected.…”

“…Phage assay. The phage assay was similar to that used previously (11), but the media were changed so that in an overlay medium the bottom layer was nutrient agar (Difco, 1.5% agar) with 2 x 10-3 M MgCl2, and the top layer consisted of 4 ml of sloppy agar (1/3 nutrient agar plus 2/3 nutrient broth (Difco) with 2 x 10-3 M MgCl2), 1.0 ml of phage suspension and 0.2 ml of a suspension (108 bacteria/ml) of the indicator strain. The indicator bacteria were grown overnight on nutrient agar.…”

Properties of Thymineless Strains of Bacillus megaterium1

“…Previous studies with thymineless strains of Bacillus megaterium KM have shown that both lysogenic and phage-sensitive derivatives undergo similar rates of thymineless death, despite the fact that lysogenic strains are induced by thymine deprivation (5,6). Since there is no evidence that phage-sensitive strains of B. megaterium carry any inducible elements (prophage or probacteriocins), it was concluded that thymineless death occurs via mechanisms unrelated to phage induction (6).…”