Some Mutant Phages Produced Directly by Bacillus Megatherium 899a With Their Rate of Occurrence

Abstract

The purpose of this study is to find out if bacteriophage mutants are produced directly by the lysogenic bacterial strain Bacillus megatherium 899a (1) and, if so, what types and frequencies are to be found. The results indicate that in all probability phage mutants are produced directly from lysogenic B. megatkeriura 899a and occur with a frequency of about one recognizable plaque mutant per 2000 normal individuals.The experiment was designed to show whether passage through a sensitive cell was a major factor in the apparent production of mutants. The possibility of passage through a sensitive cell in the lysogenic culture was controlled by contrasting B. megatherium 899a growing in two media, one in which infection was virtually certain (peptone) and one in which it was highly unlikely (asparagine) (2). If the number of mutants was approximately the same in the two cultures, it would show that the infection of a sensitive cell occurring in the lysogenic culture did not play an important role in the production of mutants. If there was a significant variation in the two cultures and it could be demonstrated that the two mutation rates were not correlated, the plating suspension could be ruled out in the occurrence of mutants.The results indicate that sensitive cells in the lysogenic culture do not play a significant role. The plating suspension test did not reveal as clear cut a result but gives every reason to believe that mutants are produced directly by B. megatherium 899a (lysogenic).An attempt has been made to isolate and classify all the mutant phages recognized during this study and data are included which give some indication of the frequency of occurrence of these mutants. Several new mutants have been found, increasing the number described to 19 (3, 4). Materials and MethodsBacterial strains.--B, megatherium 899a (lysogenic) isolated by den Dooren de Jong (1) was sent to this laboratory by" Gratia in 1949. It has been transferred weekly on 2 per cent 657

THYMINELESS INDUCTION OF BACTERIOPHAGE IN BACILLUS MEGATERIUM

“…It was obtained from strain KM:T-, a previously characterized thymine auxotroph of B. megaterium KM (Wachsman, Kemp, and Hogg, 1964a), by infecting at high multiplicities, with a phage suspension from strain 899a. B. megaterium 899 is lysogenic, and several of its substrains have been extensively studied (Gratia, 1936;Lwoff, Siminovitch, and Kjeldgaard, 1950;Northrop, 1951;Murphy, 1954;Jeener, 1959). They are not, however, auxotrophic for thymine.…”