214 NATURE OF ANTIBIOTIC ACTION 



culiar forms j spore formation or, with lower concentrations of agent, 

 the active substance is repressed j delayed nonspore-forming variants 

 are produced with a modified type of growth on nutrient media (Table 

 40). 



TABLE 40. INFLUENCE OF CULTURE FILTRATE OF STREPTOMYCES SP. ON 

 MORPHOLOGY OF BACILLUS MYCOIDES 



ous shape and length x — - 



Medium plus 5 per cent culture filtrate 



2 Elongated cells x - + 



4 Elongated cells x - + 



17 Greatly deformed cells + - + 



45 Greatly deformed cells + — + 



Control medium 



2 ++ - + 



4 ++ + + 



17 ++ + + 



45 Deformed cells rare ++ + — 



From Borodulina (80). 



X indicates growth of B. mycoides in the shape of fluffy small balls inside liquid. 



Gardner (308) reported that concentrations of penicillin lower than 

 those required for full inhibition caused a change in the type of growth 

 of CI. welchii in liquid media. The majority of the cells became greatly 

 elongated, giving rise to unsegmented filaments ten to twenty times 

 longer than the average normal cells. The same was found to hold true 

 for a number of other bacteria (Figure 26). Even gram-negative bac- 

 teria, which are relatively resistant to penicillin, showed the same ef- 

 fect. Many bacteria produced giant forms as a result of the autolytic 



