SUMMARY: The aerobic growth of adapted to a chemically defined glucose ammonium sulphate medium was studied in the same medium containing triethylene-melamine (TEM). In liquid medium containing TEM up to 205 mg./l. growth and division were only slightly retarded. With concentrations of TEM greater than about 255 mg./l. division was strongly inhibited while growth continued slowly, giving filaments the longest of which later separated from the medium as a white pellicle. Further growth and division occurred in the same culture after a lag. During continued subculture in liquid medium containing a constant concentration of TEM the lag was negligible but growth on return to drug-free liquid or solid medium was impaired. At first filament formation increased to a maximum, the growth rate fluctuated and adaptation was rapidly lost during subculture in drug-free medium. The progressive impairment of division was later opposed by a gradual adaptation which eventually produced bacteria of a more nearly normal size, with a steady growth rate and with resistance to precipitation and to higher concentrations of TEM. TEM was less active in solid medium than in liquid medium. The proportion of filaments and the size of the lenticular areas observed in colonies increased with increasing concentration of TEM but decreased with increasing age and size of the colonies.


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