The effects of varying the concentrations of the nitrogen sources in glycerol+asparagine, glycerol+asparagine+casein hydrolysate and glycerol +ammonium sulphate media on the composition and growth rate of BCG grown in shaken culture for various periods were investigated. The bacteria were fractionated and the soluble, alkali-extractable, hot acid-soluble and residual fractions analysed for carbohydrate, RNA, DNA, free lipid, soluble amino compounds and soluble phosphates.

The results indicate that several forms of growth restriction operated in these experiments: a progressive reduction in growth rate even in conditions when nutrients were not limiting, due to clumping of cells; a reduction in growth rate following any reduction in the amino acid content of the medium; a marked reduction in growth rate when the amino acid content of the medium fell below a critical level, or was replaced by ammonium ions. When the growth rate was reduced because of nutrient limitation, the carbohydrate content of the bacteria increased, but the pattern of accumulation varied with the experimental conditions. The RNA: protein ratio of the cells was little affected by growth rate.


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