Studies on the specificity of choline esterase in Helix pomatia

METABOLISM OF PENICILLIUM NOTATUM 343 and penicillin production, except insofar as the disappearance of these fractions gave an indication of the general state of mould development.The output of penicillin by the mould followed the uptake of carbon, nitrogen and sulphur by the mycelium with a lag of 2-3 days.The reappearance of sulphur and nitrogen in the medium and the decline in mycelial carbon is probably related to senescence in the older parts of the mycelium, but further investigation is necessary.The peculiar fluctuations in phosphate content of the medium are as yet inexplicable.This phenomenon may-be connected with the observation made by the author that the addition of phosphate buffer to growing cultures of Penicillium notatum produces only a transient change in the pH value which rapidly reverts to that of the parallel control culture.The inhibition experiment may be contrasted with results obtained by Mann (1943).This worker found that godium iodoacetate (M x 10-3), sodium azide (M x 1o-3) or sodium fluoride (5M x 10-3), when added to cultures of A8pergillus niger on medium containing 10 % glucose and inorganic salts, caused a complete inhibition of the phosphorus metabolism and brought respiration to a standstill.SUMMARY 1.The following metabolic fractions have been determined throughout the growth of Penicilliu?m notatum: total carbon, reducing sugar, total nitro- gen, amino-nitrogen, nitrate nitrogen, volatile base, phosphate phosphorus and total sulphur of the medium, total carbon and nitrogen of the mycelium, and the rate and quantity of C02 evolved by the growing culture.2. Penicillin production by P. notatum followed the general absorption of carbon, nitrogen and sul- phur into the mould mycelium.3. No sharp discontinuities in the metabolism of P. notatum have been observed.4. The exchange of phosphorus between the mould mycelium and the medium followed a fluc- tuating course which is as yet not understood.5. The decline in the penicillin activity of the cultures was accelerated by the addition of ammo- niumn ion although no pH change was produced by this treatment.My thanks are due to my assistants, Mr M. Fisher and Miss F. Gilder, forcarrying out muchofthe chemical analysis.