Media for Leuconostoc mesenteroides P-60 and Leuconostoc citrovorum 8081.

In the routine use of typical media for the microbiological determination of the sixteen amino acids standard curves have accumulated which reveal the amounts of each amino acid required for the growth of the assay organism when all other amino acids are present in excess. Thus it was observed that the relative amounts of the various amino acids needed by Leuconostoc mesenteroides P-60 did not coincide either with the proportions found in casein, on which many media are based, or with those of any other medium currently used for the determination of amino acids with this organism. Media containing border line amounts of one amino acid in the presence of a great excess of a related acid are often unsatisfactory for assay purposes; typical imbalances have been observed between serine and threonine (l), aspartic and glutamic acids (2), norleucine and methionine (3), valine and leucine (4), phenylalanine and tyrosine (4), and glycine and alanine (5). The degree of imbalance (excess concentration of one member of the pair) must usually be great before adverse effects upon sensitive organisms become evident, and while gross imbalances seldom appear in the media used for assay purposes, the possibility remained that the cumulative effect of minor imbalances in an ordinary medium might be responsible for Borne of the irregular responses observed in connection with the determination of amino acids. The present study deals with the responses of the two strains Leuconostoc mesenteroides P-60 and Leuconostoc citrovorum 8081 to a medium based on the requirements of the former organism, and with certain modifications in technique which improve the determination of several of the eighteen amino acids that can now be made with these organisms.