Showing papers by "Arnold L. Demain published in 1968"

Specificity of the stimulatory effect of betaine on the vitamin B12 fermentation.

Abstract: METHYL donors such as betaine and choline are known to stimulate production of vitamin B12 by certain microorganisms1. Ansbacher and Hill2 reported that of the crude microbial processes available in 1949, the best were characterized by disappearance of choline from the medium. Miller and Putter of these laboratories (unpublished) discovered that betaine and choline stimulate B12 production by Pseudomonas denitrificans; this has been confirmed3,4. Stern5 independently found these two compounds to stimulate, by as much as five to sixfold, the formation of B12 by Rhizobium trifolii, R. meliloti, Agrobacterium sp. and Bacillus megaterium.

Dependence of Diaminopurine Utilization on the Mutational Site of Purine Auxotrophy in Bacillus subtilis II. Tracer Experiments

Abstract: An attempt was made to explain the puzzling observation that in bacteria 2,6-diaminopurine can replace guanine for guanineless mutants and for xanthineless mutants (both of which can make adenosine monophosphate de novo) but not for nonexacting purine auxotrophs (which cannot make adenosine monophosphate de novo). The analogue failed to inhibit the growth of nonexacting purineless Bacillus subtilis MB-1356 growing on guanine. In fact, growth was somewhat stimulated. This eliminated a possible solution involving the inhibition of guanosine monophosphate reductase by a diaminopurine derivative. Sparing of guanine by diaminopurine was matched by an even greater sparing of adenine. Addition of a small amount of adenine to MB-1356 failed to allow unrestricted growth on diaminopurine, thus eliminating a possible solution requiring an adenine derivative for the initial deamination of diaminopurine to guanine. The same degree of sparing of adenine by diaminopurine was observed whether both purines were added together or whether the adenine was added 1 hr after diaminopurine. This eliminated the possibility that diaminopurine was wasted by a "dead-end" conversion in the absence of adenine. Consideration of these nutritional data led to the development of two additional explanations, which are examined by tracer methodology in the following paper.

Phosphohydrolases and the production of 5′‐nucleotides by direct fermentation

Abstract: A major problem involved in the direct fermentation of nucleotides is their breakdown by phosphohydrolases. Thus, adenine auxotrophs of most microorganisms produce hypoxanthine and/or inosine rather than inosine 5′-monophosphate (IMP) while guanine auxotrophs excrete xanthosine rather than xanthosine 5′-monophosphate (XMP). Examination of a Bacillus subtilis mutant producing hypoxanthine plus inosine revealed at least four phosphohydrolases, three of which could attack nucleotides. Even when the extracellular nucleotide phosphohydrolase was inhibited by Cu+2 and its surface-bound alkaline phosphohydrolase was repressed and inhibited by inorganic phosphate, or removed by mutation, the breakdown products were still the only products of fermentation. Under these conditions, the third enzyme, a surface-bound non-repressible nucleotide phosphohydrolase was still active. It appears, at least in B. subtilis, that excretion is dependent upon breakdown by this enzyme and if hydrolysis does not occur, excretion of purine nucleotides is feedback inhibited by the resultant high intracellular IMP concentration. Corynebacterium glutamicum mutants, on the other hand, can excrete intact nucleotides, and direct fermentations for IMP, XMP, and GMP have been described. An examination of phosphohydrolases in a GMP-producing culture revealed no extracellular or surface enzymes. Disruption of the cells resulted in liberation of cellular phosphohydrolase activity with a substrate specificity remarkably similar to the flavorenhancing properties of the 5′-nucleotides. The order of decreasing susceptibility was GMP, IMP, XMP; AMP was not attacked.