Microbiology of saturated salt solutions and other harsh environments. II. Ribonucleotide dependency in the growth of a salt-habituated Penicillium notatum in salt-free nutrient media.

A strain of Penicillium notatum has been found growing upon media containing saturated calcium acetate which upon passage through media containing saturated KC1 loses its ability to grow at normal rates in salt-free glucose-peptone medium. This salt-habituated form can be restored to a near-normal growth rate by adding yeast extract, RNA or RNA-hydrolysates, but not by DNA or its hydrolysate. The 4 RNA nucleotides in combination replace yeast extract whereas riboside and base combinations do not. Adenylic, guanylic or cytidilic acids, singly or in various combinations, are even more effective, but uridylic acid alone is not active at all. Ribonucleotide pairs including uridylic acid are less active, but 3 ribonucleotide combinations are highly effective, even in the presence of uridylic acid. Differential effects were evident in mycelial form and sporulation, as well as growth. In addition to a direct role in Penicillium RNA metabolism, the significance of ribonucleotides in energy metabolism or cell wall synthesis is mentioned as alternatives to explain their restorative effects.