Fungi Capable of Growing in Strongly Acid Media and in Concentrated Copper Sulfate Solutions.

It is well established that the bacterium Thiobacillus thiooxidans is capable of growing in very strong mineral acid solutions and of producing, from elementary sulfur, sulfuric acid solutions more concentrated than 1 N and a reaction considerably below pH 1. This organism had been considered unique in its tolerance to acid until Starkey and Waksman (1943) demonstrated that certain fungi, Acontium velatum Moore, and an unidentified dematiaceous mold were able to develop in a medium initially as acid as 2.5 N sulfuric acid and in a normal sulfuric acid solution saturated with copper sulfate. We were able to confirm the tolerance to extreme acidities of some fungi with three isolates and tolerance to copper sulfate with two of them. The first isolate, no. 7752, was obtained from a bottle of N/5 sulfuric acid reagent, the second, no. 9010, from soil rubbish picked up from an athletic running track, and the third, no. 9024, from another sample of standard sulfuric acid reagent. Numbers 7752 and 9024 are possibly the same as Starkey and Waksman's unidentified dematiaceous mold. It has been tentatively identified as Trichosporon cerebriforme (Kambayashi) Ota by Dr. R. L. Bouthilet. Difficulties in getting authentic cultures for comparison or original descriptions published in Japan have made it impossible for him to make an absolute identification as yet. The third isolate died out before it was identified. The first experiment demonstrates that when T. cerebriforme (which breaks up readily into what we interpreted as arthrospores, but Starkey and Waksman as chlamydospores) is inoculated, in amounts so small as to be invisible in the culture, into amedium consisting of 1, 1.5, or 2 N solutions of sulfuric acid plus 0.1 per cent glucose and 0.1 per cent peptone, a growth results easily visible as dark, almost black, globose masses of hyphae. Growth was evident in about 10 days with the 1 N acid solution, but prolonged incubation was necessary to obtain the maximum yields. The incubation was at room temperature. The second experiment was in part a confirmation of the first. Narrowmouthed bottles of about 400-ml capacity, half filled with media, were used. Some were sealed with glass stoppers; others were plugged with cotton wool. The media in the second experiment were essentially the same as in the first, except that some were more strongly acid, and some were not autoclaved. The normalities of the media were determined before and after incubation. Following