AQUALINDERELLA FERMENTANS GEN. ET SP. N., A PHYCOMYCETE ADAPTED TO STAGNANT WATERS. II. ISOLATION,CULTURAL CHARACTERISTICS,AND GAS RELATIONS

This newly described member of the Leptomitales was incapable of growth in air on complex media routinely used to culture its nearest relatives. All attempts to isolate it in pure culture were unsuccessful until it was held in an atmosphere established by burning a candle in a sealed jar. Under these conditions it grew vigorously on various complex media and could be readily propagated in the laboratory in pure as well as in unifungal gross cultures. Like a number of other aquatic phycomycetes, A qualinderella fermentans proved to be a strong acid producer, its cultures requiring frequent neutralization during active growth. Work with pure cultures revealed a combination of gas relationships not described before among the fungi. A high level of atmospheric CO₂ is required, with good growth occurring between 5 and 20%. Growth also takes place under 99% CO₂. Supplemental CO₂ is partially replaceable by succinate. A. fermentans exhibits undiminished growth in an atmosphere of CO₂-supplemented hydrogen, essentially devoid of oxygen (leuco-methylene blue). These features are accompanied by an obligately fermentative energy metabolism. Ecologically, A. fermentans is adapted to an environment poor in oxygen and rich both in carbon dioxide and in fermentable organic matter. Such environments are likely to prevail in the warm, stagnant pools where this water mold has been found growing on submerged fruits. In many aspects of its cultural behavior and metabolism A. fermentans resembles another highly fermentative water mold, Blastocladia (Blastocladiales, Chytridiomycetes). The suggestion is made that in both instances parallel regressive evolution has occurred.