The complete life cycle of two odoriferous aquatic actinomycetes was observed in slide cultures. Branching of the vegetative mycelium yielded sporogenous hyphae. Frequent intimate contacts were observed between vegetative hyphae produced by the same or by different spores. No "initial cells" were detected. Contrary to previous reports, these aquatic actinomycetes appeared to be true streptomycetes and lacked an isogamous reproductive pattern. Vegetative mycelium developed pigments, sporogenous hyphae and odor under aerobic conditions, but not when grown under an atmosphere of inert gases or in the presence of 300 ppm malonate. Only small amounts of sporogenous hyphae could be produced by washed vegetative mycelium suspended in a balanced salt solution. Members of the genus Streptomyces have not commonly been reported from freshwater. Waksman in The Actinomycetes, Vol. 1, 1959, has stated that "Most of the species isolated appear to be largely members of the genus Micromonospora"; and cited the work of Erikson (1941), Colmer & McCoy (1943), Umbreit & McCoy (1941), as the basis for his statement. A description of streptomycetes occurring in American freshwater was made by Silvey & Roach (1953). Their studies linked these aquatic organisms to the production of unpalatable tastes and odors in water supplies of the southwestern United States. In later work Roach & Silvey (1958) proposed that these aquatic streptomycetes possessed an isogamous pattern of sexual sporulation. On this basis they separated them from the other genera found in the family Streptomycetaceae. Terrestrial streptomycetes have received much attention largely because of their ability to produce antibiotics. Numerous studies have demonstrated that genetic characteristics can be transferred between streptomycete auxotrophs (Hopwood & Sermonti, 1962). Klieneberger-Nobel (1947) was first to suggest a morphological foundation on which the above genetic information could rest. She reported that the vegetative or "primary mycelium" formed nests in which diploid "initial cells" were formed. These initial cells would germinate to yield the aerial or "secondary mycelium" in which reductional division would take place prior to sporulation. Unfortunately the complete duplication of her work has never been accomplished. The observations of Klieneberger-Nobel were vigorously challenged by Erikson (1949, 1955) on the basis that the initial cells were results of cultural and staining artifacts rather than actual developmental stages, and that vegetative hyphae tend to oppose contact. However, Davis (1960) observing living specimens reported that the vegetative hyphae did not actively oppose one another and interpreted the points at which these hyphae were touching as anastomoses. But Hopwood (1960), using similar live culture techniques and producing photographs with similar arrangements of hyphae, could not find any conclusive evidence for hyphal fusion or anastomosis. He concurred with 0rskov (1923) and 1 Present Address: Institute of Microbiology, Rutgers-The State University, New Brunswick, New Jersey. These investigations were supported in part by National Institutes of Health grants Nos. AI-00558-8,9. We also thank Dr. H. A. Lechevalier, Rutgers-The State University, for his help in the preparation of this manuscript. TRANS. AMER. MICROSC. Soc. 85,(3): 390-3918. 1966. This content downloaded from 207.46.13.124 on Wed, 22 Jun 2016 05:57:58 UTC All use subject to http://about.jstor.org/terms HIGGINS AND SILVEY-STUDIES ON FRESHWATER ACTINOMYCETES 391 WAX SEAL ON VINYL DISC SLIDE
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