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Studies were conducted to determine whether the differential toxicities of the two valence states of Cr (+3 and +6) occur with fungi as they do with bacteria as noted in previous studies. It was found that mycelial growth rates were inhibited more by Cr/sup 6 +/ than by Cr/sup 3 +/. Hexavalent Cr was also more toxic than equivalent trivalent Cr to spore formation and spore germination of the fungi tested. The greater toxicity of hexavalent Cr than of trivalent Cr to fungi is in agreement with the results observed with the bacterial studies. (JMT)

Coliphage T1 was more sensitive than its host bacterium,Escherichia coli B, to nickel (Ni). A 5-h exposure to 100 ppm Ni in nutrient broth did not adversely affect T1, whereas 10 and 20 ppm Ni extended the lag phase of growth ofE. coli B, and no growth occurred with 40 or more ppm Ni. 5 ppm Ni enhanced the survival (after 4 wk) of T1 in sea or simulated estuarine water but was toxic (i.e., reduced viral infectivity) in lake water; 50 ppm Ni was not toxic to T1 in sea water, was moderately toxic in estuarine water, but was highly toxic in lake water; and 100 ppm Ni was toxic in all systems, with the sequence of loss in viral infectivity being lake > estuarine > sea water. 100 ppm Ni was not toxic to T1 in nutrient broth, even after 3 wk of exposure, probably because of the protective effect of the organic compounds in the broth.

The mechanisms and sites of adsorption and binding of phages T1 and T7 of Escherichia coli, of reovirus type 3, and of herpesvirus hominis type 1 to montmorillonite (M) and kaolinite (K) were influenced by the characteristics of the clays (primarily by their cation exchange capacity and the ratio of the number of negatively-to positively-charged sites), the types and amounts of cations that were predominant on the exchange complexes and in the ambient solution, the characteristics of the viruses, and the presence of organics and other viruses. The viruses were protected by the clays, especially by M, against abiological inactivation by temperature and chemicals, but viruses bound to the clays were capable of infecting host cells. Adsorption of the coliphages to yeasts and bacteria, including actinomycetes and the host bacteria, was significantly less than to M and K. These observations have implications for the retention, movement, and persistence of viruses in soils, sediments, and particulate-laden waters.

Coliphages T1 and T7 of Escherichia coli were absorbed by kaolinite (K) and montmorillonite (M). Maximum adsorption of T7 (96%) to M was greater than that of T1 (84%), but the adsorption of both coliphages to K was the same (99%). Positively charged sites (i.e., anion exchange sites) on the clays appeared to be primarily responsible for the adsorption of T1 to K but only partially responsible for the adsorption of T1 to M; equilibrium adsorption isotherms of T1 to K and M did not show a correlation between adsorption and the cation exchange capacity of the clays, and the reduction in adsorption caused by sodium metaphosphate (a polyanion that interacts with positively charged sites on clay) was more pronounced with K than with M. The equilibrium adsorption isotherms of T7 to K and M suggested a correlation between adsorption and the cation exchange capacity of the clays. However, studies with sodium metaphosphate indicated that T7 also adsorbed to positively charged sites on the clays, especially on K. Adsorption of the coliphages to positively charged sites was greater with K than with M, probably because the ratio of positively charged sites to negatively charged sites was greater on K than on M.