Pseudomonas sp. was isolated from sewage effluent by elective culture with nitrilotriacetic acid (NTA) as its sole nitrogen and carbon source for growth. NTA-nitrogen was converted to biomass and ammonium by growing cultures with small quantities of nitrite (< 1 ppm) being produced. Washed cell suspensions degraded all of the NTA-nitrogen to ammonium before total conversion of the NTA-carbon to carbon dioxide and water. Resting cell suspensions grown from NTA oxidized NTA, aminodiacetic acid, and glycine immediately, whereas methylaminodiacetic acid was oxidized only after an adaptive lag period, and sarcosine was not oxidized at all. Oxidation of aminodiacetic acid was always more rapid than NTA. Nitrosamines or other nitroso compounds were not found in culture or resting cell supernatants incubated with NTA.

An improved method for enumerating denitrifying bacteria from soil by use of the most‐probable‐number method is outlined. Difco nitrate broth was used, and culture tubes near the dilutions to extinction were analyzed for the disappearance of nitrate‐nitrite. The distinction between denitrifying and nondenitrifying bacteria was clearly defined and thus minimized visual subjective errors. Earlier methods which assumed that a pH increase was due solely to denitrification were shown to be ambiguous by comparison between culture tubes for nitratenitrite disappearance; 1 out of every 4 tubes compared gave an erroneous reading for dentirification. The distribution of denitrifying bacteria within two different soil profiles showed a definite logarithmic decrease in numbers with depth.

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Denitrification rates were studied in four large soil columns using Hanford sandy loam and Moreno silty clay loam soils. One column of each soil was amended with sulfur to serve as an energy source for the bacterium Thiobacillus denitrificans. Limestone was also added as a pH buffer. The other column of each soil was left untreated to serve as a control. A solution of Ca(NO3)2 containing 425 ppm NO3‐N was perfused continuously through the columns. The columns were monitored periodically at depths of 10, 30, 50, 70, and 90 cm for nitrate, nitrite, redox potential (Eh) and microbial numbers. Highly anaerobic conditions developed in all columns as was evidenced by low Eh values at each depth. All of the nitrate was reduced in each column, and nitrates penetrated to lower depths in the untreated columns. Nitrite concentrations were found to be negligible. Denitrification rate constants were established as 0.174, 0.520, 0.186, and 1.426 days−1, for the Hanford‐untreated, Hanford‐treated, Morneo‐untreated, and Moreno‐treated columns, respectively. Sulfur additions to field soils which are low in microbial energy sources could be an effective method of reducing the nitrate level in waters percolating through the profile.

A nonaxenic sewage culture metabolized 1,1-diphenylethylene by two different pathways involving hydration to form 2,2-diphenylethanol and oxidation and fission of one of the benzene rings to form atropic acid. Five different bacterial strains which grew on 1,1-diphenylethylene were isolated; all were gram-negative rods comprising the genera Pseudomonas, Acetomonas, and Acinetobacter. A fungal isolate, Cladosporium, which used diphenylethylene as a sole carbon source, was also obtained from the same enrichment procedure.