Different soils were exposed to 2450 MHz microwaves in the laboratory and in the field. The effect of microwave radiation on soil microorganisms was assessed by classical microbiological techniques. It was found that soil bacteria, bacterial spores, actinomycetes, fungi, nitrogen-fixing bacteria, and nitrifying bacteria were resistant to 40,000 joules of microwave energy applied to each cm of soil surface. Weed seeds exposed to much lower levels of radiation were uniformly inactivated in laboratory and field experiments. Bacteria became susceptible to microwaves when removed from their natural habitat but they were not affected by soil moisture. There appear to be no residual effects of microwaves in the soil and the effects on microorganisms seem to be nonselective except that fungi, as a class, were more susceptible. A “heat shock” activation of bacterial and fungal spores was observed. From the data presented, it is reasonable to assume that microwaves can be used to control field weeds without damage to the soil microorganisms.

Some precise data, obtained by E. L. Schmidt, on nitrification in soil by a single species of Nitrobacter is analyzed in terms of logistic growth kinetics. Nitrite oxidation continues after growth ceases because of maintenance and wasted metabolism of these microorganisms.

Foram analisadas 19 amostras de SAL (NaCl), tipo grosso, oriundas de diferentes salinas, para verificação da flora microbiana e presença de bactérias nocivas em Microbiologia Alimentar. O material apresentou grande contaminação por microrganismos saprófitas, bactérias aeróbias e anaeróbias, Gram positivas e negativas, proteolíticas, pigmentadas, esporuladas, leveduras e fungos. A alta incidência das bactérias halofílicas "vermelhas", responsáveis pela deterioração de carnes, pescados e outros produtos salgados foi estudada. A freqüência, em 15 amostras de SAL, de bactérias esporuladas termorresistentes foi calculada em 33%, possuindo um SAL germe termofílico. Para anaeróbios a positividade foi de 80%, havendo esporulação em 40% das culturas isoladas. Os índices para leveduras e fungos foram de 73% e 93%, respectivamente.<br>19 samples of marine salt (NaCl), granular type, from different salines, were analized to verify the microbial flora and the presence of "food-poisoning" bacteria. The material presented a great contamination by saprofit microorganisms, aerobic and anaerobic bacteria Gram positives and negatives, proteolitics, pigmented, sporulated, yeast and fungi. The high incidence of "red halophilic bacteria", responsible for meat deterioration, fish and other salted products, was studied. The frequence, in 15 samples of salt, of sporulated heat-resistant bacteria was estimated at 33% containing one salt termophilic germ. For anaerobic microorganisms the positiveness reached 80%, sporulation processed in 40% of the isolated cultures. The index for yeast and fungi was 73% and 93%, respectively.

After treating soil with labeled substrate and incubating for various periods of time, carbohydrates were extracted using several reagents. The C in the extracts was determined and interpretations were made relative to soil polysaccharide synthesis. Microorganisms utilized glucose more rapidly than dextran and polymers of high molecular weight containing C had been synthesized by 2 days in the glucose-treated soil. Soils treated with either substrate showed a significant increase in mannose at 5 days in the high molecular weight of polysaccharides examined. Presumably this was of fungal origin.

The hexane-acetone method was used to measure the phospholipid P content of some cocoa soils. The values which ranged from 1_75 IJ-g P g-l soil to 12_93 IJ-g P g-l are more in line with European levels than North American levels. Soil-extract dilution plates revealed 16 x 10y - 81 X 10y bacteria per gram in the 0-15 cm layer. Even though plant residues contributed significantly to the phospholipid P content of soil, microorganisms are considered to be the major source. The increase in soil inorganic P at a time when cocoa required most of its P, the decrease in both the phospholipid P and organic P and the time of application of fertilizer P were suggested as possible reasons why available P estimated by the conventional methods are not related to P response by cocoa.