Haim B. Gunner

The distribution and persistence of diazinon applied to plant and soil and its influence on rhizosphere and soil microflora

Summary1. Evidence was obtained of the rapid translocation of radioactive Diazion through bean plants and its emergence in bean root exudates maintained under sterile conditions.2. The presence of bean rhizosphere microflora did not appear to be a factor in the metabolism of Diazinon by the bean plant.3. Diazinon applied at the rate of 3 lbs per acre to soil under non-sterile conditions persisted for as long as 180 days after application. No Diazinon was detectable after 10 weeks in soil receiving 0.3 lbs per acre.4. Diazinon or its degradation products exerted a selective effect common to both soil and rhizosphere microflora which expressed itself in the selective enrichment of a cocoidal rod. Numbers of fungi seemed unaffected by the presence of Diazinon. After 180 days a large number of the genus Streptomyces appeared as a seeming climax population.5. The predominant microbial isolate utilized Diazinon as a sulfur, phosphorus, carbon and nitrogen source in that order of preference. The biodegradability of Diazinon was conditioned by its solubilization in a suitable carrier, and by the presence of an additional carbon source.

Bacterial suppression of chlorella by hydroxylamine production

An actively nitrifying Arthrobacter sp. isolated from a lake inhibited the growth of Chlorella vulgaris. This was found to be due to hydroxylamine released by the bacterium during the oxidation of ammonium or other reduced nitrogen compounds. Plates containing Plate Count Agar streaked with Arthrobacter, accumulated 5 μg ml−1 hydroxylamine-N. Chlorella was sensitive to less than 0.24 μg ml−1 hydroxylamine-N. Non-nitrifying bacterial isolates of lacustrine origin did not demonstrate inhibiting activity. Our results indicate that nitrifying microorganisms may thus affect the population dynamics of algae in eutrophic lakes.

Studies on the biodegradation of parathion

SummaryFour compounds formed as the results of parathion degradation byChlorella pyrenoidosa proteose were identified or partly characterized in these studies. The major parathion metabolite, aminoparathion, was shown by bioassay to be nontoxic to vinegar flies at the levels tested. Evidence is presented that aminoparathion is released rapidly from algal cells after this compound is formed from parathion. Metabolites of unknown chemical structure which were detected were partially characterized as follows:Metabolite 1- contains sulfur and phenyl ring, strong cholinesterase inhibitor.Metabolite 2- contains sulfur, lacks phenyl ring, not a cholinesterase inhibitor at levels tested.Metabolite 3- contains phenyl ring but not sulfur, a strong cholinesterase inhibitor. Probably an oxon of parathion. The findings herein support previous conclusions that biotic forces, rather than abiotic factors, are of greater importance to the degradation of parathion under natural conditions extant in a temperate climate.

Selective Feeding of Tubificids on Bacteria

THE characteristic abundance of tubificid worms in the benthic ooze of sewage outfalls, their curious up-ended posture and sedentary feeding habit suggest a saprobic, non-selective type of nutrition. Feeding has been interpreted as a continuous process of indiscriminate ingestion and pumping of an endless column of sapropel through the digestive tract1. We have gathered evidence, however, which does not support this generalization, but indicates selective feeding.

Nitrite and nitrate synthesis from pyruvic-oxime by anAlcaligenes sp.

AnAlcaligenes sp. isolated from soil was characterized as to its ability to oxidize and grow on pyruvic-oxime. Abundant nitrification of pyruvic-oxime was demonstrated with maximal nitrite and nitrate production of 1867 mg NO2−-N per liter and 42 mg NO3−-N per liter. TheAlcaligenes sp. oxidized hydroxylamine and this metabolism was stimulated when either acetate or pyruvate was present. This organism was also capable of limited pyruvic-oxime oxidation when cultured in an acidic medium. The metabolism of pyruvic-oxime and nitrification by theAlcaligenes sp. in the environment are discussed.

Microbial populations as determinants in protozoan succession

Abstract Twelve species of ubiquitous soil and water bacteria were randomly selected as substrates for a soil ciliate. Six species (particularly Escherichia coli and Aerobacter aerogenes) supported a flourishing protozoan population, while the remaining six (predominantly of the genus Arthrobacter) were of meagre nutritive value. Preliminary investigations indicate the presence of a toxic cytoplasmic principle that limits protozoan predation. This factor may account for the universal distribution and persistence of Arthrobacter while their nutritive attractiveness may explain the rapid disappearance of coliforms from soil and water.

Microfloral response to aquatic weed decomposition

Abstract Microfloral response to the liberation of N and P from decomposing water milfoil tissue ( Myriophyllum heterophyllum ) was determined under various laboratory conditions. The death and decay of the macrophyte released ammonia and phosphate in concentrations sufficient to promote algal growth. The oxidation of ammonia by resident nitrifiers exercised a striking impact on microfloral succession. Nitrification was accompanied by a decrease in pH and thereafter by a decline in the numbers of bacteria and protozoa. Subsequently, coincident with the accumulation of nitrite and nitrate, the numbers of the resident green algal communities rose dramatically. These results, coupled with field observations, indicate that nutrient released by decomposing aquatic weeds and the changes attendant upon nitrification are of significance in the distribution and abundance of aquatic microflora.

Differential response of soil microflora to diazinon

Summary1. Bacteria whose growth was inhibited by Diazinon had diminished rates of oxygen uptake in the presence of Diazinon with ethanol, citrate, glutamate, succinate, malate and sometimes glucose or sucrose as substrate.2. Bacteria whose growth was not inhibited by Diazinon had rates of oxygen uptake in the presence of Diazinon as high as those in the absence of Diazinon with all substrates tested.3. Only Diazinon inhibited both oxygen uptake and growth over a five day period. Diazoxon inhibited oxygen uptake but only retarded growth. When the hydrolysis products of Diazinon were added, 2-isopropyl-4-methyl-6-hydroxypyrimidine did not inhibit either growth or oxygen uptake; diethyl-phosphorothioate caused an increase in oxygen uptake but no significant increase in growth.4. In a mixed culture where two organisms sensitive to Diazinon were dominant over a third Diazinon- esistant organism, the presence of Diazinon reversed the ecological balance with resulting dominance of the resistant form.

Studies On a Growth Supplement for Caenorhabditis Briggsae From Freeze-Dried Bacteria

Freeze-dried bacteria isolated from Panagrellus redivivus, contained a growth supplement that initially supported rapid growth and reproduction of Caenorhabditis briggsae. However, after four serial subcultures, the nematodes became sluggish and eventually died. Evidence is given that C. briggsae utilizes the bacterial cell as a food source, thereby showing that the bacterium-nematode relation is not one of mutualism.

The effect of microbial mycolytic agents on Trichophyton rubrum

Synopsis-AbstractChitinolytic microorganisms isolated from forest soil and from healthy gypsy moth larvae (Porthetria dispar (L.) were screened for their ability to lyseTrichophyton rubrum mycelia. A few of these isolates were mycolytic on both autoclaved and on actively growing, intact,T. rubrum mycelia. Supernatants from these isolates, utilizing liveT. rubrum as the sole carbon source, showed the same mycolytic ability. Assays of the supernatants for enzymatic activity revealed exocellular, stable enzymes that released reducing substances including N-acetylglucosamine from the mycelia.