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Biomedical subjects

C M Tu

Publications and source records attributed to C M Tu.

15 recordsLinked to original sources
PubMed1979

Influence of pesticides on acetylene reduction and growth of microorganisms in an organic soil.

The effects of 32 pesticides at two concentrations on acetylene reduction (non-symbiotic nitrogen fixation), nitrogen fixers, bacteria and fungi in an organic soil were assessed. None of the pesticide treatments suppressed C2H2 reduction as compared to controls. No significant inhibition of the population of non-symbiotic nitrogen fixers occurred. However, stimulatory effects were observed with treatments of fensulfothion, fonofos, oxamyl, DDR, TeloneR and Telone CR. Bacterial and fungal populations showed temporary declines but all recovered within 7 days to levels similar to or higher than those in the controls.

Acetylene↗
PubMed1978

A screening technique for assessing effects of pesticides on population and activities of non-target soil microorganisms.

A simplified technique for assessing the effect of pesticides on non-target soil microorganisms was developed. Changes in microbial population determined by the dilution plate method, in nitrification by the soil perfusion technique, and in oxygen consumption using a differential respirometer are the only measurements required. A comparison of the effects observed for three pesticides, dieldrin, chlorpyrifos and Vorlex, in three soil types with those produced by an antibiotic, a fungicide, a nitrification inhibitor and steam pasteurization of the soil clearly demonstrate the effectiveness of the simple technique.

Chlorpyrifos↗
PubMed1977

Effects of pesticide seed treatments on Rhizobium japonicum and its symbiotic relationship with soybean.

Seventeen Rhizobium japonicum cultures isolated from soybean nodules induced formation of nodules on taproots of soybean plants. All isolates reduced acetylene to ethylene to different extents in vitro. Paper disc assay indicated that two insecticides, lindane (gamma-1,2,3,4,5,6-hexachlorocyclohexane), chlorpyrifos (O,O-diethyl O-3,5,6-trichloro-2-pyridyl phosphorothioate), and a fungicide, thiram (tetramethylthiuram disulphide) individually or in combination caused significant inhibition of the growth of R. japonicum No. 16. The effects of insecticide-fungicide seed treatments on the nitrogenase activity of soybean plants in nitrogen-fixing capacity, weights of leaves, stems, and nodules were determined. Thiram, singly or in combination with lindane and/or chlorpyrifos, significantly delayed growth of the plants and affected the activity of nitrogenase in the fixation of nitrogen 3 weeks after treatments. No drastic effect of any of the pesticide treatments on soybean plant growth was observed after 8 weeks.

Acetylene↗
PubMed1976

Utilization and degradation of lindane by soil microorganisms.

Of 147 microorganisms isolated from a loamy sand, 71 showed good growth with lindane (gamma-1,2,3,4,5,6-hexachlorocyclohexane) and produced chloride in an aqueous medium. Thirteen soil microorganisms were selected to study the utilization of lindane. Lindane was metabolized by the microbes to gamma-2,3,4,5,6-pentachloro-1-cyclohexene (gamma-PCCH), alpha-3,4,5,6-tetrachloro-1-cyclohexene (alpha-TCCH), beta3,4,5,6-tetrachloro-1-cyclohexene (beta-TCCH), gamma-3,4,5,6-tetrachloro-1-cyclohexene (gamma-TCCH), and pentachlorobenzene (PCB). Cells of Pseudomonas sp. No. 62 grown on lindane simultaneously adapted to gamma-PCCH, alpha-TCCH, beta-TCCH, gamma-TCCH, PCB, 1,2,3,4,-tetrachlorobenzene (1,2,3,4-TCB) and 1,2,4,5-tetrachlorobenzene (1,2,4,5-TCB). The bacteria degraded each of these chemicals at least partially as indicated by an increased rate of oxygen consumption.

Actinomycetales↗
PubMed1975

Interaction between lindane and micorbes in soils.

Three lindane (gamma-1,2,3,4,5,6-hexachlorocyclohexane) treated soils were studied under laboratory conditions to determine the interaction between lindane and the soil microorganisms. Microbial populations and respiration were monitored to study insecticide effects. Formation of lindane degradation products and chloride content were examined to determine effects of the microorganisms. Some populations in lindane treated soils showed temporary declines but all ultimately recovered to at least the level of the controls in 16 weeks. Respiration was stimulated over a 9-week period especially in the sandy and clay loams, suggesting the possibility of microbial degradation of the insecticide. Lindane degradation products separated and identified by TLC included gamma-2,3,4,5,6-pentachloro-1-cyclohexene (gamma-PCCH), gamma-3,4,5,6,-tetrachloro-1-cyclohexene (gamma-TCCH), gamma-3,4,5,6-tetrachloro-1-cyclohexene (gamma-TCCH), and pentachlorobenzene (PCB). Chloride production increased in soils treated with higher levels of lindane.

Bacteria↗
PubMed1972

Effect of four nematocides on activities of microorganisms in soil.

Tests were conducted to determine the effects of four nematocides, Dasanit, carbofuran, D-D, and Vorlex on microbial activities in a loamy sand. The results indicated that bacterial and fungal populations initially decreased with some nematocide treatments but recovered rapidly to levels similar to those in the controls. In some instances, ammonium production from added peptone increased in the nematocide-treated soils, whereas mineralization of soil organic nitrogen and nitrification and oxidation of elemental sulfur were depressed. Oxygen consumption generally increased in proportion to the concentration of nematocide in the soil. However, with Vorlex, an increase in respiration was evident at the lower concentration, whereas an inhibitory effect occurred at the higher concentration. The study indicated that indigenous soil microorganisms can tolerate these chemicals used for control of nematodes in soil.

Ammonia↗
PubMed1970

Effect of four organophosphorus insecticides on microbial activities in soil.

Laboratory tests were conducted with four organophosphorus insecticides, Bay 37289 (O-ethyl O-2,4,5-trichlorophenyl ethylphosphonothioate), diazinon [O,O-diethyl O-(2-isopropyl-4-methyl-6-pyrimidinyl) phosphorothioate], Dursban (O,O-diethyl O-3,5,6-trichloro-2-pyridyl phosphorothioate), and Zinophos (O,O-diethyl O-2-pyrazinyl phosphorothioate), applied to a sandy loam at rates of 10 and 100 mug/g to determine whether these materials caused any serious effects on microbial activities related to soil fertility. All insecticides showed an effect on fungi and bacteria for the first and second week of incubation, but, subsequently, the populations returned to levels similar to those obtained in the controls. All insecticide applications increased ammonium production, but, in some instances, there appeared to be a slight depression of nitrification. Sulfur oxidation was equal to or better than that obtained with untreated soil in most cases. There was no significant effect on phosphorus mineralization. Oxygen consumption indicated that microbial respiration increased in proportion to the concentration of insecticides, suggesting the possibilities of microbial degradation of the insecticides or their degradation products and of uncoupling oxidative phosphorylation.

Actinomyces↗