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PubMed2001

Soil microbial population dynamics following bioaugmentation with a 3-chlorobenzoate-degrading bacterial culture. Bioaugmentation effects on soil microorganisms.

Changes in microbial populations were evaluated following inoculation of contaminated soil with a 3-chlorobenzoate degrader. Madera sandy loam was amended with 0, 500, or 1,000 microg 3-chlorobenzoate g(-1) dry soil. Selected microcosms were inoculated with the degrader Comamonas testosteroni BR60. Culturable bacterial degraders were enumerated on minimal salts media containing 3-chlorobenzoate. Culturable heterotrophic bacteria were enumerated on R2A. Isolated degraders were grouped by enterobacterial repetitive intergenic consensus sequence-polymerase chain reaction fingerprints and identified based on 16S ribosomal-DNA sequences. Bioaugmentation increased the rate of degradation at both levels of 3-chlorobenzoate. In both the 500 and 1,000 microg 3-chlorobenzoate g(-1) dry soil inoculated microcosms, degraders increased from the initial inoculum and decreased following degradation of 3-CB. Inoculation delayed the development of indigenous 3-chlorobenzoate degrading populations. It is unclear if inoculation altered the composition of indigenous degrader populations. In the uninoculated soil, degraders increased from undetectable levels to 6.6 x 10(7) colony-forming-units g(-1) dry soil in the 500 microg 3-chlorobenzoate g(-1) dry soil microcosms, but none were detected in the 1,000 microg 3-chlorobenzoate g(-1) dry soil microcosms. Degraders isolated from uninoculated soil were identified as one of two distinct Burkholderia species. In the uninoculated soil, numbers of culturable heterotrophic bacteria initially decreased following addition of 1,000 microg 3-chlorobenzoate g(-1) dry soil. Inoculation with C. testosteroni reduced this negative impact on culturable bacterial numbers. The results indicate that bioaugmentation may not only increase the rate of 3-chlorobenzoate degradation but also reduce the deleterious effects of 3-chlorbenzoate on indigenous soil microbial populations.

Biodegradation, Environmental↗
PubMed1977

[The effect of biocides on the microflora of soils and their degradation. I. The selection of suitable biocides and ways of selective influences in soil-microorganisms (author's transl)].

The influence of 544 biocides on soil-microflora was investigated by a special plate-test and by a soil-test. Fungi were particularly sensitive to active substances. They were more inhibited by a greater number of substances, by lower concentrations and by a larger time-interval than bacteria. A differentiated sensitivity of fungi becomes apparent. The pseudomonads, a species of Agrobacter (AIA), flavobacteria and some coryneforme bacteria were relatively resistant. Actinomyces responded similar to fungi. The plate-test is suitable as preliminary test for the selection of substances retarding the degradation of straw. These organisms already favoured by treatments with active substance locate in higher quantities in such soils where the biological balance was disturbed in after the injection. Therefore, the effect of the active substance exceeds that of the injection. The displacement-effect by bacteria resistant to active substances and little active against cellulose plays a minor role in opposite to bacteria active against cellulose, because bacteria don't develop any homogeneous protective coat. A priority effect is therefore excluded.

Bacteria↗
PubMed1976

Microbial degradation of the thiolcarbamate herbicide, diallate, in soils and by pure cultures of soil microorganisms.

The disappearance of the herbicide, Avadex (40% diallate), from five agricultural soils (differing in either pH, carbon content, or nitrogen content), incubated under sterile and non-sterile conditions, was followed for a period of 20 weeks. Avadex was rapidly lost from microbiologically active soils, with over 50% of the applied (2.5 ppm) dosage disappearing within four weeks; losses from sterile soils were much slower with recoveries of over 50% after 20 weeks. Incubation of soil with Avadex to which 14C-labeled diallate had been added resulted in rapid formation of 14CO2 from microbiologically active samples and only very slow 14CO2 formation from sterile samples. Substantial quantities of radioactivity were retained as unextractable residues in both sterile and non-sterile soils after senven days incubation. From these data it was concluded that the disappearance of the herbicide from non-sterile soils was mainly due to microbial degradation and to binding of diallate or its metabolites as residues to undefined soil components. Losses from sterile soils were attributed to both binding of residues and to a slow chemical degradation. Avadex degradation by pure cultures was studied using representative fungi isolated from the five soils. Of the fungi tested, Phoma eupyrena, Penicillium janthinellum, and Trichoderma harzianium coudl degrade at least 20% of the applied (2.5 ppm) herbicide after ten days incubation. Degradation of Avadex in soil cultures of T. harzianum was found to be slower than degradation in liquid nutrient cultures.

Biodegradation, Environmental↗
PubMed1975

Infrared color photomicrography of soil microorganisms.

The infrared color photomicrography technique for detecting unstained microbial cells in soil is revised for use with Kodak's recently introduced Ektachrome infrared film. Thes new version of the film required achromatic objectives instead of apochromats, and the use of a blue filter in addition to the previously required red filter. These filters also improve the visual focus capability of the operator. It was found that dry soil smears can be photographed as either immersion oil or aqueous mounts. Several makes of bright-field transmitted-light microscopes gave similar results. Phase microscopy, however, produced deteriorated image quality although the proper 'false' colors were produced.

Bacteria↗
PubMed1994

The effect of L-tryptophane on yield of field bean and activity of soil microorganisms.

The pot trial was performed to study the effect of L-tryptophane (as an auxin precursor) applied in the amount 0.3 and 3.0 mg per 1 kg of the soil on yield and the chemical composition of field bean. The effects of this compound on dehydrogenases activity in the cells Rhizobium leguminosarum isolated from root nodules, soil dehydrogenases activity and number of microorganisms from different systematic or physiological groups were also studied. The effects of L-tryptophane were compared to indole-3-acetic acid (IAA) after application to soil in the rate 0.2 mg per 1 kg of the soil of foliar spraying in the rate 20 mg Din 1 dm3 of distilled water. Studies were carried out in three experimental series: without microorganisms or with addition of Azotobacter sp. or Rhizobium leguminosarum biovar. viciae to the soil. It was found that L-tryptophane and IAA did not affect the yield of above ground part and roots of field bean and their effects on macronutrients concentration were not direct and dependent on the nutrient and experimental series. L-tryptophane and auxine increased the dehydrogenases activity in the cells of Rhizobium leguminosarum isolated from root nodules and the effect on the activity of soil dehydrogenases and urease was dependent on the rate of L-tryptophane. This chemical adversely affected the numbers of some microorganisms groups.

Azotobacter↗
PubMed1977

Degradation of carbaryl by soil microorganisms.

Four days after carbaryl-naphthyl-1-14C was mixed with soil from a field treated 6 months previously with 4 lb/A of the same insecticide, only 28% of the radiocarbon remained. Approximately 90% remained in soils with no history of pesticide applications. However, dissipation of the carbaryl-14C residues from the latter soils continued at a rather steady rate over a 120-day test period, whereas there was little dissipation after 4 days from the former. Consequently, the total 14C-residue levels were about the same, 15 to 20% of applied, when the last samples were taken. Carbaryl, per se, was the only apolar 14C-residue recovered from the soil and only small quantities, less than 2% of the amount applied, of extractable polar metabolites were encountered. Almost all of the terminal residues were unextractable from the soil with mixtures of acetone and water. Much of the loss of 14C-residues from the soil was attributed to the liberation of 14C-carbon dioxide as a result of microbial degradation of the naphthalene ring. Several fungal and bacterial isolates degraded carbaryl in the same manner as observed with soil incubations, but the rates of degradation were much slower.

Bacteria↗
PubMed1982

Effects of plutonium on soil microorganisms.

As a first phase in an investigation of the role of the soil microflora in Pu complex formation and solubilization in soil, the effects of Pu concentration, form, and specific activity on microbial types, colony-forming units, and CO(2) evolution rate were determined in soils amended with C and N sources to optimize microbial activity. The effects of Pu differed with organism type and incubation time. After 30 days of incubation, aerobic sporeforming and anaerobic bacteria were significantly affected by soil Pu levels as low as 1 mug/g when Pu was added as the hydrolyzable Pu(NO(3))(4) (solubility, <0.1% in soil). Other classes of organisms, except the fungi, were significantly affected at soil Pu levels of 10 mug/g. Fungi were affected only at soil Pu levels of 180 mug/g. Soil CO(2) evolution rate and total accumulated CO(2) were affected by Pu only at the 180 mug/g level. Because of the possible role of resistant organisms in complex formation, the mechanisms of effects of Pu on the soil fungi were further evaluated. The effect of Pu on soil fungal colony-forming units was a function of Pu solubility in soil and Pu specific activity. When Pu was added in a soluble, complexed form [Pu(2)(diethylenetriaminepentaacetate)(3)], effects occurred at Pu levels of 1 mug/g and persisted for at least 95 days. Toxicity was due primarily to radiation effects rather than to chemical effects, suggesting that, at least in the case of the fungi, formation of Pu complexes would result primarily from ligands associated with normal (in contrast to chemically-induced) biochemical pathways.

Journal Article↗
PubMed1995

Characterization of two proteinase inhibitor (ATI) cDNAs from alfalfa leaves (Medicago sativa var. Vernema): the expression of ATI genes in response to wounding and soil microorganisms.

cDNAs encoding two Bowman-Birk proteinase inhibitors were isolated from the leaves of alfalfa (Medicago sativa). The cDNAs are derived from a small gene family (3 to 10 genes) encoding alfalfa trypsin inhibitors (ATIs). Each cDNA clone encoded a mature ATI that was part of a larger, putative preprotein. ATI mRNAs are continuously expressed in flower parts, but are mechanically wound-inducible in the stems and leaves. ATI mRNA is shown to be continuously present in roots of soil-grown plants, but its presence is primarily in response to microorganisms present in the soil. Additionally, while mechanical wounding of the alfalfa roots induced ATI mRNA synthesis both in the roots and in the leaves, microbial infection of the roots triggered ATI mRNA synthesis in the roots but not in the leaves. These results suggest that both local and systemic signalling pathways for proteinase inhibitor synthesis are present in alfalfa plants.

Amino Acid Sequence↗
PubMed1981

Effect of fire on soil microorganisms in a Meghalaya pine forest.

The effect of man-made fire on soil microbial population in a natural subtropical pine forest eco-system, was studies. a nearly fifty years old pine (Pinus kesiya Royle) forest was cut and burnt in March 1977. Another half of this pine forest was left uncut and unburnt. Microbial population was destroyed completely just after the burning and recolonization occurred after some days. Bacteria and actinomycetes were found to be the first colonizers followed by fungi. Burning initiated better growth and higher population of bacteria after two or three showers. Bacterial population was highest in July in burnt and in May in unburnt forest. Maximum fungal population in burnt site was recorded in July while it was highest in april and May in unburnt site. Penicillium spp., Cladosporium sp. and Trichoderma sp. were found to be first colonizing fungi just after the burning. In unburnt forest eco-system Absidia sp., Trichoderma sp., Fusarium sp. and Penicillium spp. were found to be dominant.

Bacteria↗
PubMed1977

Ethylene production by soil microorganisms.

Ethylene-producing strains of Penicillium cyclopium and P. crustosum were isolated from soil. These isolates produced ethylene on a variety of carbon growth substrates including phenolic acids. The quantities of ethylene produced on the various substrates varied, and the subtrate-ethylene prosuction pattern for P. cyclopium strains differed significantly from that of P. crustosum strains.

Acetates↗
PubMed1970

Improved methodology for isolating soil microorganisms.

Polyurethane foam cylinders and a replica-stamp technique were used for plating soil samples. This in conjunction with the addition of NaCl to the isolation medium substantially increased the variety of isolates recovered.

Journal Article↗
PubMed1996

Soil microorganisms as controllers of atmospheric trace gases (H2, CO, CH4, OCS, N2O, and NO).

Production and consumption processes in soils contribute to the global cycles of many trace gases (CH4, CO, OCS, H2, N2O, and NO) that are relevant for atmospheric chemistry and climate. Soil microbial processes contribute substantially to the budgets of atmospheric trace gases. The flux of trace gases between soil and atmosphere is usually the result of simultaneously operating production and consumption processes in soil: The relevant processes are not yet proven with absolute certainty, but the following are likely for trace gas consumption: H2 oxidation by abiontic soil enzymes; CO cooxidation by the ammonium monooxygenase of nitrifying bacteria; CH4 oxidation by unknown methanotrophic bacteria that utilize CH4 for growth; OCS hydrolysis by bacteria containing carbonic anhydrase; N2O reduction to N2 by denitrifying bacteria; NO consumption by either reduction to N2O in denitrifiers or oxidation to nitrate in heterotrophic bacteria. Wetland soils, in contrast to upland soils are generally anoxic and thus support the production of trace gases (H2, CO, CH4, N2O, and NO) by anaerobic bacteria such as fermenters, methanogens, acetogens, sulfate reducers, and denitrifiers. Methane is the dominant gaseous product of anaerobic degradation of organic matter and is released into the atmosphere, whereas the other trace gases are only intermediates, which are mostly cycled within the anoxic habitat. A significant percentage of the produced methane is oxidized by methanotrophic bacteria at anoxic-oxic interfaces such as the soil surface and the root surface of aquatic plants that serve as conduits for O2 transport into and CH4 transport out of the wetland soils. The dominant production processes in upland soils are different from those in wetland soils and include H2 production by biological N2 fixation, CO production by chemical decomposition of soil organic matter, and NO and N2O production by nitrification and denitrification. The processes responsible for CH4 production in upland soils are completely unclear, as are the OCS production processes in general. A problem for future research is the attribution of trace gas metabolic processes not only to functional groups of microorganisms but also to particular taxa. Thus, it is completely unclear how important microbial diversity is for the control of trace gas flux at the ecosystem level. However, different microbial communities may be part of the reason for differences in trace gas metabolism, e.g., effects of nitrogen fertilizers on CH4 uptake by soil; decrease of CH4 production with decreasing temperature; or different rates and modes of NO and N2O production in different soils and under different conditions.

Animal Population Groups↗