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PubMed1999

Microbial activities related to C and N cycling and microbial community structure in the rhizospheres of Pinus sylvestris, Picea abies and Betula pendula seedlings in an organic and mineral soil.

The aim of this study was to determine whether Scots pine (Pinus sylvestris L.), Norway spruce (Picea abies (L.) Karst.) and silver birch (Betula pendula Roth) seedlings have a selective influence on the soil microbial community structure and activity and whether this varies in different soils. Seedlings of pine, spruce and birch were planted into pots of two soil types: an organic soil and a mineral soil. Pots without seedlings were also included. After one growing season, microbial biomass C (C(mic)) and N (N(mic)), C mineralization, net ammonification, net nitrification, denitrification potential, phospholipid fatty acid (PLFA) patterns and community level physiological profiles (CLPPs) were measured in the rhizosphere soil of the seedlings. In the organic soil, C(mic) and N(mic) were higher in the birch rhizosphere than in pine and spruce rhizosphere. The C mineralization rate was not affected by tree species. Unplanted soil contained the highest amount of mineral N and birch rhizosphere the lowest, but rates of net N mineralization and net nitrification did not differ between treatments. The microbial community structure, measured by PLFAs, had changed in the rhizospheres of all tree species compared to the unplanted soil. Birch rhizosphere was most clearly separated from the others. There was more of the fungal specific fatty acid 18:2omega6,9 and more branched fatty acids, common in Gram-positive bacteria, in this soil. CLPPs, done with Biolog GN plates and 30 additional substrates, separated only birch rhizosphere from the others. In the mineral soil, roots of all tree species stimulated C mineralization in soil and prevented nitrification, but did not affect C(mic) and N(mic), PLFA patterns or CLPPs. The effects of different tree species did not vary in the mineral soil. Thus, in the mineral soil, the strongest effect on soil microbes was the presence of a plant, regardless of the tree species, but in the organic soil, different tree species varied in their influence on soil microbes.

Journal Article↗
PubMed1990

Influence of interfaces on microbial activity.

Bacterial adhesion in natural and artificial systems has been critically reviewed to investigate the influences exerted by the presence of interfaces. Numerous investigations have demonstrated that, in the presence of a solid phase, the activity of bacterial cultures is changed. Reviewing relevant literature, two problems were encountered. One is of an experimental nature. Due to lack of similarity in experimental conditions, disparate experiments often cannot be compared; their results may even appear conflicting. The other problem is of an interpretational nature: several hypothetical theories exist which try to explain the effect of surfaces on microbial activity. These theories often confuse changes in the medium and limitations in mass transfer which are due to the presence of solid surfaces (indirect influences) with changes in cell properties (direct influences). Whenever a surface is reported to influence the metabolism of bacteria, the action is found almost exclusively to be due to changes in the medium or environment and is therefore indirect. Based on data reported in the literature, and by using thermodynamic and kinetic considerations, it is concluded that so far neither experimental nor theoretical evidence exists for a direct influence of interfaces on microbial activity.

Bacteria↗
PubMed2005

Use of microbial activity parameters for determination of a biosolid stability index.

Variations in microbial activity during the aerobic digestion of sludge generated at wastewater treatment plants were studied. Results obtained by the measurement of enzymatic activity and microbiological parameters were compared with those determined by traditional methods (COD, suspended solids, etc.). Their variation with digestion time was monitored for batch digestion over a period of 135 days. The relationship between these measurements and control parameters of the sludge was also investigated. It was found that the traditional physicochemical and microbiological parameters present a series of problems which detract from their usefulness. The enzymatic parameters dehydrogenase activity (primary metabolism) and esterase activity (secondary metabolism) are better able to characterise the process, and the ratio of these two variables may be used to estimate the degree of endogenesis and, consequently, the degree of stability of the aerobic sludge digestion. In addition, these techniques are swift and simple to employ.

Enterobacteriaceae↗
PubMed1980

Variation in microbial activity in histosols and its relationship to soil moisture.

Microbial biomass, dehydrogenase activity, carbon metabolism, and aerobic bacterial populations were examined in cropped and fallow Pahokee muck (a lithic medisaprist) of the Florida Everglades. Dehydrogenase activity was two- to sevenfold greater in soil cropped to St. Augustinegrass (Stenotaphrum secundatum (Walt) Kuntz) compared with uncropped soil, whereas biomass ranged from equivalence in the two soils to a threefold stimulation in the cropped soil. Biomass in soil cropped to sugarcane (Saccharum spp. L) approximated that from the grass field, whereas dehydrogenase activities of the cane soil were nearly equivalent to those of the fallow soil. Microbial biomass, dehydrogenase activity, aerobic bacterial populations, and salicylate oxidation rates all correlated with soil moisture levels. These data indicate that within the moisture ranges detected in the surface soils, increased moisture stimulated microbial activity, whereas within the soil profile where moisture ranges reached saturation, increased moisture inhibited aerobic activities and stimulated anaerobic processes.

Journal Article↗
PubMed1999

Effects of storage on measurements of potential microbial activities in stream fine benthic organic matter.

Sample storage can significantly influence measured microbial activities in stream fine benthic organic matter (FBOM), possibly confounding effects of sample variability and short-term changes in activity. Denitrification potential, acetylene reduction and respiration rates, mineralizable N and extractable ammonium concentrations, and beta-glucosidase and phosphatase enzyme activities of FBOM from first-order mountain streams in the western Oregon Cascade Mountains were assayed at various times after collection to determine potential storage effects. Denitrification potential, phosphatase activity, and extractable ammonium remained stable over a minimum of 11 h of storage at 5 degrees C. Mineralizable N concentrations, respiration rates, and beta-glucosidase activity all decreased within 12 h of collection. Results varied for acetylene reduction. Once assay conditions were established, denitrification potential and respiration rates were linear with incubation time. Based on paired t-tests, measures of acetylene reduction, denitrification potential, respiration rate, beta-glucosidase activity, and phosphatase activity were generally similar at a 1-wk interval within the same stream reaches.

Acetylene↗
PubMed2006

Demonstration of nitric oxide synthase activity in crustacean hemocytes and anti-microbial activity of hemocyte-derived nitric oxide.

We determined the biochemical characteristics of nitric oxide synthase (NOS) in hemocytes of the crayfish Procambarus clarkii and investigated the roles of hemocyte-derived NO in host defense. Biochemical analysis indicated the presence of a Ca2+ -independent NOS activity, which was elevated by lipopolysaccharide (LPS) treatment. When bacteria (Staphylococcus aureus) and hemocytes were co-incubated, adhesion of bacteria to hemocytes was observed. NO donor sodium nitroprusside (SNP) significantly increased the numbers of hemocytes to which bacteria adhered. Similarly, LPS elicited bacterial adhesion and the LPS-induced adhesion was prevented by NOS inhibitor NG-monomethyl-L-arginine (L-NMMA). Finally, plate count assay demonstrated that addition of LPS to the hemocytes/bacteria co-incubation resulted in a significant decrease in bacterial colony forming unit (CFU), and that L-NMMA reversed the decreasing effect of LPS on CFU. The combined results demonstrate the presence of a Ca2+ -independent LPS-inducible NOS activity in crayfish hemocytes and suggest that hemocyte-derived NO is involved in promoting bacterial adhesion to hemocytes and enhancing bactericidal activity of hemocytes.

Animals↗
PubMed2006

Effect of modified Fenton's reaction on microbial activity and removal of PAHs in creosote oil contaminated soil.

This study describes the removal of polycyclic aromatic hydrocarbons (PAHs) from creosote oil contaminated soil by modified Fenton's reaction in laboratory-scale column experiments and subsequent aerobic biodegradation of PAHs by indigenous bacteria during incubation of the soil. The effect of hydrogen peroxide addition for 4 and 10 days and saturation of soil with H(2)O(2) on was studied. In both experiments the H(2)O(2) dosage was 0.4 g H(2)O(2)/g soil. In completely H(2)O(2)-saturated soil the removal of PAHs (44% within 4 days) by modified Fenton reaction was uniform over the entire soil column. In non-uniformly saturated soil, PAH removal was higher in completely saturated soil (52% in 10 days) compared to partially saturated soil, with only 25% in 10 days. The effect of the modified Fenton's reaction on the microbial activity in the soil was assessed based on toxicity tests towards Vibrio fischeri, enumeration of viable and dead cells, microbial extracellular enzyme activity, and oxygen consumption and carbon dioxide production during soil incubation. During the laboratory-scale column experiments, the toxicity of column leachate towards Vibrio fischeri increased as a result of the modified Fenton's reaction. The activities of the microbial extracellular enzymes acetate- and acidic phosphomono-esterase were lower in the incubated modified Fenton's treated soil compared to extracellular enzyme activities in untreated soil. Abundance of viable cells was lower in incubated modified Fenton treated soil than in untreated soil. Incubation of soil in serum bottles at 20 degrees C resulted in consumption of oxygen and formation of carbon dioxide, indicating aerobic biodegradation of organic compounds. In untreated soil 20-30% of the PAHs were biodegraded during 2 months of incubation. Incubation of chemically treated soil slightly increased PAH-removal compared to PAH-removal in untreated soil.

Aliivibrio fischeri↗
PubMed2004

Variation of the microbial activity during the acclimation phase of a SBR system degrading 4-chlorophenol.

The variation of microbial activity during acclimation to 4-chlorophenol (4CP) in an aerobic automated sequencing batch reactor was studied. The results show a reduction in degradation time as the acclimation process occurred. During acclimation for an initial concentration of 50 mg 4CP/L, degradation time was reduced from 40 h to 50 min after 10 cycles. In the case of an initial concentration of 100 mg/L, degradation time was reduced from 52 h to 1.16 h, also after 10 cycles. Doubling the initial concentration of a previously acclimated sludge produces only a slight increase in degradation time. It was found that as acclimation took place, the affinity of the consortia to biodegrade the toxic increased, whereas the ability to biodegrade acetate decreased. The evolution of the substrate uptake rate over time during the acclimation period was highly correlated with an exponential relationship. It was also observed that acclimation decreased both the production of a toxic metabolite and the sludge volumetric index.

Acclimatization↗
PubMed2006

Microbial activity in weathering columns.

The aim of the present work was to evaluate the metabolic activity of the microbial population associated with a pyritic tailing after a column-weathering test. For this purpose, a column 150cm high and 15cm diameter was used. The solid was a tailing with 63.4% pyrite and with minor amounts of Cu, Pb and Zn sulfides (1.4, 0.5 and 0.8%, respectively). The column model was the habitual one for weathering tests: distilled water was added at the top of the column; the water flowed down through tailings and finally was collected at the bottom for chemical and microbiological analysis. Weathering was maintained for 36 weeks. The results showed a significant presence of microbial life that was distributed selectively over the column: sulfur- and iron-oxidizing aerobic bacteria were in the more oxygenated zone; anaerobic sulfur-reducing bacteria were isolated from the samples taken from the anoxic part of the column. Activity testing showed that (oxidizing and reducing) bacteria populations were active at the end of the weathering test. The quality of the water draining from the column was thus the final product of biological oxidation and reduction promoted by the bacteria consortia.

Bacteria, Aerobic↗
PubMed2001

The effect of the herbicide diuron on soil microbial activity.

The inhibitory effect of the herbicide diuron [3-(3,4-dichlorophenyl)-1,1-dimethylurea] on microbial activity in red Latosol soil was followed using microcalorimetry. The activity of the micro-organisms in 1.50 g of soil sample was stimulated by addition of 6.0 mg of glucose and 6.0 mg of ammonium sulfate under 35% controlled humidity at 298.15 (+/- 0.02) K. This activity was determined by power-time curves that were recorded for increasing amounts of diuron, varying from zero to 333.33 micrograms g-1 soil. An increase in the amount of diuron in soil caused a decrease of the original thermal effect, to reach a null value above 333.33 micrograms g-1 of herbicide. The power-time curve showed that the lag-phase period and peak time increased with added herbicide. The decrease of the thermal effect evolved by micro-organisms and the increase of the lag-phase period are associated with the death of microbial populations caused by diuron, which strongly affects soil microbial communities.

Ammonium Sulfate↗
PubMed1995

Highly active microbial communities in the ice and snow cover of high mountain lakes.

An exploratory study carried out in Pyrenean and Alpine lakes shows that a rich, active microbial community lives in the slush layers of the winter cover of such lakes in spite of the low temperature and the seasonal occurrence of the habitat. Bacteria were very diverse in morphology, with filaments reaching up to 100 (mu)m long; flagellates, both autotrophic (chrysophytes, cryptophytes, dinoflagellates, and volvocales) and heterotrophic, and ciliates were abundant, reaching biovolume values up to 2.7 x 10(sup6) (mu)m(sup3) ml(sup-1). Species composition was very variable, with dominance depending on date and depth. Although many species were typical of lake plankton communities, some were restricted to the slush, for instance the predatory ciliates Dileptus sp. and Lacrymaria sp., and others were restricted to the surface pools, such as the snow algae Chlamydomonas nivalis. Microbial biomasses and usually bacterial and algal activities were greater in the slush layers than in the lake water. Photosynthesis rate in the upper cover layers reached values up to 0.5 (mu)g of C liter(sup-1) h(sup-1), and high bacterial activities up to 226 pmol of leucine incorporated liter(sup-1) h(sup-1) and 25 pmol of thymidine incorporated liter(sup-1) h(sup-1) were measured. For most species, lake water flooding the ice and snow cover could provide an inoculum. Differential growth depending on the environmental conditions (nutrients, organic matter, light) of a particular slush layer could provide dominance of different groups or species. However, there was no obvious colonizing mechanism for those species not appearing either in plankton or in communities on top of the snowpack.

Journal Article↗
PubMed2005

Feasibility study of bioremediation of a drilling-waste-polluted soil: stimulation of microbial activities and hydrocarbon removal.

The objective of this study was to determine the feasibility of bioremediation as a treatment option for an aged and chronically polluted drilling waste soil located at the Southeast of Mexico. The polluted drilling-waste site with a mean total petroleum hydrocarbon concentration (TPHs) of 39,397 +/- 858 mg/kg was treated with one dose of a nutrient-surfactant commercial product at 40 mg/kg soil and two doses of H2O2 (50 and 100 mg H2O2/kg soil). In this study, the parameters that were monitored include soil respiration, heterotrophic and hydrocarbon-degrading bacteria as biological indicators, catalase and dehydrogenase activities, and TPHs degradation as decontamination parameters. The results demonstrated that the microbial activities can be stimulated in a polluted drilling-waste site by the addition of H2O2 and commercial product, thereby resulting in increasing TPHs degradation. These aspects must be taken into account when biodegradation studies involve the application of a commercial product.

Analysis of Variance↗
PubMed2005

Anti-microbial activity and film characterization of thiazolidinone derivatives of chitosan.

Thiazolidinone derivatives (TDCs) were prepared by converting chitosan into chitosan's Schiff's bases (CSBs), followed by treatment with mercaptoacetic acid. Both CSBs and TDCs were tested for antimicrobial activity against four different bacteria. All TDCs showed comparatively better anti-microbial activity without much affecting basic physical properties of chitosan such as film-forming capacity, tensile strength, etc. This indicates that chitosan derivatives with a thiazolidinone moiety might be a better material for wound dressing.

Anti-Bacterial Agents↗
PubMed2002

Calorimetry: a tool for assessing microbial activity under aerobic and anoxic conditions.

For many years, calorimetric measurements have been used for understanding, modelling, controlling, and optimising chemical reactions. Calorimetry could be as well utilised to investigate biological processes, which however, involve very small amount of heat and therefore require very sensitive instruments. For this purpose, a Mettler Toledo RCI (Reaction calorimeter) was modified, changing both hardware and software, increasing its resolution up to 5 10m W/l. Such sensitivity allows the monitoring of aerobic and anoxic processes. This paper points out the excellent agreement between calorimetric and respirometric data, obtained simultaneously under aerobic conditions using activated sludge from a lab-scale scale reactor. Heat production rate can be directly converted in oxygen uptake rate by means of a correlation factor, whose value is approximately the same for all aerobic respiratory metabolisms. Taking into account this factor, calorimetric data were introduced in a chemical oxygen demand based model and processed for the estimation of kinetic parameters of heterotrophic biomass. Aerobic heterotrophic, denitrifying, and autotrophic nitrifying activity were determined by specific calorimetric tests. The effect of potentially toxic or inhibitory substances on the activity of all microbial communities was as well pointed out in these measurements.

Bacteria, Aerobic↗
PubMed2001

Microbial activity in aquatic environments measured by dimethyl sulfoxide reduction and intercomparison with commonly used methods.

A new method to determine microbial (bacterial and fungal) activity in various freshwater habitats is described. Based on microbial reduction of dimethyl sulfoxide (DMSO) to dimethyl sulfide (DMS), our DMSO reduction method allows measurement of the respiratory activity in interstitial water, as well as in the water column. DMSO is added to water samples at a concentration (0.75% [vol/vol] or 106 mM) high enough to compete with other naturally occurring electron acceptors, as determined with oxygen and nitrate, without stimulating or inhibiting microbial activity. Addition of NaN(3), KCN, and formaldehyde, as well as autoclaving, inhibited the production of DMS, which proves that the reduction of DMSO is a biotic process. DMSO reduction is readily detectable via the formation of DMS even at low microbial activities. All water samples showed significant DMSO reduction over several hours. Microbially reduced DMSO is recovered in the form of DMS from water samples by a purge and trap system and is quantified by gas chromatography and detection with a flame photometric detector. The DMSO reduction method was compared with other methods commonly used for assessment of microbial activity. DMSO reduction activity correlated well with bacterial production in predator-free batch cultures. Cell-production-specific DMSO reduction rates did not differ significantly in batch cultures with different nutrient regimes but were different in different growth phases. Overall, a cell-production-specific DMSO reduction rate of 1.26 x 10(-17) +/- 0. 12 x 10(-17) mol of DMS per produced cell (mean +/- standard error; R(2) = 0.78) was calculated. We suggest that the relationship of DMSO reduction rates to thymidine and leucine incorporation is linear (the R(2) values ranged from 0.783 to 0.944), whereas there is an exponential relationship between DMSO reduction rates and glucose uptake, as well as incorporation (the R(2) values ranged from 0.821 to 0.931). Based on our results, we conclude that the DMSO reduction method is a nonradioactive alternative to other methods commonly used to assess microbial activity.

Bacteria↗
PubMed2002

Synthesis and anti-microbial activity of isothiosemicarbazones and cyclic analogues.

It is known that some derivatives of both thiourea and thiosemicarbazide exhibit potent anti-microbial activity. In order to investigate the effects on the biological properties of structural modifications of such structures, we have synthesised and studied some arylidenisothiosemicarbazones. In this paper we report on the synthesis and structure-activity relationships of some isothiosemicarbazones, where the arylidene group has been replaced with a cycloalkyl group and the sulfur atom has been either differently substituted or enclosed in a thiazole ring.

Animals↗
PubMed2006

Microbial activity in pig slurry-amended soils under aerobic incubation.

A 120-day aerobic incubation experiment was conducted to study the effects of pig slurry application on soil microbial activity. Pig slurry was added to soil at rates of 0 (control treatment), 150 and 300 m(3) ha(-1). Soil samples were taken after 0, 7, 14, 30, 45, 60, and 120 days of incubation and analyzed for total organic C and microbial biomass C contents, and basal respiration. Most of the organic C applied to soil with pig slurry was readily decomposed within 30 days. During the first phase (0 to 14-30 days), the addition of pig slurry to the soil, especially at the larger rate, increased microbial biomass C content, microbial biomass C/total organic C ratio, basal respiration, and metabolic quotient. The microbial growth and the increase of their activity that these results reflected were not persistent, since the initially measured values in pig slurry-amended soils decreased and reached those of the control soil in a relatively short time.

Aerobiosis↗