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PubMed1990

Oscillometric instrument for the non-invasive detection of low-level microbial activity. Part 2: Growth characteristics, detection limits and impedimetric assays.

Instrument performance and application was evaluated with a variety of microbial suspensions. Data were compared with those obtainable from current commercial apparatus in terms of resolution and detection times. Trials with growing and non-growing cultures indicated periodic synchronous ion exchange processes. Media composition, particularly salt and nutrient ratios, remain crucial to early and rapid detection of viable microbial activity at low concentrations. With appropriate conditions very significant improvements in detection times with typical detection thresholds of 300 min for start concentrations of 10(2) are shown. It is concluded that with regard to resolution and stability, the system out-performs current systems and is superior in terms of potential test costs, sample handling and sample transport.

Asparaginase↗
PubMed2006

Effects of Cr3+, Cr6+ and tannery sludge on C and N mineralization and microbial activity in semi-arid soils.

The aim of this study was to evaluate the effect of two Cr species (Cr(3+) and Cr(6+)) on N and C mineralization and dehydrogenase activity in semi-arid soils. The Cr species (250 mg kg(-1)soil) were either added alone or mixed with tannery sludge (0.0125 g g(-1)) to three soils: cultivated soils, and outside and under the canopy of mesquite trees were then incubated for 180 days at 25 degrees C. Sole Cr(6+) addition had a higher inhibition of CO(2) production rate in cultivated soil (58-73%) than in soils under the canopy and outside the canopy. Soil outside the canopy amended with Cr(6+) showed the highest inhibition of dehydrogenase activity (40-100%) followed by cultivated and under the canopy soils. However, Cr(6+) added alone increased the inhibition of nitrification in soil outside the canopy (68-84%, from 30 to 120 days), followed by under the canopy and cultivated soils. The addition of tannery sludge to Cr(6+) significantly reduce the CO(2) production rate and dehydrogenase activity in all three soils, and increased the inhibition of nitrification in the following order: outside the canopy, cultivated and under the canopy soils. The addition of Cr(3+) or Cr(3+) plus tannery sludge either stimulated or inhibited CO(2) production rate, dehydrogenate activity and ammonification in the three soils in no clearly defined order. Measurement of dehydrogenase activity was the best tool for assessing the harmful effect of Cr(6+) on soil microbial activity in semi-arid soils exposed for an extended period.

Carbon↗
PubMed2001

Anti-microbial activity and cell binding are controlled by sequence determinants in the anti-microbial peptide PR-39.

PR-39 is a member of the proline-rich group of cathelicidin peptides, a class of anti-microbial peptides found in skin and in leukocytes. In addition to their innate defense function, these proline-rich peptides influence a number of mammalian cell processes, including inflammation, development, differentiation, and metastatic transformation. To characterize the mechanism further, through which proline-rich cathelicidin peptides may exert their numerous effects, we altered various conserved peptide sequence motifs using a biologically active fragment of PR-39 [PR-39(15)] as the template: We altered the N-terminal charge of its SH3 binding motif, substituted tryptophan for a conserved intervening leucine, and modified a proline-arginine stretch (residues 10-13). These peptide variants were tested for binding known targets of PR-39 and for biologic activity in mammalian and bacterial systems. We found that the N-terminal arginines are crucial for protein binding and that modification in this domain results in loss of affinity and specificity in binding to generalized and SH3-containing targets. The N-terminal charged residues are also required for NIH 3T3 syndecan induction and anti-microbial activity. In addition, modification of more C-terminal residues eliminates anti-bacterial activity while having less of an effect on peptide interactions in mammalian cell assays. This study shows that the presence of a charged N-terminus is important for peptide activity in both mammalian and bacterial systems whereas the C-terminal alterations of PR-39(15) more definitively affect anti-bacterial activity.

3T3 Cells↗
PubMed2003

Nutrient level, microbial activity, and alachlor transformation in aerobic aquatic systems.

Alachlor (2-chloro-N-(2,6-diethylphenyl)-N-(methoxymethyl)acetamide) is a moderately toxic herbicide that is frequently found in agriculturally impacted surface waters. To assess primary mechanism(s) that affect its fate in aquatic systems, two field experiments were performed using large mesocosms (n=39) and smaller microcosms with and without microbial inhibitors (n=16). The mesocosm experiment tested the effect of fertility conditions on alachlor fate, assessing alachlor disappearance over time under oligotrophic (total phosphorus (TP) <12 microg/L) through hypereutrophic (TP>80 microg/L) water conditions. Whereas, the microcosm experiment assessed alachlor fate in the presence of microbial inhibitors that selectively blocked eubacterial (chloroamphenicol, streptomycin, and penicillin combined), eukaryotic (cycloheximide), and universal (all inhibitors) microbial activity. First-order alachlor transformation rate coefficients ranged from 0.006 to 0.042 day(-1) when microbial inhibitors were not present (half-lives from 16 to 122 days) with the highest rates occurring in hypereutrophic waters. Statistics indicated that mean TP, and universal and eubacterial small sub-unit rRNA level most closely correlated with transformation rate. Further, the inhibitor study indicated that alachlor transformation was biotic (>90%), but that high transformation rates only occurred when eubacterial and eukaryotic domains were both metabolically active. Our results confirm that alachlor transformation is primarily biotic; however, efficient biotransformation only occurs when both major microbial domains in aerobic systems are active.

Acetamides↗
PubMed1988

[Effect of the mode of incorporation of lucerne serum on digestibility and microbial activity in the rumen].

The extraction of protein from lucerne produces some liquid residue (called lucerne serum), the effects of which were studied on rumen microbial activity in 6 adult fistulated wethers. The introduction of the serum directly into the rumen stimulated cellulolytic activity whereas its incorporation into the lucerne solid residue before dehydration seemed to have no effect.

Animals↗
PubMed2005

Microcosm experiments to assess the effects of temperature and microbial activity on polychlorinated biphenyl transport in anaerobic sediment.

Increased polychlorinated biphenyl (PCB) loadings from sediment to the water column under low-flow conditions during late spring and summer months have been observed in the Grasse River (Massena, NY) and other PCB-contaminated rivers in the United States. Temperature appears to be an important factor affecting this phenomenon, as increased sediment temperature leads to increased microbial and bioturbator activity as well as increased rates of diffusion and desorption. Laboratory-scale sediment microcosms were developed and used to study with fine-scale resolution the effects of temperature and microbial activity on PCB transport in river sediment. Over the time course of these experiments, with the extraction procedures used, irreversible sorption of each congener to sediment was observed and increased with aging of the sediment. Temperature-dependent transport was observed for PCB congeners 2,4,5-trichlorobiphenyl (BZ29), 2,5-dichlorobiphenyl (BZ9), and 2-chlorobiphenyl (BZ1) in Grasse River sediment and a synthetic sediment system. The fastesttransport of the congeners occurred in biologically active Grasse River sediment followed by biologically inactive (autoclaved) Grasse River sediment, and synthetic sediment. The increased transport in biologically active sediment demonstrated the importance of microbial activity, in particular gas bubble generation, in PCB transport in near-surface sediments.

Anaerobiosis↗
PubMed1982

Fluorescein diacetate hydrolysis as a measure of total microbial activity in soil and litter.

Spectrophotometric determination of the hydrolysis of fluorescein diacetate (FDA) was shown to be a simple, sensitive, and rapid method for determining microbial activity in soil and litter. FDA hydrolysis was studied in soil and straw incubated for up to 3 h. Hydrolysis was found to increase linearly with soil addition. FDA hydrolysis by pure cultures of Fusarium culmorum increased linearly with mycelium addition both in shake cultures and after inoculation into sterile soil. FDA hydrolysis by Pseudomonas denitrificans increased linearly with biomass addition. The FDA hydrolytic activities in soil samples from different layers of an agricultural soil were correlated with respiration. Acetone was found to be suitable for terminating the reaction.

Journal Article↗
PubMed2000

Life at the oxic-anoxic interface: microbial activities and adaptations.

Molecular oxygen is one of the most important reactants in biogeochemical cycles. Due to its low solubility in water, the consumption of oxygen leads to the development of oxic-anoxic interfaces, which separate aerobic from anaerobic processes in virtually all environments, ranging in scale from oceanic sediments to the fecal pellets of a small soil invertebrate. Three case studies were selected to illustrate the basic situation and the specific characteristics of oxic-anoxic interfaces: sediments, the rhizosphere of aquatic plants, and the intestinal tract of insects. Each system is governed by the same general principles, but striking differences arise from, e.g., the nature of the major microbial activities and the mechanisms controlling metabolite fluxes. Also scale and dimensional differences as well as the consequences of temporal fluctuations are of fundamental importance. Recent developments in microbial ecology, which often combine traditional and modern approaches, have significantly furthered our understanding of the specific microniches and the metabolic and behavioral adaptations of microorganisms to life at the oxic-anoxic interface. New concepts help to define the targets of future studies: the spatial organization of microbial populations, their microenvironments and in situ activities, and the functional interactions within structured microbial communities.

Adaptation, Physiological↗
PubMed2006

Response of microbial activities to heavy metals in a neutral loamy soil treated with biosolid.

Application of biosolid on land has been widespread in numerous countries for last several decades. This study performed incubation experiments by mixing a neutral loamy soil and biosolid enriched in Cu, Pb and Zn to explore how heavy metal affects soil mineralization and microbial biomass. The experimental results indicated that large nutrient, microorganism and C sources from biosolid were beneficial to microbial respiration. However, compared to the biosolid alone treatment, the supplemented Cu, Pb and Zn in biosolid reduced the mineralized C by roughly 36%. This phenomenon was probably caused by a portion of the Cu, Pb and Zn being complexed with organic matter to prevent decomposition of organic carbon by microorganisms. Equally, soil treated with biosolid increased the quantity of mineralized N by approximately five-fold and accelerated the rate of N mineralization by about one-fold compared to untreated soil. Notably, addition of heavy metals impaired the mineralization process, particularly when Pb reached about 64%. The reduced N mineralization occurred for similar reasons to the microbial respiration. The addition of biosolid in soil considerably increased the amount of mineralizable N; however, the increase was lower in biosolid-treated soil spiked by heavy metals. The addition of heavy metals in the soil-biosolid mixture clearly reduced the microbial biomasses C (MBC) and N (MBN), indicating that the microbial activities had been disrupted by the heavy metals. The microbial biomass C/N ratio had changed initially from 8 to 13 at the end of incubation period, owing to various groups of microbes expressing different mechanisms of metabolism, indicating that the microbial population had changed from bacteria to fungi, which had higher metal tolerance.

Bacteria↗
PubMed2005

Bioremediation of oil refinery sludge by landfarming in semiarid conditions: influence on soil microbial activity.

Bioremediation of a refinery sludge containing hydrocarbons in a semi-arid climate using landfarming techniques is described. The objective of this study was to assess the ability of this technique to reduce the total hydrocarbon content added to the soil with the refinery sludge in semiarid climate (low rain and high temperature). In addition, we have evaluated the effect of this technique on the microbial activity of the soil involved. For this, biological parameters (carbon fractions, microbial biomass carbon, basal respiration and ATP) and biochemical parameters(different enzymatic activities) were determined. The results showed that 80% of the hydrocarbons were eliminated in eleven months, half of this reduction taking place during the first three months. The labile carbon fractions, MBC, basal respiration and ATP of the soils submitted to landfarming showed higher values than the control soil during the first months of the process, although these values fell down by the end of the experimental period as the hydrocarbons were degraded by mineralisation. All the enzymatic activities studied: oxidoreductases such as dehydrogenase activity, and hydrolases of C(beta-glucosidase activity) and N Cycle (urease and protease) showed higher values in the soils amended with the refinery sludge than in the control. As in the case of the previous parameters, these value fell down as the bioremediation of the hydrocarbons progressed, many of them reaching levels similar to those of the control soil after eleven months.

Biodegradation, Environmental↗
PubMed1993

Control of microbial activity by flow injection analysis during high cell density cultivation of Escherichia coli.

The application of an automated flow injection analysis (FIA) system for on-line determination of microbial activity, during high cell density cultivations of Escherichia coli is reported. Based on a bioelectrochemical principle, the FIA method used a redox mediator (potassium hexacyanoferrate(III)) to facilitate electron transfer from the microorganisms to an electrochemical detector. Assays were carried out using a new sampling device which provided aseptic operation by use of a valve and chemical sterilisation. No sample dilution or pretreatment was necessary for biomass concentrations up to approx. 40 g l-1. The sample volume was 0.5 ml and the overall analysis time was 5 min. FIA signals were found to correlate well with the oxygen uptake rate (OUR). Changes in metabolic activity due to low substrate levels or high inhibitor concentrations in the cultivation medium became obvious from the FIA signals.

Bacteriological Techniques↗
PubMed1990

Synthesis and anti-microbial activity of benzo-condensed heterocyclic derivatives.

The synthesis of 2,4-dione derivatives of 1,5-benzodithiepine, 1,5-benzodiazepine and 1,5-benzothiazepine and the anti-microbial activity in vitro of these derivatives and of analogous of 1,5-benzodioxepine, 1,5-benzoxathiepine and 1,5-benzoxazepine, previously prepared, are reported. Some of these compounds showed a good activity against some Gram positive microorganisms and blastomycetes.

Anti-Bacterial Agents↗
PubMed2005

Effects of N- and C-terminal truncation of HP (2-20) from Helicobacter pylori ribosomal protein L1 (RPL1) on its anti-microbial activity.

HP (2-20) [derived from the N-terminal region of Helicobacter pylori Ribosomal Protein L1 (RPL1)], a 19-mer peptide, possesses broad-spectrum anti-microbial activity. As the N- (residues 2-3) and C-terminal (residues 14-20) residues can be deleted without affecting antimicrobial activity, we have now determined the minimum chain length necessary for the retention of antimicrobial activity, and its mode of action. The N- (residues 2-3) and C-terminal (residues 17-20) truncated fragments [HP (4-16)] induce increased antibiotic activity against several bacterial strains without hemolysis. Flow cytometric analysis, scanning electron microscopy and fluorescence confocal microscopy revealed that HP (4-16) acted rapidly on the plasma membranes of the fungal cells in a salt- and energy-independent manner.

Amino Acid Sequence↗
PubMed1976

Evaluation of some biological tests as parameters for microbial activities in soils. I. Laboratory experiments.

The experiments were confined to the effects of the addition of different sources of carbon (glucose, wheat straw, and sawdust) on the microbial activities in soils: loamy sand, loam and saline clay were used. The parameters used for this purpose were total bacterial counts, dehydrogenase test, CO2 evolution, and oxidation of organic carbon. Salinity of soils had deleterious effects on all the parameters used. Addition of organic matter resulted in marked increases in bacterial counts, formazan production, and CO2 evolution. Glucose showed the most rapid effect and highest levels. Wheat straw yielded the highest results and sawdust always showed the least effect.

Bacteria↗
PubMed2005

Using redox potential to detect microbial activities during clavulanic acid biosynthesis in Streptomyces clavuligerus.

Production of clavulanic acid (CA) by Streptomyces clavuligerus in a shake-flask culture increased from 92 to 180 mg l(-1) with an increased O2 transfer efficiency (0.039 --> 0.058 s(-1)), which maintained the redox potential values above -250 mV. Compared with traditional measures, such as dissolved O2 concentration and respiratory activity, the redox potential can easily be determined and correlates closely with CA production. It can therefore be used to monitor microbial activities during biosyntheses of secondary metabolites.

Bioreactors↗
PubMedDate not supplied

Real-time determination of microbial activity of pasteurized fluid milk using a novel microrespirometer method.

The effectiveness of the rapid CO2 evolution rate (CER) method was evaluated by using a novel noninstrumental microrespirometer to determine the microbial activity of pasteurized milk and comparing it with traditional culturing methods in homogeneous milk samples. Three different kinds of milk (skim, 1% fat, and whole) stored at 2 temperatures (4 degrees and 7 degrees C) were measured daily for CER, aerobic plate count (APC), and psychrotrophic bacterial count. The mean initial rates of CO2 evolution for all 3 samples stored at the 2 temperatures ranged from 3.42 to 3.71 microL/h/mL and increased to 29 microL/h/mL and above on the final day of the experiment. Regression analysis showed a high correlation (R = 0.98-0.99) between the APC and CER results in combined milk samples. A cut-off value of CER (25 microL/h/mL) for milk spoilage at refrigeration temperatures was identified. The real-time CER method shows promise as a potential alternative to the traditional culture method.

Animals↗
PubMed2006

Synthesis and anti-microbial activity of pyrazolylbisindoles--promising anti-fungal compounds.

A series of pyrazolylbisindole derivatives have been synthesized by reacting substituted pyrazole aldehydes with substituted indoles using phosphotungstic acid, a Keggin type heteropoly acid as catalyst. The synthesized pyrazolylbisindoles were evaluated for anti-microbial activities. The effect of pyrazolylbisindoles on the mycelial growth of plant pathogenic fungi is revealed. Entries 3c and 3d emerged as the most interesting compounds in this series exhibiting excellent anti-fungal activity.

Anti-Bacterial Agents↗
PubMed2006

The anti-microbial activity of electrolysed oxidizing water against microorganisms relevant in veterinary medicine.

Standards of the German Association of Veterinary Medicine (DVG) for the evaluation of chemical disinfectants were used to assess the anti-microbial efficacy of electrolysed oxidizing water (EOW). Enterococcus faecium, Mycobacterium avium subspecies avium, Proteus mirabilis, Pseudomonas aeruginosa, Staphylococcus aureus and Candida albicans were exposed to anode EOW (pH, 3.0+/-0.1; oxidation-reduction potential (ORP), +1100+/-50 mV; free chlorine, 400+/-20 mg/l Cl2) and combined EOW (7:3 anode:cathode, v/v; pH, 8.3+/-0.1; ORP, 930-950 mV; free chlorine, 271+/-20 mg/l Cl2). In water of standardized hardness (WSH), all bacterial strains were completely inactivated by a 30 min exposure to maximum 10.0% anode EOW (approximately 40.0 mg/l Cl2) or 50.0% combined EOW (approximately 135.5 mg/l Cl2). The sensitivity ranking order for anode EOW to the bacterial test strains was P. mirabilis>S. aureus>M. avium ssp. avium>E. faecium>P. aeruginosa. P. mirabilis and S. aureus decreased to undetectable levels after 5 min of exposure to 7.5% anode EOW (approximately 30.0 mg/l Cl2). Candida albicans was completely inactivated by a 5-min exposure to 5.0% anode EOW. Both, anode and combined EOW exhibited no anti-microbial activities in standardized nutrient broth or after addition of 20.0% bovine serum to the WSH. Further research is necessary to evaluate the efficacy of EOW as a disinfectant under operating conditions in animal production facilities.

Animals↗