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At least 1,387 records · Page 77Linked to original sources
PubMed1991

Activity of antibiotics against microorganisms ingested by mononuclear phagocytes.

The data available on the activity of antibiotics against microorganisms ingested by mononuclear phagocytes are reviewed. The antibacterial activity of penicillins against Staphylococcus aureus is enhanced by human monocytes. This enhancement is possibly brought about by a peptidoglycan-degrading enzyme that is produced and secreted by monocytes. Aminoglycosides affect bacteria ingested by mononuclear phagocytes, but their intracellular activity is limited as compared with that of non-phagocytosed bacteria. Clindamycin, erythromycin, ciprofloxacin and rifampicin are effective against intracellular bacteria. The first three of these antibiotics do not show enhanced activity against phagocytosed bacteria, contrary to what might be expected from their high cell-associated concentrations.

Aminoglycosides↗
PubMed1987

The evolution of glutathione metabolism in phototrophic microorganisms.

Of the many roles ascribed to glutathione (GSH) the one most clearly established is its role in the protection of higher eucaryotes against oxygen toxicity through destruction of thiol-reactive oxygen byproducts. If this is the primary function of GSH then GSH metabolism should have evolved during or after the evolution of oxygenic photosynthesis. That many bacteria do not produce GSH is consistent with this view. In the present study we have examined the low-molecular-weight thiol composition of a variety of phototrophic microorganisms to ascertain how evolution of GSH production is related to evolution of oxygenic photosynthesis. Cells were extracted in the presence of monobromobimane (mBBr) to convert thiols to fluorescent derivatives, which were analyzed by high-pressure liquid chromatography. Significant levels of GSH were not found in the green bacteria (Chlorobium thiosulfatophilum and Chloroflexus aurantiacus). Substantial levels of GSH were present in the purple bacteria (Chromatium vinosum, Rhodospirillum rubrum, Rhodobacter sphaeroides, and Rhodocyclus gelatinosa), the cyanobacteria [Anacystis nidulans, Microcoleus chthonoplastes S.G., Nostoc muscorum, Oscillatoria amphigranulata, Oscillatoria limnetica, Oscillatoria sp. (Stinky Spring, Utah), Oscillatoria terebriformis, Plectonema boryanum, and Synechococcus lividus], and eucaryotic algae (Chlorella pyrenoidsa, Chlorella vulgaris, Euglena gracilis, Scenedesmus obliquus, and Chlamydomonas reinhardtii). Other thiols measured included cysteine, gamma-glutamylcysteine, thiosulfate, coenzyme A, and sulfide; several unidentified thiols were also detected. Many of the organisms examined also exhibited a marked ability to reduce mBBr to syn-(methyl,methyl)bimane, an ability that was quenched by treatment with 2-pyridyl disulfide or 5,5'-bisdithio-(2-nitrobenzoic acid) prior to reaction with mBBr. These observations indicate the presence of a reducing system capable of electron transfer to mBBr and reduction of reactive disulfides. The distribution of GSH in phototrophic eubacteria indicates that GSH synthesis evolved at or around the time that oxygenic photosynthesis evolved.

Bacteria↗
PubMed1991

Comparative study of microorganisms and sensory attributes of condiments from the fermentation of different seeds.

Seeds of African locust bean, melon, castor oil bean and soybean were processed and fermented for 3 days to produce local condiments in the laboratory with a method that simulated the traditional production process. Microorganisms associated with their fermentation and the organoleptic properties of the products were compared. Altogether, seven species of bacteria were involved in the fermentation. These included five Bacillus spp. and one species each of Pseudomonas and Staphylococcus. Their occurrence vary between the seeds on the different days of fermentation. However, Bacillus spp. were present in all the seeds throughout the fermentation period. The sensory evaluation preference rating for the four products was highest for soybean condiment, followed by that made from locust bean. Melon condiment was the least preferred among the four products. Statistical analysis showed that there were significant differences (P less than or equal to 0.05) among the four products for each of the four organoleptic properties evaluated by the judges and also for titratable acidity. Glutamic acid level of soybean condiment was highest (0.31%) among the four products with that of melon being the lowest (0.04%). These results could serve as useful indices for the development of starter culture and optimization of production process in commercializing the production of these local condiments.

Bacillus↗
PubMed2001

Stress-induced evolution and the biosafety of genetically modified microorganisms released into the environment.

This article is focused on the problems of reduction of the risk associated with the deliberate release of genetically modified microorganisms (GMMs) into the environment. Special attention is given to overview the most probable physiological and genetic processes which could be induced in the released GMMs by adverse environmental conditions, namely: (i) activation of quorum sensing and the functions associated with it, (ii) entering into a state of general resistance, (iii) activation of adaptive mutagenesis, adaptive amplifications and transpositions and (iv) stimulation of inter-species gene transfer. To reduce the risks associated with GMMs, the inactivation of their key genes responsible for stress-stimulated increase of viability and evolvability is proposed.

Adaptation, Physiological↗
PubMed1997

Use of gas chromatography-ion trap tandem mass spectrometry for the detection and characterization of microorganisms in complex samples.

Gas chromatography-mass spectrometry (GC-MS) can be applied to detect and characterize microorganisms in clinical and environmental samples, and microbial contaminants in biotechnological production cultures. With this approach, unique microbial monomeric compounds, known as chemical markers, are used as analytes. In the present article, two GC-MS-based techniques, viz. GC-ion trap tandem MS (GC-MS-MS) and conventional quadrupole GC-MS used in the selected ion monitoring mode, were compared regarding their ability to detect 3-hydroxy fatty acids, muramic acid, and ergosterol (markers for endotoxin, peptidoglycan, and fungal biomass, respectively) in complex matrices. When using GC-MS-MS, daughter ion spectra were obtained for all markers present in amounts close to the detection limit of the GC-MS. Ion-trap GC-MS-MS shows great promise as a chemical marker analysis technique for application in clinical diagnosis, occupational and public health care, and biotechnology.

Bacteria↗
PubMed1997

Quantification of the presence and activity of specific microorganisms in nature.

Traditional techniques for assessment of microbial numbers and activity generally lack the specificity required for risk assessment following environmental release of genetically engineered microbial inocula. Immunological and molecular-based techniques, such as DNA probing and genetic tagging, were initially used to determine the presence or absence of microorganisms in environmental samples. Increasingly they are being developed for quantification of populations of specific organisms, either indigenous or introduced, in the environment. In addition, they are being used to quantify the activity of particular organisms or groups of organisms, greatly extending the range of techniques available to the microbial ecologist. This article reviews the use of traditional techniques for the quantification of microbial population size and activity and the application of molecular techniques, including DNA probing, genetic marking, use of fluorescent probes, and quantitative PCR, in combination with advanced cell detection techniques such as confocal laser scanning microscopy and flow cytometry.

Bacteria↗
PubMed1979

Conversion of 7-ketolithocholic acid to ursodeoxycholic acid by human intestinal anaerobic microorganisms: interchangeability of chenodeoxycholic acid and ursodeoxycholic acid.

Chenodeoxycholic acid, ursodeoxycholic acid and 7-ketolithocholic acid were incubated with human intestinal bacteria (source: 4 healthy males) at 37 degrees C for 72 hours in an anerobic condition. The bile acids of the products in culture medium were identified by three independent methods, thin layer chromatography, gas-liquid chromatography and GLC-mass spectrometry. Lithocholic acid, ursodeoxycholic acid and 7-ketolithocholic acid were observed in the culture of chenodeoxycholic acid. Lithocholic acid, chenodeoxycholic acid and 7-ketolithocholic acid were observed in the culture of ursodeoxycholic acid. Chenodeoxycholic acid and ursodeoxycholic acid were produced from 7-ketolithocholic acid. These data may suggest that chenodeoxycholic acid and ursodeoxycholic acid are interconvertible via 7-ketolithocholic acid by the mixed culture of human intestinal microorganisms under an anaerobic condition.

Anaerobiosis↗
PubMedDate not supplied

A simple method for quantifying activity and survival of microorganisms involved in bioremediation processes.

We have developed a substrate-induced growth response (SIGR) method for quantifying activity and population dynamics of microorganisms involved in bioremediation processes in soil and bioreactors. The biomass of organisms that can mineralize a given chemical can be estimated based on the concentration of that chemical needed to induce the growth of the standing population. Estimates of population size are obtained by using nonlinear regression techniques to fit a simple model of microbial population dynamics to biodegradation curves. Using this approach we obtain estimates of values for parameters such as initial population size and growth rate of organisms carrying out biodegradative processes. Our approach was validated by comparing model parameter estimates with independent estimates of the same parameters from the same bioremediation systems. Examples studied include pentachlorophenol degraders introduced into soil and 2,4-dinitrophenol degrading organisms in a bioreactor.

Biodegradation, Environmental↗
PubMed2002

Microorganisms in a high altitude glacier ice in Tibet.

Eighty-one strains of viable microorganisms were recovered from 23 samples collected from Ice Core 3 of Malan Glacier (China, 91 degrees 45.3' E, 35 degrees 48.4' N) drilled at high altitude (5620 m). All the strains were prokaryotes--75 of bacteria (including spore-forming ones) and 6 of actinomycetes. The characteristic genera differ from those of Arctic and Antarctic ice, in which many fungi and algae are widely distributed; this shows an difference of environmental conditions between Tibet and polar regions. The variation in number and species of Bacillus in different ice core layers implied changes of environmental conditions in the past.

Bacteria↗
PubMed2001

Morphological details of microorganisms revealed by RCH-microscopy at high magnification--a ready-to-use adaptation of a light microscope.

RCH-microscopy (Relief Contrast after Hostounský) is a new method of optical microscopy in transmitted light developed with Lambda Ltd., Prague. This method was used to study bacteria, fungi including yeasts and algae at high magnification. The equipment provides a three-dimensional image of high contrast and resolution. The results of these microscopic observations can be used for both morphological (taxonomical) and ecological studies of microorganisms.

Bacteria↗
PubMed1991

Effect of the fungicides tridemorph and vinclozolin on soil microorganisms and nitrogen metabolism.

The effects of tridemorph and vinclozolin were studied on different types of microorganisms, urea hydrolysis and nitrification in soil and in culture. The fungicides adversely affected the population of bacteria, fungi and actinomycetes as a function of time of incubation. Urea hydrolysis both in culture and soil were also inhibited by the fungicides, and tridemorph was more detrimental. In soil, 45 micrograms/g of tridemorph inhibited 50% of ammonification of urea, ID50 for nitrite production was 750 micrograms/g. In urea-hydrolyzing cultures, 80, 75 and 77 mg/L of tridemorph were the ID50 values for urea hydrolysis by Micrococcus sp., Proteus sp. and P. vulgaris respectively.

Actinomycetales↗
PubMed2004

Isolation and selection of phenol-degrading microorganisms from industrial wastewaters and kinetics of the biodegradation.

Among 22 species of microorganisms isolated from phenol-containing wastewaters, Candida parapsilopsis was found to be capable of growth on a medium with 1 g/L phenol. Kinetic parameters of phenol biodegradation in a batch reactor were determined by measuring biomass growth rates and phenol concentration as a function of fermentation time. The Haldane equation described cell growth adequately, with kinetic constants mumax = 0.174/h, KS = 11.2 mg/L and Ki = 298 mg/L.

Biodegradation, Environmental↗
PubMed1998

Screening of new bioactive materials from microbial extracts of soil microorganism (I). Antimicrobial activity from 200 samples using microdilution assay.

The microdilution assay recommended by NCCLS (National Committee for Clinical Laboratory Standards) is one of the standardized methods of antibiotic susceptibility test. This method has been widely used clinically to obtain MIC values of antibiotics on pathogenic microorganisms. It is more convenient, rapid and simple to test many samples than other test methods such as agar diffusion assay and broth macrodilution assay. The screening of antimicrobial agents from microbial extracts is too laborious in its process. Therefore, a number of screening methods having more simple procedure have been developed. In our laboratory, we applied microdilution assay for screening the antimicrobial agents. This assay showed dose-response results and was more sensitive than disc diffusion assay in our system. We tested 200 samples of microbial extracts originated from 100 microbial strains and selected several samples as potential candidates. In this report, we show that the microdilution assay is more convenient method in screening of antibiotic susceptibility than those previously reported.

Anti-Bacterial Agents↗
PubMed1993

Genetically engineered microorganisms to rescue plants from frost injury.

Ice nucleation active bacteria belonging to genera Pseudomonas, Xanthomonas and Erwinia contribute to frost damage to plants by initiating the formation of ice in plants that would otherwise supercool and avoid the damaging ice formation. The biological control of frost injury can be achieved by the application of non-ice nucleation active bacteria to the plant surfaces before they become colonized by Ice+ species. ice genes have been cloned from Pseudomonas and isogenic Ice- derivatives constructed via genetic manipulations. These genetically engineered microorganisms (GEMs) have been released into the environment to control the frost damage. The incidence of frost injury to the plants has, thereby, been reduced by 50-85% during natural frosts. These GEMs do not survive in soil and show no aerial dispersal in the environment.

Amino Acid Sequence↗
PubMed1993

Synthesis of L-carnitine by microorganisms and isolated enzymes.

L-Carnitine, a quaternary ammonium compound, plays an important role in beta-oxidation of fatty acids in mammals. The increasing demand for this compound in medicine has led to the development of numerous procedures for L-carnitine production. This review discusses the possibilities of microbial and enzymatical synthesis of L-carnitine and gives an overview on the pathways of L-carnitine metabolism and related enzymes in microorganisms.

Acyltransferases↗
PubMed1997

Microorganisms and enzymes involved in the degradation of plant fiber cell walls.

One of natures most important biological processes is the degradation of lignocellulosic materials to carbon dioxide, water and humic substances. This implies possibilities to use biotechnology in the pulp and paper industry and consequently, the use of microorganisms and their enzymes to replace or supplement chemical methods is gaining interest. This chapter describes the structure of wood and the main wood components, cellulose, hemicelluloses and lignins. The enzyme and enzyme mechanisms used by fungi and bacteria to modify and degrade these components are described in detail. Techniques for how to assay for these enzyme activities are also described. The possibilities for biotechnology in the pulp and paper industry and other fiber utilizing industries based on these enzymes are discussed.

Bacteria↗
PubMed1995

Breakdown of plastics and polymers by microorganisms.

The interest in environmental issues is still growing and there are increasing demands to develop materials which do not burden the environment significantly. Awareness of the waste problem and its impact on the environment has awakened new interest in the area of degradable polymers. Biodegradation is necessary for water-soluble or water-miscible polymers because they eventually enter streams which can neither be recycled nor incinerated. It is important to consider the microbial degradation of natural and synthetic polymers in order to understand what is necessary for biodegradation and the mechanisms involved. This requires both biochemical insight and understanding of the interactions between materials and microorganisms. It is now widely requested that polymeric materials come from renewable resources instead of petrochemical sources. The microbial production of polymeric and oligomeric materials is also described.

Acrylic Resins↗
PubMed2002

[Detection of periodontal pathogenic microorganisms in atheromatous plaque. Preliminary results].

INTRODUCTION: Recent studies suggest that chronic infections, including those associated with periodontitis, increase the risk for coronary vascular disease. We hypothesize that oral microorganisms including periodontal bacterial pathogens enter the blood stream during transient bacteremias where they may play a role in the development and progression of atherosclerosis. MATERIALS AND METHODS: To test this hypothesis, 34 human specimens obtained during carotid endarterectomy or bypass procedures were examined by use of specific oligonucleotide primers for Porphyromonas gingivalis, Prevotella intermedia, Actinobacillus actinomycetemcomitans and Bacteroides forsythus in polymerase chain reaction (PCR) assays. RESULTS: Twenty (59%) of the 34 specimens tested positive for bacterial 16S rDNA. Subsequent hybridization of the bacterial 16S rDNA positive specimens with species-specific oligonucleotide probes revealed that 32.4% of the 34 atheromas tested positive for at least one of the target periodontal pathogens. Further analysis of the results in the bacterial positive group (n = 20) shows that 55% of the atheromas tested positive for at least one of the target periodontal pathogens. CONCLUSION: These findings indicate that periodontal pathogens are present in atherosclerotic plaques, where they may play a role in the development and progression of atherosclerosis leading to coronary vascular disease and other clinical sequelae.

Adult↗