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At least 1,477 records · Page 82Linked to original sources
PubMed1988

Influence of ozone and simulated acidic rain on microorganisms in the rhizosphere of Sorghum.

Seedlings of a sorghum x sudangrass hybrid in pots of non-sterile soil-sand mix were exposed to ozone (O(3)) at 0, 0.15, or 0.30 microl litre(-1) (7 h day(-1), 3 days week(-1)) and simulated rain (SR) adjusted with H(2)SO(4) + HNO(3) to pH 5.5, 4.0, or 2.5 (2 cm in 1.5 h per event; 2 events week(-1)) over 3 weeks in a greenhouse. Ozone suppressed shoot and root growth, but increased acid content (i.e. pH < 5.5) of SR stimulated shoot growth and had inconsistent effects on root growth. Ozone x SR chemistry interactions significantly affected plant growth. Data for 'total' bacterial populations in the rhizosphere (number of colony-forming units per gram of rhizosphere soil) exhibited a curvilinear relationship with O(3) (maximum at 0.15 microl liter(-1)). Increased acid content of SR stimulated numbers of 'total' bacteria but suppressed populations of amylolytic bacteria. Ozone and acid content of SR tended to stimulate numbers of fungal propagules in the rhizosphere, but this effect was not significant. Numbers of rhizosphere bacteria capable of phosphatase activity increased linearly with O(3), but only when SR chemistry was characterised by pH 4.0. Data for other populations of rhizosphere microorganisms did not exhibit significant relationships to O3 x SR chemistry interactions.

Journal Article↗
PubMed1981

On different sensitivities of microorganisms to lowered gravitation.

The influence of lowered gravitation on biomass and CO2 production in B. megaterium, a xerophyte, and Spirillum azotocolligens, an aqueous spirillum, in liquid nutrient medium on a horizontal clinostat at 0.1 g has been studied. As controls we considered: 1) growth under stationary conditions of cultivation with test tubes oriented horizontally; 2) growth on a synchronously revolving centrifuge; and 3) growth on a swing with stirring. A horizontal clinostat at 0.1 g stimulates biomass production and CO2 release in B. megaterium as compared with the controls. Spirillum azotocolligens growth is reduced as a result of clinostating. The best development and CO2 production are observed under stationary conditions. The results do not support the assumption that microorganisms living in water are more resistant to lowered gravitation than those living in soil.

Bacillus megaterium↗
PubMed1989

Peroxides and the survivability of microorganisms on the surface of Mars.

Results of the Viking mission seem to indicate that there is a ubiquitous layer of highly oxidizing aeolian material covering the Martian surface. This layer is thought to oxidize organic material that may settle on it, and is therefore responsible for the lack of detection of organic matter on the planet's surface by Viking. The mechanism that creates the oxidizing condition is not well understood, nor is the extent of the oxidation potential of this material. It has been suggested that the oxidizing nature of the soil is due to photochemical reactions which create hydrogen peroxide and superoxides in the surface soil. One question of importance to planetary protection regarding this material is, what is its potential for destroying terrestrial microorganisms, thus making the surface of Mars "self-sterilizing"? Using data obtained by the gas exchange experiment on Viking, and for simplicity assuming that all of the O2 released came from H2O2, the concentration range for H2O2 on the surface of Mars can be calculated to be 25-250 ppm. The microbial disinfection rate by H2O2 is concentration dependent, and is highly variable within the microbial community. Data from our laboratory indicate that certain soil bacteria survive and grow to stationary phase in 30,000 ppm H2O2. However, the total number of organisms decreases in the presence of H2O2. These results indicate that it is doubtful that the presence of H2O2 alone on Mars would make the surface "self-sterilizing".

Bacteria↗
PubMed1994

Identification and origin of plant pathogenic microorganisms in recirculating nutrient solutions.

Avoidance of root-infecting microorganisms was originally considered one of the advantages of cultivation of crops in a soilless, recirculating nutrient solution. However, to date, four viral, three bacterial and 21 fungal pathogens have been identified as causal agents of root disease in hydroponically-grown crops. Root-infecting fungi, particularly those which produce a motile stage known as a zoospore, have been the primary pathogens associated with extensive crop losses. Documented sources of these root pathogens in hydroponic systems include peat, surface water such as rivers and streams, and insects. The severity of disease caused by these introduced root pathogens is primarily governed by the genetic susceptibility of each crop and the temperature of the recirculating nutrient solution.

Bacteria↗
PubMed1994

Dynamics of microorganism populations in recirculating nutrient solutions.

This overview covers the basic microbial ecology of recirculating hydroponic solutions. Examples from NASA and Soviet CELSS tests and the commercial hydroponic industry will be used. The sources of microorganisms in nutrient solutions include air, water, seeds, plant containers and plumbing, biological vectors, and personnel. Microbial fates include growth, death, and emigration. Important microbial habitats within nutrient delivery systems are root surfaces, hardware surfaces (biofilms), and solution suspension. Numbers of bacteria on root surfaces usually exceed those from the other habitats by several orders of magnitude. Gram negative bacteria dominate the microflora with fungal counts usually much lower. Trends typically show a decrease in counts with increasing time unless stressed plants increase root exudates. Important microbial activities include carbon mineralization and nitrogen transformations. Important detrimental interactions include competition with plants, and human and plant pathogenesis.

Bacteria↗
PubMed1994

Control of microorganisms in flowing nutrient solutions.

Controlling microorganisms in flowing nutrient solutions involves different techniques when targeting the nutrient solution, hardware surfaces in contact with the solution, or the active root zone. This review presents basic principles and applications of a number of treatment techniques, including disinfection by chemicals, ultrafiltration, ultrasonics, and heat treatment, with emphasis on UV irradiation and ozone treatment. Procedures for control of specific pathogens by nutrient solution conditioning also are reviewed.

Disinfection↗
PubMed1993

Immunotoxicology and expression of human cytochrome P450 in microorganisms.

Drug-induced hepatitis can be caused by an abnormal immunological response. In the case of tienilic acid- and dihydralazine-induced hepatitis, we postulated a scheme in which a P450 produced a reactive metabolite (step 1); this reactive metabolite bound to the P450 producing it (step 2) leading to a neoantigen triggering the immune response (step 3); the autoantibodies produced during the immune response recognized the P450 producing the reactive metabolite (step 4). The use of microorganisms (yeast or bacteria) expressing cloned human P450 helped in proving some steps of this postulated scheme, particularly steps 1 and 4.

Amino Acid Sequence↗
PubMed1978

Direct measurement of pure absorbance spectra of living phototrophic microorganisms.

The pure absorbance of turbid cell suspensions of various phototrophic microorganisms were determined by collecting the scattered light. A conventional spectrophotometer was used, equipped with an intergrating sphere as receiver unit, which allowed precise measurements of the absorbance in the range from zero to 0.1. In the wavelength range 300--1100 nm, where photosynthesis occurs, light scattered only once by a bacterial cell retains predominantly the forward direction. This allows measurements of pure absorption, when the concentration of cells which the light has to pass through is small. For example, by comparison of measurements of pigmented and nonpigmented cell suspensions of Rhodopseudomonas acidophila, it was shown that the total sum of scattered light can be collected. The best results were obtained using cuvettes with a light path of 0.1 cm or 0.2 cm to measure cell suspensions of about 0.2 mg dry weight per ml. For R. acidophila this corresponds to 1--3 cell layers. Extinction-, absorbance- and scattering spectra for R. acidophila are presented, in addition to the absorbance spectra for Rhodospirillum rubrum, Aphanocapsa and Scenedesmus.

Cell Count↗
PubMed1994

Comparative inhibition patterns of adenylate kinases from mammals, bird, fish and microorganisms.

The S8 inhibitions of AKs from six different sources were studied in mammals, birds, fish, and a microorganism. All AKs tested were inhibited by S8. Except for carp, all inhibited AKs from those tested were reactivated by DTT. Inhibitions of AKs by other hydrophobic inhibitors, NEM, butanol and ethanol were also studied. The inhibitions by S8 suggest that the hydrophobic pockets in the AKs cover a wide phylogenetic range. All inhibitions by S8 are reactivated by DTT. Unlike the inhibitions by S8, the characteristics of inhibitions by the other hydrophobic inhibitors differed among the AK sources tested and none was the irreversible type. The data suggest that no covalent bonds were formed with NEM. Similarly, the ability to reactivate the inhibitions by DTT differed among the AK sources. The possibility that the hydrophobic domains in the AKs may serve as part of an enzyme activity control mechanism is discussed.

Adenylate Kinase↗
PubMed1990

Topical antimicrobial testing of burn wound microorganisms: evaluation of a new technique.

A new system of determining susceptibility of burn wound microorganisms to topical antimicrobial therapy was studied. The new method, TOPITEST, employs a methacrylate vehicle impregnated with various antimicrobial agents and an agar overlay. Test plates can be inoculated by a direct swab culture of the wound or with micro-organisms isolated by other methods. This new technique was compared to an agar well diffusion (AWD) method using commercially compounded antimicrobials and biopsy-recovered organisms. The new test method provided comparable results to the more established AWD test when using biopsy-recovered organisms. Using the swab culture technique, however, TOPITEST had a high rate of failure to recover sufficient organisms from the burn wound for testing. The new, more standardized test provided results earlier than the AWD test, but may prove to be less cost effective.

Administration, Topical↗
PubMed1990

A simple plate-assay for the screening of L-malic acid producing microorganisms.

A simple plate-assay has been developed to screen microorganisms for L-malic acid production. Acid producing organisms were identified, after microbial colony growth on media containing glucose or fumaric acid as sole carbons sources, by formation of a dark halo of formazan. The halo was observed when the plate was covered with a soft agar overlay containing NAD(+)-malate dehydrogenase, NAD+, phenazine methosulfate (PMS) and 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT). The assay developed is simple, specific for L-malic acid and therefore can be used to identify L-malic acid producing filamentous fungi using glucose as carbon source (e.g. Aspergillus strains). The assay is also applicable for screening bacteria with high fumarase activity, able to convert fumaric acid to L-malic acid.

Aspergillus↗
PubMed1990

A spiral microorganism in the stomach of pigs.

Light and electron microscopic and microbiologic evaluations were performed on mucosa of stomachs from 120 healthy slaughtered pigs. Helicobacter pylori was not found, but a tightly spiralled bacterium, not previously described, was seen in histological sections and/or in carbol fuchsin stained smears in 13 (10.8%) stomachs. In paraffin sections stained with carbol fuchsin, the bacteria were seen in the mucus of the lumen of the antral pits and in the mucosa surface within and beneath the mucus. In this sections of Polilyte embedded tissue the bacteria had three to eight spiral turns per cell (mean = five), flattened ends, a Gram-negative cell-wall structure and a sheathed flagella. The urease test was positive in gastric mucosa of 13 bacteria-positive pigs (10.8%). The microorganism was not cultured and did not cross-react with polyclonal antibodies raised in rabbits against H. pylori. Superficial chronic gastritis and "borderline" gastritis were observed in antral mucosa of 10 (76.9%) and of two (15.4%) spiral bacteria-positive pigs, respectively.

Animals↗
PubMed1994

Studies on inactivation of pathogenic microorganisms in culture media and in bovine semen by photosensitive agents.

The application of three photosensitive agents for disinfection of bovine semen was investigated. Bovine microbial pathogens suspended in tissue culture medium and/or PBS and also added to bovine semen were exposed to the photosensitive agents followed by irradiation. Hematoporphyrin, hematoporphyrin derivative and thiopyronine were effective against bovine herpes virus-1, bovine viral diarrhoea virus, Mycoplasma bovigenitalium, Mycoplasma canadense, and Ureaplasma diversum in culture media. In addition, thiopyronine was effective against Leptospira pomona. Similar treatments were not effective against Leptospira hardjo, Mycoplasma bovis, or Campylobacter fetus subsp. venerealis. When microorganisms were added to bovine semen, only bovine herpes virus-1 was controlled by the photosensitive agents used at concentrations which did not appear harmful to sperm cells.

Animals↗
PubMed1987

Metabolism of three trichothecene mycotoxins, T-2 toxin, diacetoxyscirpenol and deoxynivalenol, by bovine rumen microorganisms.

The three trichothecene mycotoxins T-2 toxin, diacetoxyscirpenol (DAS) and deoxynivalenol (DON) were incubated in vitro for 12, 24 and 48 h with rumen microorganisms obtained from a fistulated dairy cow. Gas chromatographic and gas chromatographic-mass spectrometric analyses of extracts indicated all three toxins were biotransformed to a variety of deepoxy and deacylated products. DON was partially converted to a product identified as deepoxy DON. DAS was rapidly converted to four products including 15-monoacetoxyscirpenol (MAS), scirpentriol and two new compounds identified as 15-acetoxy-3 alpha,4 beta-dihydroxytrichothec-9,12-diene (deepoxy MAS) and 3 alpha,4 beta,15-trihydroxytrichothec-9,12-diene (deepoxy scirpentriol). T-2 toxin was also completely biotransformed to the products HT-2, T-2 triol and two new metabolites identified as 15-acetoxy-3 alpha,4 beta-dihydroxy-8 alpha-(3-methylbutyryloxy) trichothec-9,12-diene (deepoxy HT-2) and 3 alpha,4 beta,15-trihydroxy-8 alpha-(3-methylbutyryloxy)trichothec-9,12-diene (deepoxy T-2 triol).

Animals↗
PubMed1995

Calculation of the molecular masses of two newly synthesized thermostable enzymes isolated from thermophilic microorganisms.

Two thermostable enzymes synthesized by thermophilic microorganisms were isolated and purified. A thermostable beta-galactosidase was produced in a continuous fermentation process by Bacillus stearothermophilus TP 32 as an intracellular enzyme. After applying different concentration procedures the raw extract enzyme was prepurified on a Sephadex G-200 size exclusion column. The isolated beta-galactosidase fraction was then separated with HPLC on a TSK G 3000 SW size exclusion column to determine the molecular mass based on calibration curves of standard proteins. The other enzyme, a thermostable protease, was synthesized by Bacillus stearothermophilus TP 26 as an extracellular enzyme. After its concentration, the enzyme was purified on a classical size exclusion column (Sephacryl S-200) and on a HPLC size exclusion column (BIO-SIL TSK-250). The micropreparatively isolated fraction was separated again on this HPLC column to determine its molecular mass. The optimum temperature of both enzymes was approximately 75 degrees C.

Chromatography, Gel↗
PubMed1988

Comparative in vitro activity of lomefloxacin and other antimicrobials against 597 microorganisms causing bacteremia.

The in vitro activity of lomefloxacin, a new fluorinated quinolone antimicrobial, was compared to that of enoxacin, norfloxacin, ofloxacin, imipenem, cefotaxime, ceftazidime, and tobramycin against 597 microorganisms isolated from bacteremic patients at a university hospital. Overall, lomefloxacin had activity similar to that of enoxacin and norfloxacin but less than that of ofloxacin. Lomefloxacin had excellent activity against members of the family Enterobacteriaceae and Haemophilus influenzae, and good activity against staphylococci, including oxacillin-resistant strains, as well as many strains of Pseudomonas aeruginosa, P. maltophilia, and Acinetobacter calcoaceticus anitratus ssp anitratus.

Anti-Bacterial Agents↗
PubMed1984

Continuous cultivation of microorganisms.

This review presents selected studies on continuous cultivation including the genetics and selection of microorganisms, production of biomass, liquid fuels and other products, published in 1982-1984 and bearing a relationship to biotechnology.

Journal Article↗
PubMed1991

Field testing of genetically engineered microorganisms.

The first approved field releases of microorganisms genetically altered in the laboratory have been initiated in the past several years. While most introductions have been carried out in the United States, several tests have also occurred in the United Kingdom and Australia. Although such releases remain controversial in some areas, these pioneering studies have provided significant insight into the environmental behavior and relative safety of applying these microbes in a well-planned and carefully monitored program.

Journal Article↗