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At least 469 records · Page 26Linked to original sources
PubMed1998

Inactivation of bacteriophage lambda, Escherichia coli, and Candida albicans by ozone.

The effects of ozone (O3) on three types of microbes were studied. Test suspensions were exposed to 600 ppm O3 at room temperature. Control experiments were performed under identical conditions using oxygen gas. Bacteriophage lambda was completely inactivated at 10 min while Escherichia coli and Candida albicans were only inactivated by factors of 10(5) and 10(4) respectively at 40 min. Exposure of a mixed microbial suspension to O3 for 5 min resulted in 100% killing of bacteriophages while the viability of E. coli remained unchanged. Various body fluids containing phages were exposed to O3. Compared to buffered solution, the decrease in phage titers was significantly slower in whole blood, plasma, and albumin. Both E. coli and C. albicans had increased production of thiobarbituric-acid-reactive substances with increased O3 exposure. 3H-labelled amino acids were incorporated into E. coli. O3 treatment resulted in a loss of radioactivity, indicating leakage of cytoplasmic contents. The data indicate that microbes are inactivated by O3 at different rates, possibly related to differential membrane permeability. The milieu in which microbes are present determines the effectiveness and outcome of O3 treatment.

Bacteriophage lambda↗
PubMed1968

Isolation of mutants of Euglena gracilis with impaired photosynthesis.

Four mutant strains of Euglena gracilis have been isolated after treatment of wild type cells with ultraviolet light or the chemical mutagen nitrosoguanidine. None of the mutants is capable of autotrophic growth or photosynthetic carbon dioxide fixation. The mutant strains contain normal amounts of the enzymes of the reductive pentose phosphate cycle and are qualitatively similar to the wild type in pigment composition, but are unable to carry out the Hill reaction (light induced reduction of 2,6-dichlorophenol indophenol). Isolated mutant plastids cannot photoreduce NADP with water as the electron donor but can carry out this reaction when the electron donating system is ascorbate and 2,6-dichlorophenol indophenol. Whole cells of the mutants show the light induced oxidation of cytochrome f by light reaction I but are unable to bring about cytochrome f reduction by light reaction II. The mutants appear to be blocked at or near light reaction II in the photosynthetic electron transport chain. The mutants may represent alterations of the chloroplast genome since the mutation isolation was carried out under conditions where chloroplast viability was severely impaired, but cell viability was unaffected.

Euglena↗
PubMed1993

Bacterial growth in isoflurane vapour.

Pathogenic bacteria were grown on nutrient agar in a mixture of air and isoflurane vapour, and in air alone. The presence of isoflurane vapour in concentrations considerably in excess of those used either for anaesthesia or for sedation in intensive care had no effect either on the rate of bacterial growth or on the viability of colony forming units.

Colony Count, Microbial↗
PubMed2003

Bilayer-forming synthetic lipids: drugs or carriers?

Since their introduction as bilayer-forming synthetic compounds in the eighties, dioctadecyldimethylammonium (DODA) and dihexadecylphosphate (DHP) salts have found many uses in strategic, applied areas. In particular, DODA chloride or bromide vesicles interacted with negatively charged prokaryotic or eukaryotic cells, yielding adsorption isotherms of high affinity for the cell surface, causing cell adhesion and flocculation, changing the cell surface charge from negative to positive, and causing loss of cell viability over DODA concentration ranges that depended on the cell type being tested. This work reviews data on DODA effects on cell viability (bacteria, fungus and cultured mammalian cells) to propose DODA salts as effective anti-microbial agents that exhibit differential cytotoxicity in vitro and, therefore, deserve to be investigated as potential drugs. The full utility of these inexpensive synthetic bilayers and bilayer fragments able to act as drugs themselves and, simultaneously, as drug, gene or vaccine carriers remains hitherto unexplored.

Animals↗
PubMedDate not supplied

[Effect of various methods of immobilization on stability of a microbial biosensor based on Pseudomonas rathonis T during detection of surfactants].

The operating and storage stability of a receptor element of an amperometric biosensor based on the Pseudomonas rathonis strain T capable of degrading surfactants was tested. Microbial cells were immobilized by incorporation in gels (agar, agarose, and calcium-alginate), polyvinyl alcohol membrane, adhesion to the chromatographic paper GF/A, or by the cross-linking induced by glutaric aldehyde. Incorporation of microbial cells in agar gel provides the long-standing conservation of their activity and viability during measurements of high concentrations of surfactants and allows the receptory element of the biosensor to be rapidly recovered after the measurements.

Biosensing Techniques↗
PubMed2000

Flow cytometric analysis of microorganisms.

The application of flow cytometry to microorganisms is as old as the technique itself, but it has historically been underexploited for microbial applications. This is now being reversed and microbiologists are ideally placed to benefit from recent technological advances. While earlier papers demonstrated the use of flow cytometry for studies of viability and taxonomy, recent developments in bioinformatics and reporter gene technologies are leading to novel applications in microbiology. Variants of green fluorescent protein have been used for the study of conditional microbial gene regulation in medically important host-pathogen interactions and fluorescence-activated cell sorting is being applied to the isolation of novel mutants in directed evolution studies. This paper reviews the reasons for the delay in the application of flow cytometry to microbial problems, the range of applications, and their limitations and considers the progress made in developing new strategies for use in microbiological investigations.

Bacteria↗
PubMed2005

The effects of disinfectant foam on microbial biofilms.

This investigation examined the effects of common aqueous biocides and disinfectant foams derived from them on Pseudomonas aeruginosa biofilms. Biofilms were grown on stainless steel coupons under standardised conditions in a reactor supplemented with low concentrations of organic matter to simulate conditions prevalent in industrial systems. Five-day-old biofilms formed under ambient conditions with continuous agitation demonstrated a low coefficient of variation (5.809%) amongst viable biofilm bacteria from independent trials. Scanning electron microscopy revealed biofilms on coupons with viable biofilm bacteria observed by confocal microscopy. An aqueous solution of a common foaming agent amine oxide (AO) produced negligible effects on bacterial viability in biofilms (p>0.05). However, significant biofilm inactivation was noted with aqueous solutions of common biocides (peracetic acid, sodium hypochlorite, sodium ethylenediaminetetraacetic acid) with or without AO (p<0.05). Aereation of a mixture of AO with each of these common biocides resulted in significant reductions in the viability of biofilm bacteria (p<0.05). In contrast, limited effects were noted by foam devoid of biocides. A relationship between microbial inactivation and the concentration of biocide in foam (ranging from 0.1-0.5%) and exposure period were noted (p<0.05). Although, lower numbers of viable biofilm bacteria were recovered after treatment with the disinfectant foam than by the cognate aqueous biocide, significant differences between these treatments were not evident (p>0.05). In summary, the studies revealed significant biofilm inactivation by biocidal foam prepared with common biocides. Validation of foam disinfectants in controlled trials at manufacturing sites may facilitate developments for clean in place applications. Advantages of foam disinfectants include reductions in the volumes of biocides for industrial disinfection and in their disposal after use.

Amines↗
PubMed1983

Sodium hypochlorite decontamination of split-thickness cadaveric skin infected with bacteria and yeast with subsequent isolation and growth of basal cells to confluency in tissue culture.

The ability of sodium hypochlorite to decontaminate skin while leaving sufficient epidermal cell viability for growth in tissue culture was investigated with an in vitro system. Split-thickness cadaveric skin was infected with Staphylococcus aureus, Pseudomonas aeruginosa, and Candida albicans and subsequently treated with various concentrations of sodium hypochlorite for various time intervals. Exposure to a 0.5% solution of sodium hypochlorite for 6 min effectively decontaminated the skin while leaving 66% of the basal cells viable. The basal cells were subsequently grown to confluency in tissue culture. This study demonstrates that microbial colonization of skin can be eliminated by exposure to dilute hypochlorite. This procedure, while decontaminating the skin, leaves sufficient viability of epidermal cells for subsequent growth and expansion in tissue culture, elements essential for grafting over wounds.

Bacteria↗
PubMed1996

Improving production of aromatic compounds in Escherichia coli by metabolic engineering.

The efficiency of conversion of raw material to product is a major factor controlling the commercial viability of large-scale fermentation processes for the production of metabolites. Traditional approaches to developing microbial strains for metabolite overproduction have relied on amplifying only the enzymatic steps within the specific biosynthetic pathway of a desired product. While this approach has generally been successful for reaching high product concentrations and yields, further improvements (and hence reduced manufacturing cost) can only be achieved by redirecting carbon flux from central metabolism to the product-forming pathway. Such manipulation of central metabolic pathways promises to deliver a new generation of metabolite-producing microorganisms.

Amino Acids↗
PubMed2006

Analysis and cryopreservation of hematopoietic stem and progenitor cells from umbilical cord blood.

BACKGROUND: Umbilical cord blood (UCB) is an important source of hematopoietic stem and progenitor cells (HSC/HPC) for the reconstitution of the hematopoietic system after clinical transplantation. Cryopreservation of these cells is critical for UCB banking and transplantation as well as for research applications by providing readily available specimens. The objective of this study was to optimize cryopreservation conditions for CD34+ HSC/HPC from UCB. METHODS: Cryopreservation of CD34+ HSC/HPC from UCB after mononuclear cell (MNC) preparation was tested in a research-scale setup. Experimental variations were concentration of the cryoprotectant, the protein additive and cell concentration. In addition, protocols involving slow, serial addition and removal of DMSO were compared with standard protocols (fast addition and removal of DMSO) in order to avoid osmotic stress for the cryopreserved cells. Viability and recoveries of MNC, CD34+ cells and total colony-forming units (CFU) were calculated as read-outs. In addition, sterility testing of the collected UCB units before further processing was performed. RESULTS: The optimal conditions for cryopreservation of CD34+ HPC in MNC preparations were 10% DMSO and 2% human albumin at high cell concentrations (5 x 10(7) MNC/mL) with fast addition and removal of DMSO. After cryopreservation using a computer-controlled freezer, high viabilities (89%) and recoveries for CD34+ cells (89%) as well as for CFU (88%) were observed. Microbial contamination of the collected UCB samples was reduced to a rate of 6.4%. DISCUSSION: Optimized cryopreservation conditions were developed for UCB MNC in respect of the composition of the cryosolution. In addition, our results showed that fast addition of DMSO is essential for improved cryopreservation and post-thaw quality assessment results, whereas the speed of DMSO removal after thawing has little influence on the recoveries of CD34+ cells and CFU.

Antigens, CD34↗
PubMed2002

Biocatalyst-adsorbant systems: a viable alternative to proteolytic processes in solution.

Proteolytic biocatalysts were adsorbed and stabilized using alumina as a support medium. Two biocatalyst-adsorbant systems were prepared with different physical characteristics of the adsorbant: alumina powder and alumina pearls. Direct adsorption onto the support medium has the main advantage, over other fixation methods, that preliminary steps are not required for a good interaction between the support and the biocatalyst. Proteases were adsorbed and stabilized without modifying or sterically hindering their active sites. Parameters affecting adsorption (pH, temperature, ionic strength) were varied so as to optimize adsorption conditions. Operational viability of the immobilized biocatalysts was demonstrated, taking into account the rate of desorption, resistance to microbial attack, and stability during storage. Desorption in water was studied in batch and continuous-flow processes, at various flow rates. The systems also proved to be resistant to microorganisms. Tests for stability during storage found the systems' activity remained constant after 60 days, and they performed better than biocatalysts in solution. Proteolysis of a solution of g per litre of azocasein was carried out in continuous-flow and batch modes, using our biocatalyst-adsorbant systems we prepared. In all cases, free amino group concentrations were around 2.5 times greater after treatment with biocatalyst-adsorbants than they were in the starting solution.

Adsorption↗
PubMed1985

Hepatocyte function in sepsis: Kupffer cells mediate a biphasic protein synthesis response in hepatocytes after exposure to endotoxin or killed Escherichia coli.

Alterations in hepatic function are seen in sepsis and/or multiple system organ failure. We hypothesized that Kupffer cells (KC) within the liver may mediate functional alterations in adjacent hepatocytes (HC) in response to bacterial products. We have previously described decreases in rat HC protein synthesis during in vitro cocultivation with peritoneal macrophages in the presence of gentamicin-killed Escherichia coli (GKEC) or endotoxin (LPS). The present studies demonstrate that purified (greater than 95%), syngeneic, or allogeneic KC exposed to GKEC or LPS impart a biphasic response in cultured HC. When HC were cultured alone there was no alteration in 3H-leucine incorporation into HC protein after the addition of GKEC or LPS. When HC were cocultured with KC there was increased protein synthesis compared with HC alone (p less than 0.001). After the addition of GKEC or LPS there was an immediate increase in coculture HC protein synthesis. However, a marked decrease in coculture protein synthesis was seen 16 degrees later (p less than 0.001). To ensure that KC alone were responsible, splenic lymphocytes were added to HC alone or HC/KC coculture, but they did not alter the results. HC viability and appearance were unchanged throughout the experiments. These results show that exposure of KC to microbial products can profoundly alter HC function and support the concept of local KC modulation of HC function during sepsis.

Animals↗
PubMedDate not supplied

Salmonella typhimurium survival and viability is unaltered by suspended particles in freshwater.

Rolling microcosm experiments were conducted to determine whether suspended particles affect the survival and viability of a model pathogen, Salmonella choleraesuis, serotype typhimurium (American Type Culture Collection no. 23567), in a freshwater microbial community. Water from the Duluth, MN harbor of Lake Superior (including native microorganisms) was inoculated with clay, silt, or flocculent organic particles in a range of concentrations and a streptomycin-resistant strain of S. typhimurium. Microcosms (incubated at 20 degrees C) were rolled horizontally (3 rpm) and sampled periodically for total bacteria and total, viable, and culturable S. typhimurium. Total S. typhimurium abundance decreased rapidly in all experiments (8.5-73.1% d-1). Total bacteria did not decrease as rapidly as the S. typhimurium population in any experiment, suggesting that a microcosm effect was not responsible for the decline in S. typhimurium populations. Loss rates of attached and free cells were similar, indicating that attachment to particles did not enhance the persistence of Salmonella cells beyond our minimum detectable differences. After eight days, only 0.1 to 11.9% of the initial S. typhimurium inocula were detected by direct counts. Suspended particles had a minimal effect on the survival and viability of S. typhimurium; the losses of total, viable, or culturable Salmonella were generally the same across particle treatments and concentrations. Silt and flocculent particles affected loss rates of total and viable S. typhimurium similarly to inorganic particles (clay). It appears unlikely that suspended particles would provide a means for S. typhimurium to persist at hazardous levels in freshwater.

Flocculation↗
PubMed1975

Effects of human and rabbit serum on viability, permeability, and envelope lipids of Serratia marcescens.

The major action of serum on gram-negative organisms is thought to be on the microbial envelope. We compared the effects of normal human and rabbit serum on the envelope lipids of two strains of Serratia marcescens, one sensitive and one resistant to the bactericidal effects of serum. During killing by either serum, the sensitive strain underwent rapid permeability changes coincident with degradation of microbial phospholipids. The resistant strain exhibited none of these effects. The phospholipid degradation that accompanies killing of the sensitive strain by serum could be caused by phospholipases present in serum or by Serratia's own phospholipid-splitting enzymes. The results indicate that phospholipid breakdown is caused by activation of bacterial of bacterial phospholipases and not by serum phospholipases. This conclusion is based upon the following findings.(i1 Although rabbit serum phospholipase A was at least 10 times more active than human serum phospholipase A, phospholipid degradation in the sensitive Serratia strain was comparable during (equally rapid) killing by human or rabbit serum. (ii) Heat treatment (56 C) of both sera eliminated bactericidal activity as well as microbial lipid degradation but abolished phospholipase activity of human serum only. (iii) Virtually complete removal of phospholipase A activity from human serum by adsorption onto autoclaved Micrococcus lysodeikticus had no effect on the extent of phospholipid hydrolysis or on bactericidal activity. Activation by serum of endogenous phospholipase activity in S. marcescens was accompanied by enhanced incorporation of lipid precursors into bacterial lipids. No evidence was found for increased turnover of protein or ribonucleic acid during killing by serum.

Alkaline Phosphatase↗
PubMed2004

Production and characterization of immobilized-biomass carriers, using polyacrylamide.

Whole microbial cells from an activated sludge seed were immobilised in spherical polyacrylamide beads using a shrink/swell procedure which increased cell viability more than 100-fold over the seed material. The process was optimised with respect to the seed concentration and incubation time. It was shown that the swell procedure was essential to achieve good immobilisation and that biofilm attachment to the beads made a negligible contribution to the immobilised biomass. The physical and biological properties of the immobilised beads were determined and found to settle well and resist mechanical abrasion. In addition, their preparation did not prove toxic to the immobilised biomass. The beads produced have many applications for instance in enhancing the biomass in wastewater treatment processes. In addition the immobilisation process could be applied to a wide range of microbial consortia including pure cultures of microorganisms.

Acrylic Resins↗