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At least 1,063 records · Page 59Linked to original sources
PubMed2005

Bacteria enclosure between silica-coated membranes for the degradation of organic compounds in contaminated water.

A non-conventional technique is proposed for the enclosure of either pure bacterial cultures or entire biocoenoses, for a possible utilization in the treatment of contaminated water. Biological components have been enclosed between polyester membranes coated by silica films consisting of: (a) SiO2 and nitrocellulose, (b) SiO2, ZnS crystals and nitrocellulose, (c) SiO2, TiO2 crystals and nitrocellulose, (d) SiO2, ZnS and TiO2 crystals and nitrocellulose. Morphological, structural and mechanical features of membranes were investigated by means of optical and electron microscopy, mercury porosimetry and wear resistance tests. Degradation kinetics have been finally studied by dipping the entrapped biomass into aqueous solutions of three different model organic compounds (alpha-d-glucose, ethyl alcohol and peptone). Results are very promising: in fact, no metabolic inhibition mechanisms of microorganisms have been evidenced. The porosity of the system allows mass transfer through the membranes, hence bacteria can grow and degrade pollutants. Besides, by this system, cells are constrained, avoiding they to spread across the retainment scaffold.

Bacteria↗
PubMed2002

Intracellular superoxide dismutase, catalase, and glutathione peroxidase activities and membrane lipid peroxide levels in Fusarium acuminatum upon environmental changes in a defined medium.

The variations of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px) activities and lipid peroxide (LPO) levels in Fusarium acuminatum, an aerobic filamentous fungus, were investigated depending on the carbon and nitrogen sources during the incubation period. Fungus was cultivated in growing medium containing either maltose or saccharose in 5-25 g/L concentration range as a carbon source and either glycine or peptone in 5-35 g/L concentration range as a nitrogen source at 28 degrees C and 100 rpm. The observed highest SOD, CAT, and GSH-Px activities were 31.2+/-0.655, 62.5+/-5.23, and 1.52+/-0.0122 IU/mg in the presence of 20 g/L maltose and 73.96+/-1.48, 74.46+/-2.94, 3.48+/-0.083 IU/mg in the 15 g/L glycine-containing medium at 16 days, respectively. At the same time, the minimum LPO level was observed at 20 g/L maltose and 15 g/L glycine compared with the other carbon and nitrogen sources. The results showed a negative correlation between antioxidant enzyme activities and membrane LPO levels in F. acuminatum cells.

Adaptation, Physiological↗
PubMed2001

A comparison of human dental plaque microcosm biofilms grown in an undefined medium and a chemically defined artificial saliva.

The growth and pathogenic properties of dental plaque result from interactions between the microbiota and the oral environment and have been studied in laboratory experimental systems ranging from single or a few species (such as in chemostats) to dental plaque microcosms. Microcosm plaque is an in vitro version of natural plaque and has been explored as a microflora model because it is sited a more manipulable and controllable environment. It is obtained as microcosm biofilms in an 'artificial mouth' plaque culture system by culturing the bacteria in natural plaque-enriched saliva (i.e. salivary bacteria where a whole-saliva donor has abstained from oral hygiene for 24 h to increase the plaque bacteria in the saliva). The aim here was to examine whether a new, chemically defined analogue of saliva (defined medium mucin, DMM) could substitute for a previously used, chemically undefined medium (basal medium mucin, BMM) as an analogue of saliva for large-scale biofilm culturing. DMM contains various ions, mucin, amino acids, vitamins and growth factors at concentrations generally similar to those in saliva, whereas BMM contains yeast extract, peptones and mucin. To model the nutrient functions of salivary proteins, amino acids equivalent to 5 g/l casein were also included in DMM. In earlier studies, BMM-grown plaques were similar to natural plaques in structure, composition, growth rate and pH response to substrates. Their doubling-time patterns over a 20-day period were similar, except that the DMM-grown plaques showed biphasic growth patterns that were more pronounced than with BMM. Variation in enzyme profiles between BMM- and DMM-grown plaque, measured using the API-ZYM technique, provided evidence of nutritional effects on plaque composition. It was concluded that realistic growth rates and patterns are generated in microcosm plaque biofilms by supplying both DMM and BMM. However, the use of DMM enables specific modifications to be made to nutrient conditions during large-scale culture in our 'artificial mouth' biofilm system.

Amino Acids↗
PubMed1976

[Adenosine-dependent death of Hydrogenomonas eutropha (Alcaligenes eutrophus) H 16 (author's transl)].

Heterotrophic growth with fructose and autotrophic growth with hydrogen and carbon dioxide was entirely inhibited by adenosine at a concentration of 0.6 mg/ml in Hydrogenomonas eutropha (Alcaligenes eutrophus) H 16. Growth inhibition was not accompanied by a detectable uptake of the nucleoside. Adenosine caused a rapid inhibition of protein synthesis, followed by a decrease in nucleic acid formation. Enzyme synthesis was also impared, whilst cell respiration remained uneffected. Adenosin also caused a drastic but temporary decrease in viable cell counts. Cells incubated in presence of adenosine and fructose for several days, however, were no longer susceptable to this nucleoside. Adenosine-dependent growth inhibition turned out to be contingent upon the nature of the organic substrate. Cells growing with succinate, glutamate or peptone were less effected than cells, growing autotrophically or with fructose. No inhibition was observed in fructose-growing cells, if amino acids were also present in the medium. Several other nucleosides tested, did not show such growth inhibition, except desoxyadenosine, which, however, did not effect viable cell counts.

Adenosine↗
PubMed1997

Optimisation of methodology for enumeration of xerophilic yeasts from foods.

Xerophilic yeasts grow in intermediate moisture foods (aw, 0.65-0.85) such as sugar syrups, fruit concentrates, jams and brines. Non-osmophilic yeasts are enumerated by diluting in 0.1% peptone and then plated onto media such as malt extract or glucose yeast extract agar. In the presence of moulds the yeasts are enumerated in dichloran rose bengal chloramphenicol agar (DRBC). These procedures were demonstrated to be unsatisfactory for the enumeration of xerophilic yeasts in low aw foods. Investigations using pure cultures of xerophilic yeasts as well as naturally contaminated apple juice concentrates and glacé cherries have shown that a reduced aw diluent, in particular 30% w/w glycerol in combination with tryptone 10% glucose yeast extract agar (TGY) optimises the recovery of the yeasts, especially sublethally injured cells. The inclusion of sodium chloride in either the diluents or the culture media was not necessary to optimise the recovery of D. hansenii growing in 20% sodium chloride broths.

Agar↗
PubMed1986

Production and degradation of indole by gram-negative bacteria.

The indole reaction is performed in various modifications with regard both to the reagents and to the media used. Especially the medium has hitherto attracted little attention and there are divergent recommendations for its composition. The comparison of some broths without and with addition of tryptophan after incubation with different indole-positive species revealed that tryptone without tryptophan yielded stronger reactions than with tryptophan added. Other broths showed stronger reactions with tryptophan. Investigations revealed that numerous indole-positive as well as indole-negative species possess an enzyme system degrading indole. It is induced after one or two days of incubation and acts slowly. All species of the Morganella-Proteus-Providencia group possess it, as does Serratia. Some other species show different characteristics. The production of indole from peptone containing tryptophan and the degradation of indole by such species of bacteria are due to figures showing one or more peaks depending on time. Any false indole reactions described up to now may also be explained by the antagonism of the two enzyme systems. Therefore, the indole reaction should be standardized with regard to the medium used to avoid some of these difficulties.

Culture Media↗
PubMed2002

Regulation of crystal protein biosynthesis by Bacillus thuringiensis: II. Effects of carbon and nitrogen sources.

The regulation of crystal protein production in Bacillus thuringiensis 81 by sources of carbon and nitrogen was investigated. The highest titers of toxin were obtained on sucrose, lactose and inulin which also supported sporulation. Whey and molasses were also potential carbon substrates for toxin production. Other carbohydrates including glucose, glycerol, maltose, starch and dextrin yielded lower amounts of toxin. Nitrogen sources were found to exert the most profound controls. Peptone was the best organic nitrogen source, supporting optimum production and sporulation as well as high cell density. The formation of CryI and CryII toxin proteins was found to be differentially regulated by the inorganic nitrogenous compounds incorporated into the medium.

Bacillus thuringiensis↗
PubMed1972

Survival of Salmonella typhi in sea-water.

The bactericidal activity of natural sea-water on S. typhi is due to the combined effect of pH, salinity, toxic ions, presence of competitor and predator marine organisms, unidentified heat-labile toxic substances and competition for the limited food supply. Sea-water subjected to filtration and autoclaving lost the major part of its bactericidal activity. It is concluded that predators and competitors contribute significantly to the rapid death of S. typhi in raw sea-water. The addition of peptone decreases the bactericidal activity of sea-water. The fluctuations in the total number of competitors and predators in sea-water together with the fluctuations in the concentration of heavy metal ions may be affected by various factors. Such fluctuations are probably responsible for the variable bactericidal action of different sea-water samples.Bathing in sewage-polluted sea-water carries with it a health risk in spite of the excessive dilution of pathogenic micro-organisms in the sea and the rapid self-purification process of sea-water. The natural purifying processes are incapable of coping with massive pollution problems and should not be relied on as the sole protection offered to users of sea-water.

Calcium↗
PubMed1980

Single tube confirmatory tests for Escherichia coli.

In a multi-laboratory trial, lauryl tryptose mannitol broth (LTMB) and minerals-modified glutamate medium with added tryptophan (MMGM + T) were compared as single tube tests for the confirmation of Escherichia coli in water; the confirmed results were also compared with the production of gas from minerals-modified glutamate medium without added tryptophan (MMGM). LTMB and MMGM + T gave similar gas and indole results with about 90% of the water samples in most of the laboratories. When compared with the 'correct' results as judged by acid and gas production from lactose peptone water and indole from tryptone water, the difference in the rate of false positive reactions between LTMB and MMGM + T was insignificant; but LTMB gave a significantly lower rate of false negative reactions than MMGM + T. Gas production from MMGM without added tryptophan gave significantly higher rates of both false positive and false negative reactions. Lauryl sulphate is therefore a suitable inhibitory surfactant for use in single tube media for the confirmation of E. coli, which can be recommended.

Bacteriological Techniques↗
PubMed1970

Effect of suspending media on freeze-drying and preservation of vaccinia virus.

Unpurified and purified smallpox vaccines were prepared from calf dermal pulp, or chorioallantoic membrane (CAM) of hen eggs infected with vaccinia virus, and freeze-dried. The protective effect of various suspending media was investigated both in the course of the freeze-drying and in the period of subsequent storage of the dried product at different temperatures, including 100 degrees C.Single media consisting of either sodium glutamate or peptone were effective in the preservation of both unpurified and purified vaccines prepared from calf dermal pulp or CAM. It was shown that there was an optimal concentration of sodium glutamate for the preservation of the vaccine preparations, especially of the purified vaccine.Combined media, consisting of soluble starch, polyvinylpyrrolidone or sodium carboxymethyl cellulose with sodium glutamate, were effective with the purified vaccine when the concentration of sodium glutamate exceeded the optimum necessary for preservation.

Animals↗
PubMed1987

Survival of thermophilic campylobacters on fingertips and their elimination by washing and disinfection.

A simple impression-plate technique has been used to investigate the survival of four thermophilic campylobacter strains applied to fingertips. Campylobacters suspended in 0.1% peptone water and dried on the fingertips survived for different periods of time ranging from less than 1 to greater than or equal to 4 min. However, campylobacters suspended in chicken liquor or blood survived for much longer periods. The most resilient organism was Campylobacter jejuni NCTC 11392 which, when suspended in 50% horse blood, survived for an hour. Suspensions containing 10(6)-10(7) organisms prepared in 50% blood and dried on to fingertips were removed by thorough hand washing with either soap and water or water alone followed by drying on paper towels, but persisted on wet hands. The organisms were also eliminated by wiping the hands with a tissue saturated with 70% isopropyl alcohol for 15 sec.

1-Propanol↗
PubMed2003

Defective zoospore encystment and suppressed cyst germination of Phytophthora palmivora caused by transient leaching treatments.

The behaviour of encysting zoospores of Phytophthora palmivora during leaching conditions was studied. Zoospores encysted and germinated successfully on polycarbonate membranes after mechanical agitation. Transient (10 min) leaching treatments with nutrient-free buffer underneath the membranes resulted in abnormal encystment and poor germination. The disruption was greatest when leaching was applied during the first minutes after start of encystment and not observed after 20 min. The early sensitivity of cells to leaching coincided with the period when alkali-resistant cell walls were formed (2-6 min after mechanical agitation). Effects of calcium and organic nutrients on encystment during leaching and germination after these treatments were studied. The disruption of encystment by early leaching treatments, but not the suppression of cyst germination, was overcome by adding calcium chloride during mechanical agitation of zoospores. Leaching with calcium containing buffer resulted in suppressed cyst germination as was the case with buffer alone. Leaching with 0.1% peptone containing buffer promoted consistently high encystment and germination.

Buffers↗
PubMed2003

High cell density cultivation of Brevibacterium linens and formation of proteinases and lipase.

Brevibacterium linens forms hydrolytic enzymes which can be used to accelerate the ripening of cheese without causing bitterness. B. linens ATCC 9172 was grown to a high cell density (50 g dry wt l-1 after 60 h) in a mineral medium containing lactic acid, soy-peptone and ammonium sulphate by applying a continuous feed of nutrients. The maximal activities of L-leucine aminopeptidase and cell-associated proteinase were 286 U l-1 and 202 U l-1, respectively. The cell-associated lipolytic activity exhibited a strong and sudden increase at 46 h, resulting in a maximum of 9.5 U g-1 dry wt; thus the volumetric productivity of proteolytic and lipolytic activity was 4220 U l-1 h-1 and 7.3 U l-1 h-1, respectively.

Ammonium Sulfate↗
PubMed2002

Antibacterial activity of pepsin-digested lactoferrin on foodborne pathogens in buffered broth systems and ultra-high temperature milk with EDTA.

AIMS: To evaluate the antimicrobial activity in peptone yeast extract glucose (PYG) broth and ultra-high temperature (UHT) milk of bovine lactoferrin hydrolysate (LFH) with pepsin against the foodborne pathogens Salmonella Stanley, Escherichia coli, Listeria monocytogenes and Staphylococcus aureus. METHODS AND RESULTS: The LFH was suspended in PYG and the minimum inhibitory concentration for each pathogen determined. The LFH was also suspended in UHT milk adjusted to pH 4 or 7, samples incubated at 4 or 35 degrees C and the change in bacterial cell population determined. Experiments in UHT milk were conducted using L. monocytogenes and E. coli O157:H7. At pH 4 LFH reduced the population of E. coli O157:H7 and L. monocytogenes by approx. 2 log; however, only E. coli O157:H7 was inhibited in samples adjusted to pH 7. The addition of EDTA (10 mg ml(-1)) to UHT milk supplemented with LFH did not markedly influence the growth of E. coli O157:H7 or L. monocytogenes. CONCLUSIONS: The results suggest that, under low pH and refrigeration conditions, LFH can limit the growth or reduce the population of pathogenic bacteria in a dairy product. SIGNIFICANCE AND IMPACT OF THE STUDY: Natural preservatives that are active against Gram-negative and Gram-positive bacteria are desirable to the food industry. This study demonstrates that LFH is effective in a complex food system. Moreover, the LFH used was not purified, making its use by industry more attractive.

Animals↗
PubMed2002

Screening of pyruvate-producing yeast and effect of nutritional conditions on pyruvate production.

AIMS: To find a yeast strain that can overproduce pyruvate and to investigate the effect of nutrients on pyruvate production. METHODS AND RESULTS: Trichosporon cutaneum PD70, a yeast strain that can overproduce pyruvate, was isolated from shake-flask cultures of 132 yeast strains. Pyruvate was measured by the HPLC or DNP method (see Materials and methods). Pyruvate production reached approximately 30.0 +/- 1.0 g l(-1) in basal fermentation medium. Different nutrient supplements had great effects on pyruvate production. Some of the conditions that gave the highest yield are described. CONCLUSIONS: Exogenous thiamine supplement caused a decrease in pyruvate yield. Some amino acids, such as L-arginine, L-isoleucine and L-valine, caused a minor increase in pyruvate yield. Soybean peptone was the most suitable nitrogen source for pyruvate production. A glucose concentration of 15% in fermentation medium gave the highest yield (34.6 g l(-1)) and the highest yield against consumed glucose (0.429 g g(-1)). SIGNIFICANCE AND IMPACT OF THE STUDY: Nutrients have significant impacts on pyruvate production. As a pyruvate overproducing yeast strain independent of exogenous vitamins or amino acids, T. cutaneum PD70 provides an advantage for commercial pyruvate production.

Amino Acids↗
PubMed1974

An inhibitor of cell proliferation released by cultures of macrophages.

Culture fluids from mouse peritoneal exudate cells inhibited [(3)H]thymidine incorporation by, and proliferation of, EL-4 leukemia cells, 3T3 cells, and mitogen-stimulated spleen lymphocytes. Inhibited EL-4 leukemia cells recovered their normal proliferative capacity when washed and incubated in normal medium. The inhibitory activity resided in a low-molecular-weight substance that could be absorbed by incubation with the tumor cells. This substance was dialyzable and resistant to tryptic digestion and phosphodiesterase treatment. The mononuclear phagocytes in the peritoneal exudate seemed to be the source of the inhibitor. The inhibitory material was found in the same amounts in exudates of normal mice or mice injected with peptone or infected with Listeria monocytogenes; spleen cells adherent to plastic released the inhibitor but in lesser amount. We suggest that this inhibitor may contribute to the deleterious effects found when various cells, including neoplastic ones, are cultured in the presence of macrophages.

Animals↗
PubMed2006

Unified basis for the respirometric evaluation of inhibition for activated sludge.

This paper explores the merit of the oxygen uptake rate (OUR) profile obtained by means of respirometry as the basic mechanistic instrument for evaluating activated sludge inhibition. Experimental OUR data are generated using the synthetic peptone-based substrate and inhibition is tested with 60 mg/L hexavalent chromium and 33 mg/L nickel additions, corresponding to EC50 levels determined using the standard ISO 8192 procedure. Experimental results are evaluated by model calibration using ASM1 modified for dual hydrolysis and ASM3 modified for simultaneous growth. Model evaluations indicate that inhibition affects not only growth, but also other significant microbial mechanisms such as substrate storage and hydrolysis, leading to conclude that the proposed approach will enable to visualize the overall impact of the inhibitory compound on every stage of substrate biodegradation, through inspection and evaluation of the entire OUR profile.

Bioreactors↗
PubMed1973

Biochemical changes during growth and encystment of the cellular slime mold Polysphondylium pallidum.

The growth of the cellular slime mold, Polysphondylium pallidum, was studied on a semidefined medium in shaken suspension. When the medium contained large quantities of particulate material, growth was more rapid and the cellular size and protein content were smaller than when growth occurred on a medium containing less particulate material. The cellular levels of DNA, RNA, and protein; of lysosomal enzymes (acid phosphatase, acid proteinase); and of peroxisomal enzymes (catalase) were assayed during growth and the subsequent stationary phase that led eventually to encystment. Only DNA remained at a constant cellular level. Encystment of exponentially growing cells could also be initiated by washing them and introducing them into a soluble peptone medium. The rate of encystment was proportional to the osmolarity of this medium. The encystment process was followed with respect to the cellular levels of DNA, RNA, protein, carbohydrates, acid phosphatase, acid beta-N-Ac-glucosaminidase, and catalase. The most dramatic change occurred in the cellular cellulose content, which increased by at least an order of magnitude by the time encystment was morphologically complete. It was concluded that the encystment of this slime mold in suspension exhibits a number of biochemical similarities to the development of this and other cellular slime molds on a surface.

Acid Phosphatase↗