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At least 649 records · Page 36Linked to original sources
PubMed1977

Assimilation of liquid hydrocarbon by microorganisms. I. Mechanism of hydrocarbon uptake.

The uptake mechanism of liquid hydrocarbons of low solubility in water was investigated, using microorganisms with different affinities for liquid hydrocarbon. Microorganisms which could utilize hydrocarbon were much more adherent to hydrocarbon than those which could not. The adhesive force between Candida intermedia IFO 0761 and hydrocarbon was higher than that of Candida tropicalis ATCC 20336, though both could utilize hydrocarbon; The total hydrocarbon uptake from the drop and accommodation forms of hydrocarbons was much higher than that from dissolved hydrocarbon. The uptake rate of drop-form hydrocarbon was nearly equal to that of accommodation-form hydrocarbon for C. intermedia, but was lower for C. tropicalis which shows lower adhesion to hydrocarbon.

Adsorption↗
PubMed1977

Assimilation of liquid hydrocarbon by microorganisms. II. Growth kinetics.

The growth kinetics of a microorganism with high affinity for liquid hydrocarbon which has a low solubility in water was investigated for Candida intermedia IFO 0761 in our previous work. The microorganism contained a hydrocarbon pool in and/or on the cell. The transfer of water-soluble substrates to the cell was not the rate-limiting step in the growth of C. intermedia accompanied by clump formation with liquid hydrocarbon. The operating conditions necessary for the oxygen supply for the growth were adequate for the growth of C. intermedia on n-tetradecane. The saturation kinetics was valid for the specific growth rate of C. intermedia and specific concentration of hydrocarbon per unit cell mass; the specific growth rate was expressed by the following equation: (formula: see text).

Antifoaming Agents↗
PubMed1996

Adherence of oral microorganisms to human parotid salivary proteins.

Bacterial colonisation of oral surfaces by microorganisms may be dependent on their interaction with specific host receptor molecules. Primary oral colonisers are known to remove specific proteins from parotid saliva. The aim of this study was to determine whether these interactions facilitate microbial attachment to a surface and hence identify specific salivary components as putative host receptor molecules. Parotid saliva was resolved by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and then electroblotted onto nitrocellulose membranes. Suspensions of fluorescently labelled microorganisms were incubated with the blots and salivary components with adherent bacteria identified as fluorescent bands under ultraviolet (UV) transillumination. Species of streptococci known to be early colonisers of the clean tooth surface were found to adhere specifically to certain salivary proteins, especially to basic proline-rich proteins (PRPs). Polymorphic variations in these patterns could form the basis of differences in oral microflora, susceptibility to oral infections and consequent disease.

Bacterial Adhesion↗
PubMed1998

Polymerase chain reaction-mediated typing of microorganisms: tracking dissemination of genes and genomes.

The polymerase chain reaction (PCR) is a powerful molecular biology tool which can be used for the identification of species and strains of diverse microorganisms. By aimed amplification of characteristic genes (i.e., genes encoding ribosomal RNA molecules) and subsequent genetic analysis of amplified fragments, information on microbiological systematics and phylogeny can be obtained in a fast and efficient manner. Similar types of gene identification can be used to verify or detect genes responsible for phenotypic characteristics, whereas modified forms of the PCR enable whole genome searches for genetic polymorphisms among strains of a given species. In medical sciences, both strategies, gene and genome variability analysis by PCR, have an increasing impact on the study of the spread of especially those microbes that are multiply resistant to clinically used antibiotics. In this communication we will exemplify the usefulness of PCR-mediated typing of microorganisms from a clinical perspective while focusing on gene- versus genome-scanning. Special emphasis will be placed on analysis of the dissemination and characteristics of methicillin-resistant Staphylococcus aureus (MRSA) strains and bacterial factors providing resistance to penicillin and other beta-lactam antibiotics. Technical limitations and possibilities for improvement will be discussed.

Bacterial Typing Techniques↗
PubMed2005

Dynamic modification of microorganisms by pyrenebutanoate for fluorometric detection in capillary zone electrophoresis.

Pyrenebutanoate, a fluorescent amphiphilic probe, is suggested here as a capillary zone electrophoresis (CZE) buffer additive for dynamic modification and analysis of microbial cells. Mixed cultures of microorganisms Escherichia coli, Candida albicans, Enterococcus faecalis and Staphylococcus epidermidis were concentrated, resolved by CZE and detected. Using UV excitation for on-column fluorometric detection, a detection sensitivity for the microorganisms on the order of from one to tens of injected cells was achieved.

Candida albicans↗
PubMed2007

Development and characterization of porous silver-incorporated hydroxyapatite ceramic for separation and elimination of microorganisms.

A novel filter material for separating and eliminating microorganisms in water and gas was fabricated by incorporating silver ions into porous hydroxyapatite (HA) ceramics prepared by a starch additive technique. The porous ceramics reveal a microstructure of both large and small pores. Microorganism separating and eliminating properties of the porous silver-incorporated HA ceramics (PHA-Ag) were investigated by bacterial and viral filtration tests. The PHA-Ag demonstrated excellent separating and antibacterial effects on Escherichia coli and the mechanisms were studied. Adsorption of bacterial cells to the HA and the barricading effect of small pores contribute to the separating property of PHA-Ag, while the Ag+ ions equip the ceramics with antibacterial property. Furthermore, the PHA-Ag exhibited an observable virus-eliminating property and its probable mechanism was also discussed.

Biocompatible Materials↗
PubMed1993

Advantages of environmental scanning electron microscopy in studies of microorganisms.

Microorganisms, including bacteria, fungi, protozoa, and microalgae, are composed predominantly of water which prohibits direct observation in a traditional scanning electron microscope (SEM). Preparation for SEM requires that microorganisms be fixed, frozen or dehydrated, and coated with a conductive film before observation in a high vacuum environment. Sample preparation may mechanically disturb delicate samples, compromise morphological information, and introduce other artifacts. The environmental scanning electron microscope (ESEM) provides a technology for imaging hydrated or dehydrated biological samples with minimal manipulation and without the need for conductive coatings. Sporulating cultures of three fungi, Aspergillus sp., Cunninghamella sp., and Mucor sp., were imaged in the ESEM to assess usefulness of the instrument in the direct observation of delicate, uncoated, biological specimens. Asexual sporophores showed no evidence of conidial displacement or disruption of sporangia. Uncoated algal cells of Euglena gracilis and Spirogyra sp. were examined using the backscatter electron detector (BSE) and the environmental secondary electron detector (ESD) of the ESEM. BSE images had more clearly defined intracellular structures, whereas ESD gave a clearer view of the surface E. gracilis cells fixed with potassium permanganate, Spirogyra sp. stained with Lugol's solution, and Saprolegnia sp. fixed with osmium tetroxide were compared using BSE and ESD to demonstrate that cellular details could be enhanced by the introduction of heavy metals. The effect of cellular water on signal quality was evaluated by comparing hydrated to critical point dried specimens.

Animals↗
PubMed1981

Metabolism of phencyclidine by microorganisms.

A number of microorganisms were screened for their ability to metabolize phencyclidine. Two microorganisms, Beauveria sulfurescens and Cunninghamella echinulata, produced hydroxylated metabolites, which were identified as 1-(1-phenylcyclohexyl)-4-hydroxypiperidine and 4-phenyl-4-piperidinocyclohexanol by high-pressure liquid chromatographic analysis.

Basidiomycota↗
PubMedDate not supplied

The use of microorganisms for the study of drug metabolism.

The potential for the use of microorganisms as tools in the study of drug metabolism appears to be unlimited. The selected examples cited here are only the beginning of what could develop into a widely accepted alternative in vitro model system for studying drug metabolism in humans. As with any other in vitro model system, it is not expected that microbial systems could ever replace animals in biomedical research. The acquisition of data regarding absorption, distribution, and excretion will still require whole animal systems. However, it is clear from the examples cited that microbial systems offer a reliable, reproducible alternative to small animal models for preliminary drug metabolism studies. Due to significant species variation, small animal models may, in many cases, be less reliable than microorganisms as predictive models of human metabolism. It has been estimated that approximately 70 million animals are used each year in the U.S. for biomedical research. The development of any techniques which curtail the sacrifice of such large numbers of animals is welcomed both by animal welfare groups who wish to ensure the humane treatment of laboratory animals and by researchers who additionally appreciate the more practical and economical benefits of such alternatives.

Animals↗
PubMed1991

Use of microorganisms for the study of drug metabolism: an update.

The use of microorganisms as tools in the study of drug metabolism appears to be gaining popularity. The selected examples cited here provide additional evidence of the utility of these systems as alternative in vitro models for studying drug metabolism in humans. However, as was noted earlier, this model, nor any other in vitro model system could ever replace animals in biomedical research. However, it is apparent from the numerous examples cited here and in the previous review of this area that microorganisms are a reliable, reproducible alternative to small animals as predictive models in drug metabolism studies. The continuing development of techniques that reduce the use of animals in research is encouraged and this procedure appears to be gaining more widespread acceptance for such use.

Animals↗
PubMed1999

Extracellular iron reductases: identification of a new class of enzymes by siderophore-producing microorganisms.

This study identifies extracellular iron reductases in culture supernatant fluids of the siderophore-producing microorganisms Escherichia coli and Pseudomonas aeruginosa. These enzymes were constitutively produced and reduced and released iron from a variety of ferric chelators. Dialyzable cofactors, necessary for the transfer of electrons in the enzymatic reduction of iron, were identified. The reductases were sensitive to treatment with proteinase K and guanidine-HCl, were not associated with siderophore activity, and were apparently released from the cell as extracellular enzymes. The acquisition of 59Fe2+ by cell suspensions of E. coli and P. aeruginosa was saturable, suggesting that the ferrous iron generated by these reductases can be bound and transported. Salmonella typhimurium mutants feoB, tonB, entB, and entBfeoB, deficient in numerous known iron uptake pathways, were found to exhibit substantial extracellular iron-reducing activities over that of the parent. A hypothesis is proposed in which the extracellular iron reductases excreted by siderophore-producing microorganisms may be responsible for the mobilization of iron during conditions of iron repletion when siderophores are repressed and may also function in concert with siderophores during periods of iron starvation.

Endopeptidase K↗
PubMed1995

Formation of organic cadmium by marine microorganisms.

This research was designed with a view to finding out whether or not there is a microbial or spontaneous transformation of inorganic cadmium into a highly toxic organic derivative of this metal by microorganism obtained from the Eastern Mediterranean marine environment. Sterile and nonsterile marine bottom sediment samples were incubated at ambient temperature for different time intervals, under aerobic and anaerobic conditions, with different concentrations of CdCl2, and the medium, the atmosphere in the incubation flasks, and the sediments were assayed for their organic cadmium contents. The results were: (a) There was microbial growth in all systems containing up to 250 micrograms cadmium per milliliter of growth medium; however, with higher concentrations a complete growth-inhibition was observed. (b) Organic cadmium was found in the bottom sediments, at all cadmium levels permitting considerable microbial growth, but not in the systems' atmospheres or in the liquid growth media. (c) Under aerobic conditions higher levels of organic cadmium were found than in the anaerobic systems. (d) The microorganisms occurring in the different experimental systems were isolated and identified. The predominating species in all systems were bacteria.

Bacteria, Aerobic↗
PubMed1999

Influences of copper forms on the toxicity to microorganisms in soils.

Soil samples with wide ranges of pH (4.9 to 8.1), organic carbon (0.1 to 77%), and total Cu contents from 32 to 11700 mg kg(-1), collected near a copper mine, were used to investigate the relationships between microbial features and Cu speciation in order to clarify the form(s) of Cu adversely affecting microorganisms. The effects of Cu on soil microorganisms were evaluated by two indicators: the ratio of microbial biomass carbon to soil organic carbon (Cmic/Org-C) and Cu tolerance level of bacterial community (IC50). The sequential extraction scheme of McLaren and Crawford (1973) was used to quantify the different Cu forms (soluble and exchangeable, specifically adsorbed, and organically bound). These influences were investigated using simple correlation analysis, multiple regression analysis, and principal component analysis. The IC50 was positively correlated with the log concentration of soluble and exchangeable Cu (Ex-Cu) (r = 0.757, P<0.01). The IC50 value was also influenced by the amount of specifically adsorbed Cu. The Cmic/Org-C ratio was not significantly correlated with any Cu forms. Thus, other soil properties had more influence on the size of microbial biomass carbon in the soils used. The amount of Ex-Cu exerting high toxicity was affected by pH and the amount of total Cu.

Carbon↗
PubMed1999

Plasticity of the gastrointestinal epithelium: the M cell paradigm and opportunism of pathogenic microorganisms.

The maintenance during adult life of a large spectrum of pluripotency by stem cells originating from the endoderm seems to be the grounds for the striking plasticity of the digestive epithelium, which is able to drastically modify its differentiation pattern depending on the microenvironment. As a paradigm, Peyer's patch M cell development appears to be induced by crosstalk between lymphoid cells and/or microorganisms. Examples of pathological transdifferentiation of epithelia, also described as 'metaplasia' and affecting various organs, support the concept of intestinal plasticity. Though, the molecular processes involved in epithelial transdifferentiation have not been identified, histological analyses of these metaplastic tissues and experimental induction of transdifferentiation of normal epithelia provide lines of evidence suggesting that a modification of the local environment, such as occurs during contact of the epithelium with lymphoid cells or microorganisms, plays a key role in this process.

Epithelial Cells↗
PubMed2001

Polyesters from microorganisms.

Bacterial polyesters have been found to have useful properties for applications as thermoplastics, elastomers, and adhesives and are biodegradable and biocompatible. Poly(3-hydroxyalkanoates) (PHAs) and poly(beta-malate) are the most representative polyesters synthesized by microorganisms. PHAs containing a wide variety of repeating units can be produced by bacteria, including those containing many types of pendant functional groups which can be synthesized by microorganisms that are grown on unnatural organic substrates. Poly(beta-malate) is of interest primarily for medical applications, especially for drug delivery systems. In this chapter, the bacterial production and properties of poly(3-hydroxyalkanoates) and poly(beta-malate) are described with emphasis on the former.

Acyltransferases↗
PubMed2002

Integrated approach to explore the potential of marine microorganisms for the production of bioactive metabolites.

During the last 10 years marine organisms have provided a large number of new natural products. Interesting compounds have mainly been derived from macroorganisms such as sponges, ascidians, corals and bryozoans. The number of secondary metabolites from marine microorganisms is smaller, but rapidly increasing. Because of the enormous difficulties involved in harvesting products from marine animals, and the fact that some of the bioactive compounds are produced by associated bacteria, the advantages of sustainable production of bioactive metabolites by bacteria or fungi, under the protection of natural resources, seem to be very attractive for the future. This review describes current progress in the isolation and identification of novel marine microorganisms, the discovery of new secondary metabolites, the biotechnological approaches to overproduce them, as well as the evaluation and characterization of their bioactivity.

Antineoplastic Agents↗
PubMed1999

Microorganisms and microbial toxins.

The primary concern in food safety issues focuses on microorganisms and microbial toxins. Effective food preservation requires that the growth and proliferation of hazardous microorganisms be well controlled, and that the presence of significant quantities of microbial toxins in foods be prevented. The traditional effective preservation methodologies, such as canning, are being supplemented by new technologies which are less destructive of the food qualities. New strategies are therefore needed to prevent the transmission of microbial contamination or to prevent the formation of microbial toxins which remain in food. This paper discusses the role of modern processing methodologies in helping protect consumers from hazards of microbial origin.

Bacterial Toxins↗
PubMed2005

Screening for new metabolites from marine microorganisms.

This article gives an overview of current analysis techniques for the screening and the activity analysis of metabolites from marine (micro)organisms. The sequencing of marine genomes and the techniques of functional genomics (including transcriptome, proteome, and metabolome analyses) open up new possibilities for the screening of new metabolites of biotechnological interest. Although the sequencing of microbial marine genomes has been somewhat limited to date, selected genome sequences of marine bacteria and algae have already been published. This report summarizes the application of the techniques of functional genomics, such as transcriptome analysis in combination with high-resolution two-dimensional polyacrylamide gelelectrophoresis and mass spectrometry, for the screening for bioactive compounds of marine microorganisms. Furthermore, the target analysis of antimicrobial compounds by proteome or transcriptome analysis of bacterial model systems is described. Recent high-throughput screening techniques are explained. Finally, new approaches for the screening of metabolites from marine microorganisms are discussed.

Bacteria↗