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At least 397 records · Page 22Linked to original sources
PubMed1997

Relevance of the catheter hub as a portal for microorganisms causing catheter-related bloodstream infections.

Microorganisms causing vascular catheter-related sepsis gain access to the bloodstream through either the skin at the catheter insertion site or through the catheter hub. The catheter insertion site is probably the predominant portal for microorganisms in catheters in place for a short time, but the catheter hub may play an increasingly important role in infection in association with long-term catheters, particularly those that are subcutaneously tunneled. Although transient contamination of the catheter hub does not cause infection, certain microorganisms may migrate endoluminally and enter the bloodstream, causing bacteremia or fungemia.

Adult↗
PubMed2003

Helicobacter pylori: an invading microorganism? A review.

In this review we evaluate the pros and cons of Helicobacter pylori invasion of epithelial cells as part of the natural history of H. pylori infection. H. pylori is generally considered an extracellular microorganism. However, a growing body of evidence supports the controversial hypothesis that at least a subset of H. pylori microorganisms has an intracellular (intraepithelial) location. Most significant is the fact that H. pylori invades cultured epithelial cells with invasion frequencies similar to Yersinia enterocolitica and better than Shigella flexneri; furthermore, studies of invasion mechanisms suggest that H. pylori invasion of and survival within epithelial cells is not merely a passive event, but requires active participation of the microorganism. Although many studies of human gastric biopsy specimens have failed to demonstrate any intracellular H. pylori, some studies have revealed a minor fraction of H. pylori inside gastric epithelial cells, with possible linkage to peptic ulceration and epithelial cell damage. In conclusion, these data encourage further research to establish whether intracellular H. pylori does play a role in H. pylori colonization of the human stomach and in peptic ulcer pathogenesis.

Cell Line↗
PubMed1997

Rapid physiological characterization of microorganisms by biosensor technique.

Eleven microorganisms, Arxula adeninivorans LS3, Candida boidinii DSM 70034, Candida lactis-condensi DSM 70635, Pichia jadinii DSM 2361, Pichia minuta DSM 7018, Kluyveromyces lactis DSM 4394, Pseudomonas putida DSM 50026, Alcaligenes sp. DSM 30002, Arthrobacter nicotianae DSM 20123 as well as Issatchenkia orientalis DSM 70077 and Rhodococcus erythropolis DSM 311 were characterized by the sensor technique by injection of 30 different substrates and substrate mixtures. The obtained data which are based on the determination of respiratory rate of microorganisms are similar to physiological characteristics obtained with conventional methods. In comparison to these conventional methods the sensor technique works much more rapid and permits quantification of the data. Therefore, the described technique provides an alternative method for the characterization of microorganisms.

Bacterial Physiological Phenomena↗
PubMed1998

Screening of xenobiotic compounds degrading microorganisms using biosensor techniques.

A screening device based on microorganisms immobilised onto a Clark-type oxygen electrode was used to monitor the potential of these microorganisms for the degradation and detection of xenobiotic compounds especially their chlorinated derivatives. The sensitivity and specificity of various species of Pseudomonas, Sphinomonas, Ralstonia, Rhodococcus were characterised in relation to xenobiotic compounds by using biosensor techniques. The following groups of xenobiotics were subjects of investigation: chlorophenols, chlorobenzoates, 2,4-D, PCB, dibenzofurane and their putative intermediates. Using this simple setup it proved possible to screen microbial strains for their potential to catabolize aromatic and chloroaromatic compounds under oxygen consumption. In a kinetic regime, a reproducible signal was obtained within minutes. Based on these results the sensor technique was a suitable method for the rapid characterization of microorganisms and allowed to gather information about the substrate spectrum.

2,4-Dichlorophenoxyacetic Acid↗
PubMed1999

Pressure-regulated metabolism in microorganisms.

There has been a renewal of interest in the survival strategies employed by deep-sea, high-pressure-adapted (piezophilic) microorganisms as well as in the effects of high pressure on mesophilic, 1-atmosphere-pressure-adapted microorganisms. This is partly the result of a greater appreciation of the adaptations of microorganisms to life in extreme environments and partly the result of the development of new techniques for examining physiological and molecular processes as a function of pressure.

Bacteria↗
PubMed2000

Are microorganisms more effective than plants at competing for nitrogen?

Plant scientists have long debated whether plants or microorganisms are the superior competitor for nitrogen in terrestrial ecosystems. Microorganisms have traditionally been viewed as the victors but recent evidence that plants can take up organic nitrogen compounds intact and can successfully acquire N from organic patches in soil raises the question anew. We argue that the key determinants of 'success' in nitrogen competition are spatial differences in nitrogen availability and in root and microbial distributions, together with temporal differences in microbial and root turnover. Consequently, it is not possible to discuss plant-microorganism competition without taking into account this spatiotemporal context.

Fungi↗
PubMed2001

In situ staining with DNA-binding fluorescent dye, Hoechst 33258, to detect microorganisms in the epithelial cells of oral leukoplakia.

This study was performed to investigate the presence of microorganisms in the epithelial cells of leukoplakia. Frozen sections of 20 specimens of leukoplakia were stained with DNA-binding bisbenzimide Hoechst 33258. As a control, 20 specimens of normal oral mucosa and five specimens of normal skin were used. In all preparations of leukoplakia, small granular fluorescing structures were observed within the cytoplasm of the epithelial cells, predominantly within the cytoplasm of prickle cells, although the amount of the granular structures varied between specimens, layers of the epithelium and even areas of the epithelium within a single section. Less granular structures were observed, or none at all, in the cytoplasm of the epithelial cells of normal mucosa. No structures were observed in the cytoplasm of the epithelium of skin. The results in this study strongly suggest that microorganisms are present in the epithelial cells of oral mucosa, and that they are closely associated with the development of oral leukoplakia. It is postulated that the microorganisms in the epithelial cells could be bacteria, particularly mycoplasmas.

Adolescent↗
PubMed2001

Inherited microorganisms, sex-specific virulence and reproductive parasitism.

Parasites show an amazing repertoire of adaptations, highlighted by complex life cycles that allow both survival in the host and transmission among hosts. However, there is one heterogeneous group of microorganisms whose adaptations are perhaps even more surprising: parthenogenesis induction, feminization of genetic males, killing of male hosts and sperm-mediated sterilization of uninfected eggs. The common feature of these microorganisms is their mode of transmission: inheritance from mother to offspring. Here, we present an introduction to hereditary symbiosis, focusing on microsporidia and bacteria that manipulate host reproduction in arthropods (reproductive parasites). We also discuss the implications of one of these microorganisms, Wolbachia, for the control of arthropod pests and vectors and for the therapy of filarial diseases. Finally, we discuss whether some parasites of vertebrates might show sex-specific virulence.

Animals↗
PubMed2004

Characterization of microorganisms using UV resonance Raman spectroscopy and chemometrics.

The past decade has seen an increased interest in the application of several physicochemical analytical techniques for the rapid detection and identification of microorganisms. We report the development of UV resonance Raman (UVRR) spectroscopy for the reproducible acquisition of information rich Raman fingerprints from endospore-forming bacteria belonging to the genera Bacillus and Brevibacillus. UVRR was conducted at 244 nm, and spectra were collected in typically 60 s. Cluster analyses of these spectra showed that UVRR spectroscopy could be used to discriminate between these microorganisms to species level, and the clustering pattern from this phenotypic classification was highly congruent with phylogenetic trees constructed from 16S rDNA sequence analysis. Therefore, we conclude that UVRR spectroscopy when coupled with chemometrics constitutes a powerful approach to the characterization and speciation of microorganisms.

Bacillus↗
PubMed2005

Top-down proteomics for rapid identification of intact microorganisms.

We apply MALDI-TOF/TOF mass spectrometry for the rapid and high-confidence identification of intact Bacillus spore species. In this method, fragment ion spectra of whole (undigested) protein biomarkers are obtained without the need for biomarker prefractionation, digestion, separation, and cleanup. Laser-induced dissociation (unimolecular decay) of higher mass (>5 kDa) precursor ions in the first TOF analyzer is followed by reacceleration and subsequent high-resolution mass analysis of the resulting sequence-specific fragments in a reflectron TOF analyzer. In-house-developed software compares an experimental MS/MS spectrum with in silico-generated tandem mass spectra from all protein sequences, contained in a proteome database, with masses within a preset range around the precursor ion mass. A p-value, the probability that the observed matches between experimental and in silico-generated fragments occur by chance, is computed and used to rank the database proteins to identify the most plausible precursor protein. By inference, the source microorganism is then identified on the basis of the identification of individual, unique protein biomarker(s). As an example, intact Bacillus atrophaeus and Bacillus cereus spores, either pure or in mixtures, were unambiguously identified by this method after fragmenting and identifying individual small, acid-soluble spore proteins that are specific for each species. Factors such as experimental mass accuracy and number of detected fragment ions, precursor ion charge state, and sequence-specific fragmentation have been evaluated with the objective of extending the approach to other microorganisms. MALDI-TOF/TOF-MS in a lab setting is an efficient tool for in situ confirmation/verification of initial microorganism identification.

Amino Acid Sequence↗
PubMed2004

Vinyl chloride and cis-dichloroethene dechlorination kinetics and microorganism growth under substrate limiting conditions.

The reductive dechlorination of tetrachloroethene (PCE) and trichloroethene (TCE) at contaminated sites often results in the accumulation of cis-1,2-dichloroethene (DCE) and vinyl chloride (VC), rather than the nonhazardous end product ethene. This accumulation may be caused by the absence of appropriate microorganisms, insufficient supply of donor substrate, or reaction kinetic limitations. Here, we address the issue of reaction kinetic limitations by investigating the effect of limiting substrate concentrations (electron donor and acceptor) on DCE and VC dechlorination kinetics and microorganism growth by bacterium VS. For this, a model based on Monod kinetics, but also accounting for competition between electron acceptors and the effect of low electron donor and acceptor concentrations (dual-substrate kinetics), was examined. Competitive coefficients for VC (7.8 +/- 1.5 microM) and DCE (3.6 +/- 1.1 microM) were obtained and included in the model. The half velocity coefficient for hydrogen, the electron donor, was experimentally determined (7 +/- 2 nM) through investigating dechlorination over different substrate concentrations. This complete model was then used, along with experimental data, to determine substrate concentrations at which the dechlorinating microorganisms would be in net decay. Notably, the model indicates net decay will result if the total electron acceptor concentration (DCE plus VC) is below 0.7 microM, regardless of electron donor levels. The ability to achieve sustainable bioremediation to acceptable levels can be greatly influenced by this threshold level.

Bacteria↗
PubMed2004

Comparative evaluation of chloroethene dechlorination to ethene by Dehalococcoides-like microorganisms.

Reductive dehalogenation of tetrachloroethene (PCE), trichloroethene (TCE), cis-1,2-dichloroethene (DCE), and vinyl chloride (VC) was examined in four cultures containing Dehalococcoides-like microorganisms. Dechlorination and growth kinetics were compared using a Monod growth-rate model for multiple electron acceptor usage with competition. Included were the Victoria mixed culture containing Dehalococcoides species strain VS (from Victoria, TX), the mixed culture KB-1/VC (from southern Ontario), the Pinellas mixed culture (from Pinellas, FL), and D. ethenogenes strain 195. All cultures, with the exception of D. ethenogenes strain 195, grew with VC as catabolic electron acceptor. A dilution method was developed that allows a valid comparison to be made of dehalogenating kinetics between different mixed cultures. Using this procedure, maximum growth rates on VC were found to be similar for strain VS and KB-1/VC (0.42-0.49 +/- 0.02 d(-1)) but slower for the Pinellas culture (0.28 +/- 0.01 d(-1)). The 16S rRNA gene sequences were determined to ensure that no cross contamination between cultures had occurred. Following enrichment of the VC dechlorinating microorganisms on VC, the cultures were amended with DCE, TCE, or PCE. The three mixed cultures failed to dechlorinate PCE or did so very slowly. However, the dilution technique indicated that all experienced growth on TCE and DCE as well as on VC. Maximum growth rates on DCE alone were quite similar (0.43-0.46 d(-1)), while the Pinellas culture grew faster on TCE alone (0.49 d(-1)) than did the other two mixed cultures (0.33-0.35 d(-1)). Half-velocity and inhibition constants for growth on TCE were also determined for the three mixed cultures; both constants were found to be essentially equal and the same for the different cultures, varying between only 8.6 and 10.5 microM. The ability of the strain VS, KB-1/VC, and Pinellas cultures to utilize TCE rapidly with conversion to ethene is quite different from that of any other reported microorganism. It was separately confirmed with more traditional cell-counting techniques that strain VS coupled TCE, as well as DCE and VC, utilization with growth. This is the first report of an organism obtaining energy for growth through every step in the reduction of TCE to ethene. Also, as suggested by the dilution technique, the dehalogenating organisms in the KB-1/VC and Pinellas cultures appear to obtain growth from TCE utilization as well. Such ability to grow while dehalogenating TCE to ethene will be an important advantage for their use in bioaugmentation.

Biodegradation, Environmental↗
PubMed2006

Responses of soil microorganisms and enzymes to repeated applications of chlorothalonil.

Introduction of anthropogenic chemicals into soil may have lasting effects on soil microbial activities and thus soil health. This study was conducted with chlorothalonil to evaluate its effects on soil bacterial, fungal, and actinomycete populations and soil enzymes (acid phosphatase, alkaline phosphatase, urease, catalase, and invertase) after repeated applications. After the first addition of chlorothalonil, the soil bacterial and actinomycete populations were significantly reduced, whereas the population of soil fungi was unchanged. The most marked inhibition on soil microorganisms was observed after the second pesticide addition. However, after initial variations, soil bacteria, fungi, and actinomycetes adapted gradually to chlorothalonil, and the negative effects became transient and weaker following the third and fourth treatments. The inhibitory effect of repeated chlorothalonil applications on soil enzymes followed a similar trend to that on soil microorganisms. Repeated chlorothalonil applications did not result in significant changes in its persistence. Three bacterial strains capable of utilizing chlorothalonil as a sole source of carbon and energy for growth were isolated 21 days after the fourth treatment with chlorothalonil, which indicated that the capability of soil microorganisms for degrading chlorothalonil was formed during the experiment.

Actinobacteria↗
PubMedDate not supplied

Functions and possible provenance of primordial proteins--Part II: microorganism aggregation in clouds triggered by climate change.

Current models predict that the elevation of the Earth's surface temperature due to global warming is accompanied by a warming of the troposphere, and a thickening cloud cover associated with longer-lasting clouds, in particular over land. These effects can have an instant impact on the vitality level of microorganisms in clouds and the spreading of airborne diseases. Microorganisms could originate from locations on the Earth, or even arrive from space. Primordial proteins in nanobacteria, only recently identified in the atmosphere, could play a significant role in clouds--accelerating the formation of cloud droplets and interconnecting nanobacteria (and possibly nanobacteria and other microorganisms), thus enhancing their chances to eventually reach the Earth.

Air Microbiology↗
PubMed2002

Phosphonates and their degradation by microorganisms.

Phosphonates are a class of organophosphorus compounds characterized by a chemically stable carbon-to-phosphorus (C-P) bond. Wide occurrence of phosphonates among xenobiotics polluting the environment has aroused interest in pathways and mechanisms of their biodegradation. Only procaryotic microorganisms and the lower eucaryotes are capable of phosphonate biodegradation via several pathways. Destruction of the non-activated C-P bond by the C-P lyase pathway is of fundamental importance, and understanding of the process is a basic problem of biochemistry and physiology of microorganisms. This review offers analysis of available data on phosphonate-degrading microorganisms, degradation pathways, and genetic and physiological regulation of this process.

Bacteria↗
PubMed2001

Evaluation of a procedure to isolate culturable microorganisms from carpet dust.

Details of a method to isolate culturable bacteria and fungi from carpet dust were evaluated to isolate the greatest numbers of these agents. Four broad groups were evaluated: mesophilic and thermophilic bacteria and moderately hydrophilic and xerophilic fungi. Features studied included: 1) mixing time; 2) addition of glass beads; 3) length of time dust settled before suspensions were plated; 4) relative concentrations of microorganisms in the fibrous and fine dust fractions; and 5) storage temperature and period. The findings are preliminary because of the small number of samples, but a votexing time of at least 2 min with glass beads gave the best results in terms of the highest estimate of the concentration of culturable bacteria or fungi. Microorganisms were retrievable-from the upper portion of a suspending liquid for at least 30 min with little detectable change in concentration. Both bacteria and fungi were more abundant in the fine than the fibrous dust fraction. No significant losses were observed for samples stored up to 25 days at 5 degrees C or 25 degrees C. This procedure optimized measurement of total concentration, but may not identify the range of genera and species in dust if microorganisms present in small numbers and as single units are underrepresented relative to those in clusters and aggregates.

Air Pollution, Indoor↗
PubMed1996

The rapid identification of intact microorganisms using mass spectrometry.

Antibiotic-resistant strains of bacteria continue to emerge, increasing the need for their fast and accurate identification. Matrix-assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF-MS), has become a prominent technique in biological mass spectrometry. We report the application of MALDI-TOF-MS for the identification of intact Gram-negative and Gram-positive microorganisms taken directly from culture. Analysis of bacteria from a single colony is possible, allowing the screening of mixed cultures. Sample preparation is simple and the analysis automated, providing spectra within minutes. The spectra obtained allow identification of microorganisms from different genera, different species, and from different strains of the same species. The procedure provides a unique mass spectral fingerprint of the microorganism, produced from desorbed components of the cell wall. Consistent data were obtained from subcultures grown for 3-day and 6-day periods, from the same cultures 1 day later and from fresh subcultures 2 months later.

Coumaric Acids↗
PubMed2003

Microorganisms and autoimmunity: making the barren field fertile?

Microorganisms induce strong immune responses, most of which are specific for their encoded antigens. However, microbial infections can also trigger responses against self antigens (autoimmunity), and it has been proposed that this phenomenon could underlie several chronic human diseases, such as type 1 diabetes and multiple sclerosis. Nevertheless, despite intensive efforts, it has proven difficult to identify any single microorganism as the cause of a human autoimmune disease, indicating that the 'one organism-one disease' paradigm that is central to Koch's postulates might not invariably apply to microbially induced autoimmune disease. Here, we review the mechanisms by which microorganisms might induce autoimmunity, and we outline a hypothesis that we call the fertile-field hypothesis to explain how a single autoimmune disease could be induced and exacerbated by many different microbial infections.

Animals↗