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At least 145 records · Page 8Linked to original sources
PubMed2002

Measurement of microbial activity in soil by colorimetric observation of in situ dye reduction: an approach to detection of extraterrestrial life.

BACKGROUND: Detecting microbial life in extraterrestrial locations is a goal of space exploration because of ecological and health concerns about possible contamination of other planets with earthly organisms, and vice versa. Previously we suggested a method for life detection based on the fact that living entities require a continual input of energy accessed through coupled oxidations and reductions (an electron transport chain). We demonstrated using earthly soils that the identification of extracted components of electron transport chains is useful for remote detection of a chemical signature of life. The instrument package developed used supercritical carbon dioxide for soil extraction, followed by chromatography or electrophoresis to separate extracted compounds, with final detection by voltammetry and tandem mass-spectrometry. RESULTS: Here we used Earth-derived soils to develop a related life detection system based on direct observation of a biological redox signature. We measured the ability of soil microbial communities to reduce artificial electron acceptors. Living organisms in pure culture and those naturally found in soil were shown to reduce 2,3-dichlorophenol indophenol (DCIP) and the tetrazolium dye 2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide inner salt (XTT). Uninoculated or sterilized controls did not reduce the dyes. A soil from Antarctica that was determined by chemical signature and DNA analysis to be sterile also did not reduce the dyes. CONCLUSION: Observation of dye reduction, supplemented with extraction and identification of only a few specific signature redox-active biochemicals such as porphyrins or quinones, provides a simplified means to detect a signature of life in the soils of other planets or their moons.

Bacteria↗
PubMed1980

Microbiology of methanogenesis in thermal, volcanic environments.

Microbial methanogenesis was examined in thermal waters, muds, and decomposing algal-bacterial mats associated with volcanic activity in Yellowstone National Park. Radioactive tracer studies with [(14)C]glucose, acetate, or carbonate and enrichment culture techniques demonstrated that methanogenesis occurred at temperatures near 70 degrees C but below 80 degrees C and correlated with hydrogen production from either geothermal processes or microbial fermentation. Three Methanobacterium thermoautotrophicum strains (YT1, YTA, and YTC) isolated from diverse volcanic habitats differed from the neotype sewage strain DeltaH in deoxyribonucleic acid guanosine-plus-cytosine content and immunological properties. Microbial methanogenesis was characterized in more detail at a 65 degrees C site in the Octopus Spring algal-bacterial mat ecosystem. Here methanogenesis was active, was associated with anaerobic microbial decomposition of biomass, occurred concomitantly with detectable microbial hydrogen formation, and displayed a temperature activity optimum near 65 degrees C. Enumeration studies estimated more than 10(9) chemoorganotrophic hydrolytic bacteria and 10(6) chemolithotrophic methanogenic bacteria per g (dry weight) of algal-bacterial mat. Enumeration, enrichment, and isolation studies revealed that the microbial population was predominantly rod shaped and asporogenous. A prevalent chemoorganotrophic organism in the mat that was isolated from an end dilution tube was a taxonomically undescribed gram-negative obligate anaerobe (strain HTB2), whereas a prevalent chemolithotrophic methanogen isolated from an end dilution tube was identified as M. thermoautotrophicum (strain YTB). Taxonomically recognizable obligate anaerobes that were isolated from glucose and xylose enrichment cultures included Thermoanaerobium brockii strain HTB and Clostridium thermohydrosulfuricum strain 39E. The nutritional properties, growth temperature optima, growth rates, and fermentation products of thermophilic bacterial strains 39E, HTB2, and YTB were determined.

Anaerobiosis↗
PubMed1966

Microbial contaminants in the interiors of spacecraft components.

The hazard from microbiological contamination in the interiors of components of planetary-impacting spacecraft has been generally recognized, but techniques for experimentally evaluating the significance of this hazard have been unavailable. A goal in sterilizing early Mars-impacting payloads is the elimination of the possibility that a microbial stowaway will cause the extraterrestrial-life detection techniques falsely to indicate existence of Martian life, particularly if none exists. Another goal is the prevention of changes in Martian ecology. Several promising life-detection techniques were evaluated in an experimental study of methods to detect microbial populations inside spacecraft-type materials after pulverization or being dissolved. The type of material inspected has a greater effect on the sensitivity of the detection method than any other parameter studied. Through culturing abraded particles, a bacillus inoculum of 100 spores per milliliter can be detected in solid propellants. Fifty percent of an inoculum can be recovered from some solids soluble in nontoxic solvents. For many of the solids studied, however, the culturing techniques used were unable to detect inoculums of 10(6) spores per milliliter of solid. The techniques other than culturing did not discriminate between living and dead cells. As with products of the food and pharmaceutical industries, assurance of sterility in the final product never rests in a negative sterility test on a copy of the product. A negative sterility test is certainly most meaningful for a product for which a very sensitive sterility test has been developed. When a sensitive final-product sterility test is not available, assurance of sterility depends more heavily on other information such as the manufacturing history of the product.

Bacillus subtilis↗
PubMed1991

[Microbial colonization and succession in the large intestine of newborn infants during their stay with mothers at the maternity hospital].

Formation of microflora in the large intestine of 5-day old infants was studied in one of the Moscow maternity homes. The up-to-date procedures for isolation and identification of aerobic and anaerobic organisms were used in the study and the findings were processed on a computer. In the newborns of the maternity home of the "mother-infant" type there was observed colonization of the large intestine with aerobic and anaerobic organisms. A wave-like dynamics in the formation of the symbiotic microflora was revealed. It reflected the phenomenon of the microbial succession in the infants. The attempts to detect microbial interference between the species colonizing the large intestine showed that it was extremely rare in the 5-day old infants. This was likely the reason of the low intestine resistance to the colonization in the newborns which in its turn defined the frequent colonization of the intestine mucosa with S. aureus and the organisms of the Klebsiella, Enterobacter and Citrobacter group.

Adult↗
PubMed2005

Stable isotope probing analysis of the influence of liming on root exudate utilization by soil microorganisms.

Rhizosphere microorganisms play an important role in soil carbon flow, through turnover of root exudates, but there is little information on which organisms are actively involved or on the influence of environmental conditions on active communities. In this study, a 13CO2 pulse labelling field experiment was performed in an upland grassland soil, followed by RNA-stable isotope probing (SIP) analysis, to determine the effect of liming on the structure of the rhizosphere microbial community metabolizing root exudates. The lower limit of detection for SIP was determined in soil samples inoculated with a range of concentrations of 13C-labelled Pseudomonas fluorescens and was found to lie between 10(5) and 10(6) cells per gram of soil. The technique was capable of detecting microbial communities actively assimilating root exudates derived from recent photo-assimilate in the field. Denaturing gradient gel electrophoresis (DGGE) profiles of bacteria, archaea and fungi derived from fractions obtained from caesium trifluoroacetate (CsTFA) density gradient ultracentrifugation indicated that active communities in limed soils were more complex than those in unlimed soils and were more active in utilization of recently exuded 13C compounds. In limed soils, the majority of the community detected by standard RNA-DGGE analysis appeared to be utilizing root exudates. In unlimed soils, DGGE profiles from 12C and 13C RNA fractions differed, suggesting that a proportion of the active community was utilizing other sources of organic carbon. These differences may reflect differences in the amount of root exudation under the different conditions.

Bacteria↗
PubMed2004

The role of Toll-like receptors and Nod proteins in bacterial infection.

Our understanding of innate immunity in mammals has greatly expanded following the discovery of the family of membrane-bound receptors, called the Toll-like receptors (TLRs). More recently, the nucleotide-binding oligomerisation domain (Nod) molecules, Nod1 and Nod2, which are cytoplasmic surveillance proteins, have also been shown to be involved in the innate immune response. These two classes of detection molecules, classified as "pattern recognition receptors" (PRRs), detect microbial ligands in order to initiate a defense response to fight infectious disease. These microbial ligands or "pathogen-associated molecular patterns" (PAMPs), detected by TLRs and Nods are often structural components of the microorganism that are not subject to much variation. These include such factors as lipopolysaccharide (LPS) and peptidoglycan from the cell walls of bacteria. In order to understand the role of TLRs and Nod proteins in infectious disease in vivo it is important to define the site of interaction between PRRs and PAMPS. Additionally, the challenge of mice deficient in the various PRRs in natural infection models will help to decipher the contribution of these molecules not only in the innate immune response against pathogen infection but also how these proteins may instruct the adaptive immune response in order to have a tailored immune response against a particular microbe.

Adaptor Proteins, Signal Transducing↗
PubMed2026

Microbial DNA analysis of paired blood-bronchoalveolar lavage fluid in post-HSCT patients with pneumonia implying application conditions of blood as a surrogate in pathogen detection.

BACKGROUND: Blood testing aids pneumonia diagnosis, but its effectiveness varies. Given the invasiveness of bronchoalveolar lavage fluid (BALF) sampling versus blood testing's simplicity, this study investigates when blood can reliably substitute for BALF in detecting microbial presence, especially for pathogens. RESULTS: Metagenomic sequencing was performed on paired BALF-blood samples from 21 post-HSCT immunocompromised (ICP) and 21 immunocompetent (ICT) patients. The ICP cohort was expanded to 62 for biomarker validation. Host responses were profiled via metatranscriptomics (30 BALF samples). Microbial alpha and beta diversity differed significantly between blood and BALF in ICP, but not ICT, patients. ICP patients' BALF contained a greater diversity and abundance of microbes. A higher proportion of microbial DNA sequences in ICP patients' blood was also present in their BALF, suggesting a potentially more permeable alveolar-capillary barrier. Related genes (e.g., NABA CORE MATRISOME, extracellular matrix organization, cell-cell adhesion) were downregulated. Upregulated pathways like VEGFA-VEGFR2 signaling and Rho GTPases suggested increased vascular permeability. In ICP patients, 419 microbial sequences in blood indicated their presence in the lower respiratory tract with > 70% certainty. CONCLUSION: Host immune status significantly influences blood-BALF microbial diversity differences. Shared blood-BALF microbial DNA sequences show potential for aiding pneumonia pathogen diagnosis, offering a novel biomarker identification approach.

Humans↗
PubMed2002

Sensitivity and rapidity of blood culture bottles in the detection of cornea organ culture media contamination by bacteria and fungi.

AIMS: To test the bactericidal activity of standard organ culture medium, and to compare the sensitivity and rapidity of blood culture bottles with conventional microbiological methods for detection of bacteria and fungi inoculated in a standard cornea organ culture medium. METHODS: The bactericidal activity of contaminated standard organ culture medium containing 100 IU/ml penicillin, 0.1 mg/ml streptomycin, and 0.25 micro g/ml amphotericin B was evaluated after 48 hours of incubation at 31 degrees C with five inocula of 14 bacteria. Two yeasts (Candida spp) and one Aspergillus were also tested. Contaminated media were then inoculated in three blood bottles (aerobic, anaerobic, fungal) placed in a Bactec 9240 automat; three conventional microbiological broths were the control. Changes in colour of organ culture medium and growth on conventional broth were screened daily by visual inspection. The sensitivity and rapidity of detection of contamination were compared between the three methods: blood bottle, conventional, and visual. RESULTS: Organ culture medium eradicated five bacteria irrespective of the starting inoculums: Streptococcus pneumoniae, Branhamella catarrhalis, Escherichia coli, Propionibacterium acnes, and Haemophilus influenzae. For micro-organisms where the medium was ineffective or bactericidal only (methicillin resistant Staphylococcus aureus, methicillin sensitive Staphylococcus aureus, Staphylococcus epidermidis, Staphylococcus haemolyticus, Pseudomonas aeruginosa, Acinetobacter baumannii, Bacillus subtilis, Klebsiella pneumoniae, Enterococcus faecalis, Candida albicans, Candida kruzei, Aspergillus fumigatus), the blood bottle, conventional, and visual methods detected microbial growth in 100%, 76.5%, and 70% of cases respectively. Mean detection time using blood bottles was 15.1 hours (SD 13.8, range 2-52). In cases of detection by the blood bottle method and the conventional method, the former was always faster: 95.5% against 65.2% detection within 24 hours (p=0.022) respectively. CONCLUSIONS: Blood bottles detect more efficiently and more rapidly a wider range of bacteria and fungi than the conventional microbiological method and the visual inspection of organ culture media.

Bacteria↗
PubMed2000

Recalls of foods and cosmetics due to microbial contamination reported to the U.S. Food and Drug Administration.

In the U.S., food product recalls serve as an important intervention in stemming the consumption of food products contaminated with infectious disease agents. We summarize the number and nature of foods and cosmetics recalled as a result of microbial contamination reported to the U.S. Food and Drug Administration (FDA) for the period 1 October 1993 through 30 September 1998. During this period, microbial contamination of food and cosmetic products was the leading cause for recalls, accounting for a total of 1,370 recalls (36% of all products recalled). Listeria monocytogenes accounted for the greatest number of food products recalled because of microbial contamination, whereas Pseudomonas aeruginosa was the most common microbe associated with recalls of cosmetic products. Dairy products, followed by seafood and pastry items, were the types of products most often associated with recalls due to microbial contamination. The FDA was the entity most often responsible for detecting microbial contamination of foods and cosmetics (33% of all such recalls), followed by state regulatory agencies (24%), and manufacturers/retailers (21%). Nineteen percent of recalls were associated with at least one reported case of illness. Salmonella was the pathogen most often implicated in reports of illness associated with these recalled products.

Animals↗