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PubMed1986

Psychrophilic and psychrotrophic microorganisms.

Psychrophilic and psychrotrophic microorganisms have the ability to grow at 0 degree C. Psychrotrophic microorganisms have a maximum temperature for growth above 20 degrees C and are widespread in natural environments and in foods. Psychrophilic microorganisms have a maximum temperature for growth at 20 degrees C or below and are restricted to permanently cold habitats. This ability to grow at low temperature may be correlated with a lower temperature characteristic than that of the mesophiles, an increasing proportion of unsaturated fatty acids in the lipid phase of the cell membrane, which makes it more fluid, and a protein conformation functional at low temperature. The relatively low maximum temperature of growth for these microorganisms is often considered to be due to the thermolability of one or more essential cellular components, particularly enzymes, while some degradative activities are enhanced, resulting in an exhaustion of cell energy, a leakage of intracellular substances or complete lysis. Psychrotrophic microorganisms are well-known for their degradative activities in foods. Some are pathogenic or toxinogenic for man, animals or plants. However in natural microbial ecosystems psychrotrophic and psychrophilic microorganisms can play a large role in the biodegradation of organic matter during cold seasons.

Bacteria↗
PubMed1991

Soil and groundwater transport of microorganisms.

Releases of GEMs into the environment are expected to increase in the next few years, with the most dramatic increases resulting from the application of pest-control agents in agriculture and forestry. Of major significance in assessing the environmental risk impact of GEMs is an understanding of their survival and transport in soil and subsurface environments. While information on the transport and survival of microorganisms through soil is available, it is neither abundant nor extensive in terms of microbial types tested or soils examined. Though the transport of microorganisms from an application site depends primarily upon passive mechanisms, broad generalizations pertaining to the transportability of a specific microorganism within a particular soil environment may not be possible. Indeed, to extrapolate from information about one microbe to another, or from one geographical location to another, may not be appropriate. What is clear, however, is that the broader the data base, the more powerful the argument for making reasoned judgement, and consequently the more satisfactory the results of the predictive process. Several inherent difficulties exist in studying the transport behavior of GEMs in soil and subsurface environments. Detection of low microbial numbers or of stressed microbial populations is exceedingly difficult with traditional technology. In an effort to improve detection sensitivity, many improved methods of monitoring GEMs in the soil and subsurface are currently under development (Chaudhry et al. 1989). Beyond the difficulties of making accurate measurements of microorganisms to determine their spatial and temporal situation in the soil and subsurface environment, lies the need to ascertain the dynamic relationships between indigenous populations of microorganisms and how they may interact with a released GEM. Also, research strategies have not adequately addressed methods to predict the potential interactions between GEMs and natural microorganisms. These issues must be addressed if environmental risk assessment is to be valuable. There is clearly a need for focused research on the survival and transport of GEMs in these environments.

Bacteria↗
PubMedDate not supplied

Measurement of UV radiation using suspensions of microorganisms.

The measurement of solar UV radiation is usually performed using physical devices like photodiodes or photomultipliers or with chemical substances (actinometry). The application of biological material such as microorganisms for this purpose has gained increasing importance in the last few years. The microorganisms may be dried and spread on a flat surface or they may be in aqueous suspensions contained in UV-transparent vessels. If the measurements are done on flat surfaces, the irradiance weighted by the action spectrum of the dried microorganism used is the result of the measurement. If aqueous suspensions of microorganisms are used, contained for instance in spherical vessels, the fluence weighted by the action spectrum of the microorganisms in the aqueous suspension is the result. A problem of this method of measurement can be that inside the vessel the distribution of UV radiation is usually not homogeneous, causing distributions of fluences among the irradiated microorganisms, which may result in variation of the results depending on the mixing characteristics of the suspension during irradiation.

Bacillus subtilis↗
PubMed2000

Testing the significance of microorganism identification by mass spectrometry and proteome database search.

We derive and validate a simple statistical model that predicts the distribution of false matches between peaks in matrix-assisted laser desorption/ionization mass spectrometry data and proteins in proteome databases. The model allows us to calculate the significance of previously reported microorganism identification results. In particular, for deltam = +/-1.5 Da, we find that the computed significance levels are sufficient to demonstrate the ability to identify microorganisms, provided the number of candidate microorganisms is limited to roughly three Escherichia coli-like or roughly 10 Bacillus subtilis-like microorganisms (in the sense of having roughly the same number of proteins per unit-mass interval). We conclude that, given the cluttered and incomplete nature of the data, it is likely that neither simple ranking nor simple hypothesis testing will be sufficient for truly robust microorganism identification over a large number of candidate microorganisms.

Bacillus subtilis↗
PubMed2000

In vitro evaluation of the retention of three species of pathogenic microorganisms by three different types of toothbrush.

The retention and survival of microorganisms on toothbrushes pose a threat of recontamination for certain patients at risk. In order to measure the influence of brush design and optimize the choice of toothbrush model for complementary studies, the in vitro retention of three microbial species (Porphyromonas gingivalis ATCC 33277, Streptococcus mutans ATCC 25175 and Candida albicans ATCC 26555) was evaluated for three types of toothbrush. Two series of standardized experiments were carried out for each brush and microorganism. The first series tested the retention of the microorganisms on the head portion of the brush, while the second measured retention on the head of the brush and the part of the handle inserted in the mouth during brushing. For each series, the microorganisms were counted at T0 and T24 (after storage of the brushes at room temperature for 24 h). Depending on the microorganism studied, from 0.2% to 2% of the initial inoculum was retained on the brush. The number detected increased with the size of the exposed area. After 24 h, P. gingivalis and S. mutans were found on only one type of brush. C. albicans survived on all three. These results confirm that microorganisms can quickly colonize toothbrushes.

Candida albicans↗
PubMed1993

Effects of Mn2+ and Mg2+ on assimilation of NO3- and NH4+ by soil microorganisms.

Although it has been demonstrated that Mn2+ and Mg2+ can influence the activity of glutamine synthetase in various organisms, there is little information concerning the effects of these cations on the activity of this enzyme in soil microorganisms or on ability of these microorganisms to assimilate NO3- and NH4+. We studied the effects of different concentrations of Mn2+ and Mg2+ on assimilatory NO3- reduction and NH4+ assimilation in cultures of two microorganisms commonly found in soil [Pseudomonas fluorescens (ATCC 13525) and Azotobacter chroococcum (ATCC 9043)] and in an enrichment culture of soil microorganisms. We found that Mn2+ strongly inhibited NH4+ assimilation by soil microorganisms and blocked the inhibitory effect of NH4+ on assimilatory NO3- reductase (ANR) activity, thereby uncoupling ANR activity from nitrogen assimilation and causing the NH4+ formed by ANR activity to be released to the environment. Mg2+ counteracted the effect of Mn2+ on microbial metabolism of nitrogen, which suggests that the overall effect of these cations on nitrogen assimilation by soil microorganisms will depend on the ratio of their concentrations in soil.

Azotobacter↗
PubMed2001

Spatial distribution of microorganisms and measurements of oxygen uptake rate and ammonia uptake rate activity in a drinking water biofilter.

The biofilm characteristics (population dynamics and biofilm composition) in a biological filter for the removal of iron, manganese and ammonium were studied in a drinking water treatment plant. The objective was to examine the spatial distribution and biological composition of active biomass that grows in a biological filter and to verify the effect of the backwashing on the quantity of fixed biomass and on the density and activity of the biological population. Heterotrophic microorganisms activity was higher in the upper layer of the filter. Nitrifying microorganisms colonized the biofilter in a stratified manner and their activity was higher in the second layer of the filter. A total of 14 species of ciliated protozoa and 7 species of filamentous microorganisms were found in the biofilters. Ciliates were concentrated in the filterbed layer in which the heterotrophic activity was higher. The grazing activity of ciliates on heterotrophic bacteria reduced the competition pressure on nitrifying microorganisms, supporting their growth and thus raising the ammonium removal efficiency. In general, filamentous microorganisms appeared to be indifferent to operating changes in the plant such as backwashing and filtering cycles. Crenothrix was the prevalent filamentous microorganism in terms of both frequency and abundance; it was found prevalently in the first layer where the oxidisation of iron and manganese occurred.

Ammonia↗
PubMed1998

Control of exposure to airborne viable microorganisms during remediation of moldy buildings; report of three case studies.

Three different techniques for reducing exposure to microorganisms were tested during remediation of moldy buildings. Concentrations of spores (fungi and actinomycetes) were determined by filter sampling before, during, and after remediation. The local exhaust method used for asbestos dismantling was the most effective control method. In the construction zone, concentrations of microorganisms were 4-25 times higher during remediation than before it. In the adjacent area no increase in concentrations was seen. When the construction zone was placed under negative pressure with a fan and isolated with a plastic barrier, concentrations of microorganisms were about 100 times higher there during remediation work. Nevertheless, levels remained low in the adjacent area. The use of a portable exhaust fan with a side-draft hood decreased concentrations of fungi to one-tenth compared with demolition without the control technology. Furthermore, this method prevented the migration of fungal spores from the construction zone to the adjacent area, although it was less effective in prevention of actinomycete spore migration. It also decreased the levels of microorganisms in the construction zone below the preconstruction level within 2 hours. This study showed that levels of airborne microorganisms, including from the working area to adjacent area, can be reduced with commonly used dust control methods during demolition work. However, microorganism levels in the construction zone remained elevated. Therefore, personal protection of construction workers is needed even with control techniques.

Air Microbiology↗
PubMed1998

Methods for quantitative assessment of airborne levels of noninfectious microorganisms in highly contaminated work environments.

Exposure to high airborne levels of noninfectious microorganisms is recognized as a cause of respiratory symptoms and disease among workers handling biological materials, such as farmers, sawmill workers, and workers handling municipal waste and fuel chips. Risk assessment is difficult because occupational exposure limits for noninfectious microorganisms have not been established. Many different methods are used for the measurement of airborne microorganisms, which are based on impaction, impingement, or filtration. Samples can be analyzed by methods that are culture-based or nonculture-based and that may estimate different microbial entities: culturable microorganisms by culture-based methods, microbial cells by microscopic methods, and microbial constituents and products by chemical, biochemical and immunochemical methods. Sources of errors and validation studies of these methods are reviewed and methods are evaluated for exposure assessment in epidemiological studies and for future compliance testing. At present it is not clear which microbial bioaerosol components should be assessed. Culture-based methods are probably not satisfactory because nonviable microorganisms and microbial constituents and products also may cause health effects. Culture-based methods are poor surrogates for nonculture-based methods and have poor precision. However, identification of microorganisms is most readily performed by culture-based methods. Filter sampling is preferred for personal exposure measurements because filters can be analyzed by a variety of nonculture-based methods, and filter sampling may be adapted to recently adopted criteria for health-related size fractions.

Aerosols↗
PubMed1987

Quantitation of microorganisms associated with the particulate phase of ruminal ingesta.

Microbial organic matter associated with rumen particulate and fluid phases was quantified using 15N as the microbial marker in two rumen fistulated cows fed a 65% alfalfa haylage diet. During two collection periods, feed was removed 1 h after initiation of feeding, and cows were dosed with (15NH4)2SO4. Whole rumen contents were sampled before feeding and at various times up to 12 h after feeding. Fluid microorganisms were those that passed through eight layers of cheesecloth. Particle-associated microorganisms were obtained by chilling squeezed particles prior to seven successive extractions with saline solution. The amount of microorganisms removed from particles ranged from 32.1 to 59.9% as measured by 15N. Organic matter (mg/mL strained rumen fluid equivalent) of fluid and particle-associated microorganisms was respectively: 10.7 and 47.5; 12.5 and 35.5; 12.2 and 30.1; 10.7 and 26.1; 10.9 and 26.7; and 8.9 and 20.6, at 2, 3, 4, 7, 9 and 11 h after initiation of feeding. These ratios indicated that 70-80% of microbial organic matter in whole rumen contents was associated with the particulate phase and that particle-associated microbial organic matter was greatest soon after feeding. Analysis of 15N in extracted rumen particles indicated that 50-65% of particle nitrogen and 17-27% of particle dry matter was of microbial origin. These results provide evidence that particle-associated microorganisms make up a major proportion of the total microorganisms in ruminal ingesta and that a large proportion of ingesta particle N can be of microbial origin.

Amino Acids↗
PubMed1987

Human serum antibody responses to oral microorganisms. IV. Correlation with homologous infection.

Recent microbiological studies of periodontal disease in humans have supported the concept of a specific bacterial etiology. While individual agents have not been unequivocally identified, numerous Gram-negative members of the subgingival microflora have been implicated. In addition, elevations in systemic antibody responses have been consistent with certain oral microorganisms being involved in an infectious process associated with the disease. This report delineates the relationship between elevated systemic antibody levels and oral colonization with the homologous microorganism at active disease sites. Thirty-four patients with various types of periodontal disease were examined. Using ELISA, each patient was shown to have an elevated antibody response to at least one organism from a battery of 18 oral microorganisms that were tested. Subsequently, subgingival plaque was cultured from disease-active and -inactive sites of each subject. The results demonstrated that the same microorganism to which the individual exhibited elevated serum antibody responses was detected in nearly 55% of the disease-active sites, while only 18% of the inactive sites showed the microorganism. Certain microorganisms including Actinobacillus actinomycetemcomitans, Bacteroides gingivalis, Eikenella corrodens and Wolinella recta were primarily or exclusively correlated with active disease lesions. These findings support the hypothesis that elevated systemic antibodies to periodontopathic bacteria are reflective of subgingival colonization and exist as a response to a bacterial infection at disease-active sites.

Adolescent↗
PubMed1993

Release of recombinant microorganisms.

This review addresses current environmental applications of naturally occurring, nonrecombinant microorganisms and potential future genetic modifications of such organisms, as well as releases of recombinant microorganisms that have occurred to date. Awareness of the current uses of nonrecombinant microorganisms provides insight into the diversity of habitats in which recombinant microorganisms may be released in the future, while an examination of potential and realized genetic modifications provides insight into the variety of applications for which recombinant microorganisms may be used. Analysis of the behavior, persistence, and dispersal of nonrecombinant strains further provides valuable information required for the assessment of the risk involved in release of recombinant derivatives of those strains. Approximately 27 distinct releases of recombinant microorganisms have occurred to date. This review assesses what has been learned from such releases regarding persistence, dispersal, and potential deleterious environmental effects.

Bacteria↗
PubMedDate not supplied

Specific resistance to filtration of biomass from membrane bioreactor reactor and activated sludge: effects of exocellular polymeric substances and dispersed microorganisms.

This study investigates the effect of dispersed microorganisms and exocellular polymeric substances on biomass dewaterability. Specific resistance to filtration (SRF) was measured for biomass from a membrane bioreactor and a completely mixed activated sludge system. Both laboratory-scale reactors were fed with synthetic wastewater and operated at a high food-to-microorganism ratio (F/M) (1 to 11 kilograms chemical oxygen demand per kilogram mixed liquor volatile suspended solids per day [kgCOD/(kg MLVSS.d)]) and short solids retention times (0.25 to 5 d). The SRF values were affected by strong interactions of three parameters: (1) the mixed liquor suspended solids concentration, (2) the amount of dispersed microorganisms, and (3) the exocellular polymeric substances (EPS) concentration. At F/M smaller than 2 kg COD/(kg MLSS.d) and mixed liquor suspended solids (MLSS) concentration higher than 2000 mg/L, increasing amount of dispersed microorganisms in the biomass yielded higher SRF values. However, at high F/M (> 5 kg COD/kg MLSS.d) and low MLSS concentrations (< 600 mg/L), lower EPS concentrations resulted in slightly smaller SRF values, even though the amount of dispersed microorganisms in the biomass was much higher. Thus, at low MLSS concentrations, EPS concentrations rather than the amount of dispersed microorganisms tend to control SRF.

Bacteria↗
PubMed1995

Persistence of 99mTc-labelled microorganisms on surfaces of impression materials.

Impression materials or prostheses can be contaminated with oral microflora and provide a significant source for cross-contamination. A study of such contamination was carried out using an approach different from that of infection control, which has often been investigated in previous studies. The study focused on microorganisms known to cause local and systemic diseases and which are normally found in the oral flora. The persistence of Streptococcus mutans (S. mutans), Escherichia coli (E. coli), Staphylococcus aureus and Candida albicans (C. albicans) on zinc-oxide eugenol, silicone rubber, irreversible hydrocolloid and polyether-rubber was investigated using 99mTc-labelled microorganisms. Ten specimens from each of the four impression materials were prepared as discs of 3 mm in height and 10 mm in diameter. After the specimens had been placed into a suspension of 99mTc-labelled microorganisms, remaining radioactivity was counted in a gamma counter. According to own findings, S. mutans was the most, and E. coli the least persistent on the specimen surfaces. The number of microorganisms removed after washing was less than the amount remaining on the surfaces. C. albicans was removed most easily from all impression surfaces that bore persistent microorganisms after washing. Other microorganisms showed various degrees of persistence according to the impression material.

Alginates↗
PubMed1986

Rapid separation and quantitation of mixed microorganisms by filtration and bioluminescence.

A membrane filtration/bioluminescence system was developed for the differentiation and quantitation of mixed populations of microorganisms. Samples containing microorganisms were filtered through two membrane filters of descending pore size. The microorganisms retained on the filter contain ATP that can be extracted and measured on the filter via the firefly luciferase-luciferin bioluminescence assay. Results, obtained in less than 20 min, show a good correlation (r greater than or equal to 0.95) between the light produced and the number of organisms in the sample. Using these techniques, Escherichia coli can be separated from yeast or mold and measured in samples containing both microorganisms. When lysostaphin is used to selectively lyse Staphylococci on the filter, the specific quantification of these bacteria among other microorganisms can also be accomplished. The filtration/bioluminescence technique offers the potential of being a rapid and sensitive method to differentiate and detect microorganisms, by selective sizing or lysing, in a variety of samples.

Adenosine Triphosphate↗
PubMed2001

Exposure to airborne microorganisms in fiberboard and chipboard factories.

Microbiological air sampling was performed in one fiberboard factory and two chipboard factories located in south-eastern Poland. It was found that the levels of bacteria, fungi, dust and bacterial endotoxin in the air of examined facilities were high during initial stages of the production cycle (shredding of waste wood, storing of chips) and then sharply decreased during further stages of this cycle (forming and formatting of the boards). In the fiberboard factory, the concentration of airborne microorganisms at the initial stages of production cycle was 71.8-95.2 x 10(3) cfu/m3 and dropped in further stages to the level of 8.4-17.5 x 10(3) cfu/m3. Fungi (mostly Aspergillus fumigatus and Penicillium spp.) were prevailing microorganisms in the air of the fiberboard factory, forming 46.0-87.3% of the total airborne microflora. The concentrations of microorganisms in the air of the chipboard factories were significantly lower compared to the fiberboard factory (p<0.05). During initial stages of production cycle they were within the range of 12.9-101.5 x 10(3) cfu/m3, while during forming and formatting of boards within the range of 5.3-12.4 x 10(3) cfu/m3. On average, the most common microorganisms in the air of the chipboard factories were corynebacteria (mostly Arthrobacter spp. and Corynebacterium spp.) which formed 24.4-64.6% of the total microflora. The values of the respirable fraction of airborne microflora in the fiberboard and chipboard factories varied within a fairly wide range and were between 20.5-91.1%. Altogether, 38 species or genera of bacteria and 16 species or genera of fungi were identified in the air of examined factories, of which respectively 14 and 9 species or genera were reported as having allergenic and/or immunotoxic properties. The concentration of bacterial endotoxin in the air of examined factories was greatest, similarly to the concentration of microorganisms, during the initial stages of the production cycle: 103.1-1974.0 EU/m3 in the fiberboard factory, and 3.2-217.4 EU/m3 in chipboard factories. In conclusion, the workers of fiberboard and chipboard factories may be exposed during the initial stages of the production cycle (shredding of waste wood, storing of chips) to high levels of airborne microorganisms and endotoxin posing respiratory hazard.

Air Microbiology↗
PubMedDate not supplied

[Mathematical model of the interaction of components in a plant-rhizospheric microorganisms system at the higher level of carbon dioxide in atmosphere].

A mathematical model describing the interaction of plants and rhizospheric microorganisms on complete mineral medium at a higher CO2 level in the atmosphere was constructed. The positive effect of CO2-enrichment on the system plant--rhizospheric microorganisms was shown. The effect of rhizospheric microorganisms on plant growth at normal and high level of carbon dioxide was demonstrated. It was shown that the biomass of plant in the system is smaller than the biomass of plant growing without microorganisms. It was experimentally demonstrated that a simple ecosystem wheat--Pseudomonas putida--artificial soil develops and functions differently than its individual constituents in the case of a wheat-artificial soil system. With unlimited nutrition and a higher CO2 level (0.06%), plants with roots inoculated with microorganisms have a smaller biomass than plants that were not inoculated with microorganisms.

Algorithms↗
PubMed2003

[Ecological distribution of soil microorganism in artificial greenbelt in hinterland of Takilimakan Desert and their relations with soil factors].

Studies on the distribution of soil microorganisms in the artificial greenbelt in hinterland of Takilimakan Desert and the effects of soil features on the distribution showed that under saline water irrigation, the activities of soil microorganisms increased sharply, and the soil structure and nutrient status were improved. Among soil microorganisms, bacteria were predominant, actinomyces were the next, and fungi were the least. There were more microorganisms in upper than in deeper soil layers. Soil microorganisms near shelter-forest had a higher activity, and their quantities over 3 m from shelter-forest were almost equal to those in shifting sand. The quantities of soil microorganisms varied with seasons, and there were distinct differences among different sites of forests. Among the measured 11 soil factors, the interactions between pairs of soil available phosphorus-available potassium, organic matter-available potassium, available nitrogen-available potassium, available nitrogen-available phosphorus, organic matter-available phosphorus, available phosphorus-available nitrogen, total nitrogen-available potassium, available potassium-available phosphorus, total nitrogen-available phosphorus, and water contents-available nitrogen were significant, with the correlation coefficients of 1.37-2.58. The direct effects of available phosphorus, available nitrogen, and total nitrogen on the microbial quantity were significant, with the coefficient of 1.01-2.58.

Conservation of Natural Resources↗