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PubMed1968

The biological effectiveness of solar electromagnetic radiation in space.

An attempt has been made to determine the solar ultraviolet action spectrum for dried coliphage T-1 exposed to space under various filters at sounding rocket altitudes between 80 to 150 km. The survival of these microorganisms was compared with the preliminary results of laboratory ultraviolet irradiation experiments using monochromatic light sources of wavelengths of 1633 angstroms, 2062 angstroms, 2537 angstroms and of 3064 angstroms to 3200 angstroms. The results indicate that ultraviolet light of wave-lengths between 2000 angstroms to 3000 angstroms was mainly responsible for the killing of the filter protected microorganisms. More studies of the biological action spectrum of the vacuum ultraviolet light including the Lyman alpha emission are needed to determine the cause of the more than 100 fold higher death rate of the microorganisms which were not protected during the space exposure by filters.

Altitude↗
PubMedDate not supplied

[Interaction of topotecan, DNA topoisomerase I inhibitor, with double-stranded polydeoxyribonucleotides. 4. Topotecan binds preferably to the GC base pairs of DNA].

Interaction of topotecan (TPT) with synthetic double-stranded polydeoxyribonucleotides has been studied in solutions of low ionic strength at pH = 6.8 by linear flow dichroism (LD), circular dichroism (CD), UV-Vis absorption and Raman spectroscopy. The complexes of TPT with poly(dG-dC).poly(dG-dC), poly(dG).poly(dC), poly(dA-dC).poly(dG-dT), poly(dA).poly(dT) and previously studied by us complexes of TPT with calf thymus DNA and coliphage T4 DNA have been shown to have negative LD in the long-wavelength absorption band of TPT, whereas the complex of TPT with poly(dA-dT).poly(dA-dT) has positive LD in this absorption band of TPT. Thus, there are two different types of TPT complexes with the polymers. TPT has been established to bind preferably to GC base pairs because its affinity to the polymers of different GC composition decreases in the following order: poly(dG-dC).poly(dG-dC) > poly(dG).poly(dC) > poly(dA-dC).poly(dG-dT) > poly(dA).poly(dT). The presence of DNA has been shown to shift monomer-dimer equilibrium in TPT solutions toward dimer formation. Several duplexes of the synthetic polynucleotides bound together by the bridges of TPT dimers may participate in the formation of the studied type of TPT-polynucleotide complexes. Molecular models of TPT complex with linear and ring supercoiled DNAs and with deoxyguanosine have been considered. TPT (and presumably all camptothecin family) proved to be a representative of a new class of DNA-specific ligands whose biological action is associated with formation of dimeric bridges between two DNA duplexes.

Base Pairing↗
PubMed2003

Environmental factors influencing the microbiological contamination of commercially harvested shellfish.

Filter-feeding bivalve molluscs (such as oysters, clams, mussels and cockles) can concentrate contaminants from the water column. The extent of faecal contamination in shellfish is usually estimated by determining the concentration of faecal coliforms and/or Escherichia coli. Three sample points in each of three geographically separate commercial shellfisheries were selected for analysis for the effect of season, spring/neap and high/low tidal cycles, rainfall and wind direction on the results of routine E. coli monitoring. General linear modelling was used for the analyses. The principle factors affecting the contamination of shellfisheries were season, high/low tidal cycle and rainfall. The effects varied between harvesting areas and between individual sampling points within harvesting areas. Undertaking such analyses for all harvesting areas would contribute to the management of monitoring programmes and assist in the evaluation of potentially contaminating sources, such as sewage discharges. The type of analyses undertaken on E. coli monitoring data would also be pertinent for the analysis of putative viral indicators, such as F+ coliphage, and could be extended to data on bacterial and viral pathogens.

Animals↗
PubMed2003

Inactivation differences of microorganisms by low pressure UV and pulsed xenon lamps.

UV disinfection has been applied to water treatment in recent years with low-pressure and medium-pressure UV lamps mainly used as the light source. In general, UV disinfection is considered to be inefficient with water of high turbidity because of inhibition of light penetration. Additionally, photoreactivation may be a problem that should be considered in case a disinfected water is discharged to the environment where sunlight causes reactivation. Recently, other types of lamps have been proposed including a flush-type lamp (such as a pulsed-xenon lamp) that emits high energy and wide wavelength intermittently. In this study, the difference between inactivation efficiencies by low-pressure UV (LPUV) and pulsed-xenon (PXe) lamps was investigated using two coliphage types and three strains of Escherichia coli. PXe had a suppressive effect on photoreactivation rate of the E. coli strains even though there was no significant effect on inactivation rate and maximum survival ratio after photoreactivation. PXe also had a benefit when applied to high turbidity waters as no tailing phenomena were observed in the low survival ratio area although it was observed in LPUV inactivation. This efficiency difference was considered to be due to the difference in irradiated wavelength of both lamps.

Escherichia coli↗
PubMed2003

Effectiveness of guideline faecal indicator organism values in estimation of exposure risk at recreational coastal sites.

Decay rates in coastal water and sediment for the bacterial pathogens Salmonella typhimurium and S. derby were compared in laboratory-based microcosms with results previously obtained for a number of faecal indicators. In general, the decay rates of Salmonella spp. were greater than either enterococci or coliphage in overlying water and sediment. Decay rates of E. coli were similar to Salmonella spp. in overlying water, although greater in sediment. Raised temperature resulted in an increased decay rate for all organisms in the overlying water (and to a lesser extent in the surface sediment layer). It was demonstrated that decay rates for both S. typhimurium and S. derby were greater in overlying water compared with sediment. This suggested that sediments may be acting as a reservoir for pathogenic microorganisms released into the coastal environment during recreational activity and should be considered when estimating environmental exposure. Using measured decay rates and available dose-response data, a quantitative microbial risk assessment (QMRA) utilising Monte Carlo simulation was undertaken to estimate the risk of infection to Salmonella spp. following exposure to recreational coastal water subject to a range of faecal contamination levels. In waters of extremely poor quality, subject to contamination by faecal coliforms (10(6) CFU/100 mL), the maximum probability of infection on the day of an accidental release was above 2.0 x 10(-1) and remained above 1 x 10(-3) for three days following the initial high concentration.

Escherichia coli↗
PubMed1992

[Construction of linear plasmid vectors for cloning in Escherichia coli cells].

Prophage of the temperate coliphage N15 is a linear plasmid with covalently closed ends. The central part of plasmid N15 genome responsible for vegetative phage growth was replaced by DNA fragments containing genes for selective markers which have unique restriction sites. As a result a family of linear plasmid vectors was constructed. Their size is about 20 kb and their capacity is comparable with that of cosmid vectors.

Bacteriophages↗
PubMed2004

Tracking the origin of faecal pollution in surface water: an ongoing project within the European Union research programme.

The objectives of this study are to generate knowledge about methods to track the sources of faecal pollution in surface waters, with the aim of having one or a few easy procedures applicable to different geographic areas in Europe. For this, a first field study using already proposed methods (genotypes of F-specific RNA bacteriophages, bacteriophages infecting Bacteroides fragilis, phenotypes of faecal coliforms and enterococci, and sterols) has been done in five areas representing a wide array of conditions in Europe. The present faecal indicators (faecal coliforms, enterococci, sulfite reducing clostridia and somatic coliphages) have also been included in this first field study. At the same time some emerging methods have been settled or adapted to water samples and assayed in a limited number of samples. The results of this first field study indicate that no single parameter alone is able to discriminate the sources, human or non-human, of faecal pollution, but that a 'basket' of 4 or 5 parameters, which includes one of the present faecal indicators, will do so. In addition, numerical analysis of the data shows that this 'basket' will allow the successful building of predictive models. Both the statistical analyses and the studied predictive models indicate that genotype II of F-specific RNA bacteriophages, the coprostanol and the ratio coprostanol: coprostanol+epicoprostanol are, out of the studied parameters, those with a greater discriminating power. Either because unsuccessful adaptation of the methods to water samples or because the preliminary assays in water samples indicated low discriminating capability, only three (sorbitol-fermenting bifidobacteria, some species of bifidobacteria detected by PCR with specific primers and phages infecting Bacteroides tethaiotaomicron) of the newly assayed methods have been considered for a second field study, which is currently underway. Expectations are that these new tools will minimize the number of parameters in the 'basket', or at least minimize the difficulty in assaying them.

Bacteriophages↗
PubMed1979

[Hybrid plasmid pSD1 containing the immunity region of bacteriophage lambda].

Hybrid plasmid pSD1 carrying the immunity region of the coliphage lambda and bio operon have been obtained by means of studying the efficiency of transcription DNA fragments in the plasmid RSF2124. The molecular weight of this plasmid is 17.2 Md. The growth inhibition of phage lambdavir has been observed in cells carrying the new hybrid plasma. The properties of the plasmid pSD1 and probable reasons of the growth inhibition of phage lambdavir are discussed. The hybrid plasmid pSD2 carrying genes R, A and J of phage lambda has been constructed on the basis of the plasmid RSF2124. There are cohesive ends in this plasmid which make possible its packing in the phage lambda head. Hybrid plasmid pSD3 carrying genes P and Q of phage lambda has also been constructed.

Bacteriophage lambda↗
PubMed1992

Morbidity among bathers exposed to polluted seawater. A prospective epidemiological study.

As the first phase of a major programme to develop epidemiologically derived recreational water quality criteria for South Africa, a preliminary epidemiological-microbiological study was conducted in Cape Town during February and March 1990. Serial trials were carried out at a clean and at a relatively polluted beach over weekends. Participants were recruited at the beach, at which time information on swimming status and sociodemography was obtained. This provided for a beach-going but non-swimming control group. Symptoms which developed subsequent to the beach visit were obtained by follow-up telephone interviews conducted 3-4 days later. Water samples collected on trial days both before and during maximum swimming activity, were analysed for enterococci, faecal coliforms, staphylococci, coliphages and F-male-specific bacteriophages. Significant differences in the indicator levels at the beaches were observed. An excess in gastro-intestinal, respiratory and skin symptoms were found among swimmers relative to non-swimmers at the polluted beach. Although not statistically significant, the results are suggestive of a relationship between swimming-associated illness and water quality. The study demonstrated the feasibility of the methodology and the results of the overall programme will form the basis for the development of epidemiologically derived recreational water quality criteria for South African beaches.

Bathing Beaches↗
PubMed2005

Microbial quality of runoff following land application of cattle manure and swine slurry.

Concentrations of human health-related microorganisms in runoff from agricultural plots (0.75 m x 2 m) treated with fresh and aged cattle manure, swine slurry and no manure (control) were determined. Three consecutive simulated rainfall events, producing 35 mm rainfall and separated by 24 h, were carried out for each plot. Fecal indicator (Escherichia coli, enterococci, Clostridium perfringens and coliphage) loads released in rainfall runoff from plots treated with fresh cattle manure, aged cattle manure and swine slurry treatments ranged from 5.52 x 10(5) to 4.36 x 10(9), 3.92 x 10(4) to 4.86 x 10(8), and 9.63 x 10(5) to 3.05 x 10(8), respectively. Plot runoff concentrations of protozoa (Cryptosporidium oocysts and Giardia cysts) ranged from 1.65 x 10(5) to 1.04 x 10(6), 2.93 x 10(3) to 2.75 x 10(5), and 9.12 x 10(4) to 3.58 x 10(6) for fresh cattle manure, aged cattle manure and swine slurry plot treatments, respectively. These results suggest that large microbial loads could be released via heavy precipitation events that produce runoff from livestock manure-applied agricultural fields, of even modest size, and could have a significant impact on water bodies within the watershed. Because of the lack of multiplication in the environment, highly elevated concentrations in manured land runoff, and correlation to protozoan parasite presence, Clostridium may be an alternative indicator for livestock manure contamination.

Agriculture↗
PubMed2005

Particle and microorganism removal in floating plastic media coupled with microfiltration membrane for surface water treatment.

Floating plastic media followed by hollow fiber microfiltration membrane was applied for surface water treatment. The performance of the system in terms of particle and microorganisms was investigated. The floating filter was examined at different filtration rates of 5, 10 and 15 m3/m2 x h. Treated water was then fed into a microfiltration unit where different filtration rates were examined at 0.6, 1.0 and 1.4 m3/m2 x d. It was found that polyaluminum chloride was the best coagulant for the removal of particle, algae and coliform bacteria. Average turbidity in treated water from the floating plastic media filter was 3.3, 12.2 and 15.5 NTU for raw water of 80 NTU and 12.9, 11.7 and 31.2 NTU for raw water of 160 NTU after 6 hours at the filtration rates of 5, 10 and 15 m3/m2 x h, respectively. The microfiltration unit could further reduce the turbidity to 0.2-0.5 NTU with low transmembrane pressure development of 0.3-3.7 kPa. Microfiltration membrane could retain most of algae and coliform bacteria remaining in the effluent from the pretreatment unit. It was found that at higher turbidity, algae and coliform bacteria removal efficiencies were achieved at lower filtration rate of the system of 5 m3/m2 x h whereas a higher filtration rate of 15 m3/m2 x h yielded better coliphage removal.

Enterobacteriaceae↗
PubMed2005

Hydrogen sulphide production tests and the detection of groundwater faecal contamination by septic seepage.

The 'H2S test' is being advanced for microbiological water quality testing where conventional coliform based methods are impractical or too expensive. It involves ambient temperature incubation of water samples with nutrient formulated to generate hydrogen sulphide when 'faecal' bacteria are present. Recently a WHO review identified several concerns including the limited number of comparative studies, formulation variability, and false positives and negatives. In response we have compared the H2S test's ability to detect and quantify faecal contamination in an aquifer impacted by septic tank leachfields with measurements obtained concurrently using conventional bacterial indicators, coliphages, faecal sterol biomarkers, Cryptosporidium and Giardia. Like these other analytes, H2S testing detected a contamination gradient ranging from high (septic liquid) to moderate (exfiltration zones), to background (e.g. domestic bores), corresponding to indicator removal + dilution by factors > 10(6). Presence/absence tests could not distinguish between heavily and slightly contaminated waters, whereas multi-tube testing (e.g. 10 x 10 mL arrays) did. It was concluded that while the WHO review concerns are justified, the H2S test performance shows promise in sanitary survey work, can be improved by employing an mpn approach and has potential to aid in the protection of source water and identifying contaminated groundwater.

Environmental Monitoring↗
PubMed2004

[Co-expression of beta-subunit with other subunits of Qbeta replicase].

In researches involving in vitro protein synthesis and self-replication system, Qbeta replicase is one of the key enzymes, which are demanded for the high availability. Qbeta replicase is a RNA-dependent RNA polymerase of Qbeta coliphage. It consists of four subunits (alpha, beta, gamma, and delta subunit), where the beta-subunit is encoded by the viral genome, while the other three subunits are host proteins normally involved in protein synthesis, namely, ribosomal protein S1 (alpha), elongation factors EF-Tu (gamma) and EF-Ts (delta). To increase the production of the Qbeta replicase holoenzyme, several types of expression vectors, including pKK, pET and others, were employed to produce Qbeta replicase. However, the beta-subunit was almost in the precipitate fraction. Considering that the four subunits of Qbeta replicase holoenzyme are in equivalent molar ratio and the amount of the subunits, ribosomal S1 and EF-Ts, being produced by the host cells is relatively low, co-expression of beta-subunit with the other three subunits was performed to know whether the availability of the host subunits is the contributing factor for the solubility of the Qbeta replicase. pBAD33-rep was constructed by cloning the beta-subunit gene into pBAD 33, a pACYC derivative, and pET21a(+) was employed as expression vector for the three other subunits. Among the different combinations of co-expression experiments, solubility was found to slightly increase by SDS-PAGE analysis when the beta-subunit was co-expressed with EF-Tu-Ts. And the replicase activity assay showed this soluble enzyme is in active form. The expression of beta-subunit was enhanced by decreasing the level of inducer IPTG in co-expression, and more soluble enzyme were obtained.

Enzyme Induction↗
PubMed2006

[Simultaneous control of microorganism, disinfection by-products and bio-stability by sequential chlorination disinfection].

A new safe chlorination disinfection process, the sequential disinfection process with short-term free chlorine plus chloramines was investigated its efficiency on control of indices of microorganism, disinfection by-products and bio-stability. This disinfection process may take the advantage of free chlorine's quick inactivation of microorganism and chloramines' low DBP yield and long-term residual. Thus, both control of microorganisms and DBPs can be achieved effectively and economically. The pilot test results show that safe chlorination disinfection process has a little better efficiency on total bacteria count, HPC and total coliform count than free chlorination disinfection, which indicate that free chlorine and chloramines might have the synergetic disinfection effect for their different attacking targets. It also had the same inactivation efficiency on polio virus and coliphage f2 as free chlorination in 120 minutes contact time. Sequential chlorination disinfection process could reduce 35.8% - 77.0% yield of trihalomethane and 36.6% - 54.8% yield of haloacetic acids. The poorer quality the water had, the more advantage the safe-chlorination disinfection had than free chlorination disinfection one. Moreover, sequential chlorination had better efficiency on bio-stability control than free chlorination.

Chloramines↗
PubMed1991

Investigation of the neutral filter elution technique I. Effects of pore density and pore diameter on elution rate at pH 9.6.

To understand better the biophysical mechanism of neutral filter elution (pH 9.6), we eluted genomes of known size and shape: coliphage T4c (Mr 1.15 x 10(8), E. coli (Mr 2.7 x 10(9)), and Chinese hamster lung fibroblasts (V79, Mr 2-4 x 10(10)). DNA eluted through 15% sucrose atop the filter in a biphasic pattern. The elution rate of the initial component correlated (r greater than 0.97) exponentially with 1/Mr for monodisperse samples of DNA eluted through pore sizes 0.1-3.0 microns. Using this relationship between elution rate and Mr, we estimated Mn of polydisperse, X-irradiated (253 Gy) samples of DNA from E. coli or V79 cells to be 3.15 +/- 1.46 and 1.42 +/- 0.33, respectively, compared to expected values of 2.93 and 3.52 (10(8) Da). The best predictor of elution rate for DNA from T4c and intact and X-irradiated V79 cells was pore density, and pore diameter for DNA from X-irradiated E. coli. The rate of elution of DNA from unirradiated E. coli was unrelated to pore density or diameter. While the mechanism of neutral filter elution remains unknown, its use for linear DNAs with Mn ca. 10(8) Da appears to be valid quantitatively.

DNA↗
PubMed1990

Isolation and characterization of mycoplasma virus L3 temperature-sensitive mutants.

Mycoplasma virus L3 virions are morphologically similar to coliphage T7, contain linear double-stranded DNA of about 39 kilobase pairs, and produce a nonlytic cytocidal infection in Acholeplasma laidlawii host cells. Following nitrous acid mutagenesis, ninety-eight L3 temperature-sensitive (ts) mutants were isolated from a total of 57,000 plaque-forming units (PFU), using 37 degrees C as the permissive temperature and 41 degrees C as the nonpermissive temperature, with reversion frequencies of 10(-5) to 10(-8). Complementation tests allowed fifty-seven of the L3 ts mutants to be placed into twenty-one complementation groups. In mixed infections, recombination frequencies between mutants in different complementation groups were 10(-2) to less than 10(-6). Studies of protein synthesis in L3-infected cells showed synthesis of about twenty virus-specific proteins, including ten L3 virion proteins. After infection with L3 ts mutants from each complementation group, several different patterns of cell- and virus-specific protein synthesis were observed.

Acholeplasma laidlawii↗
PubMed1987

Purification and RNA binding properties of a C-type hnRNP protein from HeLa cells.

A protein of the C group, most likely C3 (Mr approximately 42,000, pI approximately 6, corresponding to IEF 48m,n of the HeLa protein catalogue (Celis, J. E., Bravo, R., Arenstorf, H. P., and LeStourgeon, W. M. (1986) FEBS Lett. 194, 101-109)), a minor hnRNP protein was purified to near homogeneity under nondenaturing conditions from 40 S heterogeneous nuclear ribonucleoprotein particles. Type C protein stoichiometrically disrupts the residual secondary structure of natural and synthetic RNAs, e.g. HeLa hnRNA, coliphage MS2 RNA, and poly(rU)-spermine, and decreases the Tm of duplex structures, e.g. poly[r(A + U)], by about 30 degrees C. Binding of the protein to polynucleotides is not highly cooperative and has a stoichiometry of one protein per about 10 nucleotides. Binding experiments with a variety of synthetic and natural poly- and oligonucleotides, including those containing consensus splice site sequences, indicate that the protein has a high affinity for G-rich and U-rich regions, G-rich regions being preferred. Base analogs I and T have affinities for the protein that are similar to G and U. There is little or no affinity for A- and C-rich regions. The presence of A residues in a G- or U-rich sequence does not interfere with binding while C-rich regions decrease or prevent the binding of the protein. The nucleotide specificity of type C protein, e.g. selective binding to an oligonucleotide from the 3' end of an intron, is discussed in relationship to the abundance of G and U and the relative scarcity of C residues in the processing signals in pre-mRNA.

Circular Dichroism↗
PubMed1989

[A simple and rapid method to test the permeability of condoms to viruses].

phi x 174 and T7 coliphages can be used to find out if condoms are virus-proof. Protection against hepatitis B virus or papillomavirus contamination is not assured when T7, a 65 nm broad virus, leaks through the condom. The simple test can be used to establish a quality control norm for condoms.

Bacteriophage phi X 174↗