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Researchers have confirmed that the increased turbidity seen in mountain creeks after a heavy rainfall or snowmelt is caused by increased amounts of bacteria in the water. This includes increased levels of E. coli and other coliforms, fecal streptococci, and Clostridium perfringens. Raw water surveillance programs should sample water during periods of heavy runoff, since many rivers flow into reservoirs that provide drinking water.

Escherichia coli is a better indicator of fecal water contamination than other fecal coliforms. Fecal coliforms can replicate in the environment, which would give a false-positive reading. The absence of beta-glucuronidase activity can distinguish these fecal coliforms from E. coli.

The injection of fluorescently stained bacteria into an aquifer underlying Oyster, Virginia caused a 2- to 100-fold increase in unstained cells representing the indigenous bacteria. The detachment was not caused by increased shear forces or growth, since it occurred almost immediately after the injection.

Different microbial populations occur in landfill leachate-polluted aquifers depending on the proximity to the pollution and the redox state of the water. Members of the beta subclass of Proteobacteria predominate upstream of the landfill, gram-positive bacteria predominate beneath the landfill, and beta- and delta-proteobacteria predominate downstream.

Research has been conducted on the attached and a free-living marine bacteria. The bacteria's glucose and amino acid uptake kinetics have been investigated and the results indicate that the amino acid uptake rates are higher than those of the glucose in all the analyzed samples.

There is a difference between attached and unattached microbial populations in soil and groundwater, respectively. Researchers who analyzed core samples taken from buried chalcopyrite ore and groundwater found more diverse neutrophilic heterotrophs in the ore and less diverse neutrophilic heterotrophs in groundwater.

Viable bacterial cells can easily be counted by inducing spheroplast formation using antibiotics and glycine. The resulting swollen cells are lysed by a single freeze-thaw treatment. The cells that remain are subtracted from the total number before the procedure to give the number of viable cells.

Petroleum-contaminated groundwater from crude oil storage cavities contains many bacteria that do not occur in normal groundwater. Many belong to the Proteobacteria, according to researchers who used PCR to identify 28 different 16S ribosomal DNA sequences.

Dentists should use available technology to reduce the number of bacteria in dental waterlines. Although there have been few cases of illness linked to dental waterlines, the water should still meet the standards for regular drinking water.

Results discuss the application of antibiotic resistance analysis using discriminant analysis technique for differentiating animal and human fecal isolates from waters of Florida and to relate antibiotic resistance patterns to the bacterial source. Data show that the fecal streptococcus and fecal coliform formed groups of isolates from known sources with accuracy.

Research is presented on the content of Escherichia coli and fecal coliform bacteria in urban runoff, and its interaction with seawater. Both contaminants were inversely correlated with salinity, positively correlated with turbidity, and strongly linked to watershed development.

Most of the dental water lines in dental offices exceed the maximum number of bacteria allowable in drinking water. Analysis of water samples from 55 dental offices in England showed that 95% failed to meet European Union drinking water standards and 83% failed to meet American Dental Association standards for dental water lines.

Researchers used magnetic bead sequence capture-PCR to analyze water samples from sites close to two outbreaks of Mycobacterium ulcerans disease in southeast Australia. A golf course irrigation system and a small lake both tested positive for the organism.

The Surface Water Treatment Rule and the Interim Enhanced Surface Water Treatment Rule classify some ground-water sources as 'ground water under the direct influence of surface water' (GWUDI), and ground waters classified as GWUDI must follow the same treatment guidelines as surface-water sources. The microscopic particulate analysis (MPA) method is the most widely used method to identify GWUDI; however, this method has several deficiencies. An improved protocol for classifying ground-water sources as GWUDI is presented in this paper. The procedure consists of calculating the absolute risk of illness from waterborne Giardia and Cryptosporidium in the pumped water, accounting for the uncertainty in the surface-water concentrations, hydrogeology, straining characteristics, pathogen viability in ground water, and observations of Giardia and Cryptosporidium in samples of the pumped water. In cases where the risk of illness exceeds the acceptable risk, the ground water should be classified as GWUDI. Two examples are presented to illustrate the application of the proposed method.

To improve the feasibility of soil-aquifer remediation using bioaugmentation, more efficient methods are needed to widely disperse pollutant-degrading bacteria in porous media. Under water-saturated conditions, bacteria readily adhere to soil particles, but under unsaturated conditions, bacteria preferentially accumulate at the air-water interface. Air sparging a saturated porous medium produces a mobile water interface that was hypothesized to facilitate bacterial transport. To investigate whether gas sparging increased bacterial transport relative to saturated-water conditions, the transport of three strains of bacteria and negatively charged microspheres of different relative hydrophobicities [R.sub.H] was measured in saturated and gas-sparged quartz-packed columns. Gas sparging increased (>60%) the bacterial transport in only one case (Pseudomonas fluorescens P17; [R.sub.H] = 27%). Transport of the other two strains were either unaffected by gas sparging (Mycobacterium vaccae JOB5; [R.sub.H] = 33%), or was reduced (Pseudomonas aeruginosa; [R.sub.H] = 75%) relative to water-saturated conditions. Microspheres were the most hydrophobic ([R.sub.H] = 98%) and the most retained of all particles under saturated conditions, but microsphere transport was unaffected by gas sparging. These preliminary results suggest that the effect of gas sparging on colloid transport is particle specific and not predictable from measurement of relative hydrophobicity.

Disinfecting dental unit waterlines can eliminate bacteria from the water but do not remove biofilms from the inside of the tubing. Biofilms are deposits created by bacteria. Researchers examined biofilms on tubing and measured bacteria in the water in waterlines before and after treatment with three disinfectants: bleach, glutaraldehyde, and isopropanol. A single overnight treatment with these chemicals effectively eliminated bacteria in the water and biofilm, but did not eliminate the biofilm. The bacteria eventually returned within three to 15 days.

The study characterized the microbial community found in biological filters used in the treatment of drinking water from the Ohio River. Depth profiles were also constructed for the microbial community structures using phospholipid fatty acid analysis. Fingerprinting by arbitrarily primed polymerase chain reaction as well as assessments of carbon source utilization patters were also performed. Preozonation and filter depth served as the basis for the differentiation of microbial communities from the profiles collected.

Some of the most toxic water blooms are those formed by cyanobacteria. Therefore, its detection is important for environmental safety. In response, a nucleic-acid-based assay was developed to quantify toxic cyanobacteria in water. This assay combines sample preparation with a method of chromogenic detection based on coamplification of target and competitor DNA. Testing of the assay on the genus Microcystis yielded a detection limit of 100 cells/ml with more than three orders of magnitude of quantitative range. Its suitability for automation is an added benefit aside from sensitivity.

The effects of physical, chemical and biological agents on seasonal variations in the number of inducible lysogenic bacteria in a eutrophic estuary were studied. Water samples were analyzed for prophage induction by mitomycin C treatment. Results showed that no prophage induction occurred during the warmer months. In contrast, there was no observed induction during the colder months. These findings suggest that the abundance of inducible lysogenic bacteria occurs as a function of season in an estuarine environment.

The efficacy of 12 isolation methods for mycobacteria are compared. Tryptic soy broth method or 0.05% cetylpyridinium chloride (CPC) can decontaminate surface water effectively. The 0.005% concentration of CPC is ideal for decontaminating the treated water. The ideal incubation temperature is 30 degrees centigrade. Lowenstein-Jensen medium is better culture media for water than Ogawa egg yolk, and ofloxacin and ethambutol.

Ampicillin-dextrin (AD) agar efficiently recovers Aeromonas hydrophila from drinking water and differentiates between it and other waterborne bacteria. Aeromonas spp. is enteropathogenic and survives the standard chlorination techniques. The AD medium shows yellow colonies for the genus Aeromonas and green for other genera. This technique is useful for the standard determinations of microbiological drinking water quality.

Reverse transcription-PCR, based on mRNA detection from a heat shock protein (hsp) of the Cryptosporidium parvum, is capable of detecting the presence of a single viable oocyst in concentrated environmental water samples. The reverse transcription method uses an amplification of a 590-bp region of the C.parvum hsp70 mRNA to distinguish live oocysts from dead ones. This method is an effective, economical, versatile, simple and rapid technique for the screening of waterborne pathogens.

The Aeromonas hydrophila and various other bacterial species in the oxidizing groundwaters from the Snellegem and Beernam, Belgium, which consist of Fe2+ decrease due to the generation of free radicals. The addition of compounds such as ascorbic acid and catalase, and an Fe2+ chelator, which acts on the toxic oxygen species, prevents the decrease in the number of Aeromonas cells. Free radical generation in the water leads to decrease in the propylphosphonic acid level in these waters.

Free DNA (lysates) or live donor cells naturally transform strains of the Acinetobacter calcoaceticus, incorporated in situ in river epilithon, to prototrophy. The age of the recipient indigenous community affects the transfer frequency in a laboratory setting. Though the transfer frequency is positively related with the temperature, river Taff below 10 degrees celsius fail to show any transformation. However, laboratory microorganisms are unable to reflect the actual environmental conditions.

The water in many dental units may be harboring Legionella. This bacterium is responsible for legionnaire's disease and Pontiac fever. It is normally transmitted in aerosolized water, but can also infect wounds. Researchers collected water samples from 47 dental units in Maryland and California. They analyzed the samples for Legionella using culture media, direct fluorescent antibody (DFA) and the polymerase chain reaction (PCR). PCR detected Legionella in 62% of the samples, DFA in 40% and culture in 9%. In 62% of the cases, the species detected was not the one that causes legionnaire's disease.

Point-of-use, powdered activated carbon (PAC) filters reduce the bacterial content of groundwater supplies only when the tap is left open for sometime. PAC filters decrease the heterotrophic-plate-count (HPC) and the quantity of coliforms in water, though they can be detected in some samples. Water kept stagnant overnight or longer shows an increase in the level of HPC bacteria despite the use of filters. The tap should be left open for a few minutes before using to take the complete advantage of the PAC treatment.

Bacterial biofilm in dental tubing may be a major source of contamination in dental unit water systems (DUWS). Biofilm develops when microorganisms in water adhere to a surface and multiply. Researchers conducted a series of experiments to evaluate biofilm contamination in DUWS and to assess the effectiveness of flushing and disinfection on biofilm. Bacteria-free water introduced into tubing with biofilm became contaminated within five minutes. The bacterial count increased over time and peaked at 24 hours. A 10-minute flush with bacteria-free water immediately eliminated all detectable bacteria from the tubing, although cultures revealed contamination 24 hours later. Disinfection with a bleach solution eradicated all identifiable bacteria, although scanning electron microscopy revealed that the biofilm structure remained intact.

Most dental unit water systems do not appear to harbor the Legionella pneumophila (L. pneumophila) bacterium, although some models seem prone to high levels of contamination. L. pneumophila is spread by aerosol droplets from contaminated water systems and is the most common cause of Legionnaire's disease. During a 44-month period, researchers regularly cultured water samples from the high-speed outlets and air/water syringes in 194 dental units. Forty-nine dental units were positive for L. pneumophila during the testing period. Of these, most had low contamination levels, although seven had consistently high numbers of the bacterium. Contamination was more common in the air/water syringes than in the high-speed outlets. One dental unit model called the Plan Meca 2000 was particularly susceptible to high-level contamination and required more frequent decontamination than other models.

Tests studying the reliability of the centrifugation and filtration techniques used to determine the presence of Legionella in water show that filtration using flat membrane gives the best results. All concentration methods are inaccurate and cannot be used if the Legionella concentration in the water is low. The results obtained were different from those obtained for actual water samples because of the seeded water samples used in the study.

Direct microscopic computations of respiring bacteria was conducted for drinking water samples and biofilms developed on varied opaque substrates. Water samples were incubated with the redox dye 5-cyano-2,3-ditolyl tetrazolium chloride (CTC) and an R2A medium. CTC reduction is a quick and accurate means of computation and localization of viable bacteria in drinking water.

The use of flow cytometry and cell sorting aids the isolation of abundant viable target bacteria from a sample in which low levels of target cells are present. Escherichia coli is separated from lake water and sewage by cell sorting. Both flow cytometry and cell sorting methods identify viable target cells efficiently, and separate them from heterogeneous natural microbial populations.

The use of two methods of calculation aids the detection of bacterial aerosol emission rates from wastewater aeration tanks of the Metropolitan Water Reclamation District of Greater Chicago John E. Egan Water Reclamation Plant. In the traditional method in which stack emission rate is calculated, the rate of air flow from aeration tanks is multiplied by the air concentration of bacteria. In another experimental method, the total amount of bacteria coming out of an isolated area of the aeration tank is detected. Lower values are indicated by the conventional emission rate calculation method.

The applicability of using rRNA-targeted oligonucleotide probes for the in situ identification of bacteria in drinking water was investigated. The results showed that both planktonic and surface-associated bacteria could be detected with the probes at a limit of around 10(super 3) to 10(super 4) ribosomes per cell. In addition, the percentage of positive cells were significantly higher at the surfaces than in the planktonic phase, indicating that surface-attached cells are more active than free-living cells.

The fluorigenic substrate 4-methylumbelliferyl-beta-D-glucuronide (MUG) is commonly used for the detection of Escherichia coli through its ability to detect activity of beta-glucuronidase (GUR), which is encoded by uidA. GUR activity is tested in minimal medium o-nitrophenyl-beta-D-galactopyranoside (MMO)-MUG. The validity of MMO-MUG and two other E. coli detection kits, Colilert and Colquik, were tested by examining 449 strains of E. coli for the presence of the uidA gene. The results showed that uidA levels did not correlate well with beta-glucoronidase activity or with the results of Colilert and Coliquik.

The density of bacteria that colonized operating ultrapure water systems was described. Populations of planktonic bacteria were enumerated at various parts within Milli-Q Plus and Milli-Q UV Plus systems. The results showed that MIlli-Q Plus laboratory water systems contained a range of environmental conditions that resulted in different levels of planktonic and attached populations of these bacteria. However, the quality of the final product water was excellent despite the bacterial communities.

The persistence of Aeromonas salmonicida in sterile and untreated lake water is discussed. A new viability assay was used to detect viable membranous cells from nonculturable A. salmonicida. Culture and direct detection of plasmid and chromosomal DNA was used to directly detect A. salmonicida and monitor its adaptation in mixed populations by polymerase chain reaction. Only the presence of the cells could be confirmed by the technique.

Growth of a Klebsiella pneumoniae strain under conditions similar to those in the potable water environment results in increased resistance to chloramines. An investigation was conducted to determine the physiological components responsible for this increased resistance. The results showed that growth under low-nutrient conditions could induce increases in aggregation potential and capsule production, change the composition of membrane lipids and decrease the oxidation of sulfhydryl groups. These physiological changes result in an increased resistance to chloramines.

The characteristics of the bacterial populations of membrane bioreactors in three pilot-scale wastewater treatment plants were evaluated using the colony-forming-curve (CFC) method. The results showed that the viable populations of bacteria within the bioreactors included slow-colony-forming anaerobes, which could appear 10 days after incubation. In addition, most of the sludge anaerobes showed complex nutrient requirements. These results demonstrate the usefulness of the CFC method, although limitations such as the destruction of complex interactions among species and the difficulty of growing diverse sets of populations, should be recognized.

The effect of incubation of amoebae in water samples in the detection and enumeration of suspected Legionellae contamination was determined. Water samples previously found positive for amoebae and negative for Legionellae, were examined. After incubation, Legionellae were detected in 59 of 144 samples. Three out of 63 samples that were negative for amoebae were found positive for Legionellae. Theresults suggest that incubation with amoebae can promote the proliferation of Legionellae, and that samples previously found negative for Legionellae but positive for amoebae should be rescreened.

Aeromonads isolated from patients with gastroenteritis, from the source water, treatment plant and distribution sytem in a public water supply in Iowa were characterized by ribotyping. Ribotypes identical to Aeromonas hydrophila and A. sobria were detected from multiple sites in the water system. Based on these findings, water treatment plant operational deficiencies were corrected. The results show that ribotypingis useful for detecting water-borne pathogens in water treatment plants and distribution systems.

An analysis of 82 samples of cooling tower water show that Legionella species propagate most in waters containing significant amounts of protozoa and heterotrophic bacteria maintained at a certain temperature range. Results show that Legionella sp. propagation is promoted by the presence of protozoa > 10 tothe second power MPN/100 ml and heterotrophic bacteria > 10 to the sixth power CFU/100 ml. Also, viable counts of Legionella increase significantly if the water temperature is maintained at 25 to 35 degrees.

Fluorescent rhodamine staining was used to characterize the enteric bacterial populations in natural water samples. The results showed that enteric bacteria in aquatic ecosystems are present as culturable and nonculturable cells. Therefore, standard bacteriological methods are unreliable for assessing bacterial death and survival in natural waters. As a consequence, bacterial death should be redefined to mean loss of morphological integrity, or cellular lysis. The results also showed that protozoan predation is the major cause of death of enteric bacteria in aquatic ecosystems.

Many tube-wells in Bangladesh are contaminated with zooplankton and bacteria and do not meet the drinking water standards of the World Health Organization. About 90% of the rural population of Bangladesh use these wells for their drinking water.

Test tube microcosms of upper Hudson river sediment shows reductive dechlorination and aerobic biodegradation of polychlorinated biphenyls (PCBs). At Aroclor 1242, a PCB, concentration of 37.3 micro moles per kg the biodegradation occurs at slow and constant rate; and at concentrations from 93.3 to 933 micro moles per kg, biodegradation is accelerated after four to eight weeks of acclimation period. Biodegradation is enhanced temporarily by nutrients and agitation which indicates that natural restoration is more effective than short term stimulation with nutrients.

A new method is proposed for detecting wild-type astroviruses in water from an area where a gastroenteritis epidemic was reported. The method is based on the infection of CaCo-2 cells and a molecular hybridization technique with a specific cDNA probe. It is very useful for differentiating infectious and non-infectious particles in the environment.

Examination of enterococcal isolates from different environmental sources reveals the occurrence of high-level resistance to aminoglycosides in these isolates. Multiple antibiotic resistance patterns to aminoglycosides are observed in the strains of Enterococcus faecium, E. gallinarum, E. faecalis and other Enterococcus spp. Standard procedures and membrane filtration technique help identify enterococci in the environmental samples including agricultural run off, waste water wells, rivers and creeks.

Surface samples of natural seawater were collected from Hakodate Bay, Japan, and were treated with either tributyltin-chloride (TBTCl) or cadmium sulfate. Both treatments, as well as a control group were incubated aerobically and periodically monitored for viable cell counts, and TBTCl and cadmium resistance. The results showed that 63% of cadmium-treated cells developed cadmium tolerance after one week, while 50% of the TBTCl-treated cells developed TBTCl tolerance after two weeks. The tolerace characteristics were shown to be independent. Microbial characterization showed that the predominant TBTCl-tolerant microorganisms are Vibrio species.

Direct potassium hydroxide (KOH) treatment of precipitates from centrifuged freshwater samples was found to be an easy and effective means of recovering Yersinia pseudotuberculosis. About 33.3% of the water samples tested were positive for Y. pseudotuberculosis. Recovery of the bacteria from the positive water samples was higher when modified MacConkey agar was used for plating instead of irgasan-novobiocin agar.