Prevalence, quantification and typing of adenoviruses detected in river and treated drinking water in South Africa

AIMS: Human adenoviruses (HAds), of which there are 51 serotypes, are associated with gastrointestinal, respiratory, urinary tract and eye infections. The importance of water in the transmission of HAds and the potential health risks constituted by HAds in these environments are widely recognized. Adenoviruses have not previously been quantified in river and treated drinking water samples. In this study, HAds in river water and treated drinking water sources in South Africa were detected, quantified and typed. METHODS AND RESULTS: Adenoviruses were recovered from the water samples using a glass wool adsorption-elution method followed by polyethylene glycol/NaCl precipitation for secondary concentration. The sensitivity and specificity of two nested PCR methods were compared for detection of HAds in the water samples. Over a 1-year period (June 2002 to July 2003), HAds were detected in 5.32% (10/188) of the treated drinking water and 22.22% (10/45) of river water samples using the conventional nested PCR method. The HAds detected in the water samples were quantified using a real-time PCR method. The original treated drinking water and river water samples had an estimate of less than one copy per litre of HAd DNA present. The hexon-PCR products used for typing HAds were directly sequenced or cloned into plasmids before sequencing. In treated drinking water samples, species D HAds predominated. In addition, adenovirus serotypes 2, 40 and 41 were each detected in three different treated drinking water samples. Most (70%) of the HAds detected in river water samples analysed were enteric HAds (serotypes 40 and 41). One HAd serotype 2 and two species D HAds were detected in the river water. CONCLUSIONS: Adenoviruses detected in river and treated drinking water samples were successfully quantified and typed. The detection of HAds in drinking water supplies treated and disinfected by internationally recommended methods, and which conform to quality limits for indicator bacteria, warrants an investigation of the risk of infection constituted by these viruses. The risk of infection may have implications for the management of drinking water quality. SIGNIFICANCE AND IMPACT OF THE STUDY: This study is unique as it is the first report on the quantification and typing of HAds in treated drinking water and river water. This baseline data is necessary for the meaningful assessment of the potential risk of infection constituted by these viruses.     

Physiological response of central metabolism in Escherichia coli to deletion of pyruvate oxidase and introduction of heterologous pyruvate carboxylase

We studied the physiological response of Escherichia coli central metabolism to the expression of heterologous pyruvate carboxylase (PYC) in the presence and absence of pyruvate oxidase (POX). These studies were complemented with expression analysis of central and intermediary metabolic genes and conventional in vitro enzyme assays to evaluate glucose metabolism at steady-state growth conditions (chemostats). The absence of POX activity reduced nongrowth-related energy metabolism (maintenance coefficient) and increased the maximum specific rate of oxygen consumption. The presence of PYC activity (i.e., with POX activity) increased the biomass yield coefficient and reduced the maximum specific oxygen consumption rate compared to the wildtype. The presence of PYC in a poxB mutant resulted in a 42% lower maintenance coefficient and a 42% greater biomass yield compared to the wildtype. Providing E. coli with PYC or removing POX increased the threshold specific growth rate at which acetate accumulation began, with an 80% reduction in acetate accumulation observed at a specific growth rate of 0.4 h-1 in the poxB-pyc+ strain. Gene expression analysis suggests utilization of energetically less favorable glucose metabolism via glucokinase and the Entner-Doudoroff pathway in the absence of functional POX, while the upregulation of the phosphotransferase glucose uptake system and several amino acid biosynthetic pathways occurs in the presence of PYC. The physiological and expression changes resulting from these genetic perturbations demonstrate the importance of the pyruvate node in respiration and its impact on acetate overflow during aerobic growth.     

The occurrence of a bloom-forming green alga <Emphasis Type="Italic">Pleodorina indica</Emphasis>(Volvocales) in the downstream reach of the River Malše (Czech Republic)

In mid-August 2003 a massive bloom of the green alga Pleodorina indica(Iyengar) Nozaki (Volvocales) occurred in the downstream reach of the River Male in the Czech Republic. An exceptionally long period of the hot dry weather resulted in low flow conditions and warm water temperatures. These environmental conditions combined with high nutrient concentrations led to the macroscopic appearance of P. indica in the form of an extensive surface scum formation with diurnal changes. The alga soon dominated the river phytoplankton, attaining concentrations of 2000 colonies per millilitre. The bloom persisted in the river from the 10–17 August when it was eventually flushed out. P. indica is an indigenous species of tropical climatic regions and prior to this its massive occurrence has not been reported in the temperate region of Central Europe.     

Macrophytic Communities Inhabiting the Huveaune (South-East France), a River Subject to Natural and Anthropic Disturbances

Few studies have dealt so far with the macrophytic communities inhabiting the small Mediterranean rivers in South-East France. In order to fill this gap, it was proposed to assess the effects of natural and anthropic disturbances on the biodiversity in the lowland River Huveaune (South-East France). The Mediterranean climate in this region results in strong seasonal variations in the hydrological regime: there is a long dry period and sudden episodes of flooding occur, which greatly affect the plant community dynamics. The River Huveaune is severely polluted by organic matter. Two stations were set up, one in an upstream reference sector and the other in a downstream polluted sector. The standard sampling area of 100 m² was divided into plots 4 m² in size, some of which included part of the river and part of a bank. In addition, plant inventories were drawn up over distances of 50 and 100 m. Seventeen sampling campaigns were carried out from April 2002 to October 2003, resulting in the first systematic list of macrophyte species occurring in small Mediterranean rivers in South-Eastern France. The great variability of the hydrological factors involved leads to considerable spatial and temporal variations in the biodiversity. The upstream station was found to be less severely disturbed and to show a wider range of macrophytes than the downstream station: bryophytes predominate upstream and phanerogams and macroalgae, downstream. The Macrophyte Biological Index for River (IBMR) was tested and found to be a valid means of water quality assessment in small Mediterranean rivers.     

Enhancement of inosine production by <Emphasis Type="BoldItalic">Bacillus subtilis</Emphasis> through suppression of carbon overflow by sodium citrate

Sodium citrate, added to culture medium at 2 g l⁻¹, increased inosine production by B. subtilis by 18% to 16 g l⁻¹. The phosphoenolpyruvate (PEP) pool was increased by 2.3-fold, while the pyruvate and acetate pools were decreased by 78% and 57%, respectively. Pyruvate kinase might thus be a regulatory site for inosine synthesis.     

Export of Nitrogen,Phosphorus, and Suspended Solids from a Southern New England Watershed to Little Narragansett Bay

The Pawcatuck River watershed (764 km²) is a mainly forested drainage basin with a low population density (80 people km⁻²) that discharges to a shallow estuary, Little Narragansett Bay (RI and CT, USA). In order to quantify the nitrogen (N) and phosphorus (P) flux to the estuary, we measured all forms of nitrogen and phosphorus, as well as suspended solids at the mouth of the river above tidal influence, on more than 80 occasions over an annual cycle. The annual export of total nitrogen, total phosphorus, and total suspended solids amounted to 16.0×10⁶ mol y⁻¹, 0.97×10⁶ mol y⁻¹, and 1.4×10⁶ kg y⁻¹, respectively. Nitrogen export was equally divided between dissolved inorganic (83% NO₃⁻) and organic forms, with particulate nitrogen comprising 17% of the total flux. Phosphorus export was dominated by particulate forms (67%), with dissolved inorganic phosphate contributing 30% and dissolved organic phosphorus contributing 8% of the annual flux. Preliminary nutrient budgets for the Pawcatuck watershed suggest that only about 10% of the nitrogen and phosphorus inputs are exported from the system. Strong regressions between water discharge and TN enabled us to extrapolate the data collected during the relatively dry study period to a long term average discharge year. Under normal river discharge conditions, the N flux would be approximately 26.0×10⁶ mol y⁻¹ or about 20% of the nitrogen inputs to the watershed. This value is very close to the N flux predicted by a regression developed by others from a wide range of larger watersheds. The relatively large size of the Pawcatuck watershed relative to the estuary (9.6 km²), makes Little Narragansett Bay one of the most intensively nitrogen loaded estuaries on the Atlantic coast in spite of the dominant forest cover of the watershed.     

Spawning time and early life history of Murray cod, <Emphasis Type="Italic">Maccullochella peelii</Emphasis> (Mitchell) in an Australian river

Synopsis I investigated aspects of the early life history of Murray cod in the Broken River, southern Murray-Darling Basin, Australia. I documented patterns in abundance, length, age and the amount of yolk of drifting free embryos and estimated spawning periods for adult Murray cod in two reaches throughout each breeding season between mid-October and mid-December from 1997 to 2001. Free embryos began drifting in late-October and continued until mid- to late-December. Abundances of drifting free embryos showed no obvious peak in most years and were unrelated to discharge. Length, amount of yolk and age typically varied with sampling date, but only age showed strong and negative correlations with temperature. Thus, it appears that temperature affected rates of development, and that developmental stage, not length or age, was likely to be the determinant for when free embryos left the paternal nest. Most free embryos were estimated to have spent between 5 and 7 days drifting. Spawning of Murray cod in the Broken River usually commenced in mid-October and continued until at least early December. Initiation of spawning was associated with temperatures of 15°C and above, but discharge was highly variable, and no other environmental variables were consistent across years. The mid-point of spawning – usually in the first week of November – is considered a more significant time, because it likely coincides with peak spawning, and conditions during and immediately after this time are expected to be optimal for the survival of eggs and free embryos.     

Ontogenetic Behavior and Dispersal of Sacramento River White Sturgeon, <Emphasis Type="BoldItalic">Acipenser Transmontanus</Emphasis>, with a Note on Body Color

Synopsis We studied Sacramento River white sturgeon, Acipenser transmontanus, in the laboratory to develop a conceptual model of ontogenetic behavior and provide insight into probable behavior of wild sturgeon. After hatching, free embryos initiated a low intensity, brief downstream dispersal during which fish swam near the bottom and were photonegative. The weak, short dispersal style and behavior of white sturgeon free embryos contrasts greatly with the intense, long dispersal style and behavior (photopositive and swimming far above the bottom) of dispersing free embryos of other sturgeon species. If spawned eggs are concentrated within a few kilometers downstream of a spawning site, the adaptive significance of the free embryo dispersal is likely to move fish away from the egg deposition site to avoid predation and reduce fish density prior to feeding. Larvae foraged on the open bottom, swam <1 m above the bottom, aggregated, but did not disperse. Early juveniles initiated a strong dispersal with fish strongly vigorously swimming downstream. Duration of the juvenile dispersal is unknown, but the strong swimming likely disperses fish many kilometers. Recruitment failure in white sturgeon populations may be a mis-match between the innate fish dispersal and post-dispersal rearing habitat, which is now highly altered by damming and reservoirs. Sacramento River white sturgeon has a two-step downstream dispersal by the free embryo and juvenile life intervals. Diel activity of all life intervals peaked at night, whether fish were dispersing or foraging. Nocturnal behavior is likely a response to predation, which occurs during both activities. An intense black-tail body color was present on foraging larvae, but was weak or absent on the two life intervals that disperse. Black-tail color may be an adaptation for avoiding predation, signaling among aggregated larvae, or both, but not for dispersal.     

The carbon dioxide system in the Elbe estuary

The pCO₂ distribution in thesurface waters of the Elbe estuary and German Bight was investigated during high river discharge in April 1997. pCO₂ values of about 1100 atm foundin the upper part of the estuary are, comparedto other European rivers, only moderate. In theouter estuary, the enhanced river dischargecreates a pronounced river plume reflected in decreased surface salinity.However, pCO₂ in this area(250 atm) is below atmospheric values dueto primary production. Comparison with resultswe obtained during other measuringcampaigns shows that in the outer estuarysupersaturation of CO₂ with respect to theatmosphere occurs only in early spring duringthe time of highest river discharge. In latespring and summer, intensive primary productionwithin the surface layer leads to a pronouncedundersaturation (141 atm), despite atemperature increase of more than 20 °Cfrom winter to summer. Undersaturation isenforced by stable stratification of the watercolumn during the productive seasons thatdiminishes the entrainment of CO₂from below the thermocline into the surfacewater. In winter, CO₂ is close toequilibrium with the atmosphere and controlledby physical processes. Our data suggest thatthe Elbe estuary represents a sink foratmospheric CO₂ over the investigatedseasons and that carbon cycling in this areais dominated by biological processes.     

MHC-DRB exon 2 allele polymorphism in Indian river buffalo (Bubalus bubalis)

The polymorphism of the major histocompatibility complex (MHC) class II DRB gene of riverine buffalo (Bubalus bubalis) was studied. Second exon sequences from the buffalo DRB locus, homologous to the cattle DRB3 gene, were amplified and characterized. A combination of single strand conformation polymorphism (SSCP) and heteroduplex analysis (HA) in a non-denaturing gel was used to identify new DRB second exon sequences. SSCP, HA and finally sequencing allowed the identification of 22 MHC-DRB exon 2 alleles from 25 unrelated Indian river buffalo. These are the first river buffalo DRB second exon sequences reported. A high degree of polymorphism in the sequences encoding the peptide binding regions was observed and some amino acid substitutions were found unique to the river buffalo.