Solar disinfection of poliovirus and Acanthamoeba polyphaga cysts in water - a laboratory study using simulated sunlight

AIMS: To determine the efficacy of solar disinfection (SODIS) in disinfecting water contaminated with poliovirus and Acanthamoeba polyphaga cysts. METHODS AND RESULTS: Organisms were subjected to a simulated global solar irradiance of 850 Wm(-2) in water temperatures between 25 and 55 degrees C. SODIS at 25 degrees C totally inactivated poliovirus after 6-h exposure (reduction of 4.4 log units). No SODIS-induced reduction in A. polyphaga cyst viability was observed for sample temperatures below 45 degrees C. Total cyst inactivation was only observed after 6-h SODIS exposure at 50 degrees C (3.6 log unit reduction) and after 4 h at 55 degrees C (3.3 log unit reduction). CONCLUSIONS: SODIS is an effective means of disinfecting water contaminated with poliovirus and A. polyphaga cysts, provided water temperatures of 50-55 degrees C are attained in the latter case. SIGNIFICANCE AND IMPACT OF THE STUDY: This research presents the first SODIS inactivation curve for poliovirus and provides further evidence that batch SODIS provides effective protection against waterborne protozoan cysts.     

Postharvest behaviour of five Sardinian prune varieties as affected by immersion in heated sodium bicarbonate solution

Storage behaviour of 'Core', 'Core Columbu', 'Fradis' and 'Meloni' white prunes, and a black one ('Sighera') of Sardinian germplasm were evaluated following immersion for 0 (control), 15, 30, 45 or 60 sec in water at 20, 50, 55 or 60 degrees C with or without 2% (w/v) NaHCO3 (SBC). As international varieties, fruit from one white plum ('Shiro') and one black prune ('Stanly') were subjected to the same treatments. Fruit was harvested at commercial maturity, treated and then stored for 1 month at 5 degrees C and 90% RH followed by a simulated marketing period at 20 degrees C and 80% RH for 6 days. Fruit appearance, external damage, firmness and decay percentage were monitored after storage and SMP. Treatments did not induce rind damage (browning or discoloration) to any variety. SBC at 20, 45, 50 or 55 degrees C for 15 or 30 sec was not effective in controlling decay and compared to controls no improvement was observed. Immersion for 45 or 60 sec with SBC at all temperatures improved decay control with respect to controls and best results were obtained at 50 or 55 degrees C. Immersions at 60 degrees C improved decay control, but differences were not significant compared to the control attained with solutions of SBC heated at 55 degrees C. The overall appearance of 'Core', 'Core Columbu', 'Fradis' and 'Shiro' decreased significantly after the SMP period, especially when treated at 55 or 60 degrees C for 60 sec. Fruit shrivel was the main cause of the low rating. SBC did not affect shrivel indicating that heat treatment may be the probable cause. In general, local varieties were less affected by decay than other varieties and they performed well during storage.     

Competition for cool nasal blood between trunk and brain in hyperthermic goats

An influence of brain and trunk temperatures controlled independently of each other by means of artificial heat exchangers, on the intensity of natural selective brain cooling (SBC) was studied in 6 conscious goats. Intensity of SBC was markedly enhanced by increasing brain temperature. On the other hand, a rise of trunk temperature with the cerebral temperature clamped at 39 degrees C or 40 degrees C, reduced SBC intensity in spite of a simultaneous increase in the respiratory evaporative heat loss. When brain temperature was clamped at 41 degrees C, the magnitude of SBC was essentially independent of trunk temperature. These results suggest that during hyperthermia a competition exists between trunk and brain for cool nasal blood.     

Enhancement of Solar Water Pasteurization with Reflectors

A simple and reliable method that could be used in developing countries to pasteurize milk and water with solar energy is described. A cardboard reflector directs sunshine onto a black jar, heating water to pasteurizing temperatures in several hours. A reusable water pasteurization indicator verifies that pasteurization temperatures have been reached.     

Decontamination of drinking water by direct heating in solar panels

A device was developed for direct heating of water by solar radiation in a flow-through system of copper pipes. An adjustable thermostat valve prevents water below the chosen temperature from being withdrawn. The results show that it is possible to eliminate coliform and thermotolerant coliform bacteria from naturally contaminated river water by heating to temperatures of 65 °C or above. Artificial additions of Salmonella typhimurium , Streptococcus faecalis and Escherichia coli to contaminated river water were also inactivated after heating to 65 °C and above. The total viable count could be reduced by a factor of 1000. The heat-resistant bacteria isolated from the Mlalakuva River (Tanzania) were spore-forming bacteria which exhibited greater heat resistance than commonly used test bacteria originating from countries with colder climates. To provide a good safety margin it is recommended that an outlet water temperature of 75 °C be used. At that temperature the daily production was about 50 l of decontaminated water per m² of solar panel, an amount that could be doubled by using a heat exchanger to recycle the heat.     

Laboratory study on the effects of temperature and three ventilation rates on infestations of Varroa destructor in clusters of honey bees (Hymenoptera: Apidae)

In this study, reduced levels of ventilation were applied to small clusters of bees under controlled conditions to determine whether lowered ventilation rates and the resulting increased levels of CO2 could increase the mortality rates of varroa. Two experiments were performed at two different temperatures (10 degrees C and 25 degrees C). Both experiments compared varroa mortality among high (360 liters/h), medium (42.5 liters/h), and low (14 liters/h) rates of ventilation. The clusters of bees (approximately 300 worker bees) in bioassay cages with 40 introduced varroa mites were placed into self-contained glass chambers and were randomly assigned to one of the three ventilation treatments within incubators set at either of the two temperatures. Bee and varroa mortality and the levels of CO2 concentration were measured in each of the experimental chambers. In both experiments, CO2 levels within the chamber increased, with a decrease in ventilation with CO2 reaching a maximum of 1.2 +/- 0.45% at 10 degrees C and 2.13 +/- 0.2% at 25 degrees C under low ventilation. At high ventilation rates, CO2 concentration in chamber air was similar at 10 degrees C (1.1 +/- 1.5%) and 25 degrees C (1.9 +/- 1.1%). Both humidity and CO2 concentration were higher at 25 degrees C than at 10 degrees C. Bee mortality was similar within all ventilation rate treatments at either 10 degrees C (11.5 +/- 2.7-19.3 +/- 3.8%) or 25 degrees C (15.2 +/- 1.9-20.7 +/- 3.5%). At 10 degrees C, varroa mortality (percentage dead) was greatest in the high ventilation treatment (12.2 +/- 2.1%), but only slightly higher than under low (3.7 +/- 1.7%) and medium ventilation (4.9 +/- 1.6%). At 25 degrees C, varroa mortality was greatest under low ventilation at 46.12 +/- 7.7% and significantly greater than at either medium (29.7 +/- 7.4%) or low ventilation (9.5 +/- 1.6.1%). This study demonstrates that at 25 degrees C, restricted ventilation, resulting in high levels of CO2 in the surrounding environment of small clusters of honey bees, has the potential to substantially increase varroa mortality.     

Inactivation of fecal bacteria in drinking water by solar heating.

We report simulations of the thermal effect of strong equatorial sunshine on water samples contaminated with high populations of fecal coliforms. Water samples, heavily contaminated with a wild-type strain of Escherichia coli (starting population = 20 x 10(5) CFU/ml), are heated to those temperatures recorded for 2-liter samples stored in transparent plastic bottles and exposed to full Kenyan sunshine (maximum water temperature, 55 degrees C). The samples are completely disinfected within 7 h, and no viable E. coli organisms are detected at either the end of the experiment or a further 12 h later, showing that no bacterial recovery has occurred. The feasibility of employing solar disinfection for highly turbid, fecally contaminated water is discussed.     

A test of biochemical symmorphosis in a heterothermic tissue: bluefin tuna white muscle

Selective brain cooling (SBC) is defined as a brain temperature cooler than the temperature of arterial blood from the trunk. Surrogate measures of arterial blood temperature have been used in many published studies on SBC. The use of a surrogate for arterial blood temperature has the potential to confound proper identification of SBC. We have measured brain, carotid blood, and rectal temperatures in conscious sheep exposed to 40, 22, and 5 degrees C. Rectal temperature was consistently higher than arterial blood temperature. Brain temperature was consistently cooler than rectal temperature during all exposures. Brain temperature only fell below carotid blood temperature during the final few hours of 40 degrees C exposure and not at all during the 5 degrees C exposure. Consequently, using rectal temperature as a surrogate for arterial blood temperature does not provide a reliable indication of the status of the SBC effector. We also show that rapid suppression of SBC can result if the animals are disturbed.     

Effect of water temperature on the ability of Diplostomum spathaceum miracidia to establish in lymnaeid snails

The effects of water temperature on the ability of Diplostomum spathaceum miracida to infect and establish patent infections in Lymnaea peregra and L. stagnalis were investigated. Snails were infected over a range of temperatures (6-20 degrees C) and kept thereafter at 20 degrees C or were infected at 20 degrees C and kept at either 14, 20, or 25 degrees C. Infection success was determined after 8 weeks by either observing cercarial shedding or examining snail viscera for sporocysts. The establishment of miracidia declined at lower water temperatures despite maintenance for 8 weeks at 20 degrees C while exposure of snails to miracidia at 20 degrees C and maintenance at different temperatures had little apparent effect. Infection success under these conditions was related more to the numbers of miracidia to which the snails were exposed. However, under this latter experimental regime, the time taken for the infection to become patent clearly depended upon maintenance temperature.     

Heat inactivation of Salmonella typhimurium DT104 in beef as affected by fat content

The heat resistance of an eight-strain cocktail of Salmonella typhimurium DT104 was determined at 58-65 degrees C in beef containing 7, 12, 18 or 24% fat. Inoculated beef was packaged in bags completely immersed in a circulating water bath and held at 58, 60, 62.5 and 65 degrees C for a predetermined length of time. The surviving cell population was enumerated by spiral plating heat-treated samples onto tryptic soy agar supplemented with 0.6% yeast extract and 1% sodium pyruvate. Preliminary studies on thermal inactivation of the Salmonellae isolates in chicken broth indicated no correlation between heat resistance and origin of the isolates. While linear survival curves were observed in chicken broth, inactivation kinetics in beef showed deviations from the first order kinetics, represented by an initial lag period or shoulder before any death occurred with time. Overall, increased fat levels in beef resulted in longer lag periods and lower D-values, suggesting that the lag periods must be taken into account and added to the D-values for calculating the time required at a specific temperature for achieving a specific lethality for Salm. typhimurium DT104 in beef. Thermal death times from this study will assist the retail food industry to design cooking regimes that ensure safety of beef contaminated with Salm. typhimurium DT104.     

Investigation of the survival characteristics of Rhodococcus coprophilus and certain fecal indicator bacteria.

Rhodococcus coprophilus and Clostridium perfringens survived in fresh water samples held at 5, 20, and 30 degrees C for over 17 weeks, whereas Escherichia coli and fecal streptococci disappeared after 5 weeks at all three temperatures. R. coprophilus survived for more than 8 months in sterilized sewage and deionized water at all three temperatures, whereas in normal sewage held at 20 degrees C, the survival time was 12 to 26 weeks. In samples held at 30 degrees C, survival times were shorter, probably because of interbacterial competition or protozoal predation. The results indicate that R. coprophilus may be a useful indicator of the presence of remote fecal pollution of farm animal origin, but not of recent pollution, when enumerated alone in polluted waters or wastewaters.     

Angularis oculi vein blood flow modulates the magnitude but not the control of selective brain cooling in sheep

To investigate the role of the angularis oculi vein (AOV) in selective brain cooling (SBC), we measured brain and carotid blood temperatures in six adult female Dorper sheep. Halfway through the study, a section of the AOV, just caudal to its junction with the dorsal nasal vein, was extirpated on both sides. Before and after AOV surgery, the sheep were housed outdoors at 21-22°C and were exposed in a climatic chamber to daytime heat (40°C) and water deprivation for 5 days. In sheep outdoors, SBC was significantly lower after the AOV had been cut, with its 24-h mean reduced from 0.25 to 0.01°C (t(5) = 3.06, P = 0.03). Carotid blood temperature also was lower (by 0.28°C) at all times of day (t(5) = 3.68, P = 0.01), but the pattern of brain temperature was unchanged. The mean threshold temperature for SBC was not different before (38.85 ± 0.28°C) and after (38.85 ± 0.39°C) AOV surgery (t(5) =0.00, P = 1.00), but above the threshold, SBC magnitude was about twofold less after surgery. SBC after AOV surgery also was less during heat exposure and water deprivation. However, SBC increased progressively by the same magnitude (0.4°C) over the period of water deprivation, and return of drinking water led to rapid cessation of SBC in sheep before and after AOV surgery. We conclude that the AOV is not the only conduit for venous drainage contributing to SBC in sheep and that, contrary to widely held opinion, control of SBC does not involve changes in the vasomotor state of the AOV.     

Sequential application of NaHCO3, CaCl2 and Candida oleophila (isolate 13L) affects significantly Penicillum expansum growth and the infection degree in apples

The employment of biocontrol agents to restrain postharvest pathogens is an encouraging approach, although, efficacy and consistency are still below those of synthetic pesticides. Up to date, the 'integrated control strategy' seems to be the most promising way to overcome this gap. Here, we report the feasibility to control postharvest decay caused by Penicillium expansum in apples by a 2 min, single or sequential, immersion in water with an antagonistic yeast (Candida oleophila, isolate '13L'), 2% NaHCO3 (SBC) or 1% CaCl2. The treatments were carried out, on appels cv 'Miali' either un-wounded, wounded or wound-pathogen inoculated and then stored at 2 degrees C for 30 d followed by a 6 d simulated marketing period at 20 degrees C or alternatively stored only for 7 d at 20 degrees C. As a general role, the best results were attained when CaCl2 was applied with the yeast or when preceded by the SBC treatment. When the wounding and inoculation took place 24 h before the treatment, the latter application sequence of the two salts was three times more effective compared to the treatment with the sole antagonist, and one time when performed 24 h after the treatment. Interestingly, apples immersed in the sole 2% SBC solution had the highest percentage of decay during storage and when inoculated before moving to the simulated marketing period at 20 degrees C.     

Thermophilic (55-65 degrees C) and extreme thermophilic (70-80 degrees C) sulfate reduction in methanol and formate-fed UASB reactors

The feasibility of thermophilic (55-65 degrees C) and extreme thermophilic (70-80 degrees C) sulfate-reducing processes was investigated in three lab-scale upflow anaerobic sludge bed (UASB) reactors fed with either methanol or formate as the sole substrates and inoculated with mesophilic granular sludge previously not exposed to high temperatures. Full methanol and formate degradation at temperatures up to, respectively, 70 and 75 degrees C, were achieved when operating UASB reactors fed with sulfate rich (COD/SO4(2-)=0.5) synthetic wastewater. Methane-producing archaea (MPA) outcompeted sulfate-reducing bacteria (SRB) in the formate-fed UASB reactor at all temperatures tested (65-75 degrees C). In contrast, SRB outcompeted MPA in methanol-fed UASB reactors at temperatures equal to or exceeding 65 degrees C, whereas strong competition between SRB and MPA was observed in these reactors at 55 degrees C. A short-term (5 days) temperature increase from 55 to 65 degrees C was an effective strategy to suppress methanogenesis in methanol-fed sulfidogenic UASB reactors operated at 55 degrees C. Methanol was found to be a suitable electron donor for sulfate-reducing processes at a maximal temperature of 70 degrees C, with sulfide as the sole mineralization product of methanol degradation at that temperature.     

Effects of acclimation temperature on the growth of Perna viridis (Bivalvia: Mytilidae), using the RNA/DNA ratio

Temperature affects growth rate in aquatic organisms. This can be evaluated in short term using biochemical indexes (RNA/DNA and Protein/DNA). The effect of acclimatization temperature on the instantaneous growth and physiological condition of Perna viridis was studied in organisms collected in La Esmeralda, Sucre State (Venezuela) and taken to the laboratory, where groups of 100 organisms (size 3.0 - 3.5 cm, anteroposterior measurement) were acclimatized at 15, 20, 26 or 28 degrees C during four weeks. Later they were kept in a 60 liters aquarium for another six weeks under the same conditions. Each week, ten organisms per group were extracted to measure concentrations of RNA, DNA (by a fluorometric method with ethidium bromide) and proteins (by a colorimetric method), in tissues (digestive gland, adductor muscle and gills). Protein concentration was greater and highly significant at 15 degrees C for all studied tissues. The opposite was obtained with the RNA/DNA and Protein/DNA ratios: the greatest increase was observed at the highest temperature (28 degrees C) for all tissues. At the lowest temperature there was a tendency to reduce both indexes with time. Greater instantaneous growth can be expected at higher temperatures and 28 degrees C was optimal for growth in these specimens.     

Salmonella enteritidis and aerobic mesophiles in inoculated poultry sausages manufactured with high-pressure processing

Salmonella enteritidis-inoculated poultry sausages were pressurized at 500 MPa by combining different times (10 and 30 min) and temperatures (50, 60 and 70 degrees C) or heat treated with the same temperature-time combinations and a standard cooking (75 degrees C for 30 min). Counts of Salm. enteritidis and mesophilic bacteria were determined. Most pressure treatments generated statistically higher reductions than the corresponding heat treatments alone. Lethalities of about 7.5 and 6.5 log cfu g(-1) for Salm. enteritidis and mesophiles, respectively, were found in pressurized sausages. There was no significant difference in counts between pressurization at 60 degrees C for 30 min or at 70 degrees C and the standard cooking. High-pressure processing is a suitable alternative method in poultry sausage manufacture.     

Respiratory response to temperature and hypoxia in the zebra mussel Dreissena polymorpha

The effects of temperature acclimation, acute temperature variation and progressive hypoxia on oxygen consumption rates (VO2) were determined for the zebra mussel Dreissena polymorpha. In the first experiment, after acclimation to 5, 15 or 25 degrees C for at least 2 weeks, VO2 was determined at 5 degrees C increments from 5 to 45 degrees C. VO2 increased in all three acclimation groups from 5 to 30 degrees C, corresponding to the normal ambient temperature range for this species. Mussels displayed imperfect temperature compensation at temperatures above 15 degrees C, but exhibited little acclimatory ability below 15 degrees C. In the hypoxia experiment, VO2 was determined over the course of progressive hypoxia, from full saturation (oxygen tension [PO2]=160 Torr [21.3 kPa]) to a PO2 at which oxygen uptake ceased (<10 Torr [1.3 kPa]). Mussels were acclimated to either 5, 15 or 25 degrees C for at least 2 weeks and their respiratory response to progressive hypoxia was measured at three test temperatures (5, 15 and 25 degrees C). The degree of oxygen regulation increased with increasing test temperature, particularly from 5 to 15 degrees C, but decreased with increasing acclimation temperature. The decreased metabolic rate observed for warm-acclimated animals, particularly in the upper portion of the temperature range of the zebra mussel, may allow for conservation of organic energy stores during warm summer months. Compared to other freshwater bivalves, D. polymorpha is a relatively poor oxygen regulator, corresponding with its preference for well-oxygenated aquatic habitats. In addition, a new quantitative method for determining the degree of oxygen regulation is presented.     

Sulfidogenic fluidized-bed treatment of metal-containing wastewater at low and high temperatures

The applicability of a fluidized-bed reactor (FBR)-based sulfate reducing bioprocess was investigated for the treatment of iron-containing (40-90 mg/L) acidic wastewater at low (8 degrees C) and high (65 degrees C) temperatures. The FBRs operated at low and high temperatures were inoculated with cultures of sulfate-reducing bacteria (SRB) originally enriched from arctic and hot mining environments, respectively. Ethanol was supplemented as carbon and electron source for SRB. At 8 degrees C, ethanol oxidation and sulfate reduction rates increased steadily and reached 320 and 265 mg/L.day, respectively, after 1 month of operation. After this point, the rates did not change significantly during 130 days of operation. Despite the complete ethanol oxidation and iron precipitation, the average sulfate reduction efficiency was 35 +/- 4% between days 30 and 130 due to the accumulation of acetate. At 65 degrees C, a rapid startup was observed as 99.9, 46, and 29% ethanol, sulfate, acetate removals, in respective order, were observed after 6 days. The feed pH was decreased gradually from its initial value of 6 to around 3.7 during 100 days of operation. The wastewater pH of 4.3-4.4 was neutralized by the alkalinity produced in acetate oxidation and the average effluent pH was 7.8 +/- 0.8. As in the low temperature FBR, acetate accumulated. Hence, the oxidation of acetate is the rate-limiting step in the sulfidogenic ethanol oxidation by thermophilic and psychrotrophic SRB. The sulfate reduction rate is three times and acetate oxidation rate is four times higher at 65 degrees C than at 8 degrees C.     

The effect of growth temperature on the thermotropic behavior of the membranes of a thermophilic Bacillus. Composition-structure-function relationships

The following study was carried out with the aim of widening our understanding of the thermoadaptive mechanisms of the membrane of thermophiles, using Bacillus stearothermophilus var. nondiastaticus as test-organism. The phospholipids and their acyl chain composition of this Bacillus studied in relation to the physical properties of its membrane from bacteria grown at various temperatures. Phospholipids account for 68-75 weight% of the total lipid in cells grown at 45, 55 or 65 degrees C. Phosphatidylglycerol and diphosphatidylglycerol constitute up to 90% of the total phospholipids; no amino phospholipids were found. Increasing the growth temperatures from 45 degrees to 65 degrees C caused an approximately 4-fold decrease in the proportion of the branched-chain fatty acids and a 2-fold increase in the amount of the saturated acyl chains. The reduced proportion of the branched fatty acids was mainly due to a decrease in their anteiso forms. Unsaturated fatty acids were not produced by cells grown at 65 degrees C. In accordance with the fatty acid composition, the molecular packing of phospholipids in monolayers was more expanded with phospholipids from 45 degrees C grown cells as compared with cultures grown at 55 degrees C. The thermotropic gel to liquid-crystalline phase transition of the membrane lipids was monitored by differential scanning calorimetry and fluorescence anisotropy of 1,6-diphenyl-1,3,5-hexatriene. With increase of the growth temperature the phase transition was progressively shifted to higher but narrower range of temperatures. Completion of the lipid melting occurred always at temperatures below those employed for growth. A constructed phase diagram enabled to relate the growth temperature, the fatty acid composition and the lipid apparent microviscosity at temperatures not used in the present study for growth of the thermophile. The minimum temperature for growth and the upper boundary temperature of the least saturated lipid crystallization were extrapolated in this manner; they correspond to the experimentally determined minimal growth temperature. The apparent microviscosity, a measure of membrane order, decreased gradually and conspicuously as the growth temperature was elevated. The delimiting apparent microviscosity values, at the maximal (65 degrees C) and minimal (41 degrees C) growth temperatures were 0.8 and 1.8 poise, respectively. This lack of rigorous homeostatic control of the bulk lipid viscosity prompted reevaluation of the physiological significance of 'homeoviscous adaptation' in Bacillus stearothermophilus.