Concentration of viruses in beef extract by flocculation with ammonium sulfate.

A total of 42 clinical and environmental isolates of Vibrio vulnificus were examined for plasmid carriage. Of these, only five (12%) harbored plasmids, which were of various molecular weights. In contrast, 20 of 32 (62.5%) unidentified lactose-fermenting Vibrio spp. were found to possess plasmids with masses of 2.1 to 150 megadaltons. In these isolates, multiple plasmids were common, with an average of 2.25 plasmids per plasmid-containing strain. Attempts to demonstrate a correlation with the plasmids identified in the various Vibrio spp. and a variety of phenotypic traits, production of several enzymes potentially involved in virulence, cytotoxicity for Chinese hamster ovary cells, and mouse lethality were unsuccessful. A correlation was observed, however, between the presence of a 6.5-megadalton plasmid and resistance to pteridine 0/129. It was concluded that V. vulnificus, unlike most other Vibrio spp., shows a general lack of these extrachromosomal elements.     

Influence of salts on electrostatic interactions between poliovirus and membrane filters.

Neither solutions of salts nor solutions of detergents or of an alcohol at pH 4 are capable of eluting poliovirus adsorbed to membrane filters. However, solutions containing both a salt, such as magnesium chloride or sodium chloride, and a detergent or alcohol at pH 4 were capable of eluting adsorbed virus. The ability of ions to promote elution of virus at low pH in the presence of detergent or alcohol was dependent on the size of the ions and the ionic strength of the medium. These results suggest that both electrostatic and hydrophobic interactions are important in maintaining virus adsorption to membrane filters. Hydrophobic interactions can be disrupted by detergents or alcohols. It appears that electrostatic interactions can be disrupted by raising the pH of a solution or by adding certain salts. Disruption of either electrostatic or hydrophobic interactions alone does not permit efficient elution of the adsorbed virus at low pHs. However, when both interactions are disrupted, most of the poliovirus adsorbed to membrane filters is eluted, even at pH 4.     

Regeneration of pleated filters used to concentrate enteroviruses from large volumes of tap water.

Pleated cartridge filters are capable of concentrating enteroviruses from large volumes (well over 2,000 liters) of tap water. These epoxy-fiberglass filters can be regenerated if they are treated with 0.1 N NaOH or autoclaved to inactivate any contaminating virus. The regenerated filters regained their ability to concentrate viruses from water at high flow rates.     

Regeneration of pleated filters used to concentrate enteroviruses from large volumes of tap water.

Pleated cartridge filters are capable of concentrating enteroviruses from large volumes (well over 2,000 liters) of tap water. These epoxy-fiberglass filters can be regenerated if they are treated with 0.1 N NaOH or autoclaved to inactivate any contaminating virus. The regenerated filters regained their ability to concentrate viruses from water at high flow rates.     

Influence of salts on electrostatic interactions between poliovirus and membrane filters

Neither solutions of salts nor solutions of detergents or of an alcohol at pH 4 are capable of eluting poliovirus adsorbed to membrane filters. However, solutions containing both a salt, such as magnesium chloride or sodium chloride, and a detergent or alcohol at pH 4 were capable of eluting adsorbed virus. The ability of ions to promote elution of virus at low pH in the presence of detergent or alcohol was dependent on the size of the ions and the ionic strength of the medium. These results suggest that both electrostatic and hydrophobic interactions are important in maintaining virus adsorption to membrane filters. Hydrophobic interactions can be disrupted by detergents or alcohols. It appears that electrostatic interactions can be disrupted by raising the pH of a solution or by adding certain salts. Disruption of either electrostatic or hydrophobic interactions alone does not permit efficient elution of the adsorbed virus at low pHs. However, when both interactions are disrupted, most of the poliovirus adsorbed to membrane filters is eluted, even at pH 4.     

Development and application of new positively charged filters for recovery of bacteriophages from water.

Electronegative and electropositive filters were compared for the recovery of indigenous bacteriophages from water samples, using the VIRADEL technique. Fiber glass and diatomaceous earth filters displayed low adsorption and recovery, but an important increase of the adsorption percentage was observed when the filters were treated with cationic polymers (about 99% adsorption). A new methodology of virus elution was developed in this study, consisting of the slow passage of the eluent through the filter, thus increasing the contact time between eluent and virus adsorbed on the filters. The use of this technique allows a maximum recovery of 71.2% compared with 46.7% phage recovery obtained by the standard elution procedure. High percentages (over 83%) of phage adsorption were obtained with different filters from 1-liter aliquots of the samples, except for Virosorb 1-MDS filters (between 1.6 and 32% phage adsorption). Phage recovery by using the slow passing of the eluent depended on the filter type, with recovery ranging between 1.6% for Virosorb 1-MDS filters treated with polyethyleneimine and 103.2% for diatomaceous earth filters treated with 0.1% Nalco.     

Inactivation of poliovirus and other enteroviruses by solutions of sodium fluoride at low pH.

Solutions of sodium fluoride at pH 3 to 4 inactivated enteroviruses, whereas other sodium salts had little or no effect on virus infectivity. Solutions of potassium fluoride also inactivated viruses under similar conditions. Light, temperature, and the presence of organic compounds such as detergents and fecal matter did not affect inactivation of virus by 0.4 M solutions of sodium fluoride at pH 3. to 4. Decreasing the sodium fluoride concentration below 0.04 M or raising the pH above 4 reduced the viricidal properties of the solutions. Virus adsorbed to membrane filters and sludge flocs could not be recovered after treatment of solids-associated virus with solutions of sodium fluoride.     

Concentration of viruses from large volumes of tap water using pleated membrane filters.

A method is described for the efficient concentration of viruses from large volumes of tap water in relatively short time periods. Virus in acidified tap water in the presence of aluminum chloride is adsorbed to a 10-inch (ca. 25.4 cm) fiberglass depth cartridge and a 10-inch pleated epoxy-fiberglass filter in series at flow rates of up to 37.8 liters/min (10 gallons/min). This filter series is capable of efficiently adsorbing virus from greater than 19,000 liters (5,000 gallons) of treated tap water. Adsorbed viruses are eluted from the filters with glycine buffer (pH 10.5) and the eluate is reconcentrated using an aluminum flocculation process. Viruses are eluted from the aluminum floc with glycine buffer (pH 11.5). Using this procedure, viruses in 1,900 liters (500 gallons) of tap water can be concentrated 100,000-fold in 3 h with an average recovery of 40 to 50%.     

Fluorescent-Antibody Study of Natural Finger-Like Zooloeae

Fluorescent-antibody techniques using Zoogloea ramigera 106 antiserum were used to study fresh activated sludge flocs and finger-like zoogloeae in the microbial film that developed over stored samples of activated sludge. Few cells in fresh activated sludge reacted positively with the fluorescein-labeled antiserum. Finger-like zoogloeae containing reactive cells were readily observed in the microbial film layer over stored activated sludge. Certain of the natural finger-like projections were entirely composed of cells that reacted positively to the labeled Z. ramigera 106 antiserum, whereas other projections were devoid of reactive cells.     

Diet of breeding Eleonora's falcon Falco eleonorae in Algeria: Insights for the autumn trans‐Mediterranean avian migration

How environmental changes are affecting bird population dynamics is one of the most challenging conservation issues. Dietary studies of top avian predators could offer scope to monitor anthropogenic drivers of ecosystem changes. We investigated the diet of breeding Eleonora''s falcon in an area of Northeastern Algeria in the years 2010–2012. Feathers and insect remains originating from prey plucking behavior were analyzed, providing insights into the seasonally changing diet of this raptor, as well as the trans‐Mediterranean avian migration. A total of 77 species of birds (16 Sylviidae, 11 Turdidae, and 4 Emberizidae), 3 species of insects, and 1 lizard were identified among prey remains, reflecting a diverse diet. Diet composition and prey abundance varied seasonally, faithfully correlating with the passage of migrant birds as recorded from bird ring recoveries. Our findings suggest that dietary studies of predators might be deployed to investigate changes in bird migration. We discuss our results in the context of trans‐Mediterranean migration, with early‐season prey mainly comprising trans‐Saharan migrants (Apus apus and Merops apiaster) and late‐season prey being dominated by Mediterranean winter migrants (Erithacus rubecula, Turdus philomelos, Sylvia atricapilla, and Sturnus vulgaris). Notably, we observed a significant reduction in species richness of passerine remains in 2012, potentially highlighting a decline in the diversity of avian migrants.