Freshly voided samples of the feces of cows, pigs, and humans were analyzed for the enumeration of cell-free plaque-forming units (PFU) of coliphages and Salmonella phages. Coliphage PFU counts per gram (wet weight) of feces were found to range from less than 10' to > 107. Salmonella phages were found in three out of five porcine samples, but none were found in the four bovine samples analyzed. Virulent coliphages related to the OX174/S13 serological group showed some "habitat preference" in that the S13 type of phages was
Coliphage content of sewage collected from 11 different localities in Hong Kong was determined. The number of plaque-forming units (PFU) ranged from 0.036 X 103 to 15.9 X 10' per ml. In general, urban sewage tended to be richer than rural sewage both in PFU count as well as plaque morphological variation. Seventy-seven isolates were subjected to a host range study. Fifty per cent of these were able to grow on Escherichia coli K-12 as well as E. coli B. Approximately 32% were found to be male specific, and the remaining 18 % were K-12 specific although sex-indifferent.Abundant occurrence of coliphages in sewage is generally recognized. However, no quantitative data on the density of coliphages in sewage appear to be available. Such information being of obvious importance for an understanding of bacteriophage ecology, we undertook to determine the density of coliphages in sewage from diverse sources in Hong Kong. Our findings form the subject of this communication.MATERIALS AND METHODS Organisms. The bacterial and phage strains used are described in Table 1.Media. Liquid bacterial cultures were raised in tryptone broth which contained, in 1 liter of distilled water, 10 g of tryptone (Difco) and 5 g of sodium chloride (pH 7.2 before autoclaving). For agar overiay plates, bottom and top agars were prepared by the addition of 1.2 and 0.65 g, respectively, of agar (Difco) to 100 ml of tryptone broth. Streptomycin, when used, was added to give a final concentration of 200 ug per ml of medium. Tryptone broth was used as the diluent for sewage samples and for phage lysates.Methods. General bacteriophage techniques were those described by Adams (1). Sewage samples were collected from both rural and urban areas (Table 2). Special methods pertinent to this study follow.Collection and assay of sewage sam?les. Samples (50 to 100 ml) of liquid were collected from each site in sterile glass flasks. Coarse particulate materials were removed by passing the sample through four layers of sterile cheese cloth. Filtrate was centrifuged at 4,000 X g for 30 min, and the pellet was discarded. The supernatant fraction was either assayed directly or treated with chloroform and then assayed. Chloroform treatment was given by vigorous agitation of 10 ml of supernatant and 0.5 ml of chloroform. The mixture was refrigerated for 30 min. The upper aqueous layer was plated by agar overlay method to determine the plaque-forming unit (PFU) content of the sample. A 1.25-ml portion of sample was mixed with 10.75 ml of molten soft agar at 45 C and 0.5 ml of a log phase culture of indicator cells. Samples (2.5 ml) of the mixture were spread on four bottom agar plates. Undiluted sample and its three serial 10-fold dilutions were plated by this method. Plates were incubated at 37 C for 16 to 24 hr; those showing the largest countable number of plaques were selected for further observations. All PFU assays were made with agar media containing streptomycin and seeded with the streptomycin-resistant indicator strain 58-161. Plaque morphology observations. P...
A smooth colony strain, resistant to phages V and P22, was isolated from sewage and identified as Escherichia coli (strain H). Four temperate phages plaquing on strain H were isolated from sewage. The archetype, HK620, does not plaque on strains C and K12 of E. coli nor on the LT2 strain of Salmonella enterica. Bacterial mutants resistant to a clear plaque mutant of HK620 produce rough colonies. Some are also galactose-negative, a few are histidine auxotrophs, and most show sensitivity to V. HK620 can transduce a wide variety of auxotrophic mutants of E. coli H to prototrophy. It can recombine with V but its virions resemble those of P22. z 1998 Published by Elsevier Science B.V.
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