Bacteriophages of enteric bacteria in drinking water, comparison of their distribution in two countries

The presence of bacteriophages infecting enteric bacteria was tested in more than 1500 drinking water samples in Israel and Spain. Bacteriophages tested were somatic coliphages, F-specific bacteriophages and Bacteroides fragilis bacteriophages. The three groups of bacteriophage were isolated in 100 ml water samples by the presence/absence test with similar frequencies, which ranged from 4.4% for somatic coliphages to 6.1% for bacteriophages infecting Bact. fragilis. In contrast, the frequency of isolation of bacteriophages was significantly higher than the frequency of isolation of faecal coliforms, which averaged only 1.9%. No significant differences were observed between the frequencies of isolation between the samples tested in Spain and those tested in Israel. The percentage of groundwater samples containing faecal coliforms and somatic coliphages was reduced significantly by chlorination, despite known deficiencies. However, there was no effect on the occurrence of F-specific bacteriophages and Bact. fragilis bacteriophages.     

Heat stress reduces the accumulation of rosmarinic acid and the total antioxidant capacity in spearmint (Mentha spicata L)

Selected high‐phenolic lines of spearmint were subjected to a constant 30 °C heat regimen for a period of 4 weeks to determine the effects of heat stress on soluble phenolics, phenols and rosmarinic acid biosynthesis and antioxidant capacity. Heat stress significantly reduced levels of total phenolic acids (71–87%) and soluble phenols (75–87%). This loss was concomitant with a loss of total antioxidant capacity of 21–60% after week 1 and up to 95% by week 4. High‐performance liquid chromatography profiling of heat‐stressed plants at 270 and 320 nm detected nearly a complete loss of rosmarinic acid in all seven chemotypes. High‐temperature drying of non‐heat‐stressed plants at 80 °C resulted in a similar loss of total antioxidant capacity and rosmarinic acid content an effect not observed in material that was subjected to low‐temperature drying first, followed by exposure to high temperature. This suggests that heat stress negatively regulates rosmarinic acid biosynthesis and causes a potential rapid biological breakdown of rosmarinic acid in tissues. 2,2‐Diphenyl‐1‐picrylhydrazyl radical assays of heat‐stressed and non‐stressed plants clearly show that rosmarinic acid is the major contributor to the antioxidant capacity in spearmint. Copyright © 2005 Society of Chemical Industry     

A simple test for differentiation between E. coli and A. aerogenes

An important problem in water quality control is the ability to differentiate between E. coli (faecal) and A. aerogenes (non-faecal) coliforms. To perform this differentiation, a simple test, based on a modification of the selective mFC medium and optimal incubation temperature (37°C) is proposed. Under these specific conditions E. coli bacteria develop into dark blue colonies, whereas A. aerogenes into pink ones. The intermediate coliform bacteria appear greenish-blue or pink, depending on their relation (closeness) to E. coli or A. aerogenes.     

The Mc Carthy's recursion induction principle: «Oldy» but «Goody»

We present here a very fruitful tool for proving properties of LISP functions. We implement the ancient, but quite natural and elegant, Recursion Induction Principle stated by J. Mc Carthy by using the famous fold/unfold method elaborated by R. Burstall and J. Darlington. We thus obtain a very simple and flexible method for proving theorems about LISP functions; we call it the Mc Carthy method. Furthermore the method is machine oriented and we implement it in a conversational system. We do not make any comparison with the R. Boyer and J. Moore theorem-prover since our system is not automatic. But our system is implementable in a wide range of machines and we expect to implement our method in the R. Burstall and J. Darlington system. We then shall have a very powerful system which might perform program synthesis and proofs of program properties simultaneously (in a way parallel to that followed by Z. Manna and R. Waldinger). In this paper we apply our method (by hand) to give the proof of two properties: associativity of the append operation between lists and idempotence of the reverse operation.     

Bacteriophages as viral pollution indicators

f2 Phage, attenuated Polio I (LSC) strain introduced daily to a 350 l. experimental oxidation pond showed no decrease in bacterial viruses f2 or other coliphages or Polio I strain.Ratios of coliphages to human enteric viruses ranged in flood waters from concentrations as low as 1:1 to as high as 10³:1; in wastewater at various seasons the ratio was 10⁵:1; in trickling filter effluents in winter it was 10⁴:1; in spring 10⁵:1, in summer and fall 10⁴:1, in oxidation pond effluents in winter 10³:1; in spring 10⁴:1; and in summer and fall 10³:1. Out of three epidemics in small communities caused by failure of water supply, coliphages were found to be positive. At the same time only two samples of human enteric viruses were positive (the third was contaminated with yeasts).Chlorination experiments using the experimental oxidation pond showed that f2 was most resistant, MS₂ was very resistant, and coliphages were more resistant than attenuated Polio I virus. Experiments with the oxidation pond effluents showed that coliphages were at least as or even more resistant to chlorine than human enteric viruses.     

The effect of pH on the efficiency of chlorine disinfection and virus enumeration

In the light of increasing world-wide water pollution, the controlled and effective chlorination of water is of paramount importance in the treatment of drinking water supplies. A recent publication indicated that hypochlorite ion (OCl⁻) which is formed at high pH levels appeared to be a more effective virucidal form of free chlorine than hypochlorous acid (HOCl), which occurs at lower pH levels. This was a reversal of the findings of many other research workers. The present paper reports on a further study which confirms that HOCl is a more effective virucide than OCl⁻. It also reports on comparative studies between the PFU and TCID₅₀ methods for virus evaluation at two pH levels in an attempt to find the reasons for the reversal in the results obtained.