The host-phage reactions of 20 strains of lactic streptococci currently used in cheese manufacture, and the phages active on them, were studied under a variety of conditions. The phages of the lactic streptococci conformed in their behaviour with the general behaviour of phages for other bacterial species. The burst size of phages which attack one strain of starter culture varied widely and also varied when one phage attacked different host strains. The burst size of a phage was also influenced by the host on which it was previously propagated. An increase of temperature from 30 to 37 °C usually decreased the latent period, but it increased, decreased, or had no effect on the burst size. This increase in temperature also usually decreased the percentage adsorption of phage. Rennet at a concentration of 0-02 % significantly reduced the percentage adsorption of phage in sterile reconstituted milk and also in tryptone yeast-extract broth.

When M17 broth was used as growth medium before preparation of cell walls, adsorption of phage eb7 on Streptococcus cremoris EB7 at pH 4.0 was stimulated. When preparation included treatment with trypsin, absorption of phage was 65%. Without trypsin treatment, absorption was 81%. Only 10 to 20% of the adsorption was irreversible. Treatment with pepsin or commercial rennet but not pure chymosin prevented adsorption on non-trypsin-treated cell walls. D-Galactosamine treatment of phage eb7 had an inactivating effect which was enhanced by Lrhamnose.

No abstract

To investigate the effects of hydrated lime on the survival of Cryptosporidium oocysts, the percentage viability of oocysts was assessed using fluorescent in situ hybridisation. In the absence of lime and with lime at a concentration of 1 per cent, there was a gradual decline in oocyst viability during the 10-day trial. Although the addition of 5 or 10 per cent lime caused the total number of oocysts to decrease, there appeared to be an increase in the proportion of potentially viable oocysts.