Lack of GATC sites in the genome of Streptococcus bovis bacteriophage F4.

A strong bias against GATC sites was observed in the genome of phage F4, a lytic Streptococcus bovis bacteriophage. Only three GATC sites were found within the 60.4-kbp genome of this phage. The comparative lack of GATC sequences within the F4 genome was probably not due to dam methylation, as no modification within this site was detected using methylation-sensitive isoschizomer pair restriction endonuclease analysis. The short oligonucleotide composition of available S. bovis DNA sequences suggested the existence of an unknown mechanism for counterselection of GATC sites in S. bovis bacteriophages.

Genetic homogeneity and phage susceptibility of ruminal strains of Streptococcus bovis isolated in Australia.

The genetic homogeneity of 37 strains of ruminal streptococci was investigated by comparing DNA fragment profiles on agarose gels following restriction endonuclease digestion with Hae III, Cfo I and Msp I. Thirty strains were indistinguishable from Streptococcus bovis strains, 2B, H24 and AR3. The remaining three strains were similar but not identical to a ruminal strain of Strep. intermedius (AR36). In addition, the susceptibility of these strains to infection by five bacteriophages was examined. Three of the phages (phi Sb02, phi Sb03 and phi Sb04) were specific to the strain of Strep. bovis from which they were isolated, while phages 2BV and phi Sb01 infected one and two strains, respectively, in addition to their primary host. It was concluded that although Strep. bovis is relatively homogeneous genetically, broad host range phages appear to be uncommon with this bacterial species.

Lack of surface receptors not restriction-modification system determines F4 phage resistance in Streptococcus bovis II/1.

The resistance of Streptococcus bovis strain II/1, the producer of SbvI restriction endonuclease, to F4 phage infection was demonstrated by the double-agar-layer method. Despite the presence of restriction endonuclease SbvI which can cleave F4 phage DNA to numerous fragments in vitro, the evidence that adsorption inhibition is the most important defence mechanism in phage resistance of S. bovis II/1 strain was obtained by adhesion experiments in vivo. Electron microscopy of phage-host mixtures showed many phage particles on the bacterial surface of phage-sensitive S. bovis 47/3 control strain in comparison with no phage particles seen on S. bovis II/1 (phage-resistant) strain surface.

[Regulation of microbiologic processes in the rumen of ruminants by bacteriophages of Streptococcus bovis]. / Reguliatsiia mikrobiologicheskikh protsessov v rubtse zhbachnykh zhivotnykh bakteriofagami Streptococcus bovis.

Influence of bacteriophages of Streptococcus bovis on microbial activity in the rumen was investigated in experiments on cows. Main elements of the mechanism of bacteriophage action on the microflora have been detected. The daily feeding with bacteriophages results in productive infection of sensitive to them rumen bacteria and is associated with increasing bacteriophage concentration in the rumen contents, lower number and activity of amylolytic bacteria, higher cellolytic activity and increased number of bacteria utilizing xylan, cellobiose and xylose. The fermentation is usually shifted to a higher production of propionate and butyrate at the expense of lower acetate. The regulating action of a single bacteriophage feeding on the rumen microflora and its metabolic activity stops on the fifth day. Daily introduction of bacteriophages into the ration of cows under moderate or high levels of feed increases the milk fat by 0.1-0.3%.