Concomitant Conjugal Transfer of Reduced-Bacteriophage-Sensitivity Mechanisms with Lactose- and Sucrose-Fermenting Ability in Lactic Streptococci †

Maeve C. Murphy, James L. Steele, Charles Daly, Larry L. McKay
1988 Applied and Environmental Microbiology  
Ten previously reported lactose-positive (Lac') transconjugants from Streptococcus lactis, S. cremoris, and S. lactis subsp. diacetylactis and one sucrose-positive (Suc+) transconjugant from S. lactis were examined for their sensitivity to prolate-and small isometric-headed bacteriophages. Four of the Lac+ transconjugants showed a 10to 100-fold reduction in the efficiency of plating (EOP) as well as a reduced plaque size for the prolate phage c2 and were insensitive to the small isometric phage
more » ... all isometric phage 712. A fifth Lac' transconjugant demonstrated a similar reduced sensitivity to phage c2; however, this transconjugant was able to plaque phage 712, but with a reduced plaque size and EOP. The other five Lac' transconjugants were sensitive to both c2 and 712 phages. The Suc+ transconjugant plaqued phage 712 with a reduced plaque size and EOP, but no reduction in plaque size or EOP was observed for phage c2. The Lac' and reduced bacteriophage sensitivity (Rbs+) phenotypes were correlated with specific plasmids in the Lac' transconjugants. As four of the Lac' transconjugants exhibited a phenotypically indistinguishable Rbs+, one (ABO01) was selected for further study. The Rbs+ in ABOOl for both small isometricand prolate-headed phages was not related to adsorption, and the reduced EOP for phage c2 was not related to the presence of a restriction and modification system. The latent period for phage c2 was unchanged, but the burst size was reduced 80%. The presence of the plasmid coding for Rbs+ retarded the lysis of a mitomycin C-induced prophage-containing strain. The Rbs+ mechanism appears to be abortive phage infection. This study supports previous observations that Rbs+ and conjugal transfer ability are physically linked among some group N streptococci. The results presented have implications in the identification of plasmids coding for Rbs+ and may also aid in explaining the dissemination of Rbs+ genes among lactic streptococci. plaquing with the appropriate host on M17-glucose agar (29) . Plates were incubated at 21, 30, and 37°C. Cultures for 1951 on May 5, 2020 by guest Downloaded from 736. APPL. ENVIRON. MICROBIOL. on May 5, 2020 by guest Downloaded from
doi:10.1128/aem.54.8.1951-1956.1988 fatcat:pez75agn5zfjzep6dhebpvd4la