Article thumbnail
Location of Repository

Conjugal Transfer of Bacteriophage Resistance Determinants on pTR2030 into Streptococcus cremoris Strains

By Wesley D. Sing and Todd R. Klaenhammer


Agar surface conjugal matings were used to introduce heat-sensitive phage resistance (Hsp(+)) determinants carried on the conjugal plasmid pTR2030 into Streptococcus cremoris KH, HP, 924, and TDM1. Lactose-fermenting (Lac(+)) transconjugants were selected from matings of Lac(−) variants of S. cremoris KH, HP, 924, and TDM1 with Streptococcus lactis ME2 or a high-frequency donor, S. lactis T-EK1 (pTR1040, Lac(+); pTR2030, Hsp(+)). For all of the S. cremoris strains examined, select Lac(+) transconjugants were completely resistant to plaquing by their homologous lytic phages. In all cases the plaquing efficiencies were less than 10(−9). Acquisition of a 30-megadalton plasmid (pTR2030) in the S. cremoris phage-resistant transconjugants was demonstrated by direct plasmid analysis, by hybridization with (32)P-labeled probes, or by conjugal transfer of pTR2030 out of the phage-resistant transconjugants into a plasmid-cured recipient, S. lactis LM2302. Acid production, coagulation ability, and proteolytic activity of phage-resistant transconjugants in milk were comparable to those of their phage-sensitive parents. Further, S. cremoris phage-resistant transconjugants were not attacked by phage in starter culture activity tests, which included a 40°C incubation period. The results demonstrated that phage resistance determinants on pTR2030 could be conjugally transferred to a variety of S. cremoris strains and confer resistance to phage under conditions encountered during cheese manufacture. Phage-resistant transconjugants of S. cremoris M43 and HP were also constructed without the use of antiblotic markers to select conjugal recipients from mating mixtures

Topics: Genetics and Molecular Biology
Year: 1986
OAI identifier:
Provided by: PubMed Central
Sorry, our data provider has not provided any external links therefore we are unable to provide a link to the full text.

Suggested articles

To submit an update or takedown request for this paper, please submit an Update/Correction/Removal Request.