Synergistic Effects of abiE or abiF from pNP40 When Cloned in Combination with abiD from pBF61

¹ Department of Food Science and Nutrition, University of Minnesota, St. Paul 55108

Two fragments conferring partial phage resistance were located on plasmid pNP40 from Lactococcus lactis ssp. lactis biovar diacetylactis DRC3 and cloned. A 2.3-kb PstI fragment from pNP40 containing abiF conferred partial phage resistance to prolate-headed phage c2, and a 4.8-kb PstI fragment of pNP40 containing abiE conferred partial phage resistance to small isometric-headed phage sk1. When each of the two fragments was cloned individually into a plasmid containing the abortive phage infection gene abiD from L. lactis ssp. lactis KR5, phage resistance was enhanced. When cloned with abiD, the 2.3-kb PstI fragment enhanced the resistance against prolate-headed phages, as was indicated by a 400-fold decrease in the efficiency of plating compared with that of abiD alone. When the 4.8-kb PstI fragment of pNP40 was cloned with abiD, resistance to small isometric-headed phages was enhanced, as was indicated by a greater than 50-fold decrease in efficiency of plating compared with that of abiD alone. The 4.8-kb PstI fragment of pNP40 cloned with abiD showed a large decrease (500- to 1000-fold) in efficiency of plating against prolate-headed phages, even though the 4.8-kb PstI fragment of pNP40 by itself conferred no resistance to the prolate-headed phages.

Key Words: bacteriophage • phage resistance • abortive infection • Lactococcus lactis)

Submitted on May 1, 1997
Accepted on September 15, 1997

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