Partial FI gene-independence of lambda-21 hybrid phages specifying chimeric terminases

Area of Science:

• Molecular Biology
• Virology
• Bacteriophage Genetics

Background:

• Bacteriophages, such as lambda-21, possess genes essential for their replication and life cycle.
• Terminases are key enzymes involved in phage DNA packaging.
• The FI gene product (gpFI) is known to influence the life cycle of certain phages.

Purpose of the Study:

• To investigate the role of the FI gene in the life cycle of lambda-21 hybrid phages.
• To determine the dependence of chimeric lambda-21 terminases on the FI gene product.
• To compare the growth characteristics of FI-positive and FI-negative hybrid phages.

Main Methods:

• Construction of isogenic series of FI-positive (FI+) and FI-negative (FI-) derivatives of lambda-21 hybrid phages.
• Examination of plaque formation and burst size for different hybrid phage derivatives.
• Comparative analysis of phage growth in the presence and absence of the FI gene product.

Main Results:

• Three of the four lambda-21 hybrid phages (51, 67, 33) exhibited plaque formation and small burst sizes in the absence of gpFI, but grew significantly better with gpFI.
• All three chimeric terminases showed dependence on gpFI.
• The FI- hybrid phages grew better than lambda FI-, suggesting differences in chimeric terminases.
• Hybrid 54, producing an infirm terminase, showed greater dependence on gpFI than other hybrids and lambda.

Conclusions:

• The FI gene product (gpFI) is essential for optimal growth of most lambda-21 hybrid phages with chimeric terminases.
• Chimeric terminases exhibit varying degrees of dependence on gpFI.
• Differences in chimeric terminase structure or function may explain their altered dependence on gpFI compared to wild-type lambda terminase.