Role of the Host Cell in Bacteriophage T4 Development

Author: Stitt, Barbara Landale

Year: 1978

Degree: Dissertation (Ph.D.)

Advisor: Wood, William Barry

Committee Member: Unknown, Unknown

Option: Biochemistry

DOI: 10.7907/aez8-c005

Abstract

More than six hundred mutant host-defective bacteria were selected that were able to adsorb and be killed by phage T4+ but were unable to support its growth. The mutants were categorized into seven classes and representatives were screened to determine the nature of the host block. The majority of the mutants clearly blocked in phage assembly interfered with T4+ capsid formation at the very early level of gene 31 function. gp31 acts at or before head core formation, which precedes the assembly of proheads and the formation of the capsid proper. Mutant phage able to overcome the host block carried mutations in either gene 31 or in the gene for the major capsid protein. The host mutations all mapped near purA, at two or possibly three different sites.

A host mutant class that only marginally passed our screens for assembly-related mutants had a pleiotropic effect on T4+ growth: specific, unidentified early phage proteins were made in reduced quantity or not at all; phage DNA synthesis was depressed 50%; specific late, structural phage proteins including some tail-baseplate and phage collar components were reduced or missing, and host cell lysis was delayed and slow. Phage that could overcome this block mapped in functionally undefined regions of the T4 genome, most near gene 39. The host mutation mapped to within 0.5 minutes of nalA

Possible mechanisms of action for the various host mutations are discussed.

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