Factors Influencing Attachment, Entry and DNA Synthesis of Bacteriophage ∅X174 in Escherichia Coli Host Cells
Date of Award
Dissertation - Restricted
Doctor of Philosophy (PhD)
Walter W. Fredrick
The process of infection by bacteriophage ∅X174 has
been fairly well characterized. However, the majority of
the instigators examining this problem have dealt with
the events which occur once the virus has entered its host cell. The purpose of this dissertation has been to look more closely at the early steps of ∅X174 infection,
adsorption of the phage t o the cell surface, and the
penetration of its DNA into the cell.
∅X174 does not possess some of the more elaborate
mechanisms of attachment and DNA injection as do the more complex tailed bacteriophages (e.g., T2, T4, λ). Its very simplicity has made it difficult to analyze. It adsorbs to some component in the outer membrane of the cell wall, where it undergoes a structural change and releases its DNA. The nature of this attachment site and the details of the interaction are still poorly understood.
The free viral DNA then enters the cell where it is replicated prior to the formation of several hundred progeny phage. The mechanism through which the DNA penetrates the cell membrane is unknown. Also, the extent of host cell contributions to the DNA replication process needs further examination.
The attachment of the phage particle to the cell surface
was studied by isolating the ∅X174 receptor site from the cell wall of Escherichia coli C by the method of cold osmotic shock. The effects of this site upon the virus were investigated using sucrose gradient sedimentation analyses and other biophysical and biochemical techniques. These help to provide a clear picture of the sequence of events occurring during the initial stages of ∅X infection.
The entry of ∅X174 viral DNA into host cells and its subsequent replication was also briefly examined. Inhibitors of metabolism and enzymatic processes were employed to elucidate the cellular functions involved in these events.