The first step in phage infection is the attachment of the phage to the host cell surface. This is typically accomplished by the recognition of a receptor on the outside of the bacterial cell wall such as an antigen, pilus or other structure. There is much variability from phage to phage in terms of which receptor they bind to. Bacteriophage can generally be classified into two categories, lysogenic and lytic (virulent) (Fig 6). The choice between the lytic and lysogenic cycle depends on the relative expression rates of phage repressor encoded by a cII gene (promoting lysogeny) and cro protein, capable of turning off repressor gene expression and starting the lytic pathway (Campbell, 1967). The lysogenic cycle has been observing in dsDNA
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This happens sequentially, which allows the phage assembly to take place. In tailed phages, this often begins with the head and the tail proteins independently. Once the head is assembled, the phage DNA is packed in. The tail subsequently attaches to the head. Once this is complete smaller extremities are added to the tail, for example, in the case of the T4 phage, its tail fibers. Phages remain in the bacteria as other phages are produced concurrently. Digestive enzymes encoded in the phages genome are eventually activated and transcribed, which causes the lysis of the host bacteria. This releases the newly assembled phages into the environment, each of which can infect a new host bacteria cell. T2, T4 and lambda phages are common lytic phages (Pelczar et al., 1988; Maloy et al., 1994; Gottesman and Oppenheim, 1994).
Pseudolysogeny is a form of phage-host cell interaction, where the nucleic acid of the phage resides within the bacterial cell in an unstable, inactive state. Pseudolysogeny occurs mainly when the host is exposed to starvation (Williamson et al., 2001). When proper nutrients are added, the pseudolysogenic state is resolved to result in either the establishment of true lysogeny or the initiation of the lytic production of progeny virions (Ripp and
This happens sequentially, which allows the phage assembly to take place. In tailed phages, this often begins with the head and the tail proteins independently. Once the head is assembled, the phage DNA is packed in. The tail subsequently attaches to the head. Once this is complete smaller extremities are added to the tail, for example, in the case of the T4 phage, its tail fibers. Phages remain in the bacteria as other phages are produced concurrently. Digestive enzymes encoded in the phages genome are eventually activated and transcribed, which causes the lysis of the host bacteria. This releases the newly assembled phages into the environment, each of which can infect a new host bacteria cell. T2, T4 and lambda phages are common lytic phages (Pelczar et al., 1988; Maloy et al., 1994; Gottesman and Oppenheim, 1994).
Pseudolysogeny is a form of phage-host cell interaction, where the nucleic acid of the phage resides within the bacterial cell in an unstable, inactive state. Pseudolysogeny occurs mainly when the host is exposed to starvation (Williamson et al., 2001). When proper nutrients are added, the pseudolysogenic state is resolved to result in either the establishment of true lysogeny or the initiation of the lytic production of progeny virions (Ripp and