Phage Therapy of Vibrio Harveyi 31antibiotic with the hope to prevent the bacterial epidemic. Using astronomical
amounts of antibiotic in shrimp farms cause various problems: e.g., the
extravagant expense, environmental concern, lower shrimp quality with the
excessive dose of antibiotics which become unacceptable in high standard
market. Also, this action increases the potential of antibiotic resistant
pathogens to consumers (Durans and Marshall, 2005). The study of phage
therapy is an interesting concept to pursue in the shrimp industry, especially
with regard to the green environmental concept.
INFECTION PATHWAY OF BACTERIOPHAGE
There are two main kinds of phages which are virulent and temperate
phage. Virulent phage infects the bacterial cell by the mechanism of lytic
infection only and it is also called as lytic phage. Lytic infection is
synonymous to acute infection which causes the bacterial cell death
immediately once it infects (Dimmock et al., 2001; Cairns et al., 2009). On the
other hand, temperate phage can infect bacterial cells not only by lytic
infection but also lysogenic infection. Lysogenic infection closely resembles
chronic or persistent infection as in high animals and human (Dimmock et al.,
2001). Most of the temperate phages cause lysogenic infection by integrating
their genomes into the bacterial chromosomes and exist as a parasite but does
not kill the bacterial hosts. Thus, in the lysogenic infection, the phage and
bacteria live together accommodatingly (Dimmock et al., 2001, Pasharawipas
et al., 2005). However, during division in the early stages of temperate phage
infection, the generated bacterial cells can become either lytic or lysogenic
infection. (Dimmock et al., 2001). There is no clear explanation of this
phenomenon why the temperate phage behaves to switch from lytic to
lysogenic infection. However, we know that the expression of two sets of
genomes in temperate phage substitutes between lytic and lysogenic infection
(Stahl, 1998). While the first group of genes, such as Cro gene, influences the
lytic infection, the other set of genome, for example CI gene, plays a role to
express lysogenic infection (Stahl, 1998; Dimmock et al., 2001, Oppenheim et
al., 2005). The influential factor to activate the CI and Cro genes to alternate
their roles is not well understood. However, ultraviolet and organic substances
such as mitomycin-C are reported to induce the lysogenic infection of the
temperate phage to a lytic infection (d'Ari, 1985).