Molecular Characterization and Gene Expression Profiling ... - CUSAT

6.1. Introduction
Chapter 6
Prophylactic approach is gaining more importance in aquaculture,
because of the ever increasing incidence of viral pathogens and the ban of
many antibiotics in aquaculture. Antibiotic therapy kills beneficial microbes
besides pathogens affecting aquatic ecosystem health and emergence of
resistant microbial strains leaving deadly diseases untreatable in animals.
Several alternative strategies for the prevention and control of diseases have
been proposed and have already been applied successfully in aquaculture,
such as the use of vaccines, immunostimulants and probiotics (Ahilan, 2003).
Only in the late 1980’s did the first publication on biological control in
aquaculture emerged and since then the research effort has continually
increased. In the last two decades, there has been growing interest in bio-
control of microbial pathogens in aquaculture using antagonistic
microorganisms (Westerdahl et al., 1991; Maeda, 1994). The concept of
microfloral manipulation was first appreciated by Metchnikoff in 1907, who
viewed the consumption of yoghurt by Bulgarian peasants as conferring
long span of life. Elie Metchnikoff’s work at the beginning of 20 th century is
regarded as the first work on probiotics (Fuller, 1992). He described them as
“microbes ingested with the aim of promoting good health”. Fuller (1989)
defined probiotics as ‘A live microbial feed supplement, which beneficially
affects the host animal by improving its microbial intestinal balance’. The
new definition of probiotics is that it is ‘a mono- or mixed culture of live
microorganisms which, applied to animal or man, affect beneficially the host
by improving the properties of the indigenous micro flora’.
Commonly, probiotics are considered as the counter part of
antibiotics. While antibiotics are chemical compounds produced by living
Molecular Characterization and Gene Expression Profiling of Antimicrobial Peptides in Penaeid Shrimps
338