Role of Bacterial Pathogens in Alteration of Physiological and Nutritional State of Common Cultured Fishes

Abstract

Diseases caused by bacterial are associated with substantial death in both wild newlineand cultured fishes. The authentic part of these pathogenic microorganisms may vary newlinefrom a prime pathogen to that of an opportunistic pathogen that imparts its host newlinedecline by initiating a disease process. newlineAn exoenzyme or extracellular enzyme is an enzyme which is secreted by the newlinecells and works outside of that cell. It is usually used for breaking down large newlinemolecules that would not be able to enter the cell otherwise. Bacteria secrete newlineexoenzymes to hydrolize macromolecules into smaller molecules capable of being newlinetransported across the cytoplasmic membrane into the cytoplasm which is the site of newlinemost bacterial metabolism. Extracellular enzymes produced by bacteria are one of the newlinemajor factors for their pathogenesis. Chitinase, lipase, protease and lecithinase are newlineamong these enzymes catalizing the process of infection. Some pathogenic bacteria newlineare able to produce and secrete enzymes that compromise cell structure of the host newlineand enable the bacteria to work their way further into the body. Interestingly, proteins newlinesecreted also contributes to virulence factors or enzymes such as invasins, lecithinase newlineand other common lipases and proteases (Secades and Guijarro, 1999; Lafferty, newline2008). newlineIntensive culture of fish involves high rate of stocking and the abnormal newlinedensity (crowding) of fishes, leading to susceptibility to communicable diseases, and newlineconsequent total destruction. There is a wide spread belief that an average hatchery is newlinea hot bed of disease, where ailing fish are a rule rather than an exception. newlineInfection in fishes brings about deleterious effects in their growth, resistance newlineto stress and fecundity, and in addition, they are vulnerable to predation and sub newlineoptimal environmental factors. All these variables decimate the fish, indirectly newlineimpinging a heavy economic loss to the fish farmers, and it becomes imperative for newlinethem to control the infection by constant surveillance and development of adequate newlinecontrol measures to prevent sp