SALT INDUCIBLE-PROTEINS AND CONJUGAL GENE TRANSFER OF HALOTOLERANT Staphylococcus ISOLATED FROM SALINITY SOIL

Abstract

Halotolerent bacteria are those that can tolerate a broad range of NaCl concentrations (0-32% w/v) (Hezayen et al., 2010). So, there are different categories of halotolerant microbes: not tolerate, those which tolerate only a small concentrations of salt about 1%, slightly tolerant (6-8%), moderately tolerant (18-22%) and extremely tolerant, those microbes that grow over the whole range of salt concentrations (0-32%) (Larsen, 1986). Recently, Parthiban et al. (2010) classified halophilic bacteria according to their salt requirement and growth pattern to slight halophiles which growth at 2-5% NaCl, moderate halophiles which growth at 5-20% NaCl and extreme halophiles which growth at 20-30% NaCl. Extreme halophiles are microorganisms that grow under hostile to most organisms. Some of them, such as bacteria which thrive in hypersaline environments have been recognized for their use in biotechnological remediation applications. The applied of halophilic bacteria include recovery of saline soil by directly supporting of growth of vegetation thus indirectly increasing crop yields in saline soil. The other application of halophilic bacteria was in food and pharmaceutical industries, production of enzymes, polymers and various cosmetic products. The possibility of application of halophilic bacteria in soil is recovery and the importance of microbial diversity in soil (Kannika, 2003).
Haophilic microorganisms respond to high salt external environment by accumulating osmotic in their cytosol, which protects them from cytoplasmic dehydration. Osmophily refers to the osmotic aspects of life at high salt concentrations, especially turgor pressure, cellular dehydration and desiccation. Halophily refers to the ionic requirements for life at high salt concentrations. Halophilic microorganisms usually adopt either at the two strategies of survival in saline environments: compatible solute strategy and salt-in strategy. Compatible solute strategy is employed by the majority of moderately halophlic and halotolerant bacteria, some yeasts, algae and fungi. In this strategy, cell maintains low concentrations of salt in their cytoplasm by balancing osmotic potential through the synthesis or uptake of organic compatible solutes. Hence these microorganisms are able to adapt to a wide range of salt concentrations. The compatible solutes include polyols such as glycerol, sugars and their derivatives, amino acids and their derivatives as well as quaternary amines such as glycine betaine and ectoines. Compatible solutes display a general stabilizing effect by preventing the unfolding and denaturation of proteins caused by heating, freezing and drying (Ventosa et al., 1998). The salt-in strategy is employed by true halophilies, including halophilic archaea and extremely halophilic bacteria. These microorganisms are adapted to high salt concentrations and cannot survive when the salinity of the medium is lowered. They generally do not synthesize organic solutes to maintain the osmotic equilibrium. This adaptation involves the selective influx of K+ ions into the cytoplasm. All enzymes and structural cell components must to be adapted to high salt concentrations for proper cell function (Shivanand and Mugeraya, 2011).
Extreme environments such as acidic, thermophilic, hypersaline, and arid regions, are important ‘hot spots’ of microbial ‘megadiversity’. These are habitats of microorganisms which have the genetic and physiological capacity to survive and grow under these harsh or extreme conditions (Woese, 1987; Olsen et al., 1994). Extensive studies have been made in recent years into hyper saline environments resulting in a large number of new halophilic species being isolated e.g. Oceanobacillus aswanensis, it was isolated from salted fish sauce in Aswan city, Egypt (Hezayen et al., 2010), Paenibacillus chungwensis which isolated from Marakanam salterns in India (Parthiban et al., 2010). Gram-negative halophilic (Vibrio, Alteromonas, Acinetobacter, Marinomonas and Pseudomonas) (Prado et al., 1991) and Gram positive halophilic (Staphylococcus, Marinococcus, Sporosarcina Salinococcus and Bacillus) have been recovered from saline soils, salterns and activated sludge (Farrow et al., 1992; Ajibola et al., 2005; Olukanni et al., 2006; Elisangela et al., 2009). Staphylococcus spp., Micrococcus spp. and Bacillus spp. have been isolated from sea water and tropical marine fish but little information has been reported on the species level identities or specific sources of these bacteria (Surendran et al., 1989; Uddin et al., 2001; Rao and Surendran, 2003; Swaminathan et al., 2007; Jeyasekaran et al., 2008).
The main objective of this study was to (1) isolation and characterization of some salt tolerant bacteria from salinity soil in Sharkia Governorate, (2) determine the protein pattern in halophilic bacteria and (3) studying the ability of salt tolerant gene(s) to transfer by natural gene transfer mechanisms.