Extremely Halophilic Bacterial Communities in Şereflikoçhisar Salt Lake in Turkey

Authors: MERAL BİRBİR, CENK SESAL

Abstract: Şereflikoçhisar Lake is the largest salt lake in central Turkey. This lake is a major source of solar salt for food, hide and other industries locally. Due to the economic importance of salt obtained from this lake, a microbial survey has been conducted. Six salt and three brine samples were obtained from the lake for physico-chemical and microbiological analyses. Physico-chemical analysis showed that the salts and brines contain sufficient ions and hardness to support extremely halophilic bacteria. The salt collected from the lake contained 10^4-10^6 colony-forming units of extremely halophilic bacteria per gram and brine taken from the lake contained 10^3-10^5 colony-forming units of extremely halophilic bacteria per ml. Colonial pigmentation from these samples ranged from blood-red to pale-pink. A total of 82 extremely halophilic aerobic strains were isolated from the salt and brine samples, 32 of which were randomly selected strains examined in greater detail. While brick-red colonies outnumbered all other colony pigmentations, the lake does appear to support a diverse bacterial community. Most colonies were 1 to 2 mm in diameter, circular, convex, glistening and entire. Optimum growth occurred at 25% (w/v) NaCl at 40 ºC and a pH of 7.5. Seventeen strains required at least 10% (w/v) NaCl for growth. Most cells of the strains were pleomorphic and stained Gram-negative. All strains were motile. Some of these strains produced industrially important enzymes such as lipases, gelatinases, cellulases and \beta-galactosidases. All of the strains hydrolysed Tween 80. Twenty-three strains produced gelatinase enzymes. Cellulase enzymes were produced by 14 of these strains. Only one strain showed positive \beta-galactosidase activity. Ten strains produced indol from tryptophan. Twenty-three strains showed positive methyl-red reactions. All strains showed negative Voges-Proskauer reactions. Thirty-two strains were tested by the disc diffusion method for their sensitivity to 13 different antibiotics. Most of these strains were resistant to ampicillin (10 µg), chloramphenicol (30 µg), cefadroxil (30 µg), erythromycin (15 µg), penicillin G (10U) and streptomycin (25 µg). All strains were resistant to amikacin (30 µg), ciprofloxacin (5 µg), neomycin (30 µg) and spiramycin (100 µg). Most strains were sensitive to bacitracin (10 U) and novobiocin (5 µg). Half of these strains were sensitive to sulfamethoxazole and trimethoprim (25 µg). These studies showed that Şereflikoçhisar Salt Lake is an optimal environment for extremely halophilic bacteria and the lake contains a viable, diverse, potentially and industrially important bacterial community. The extremely halophilic proteolytic bacterial contents of the salt and brine samples were too high to use directly in hide preservation. The presence of proteolytic strains in the lake's salt may cause an important quality problem in the leather business.

Keywords: Şereflikoçhisar Salt Lake, extremely halophilic bacteria, antibiotic sensivity, halophilic enzymes

Full Text: PDF