CHARACTERIZATION AND HABITATS OF BACTERIA AND YEASTS

Abstract: Several strains of bacteria and yeasts were isolated at various depths of a meromictic lake, Lake Vanda, to clarify their physiological properties in rela-tion to their habitats. Gram-negative rods, strains T-1, T-2, T-6, T-14, 3B, and Pseudomonas sp. 3G, were isolated at depths of above 30 m where the temperature is 5-7OC and the chlorinity is low. T-1, T-6, 3B, and 3G grow aerobically below 27OC, optimally about 20Â ° under low salt concentration ( < I % NaCI). Gram-negative aerobic cocci, strains 13A-F, were isolated at a depth of 69 m near the bottom where the temperature is 24OC and the chlorinity is high, up to 76.5glkg. Strain 13A grows aerobically at 12-36OC, optimally about 30Â ° under the addition of 0 to 10 % NaCI to the culture medium. T-1, T-6, 3G. and 13A contain more than 81 % of unsaturated fatty acids such as oleic acid (1 8: 1) and palmitoleic acid (16: 1). The yeast Candida sp. strains T-3, T-4, T-5, T-9, and T-11 isolated at a depth of 5 m grow below 25OC, optimally about 15OC. They are fermentable and can utilize various sugars such as glucose and sucrose. T-5 and T-9 have 74% and 86 % of unsaturated fatty acids such as linoleic acid (18: 2), respectively. The presences of psychrophilic bacteria and yeasts in the water column (5-30 m), and of halotolerant bacteria in the bottom water (69 m) well correspond to the mero-mictic property of the lake. 1