Kompantseva E I, Sorokin D Iu, Gorlenko V M, Namsaraev B B
Mikrobiologiia. 2005 May-Jun;74(3):410-9.
The structure of the phototrophic community found in Lake Khilganta (the Agin-Buryat Autonomous Area), a shallow saline soda lake (depth, 35-45 cm; water mineralization, 45 g/l; alkalinity, 30 mg-equiv/l; pH 9.5) has been studied. The bottom of the lake is covered with a 10- to 15-mm microbial mat, whose basis is formed by the filamentous cyanobacterium Microcoleus chthonoplastes. The mat exhibits pronounced layering and contains a significant amount of minerals. Six zones, which have characteristic colors and consistencies and are composed of intermittent layers, have been identified along the vertical profile. Live phototrophic bacteria have been found in the three upper zones. The bulk of the cyanobacteria is concentrated in the upper zone. In the lower zones, the development of purple bacteria has been observed. The diurnal dynamics of the vertical distribution of phototrophic microorganisms, which results from variations in the physicochemical environmental parameters, is described. Ectothiorhodospira sp. are dominant among the anoxyphotobacteria present. Their number, determined according to the inoculation method, is 10(6)-10(7) cells/ml. The purple bacteria of the genera Allochromatium, Thiocapsa, and Rhodovulum are also present. Experiments with isolated pure cultures have shown that the anoxygenic photosynthetic bacteria of Lake Khilganta are halotolerant and alkalitolerant or alkaliphilic. In liquid enrichment cultures, at pH 9.5, the ratio of anoxyphotobacteria species is close to that observed in the lake. When the pH is increased to 10.4, it is Ectothiorhodospira, which is the most adapted to life under increased mineralization and alkalinity, that predominantly develops. Photosynthetic activity has been observed in the three upper mat zones and constitutes, on average, 1.5 g C/(m2 h); the share of anoxygenic photosynthesis accounts for 75-95% of the total productivity. The main role in sulfide oxidation belongs to the phototrophic anoxyphotobacteria and cyanobacteria. In terms of the physicochemical conditions and structure of the phototrophic community, Lake Khilganta is similar to shallow saline water bodies of marine origin. The main differences consist in the increased alkalinity and in the consequent prevalence of alkaliphilic and alkalitolerant microorganisms and in the absence of representatives of the neutrophilic group of green sulfur bacteria.
对位于阿金-布里亚特自治区的希尔甘塔湖（一个浅水盐碱湖，深度35 - 45厘米；水矿化度45克/升；碱度30毫克当量/升；pH值9.5）中光合生物群落的结构进行了研究。湖底覆盖着一层10至15毫米厚的微生物垫，其基础由丝状蓝细菌微小鞘丝藻形成。该微生物垫呈现出明显的分层，并且含有大量矿物质。沿垂直剖面已识别出六个具有特征颜色和稠度且由间断层组成的区域。在上部三个区域发现了活的光合细菌。蓝细菌的主体集中在上部区域。在下部区域，观察到紫色细菌的生长。描述了由物理化学环境参数变化导致的光合微生物垂直分布的昼夜动态。在存在的厌氧光合细菌中，外硫红螺菌属占主导。根据接种法测定，其数量为10⁶ - 10⁷个细胞/毫升。还存在嗜盐色菌属、荚硫菌属和红环菌属的紫色细菌。对分离出的纯培养物进行的实验表明，希尔甘塔湖的厌氧光合细菌具有耐盐性和耐碱性或嗜碱性。在液体富集培养中，在pH值9.5时，厌氧光合细菌种类的比例与在湖中观察到的相近。当pH值升至10.4时，最适应在矿化度和碱度增加条件下生存的外硫红螺菌占主导生长。在微生物垫上部的三个区域观察到了光合活性，平均为1.5克碳/（平方米·小时）；厌氧光合作用的份额占总生产力的75 - 95%。硫化物氧化的主要作用属于光合厌氧光合细菌和蓝细菌。就光合生物群落的物理化学条件和结构而言，希尔甘塔湖类似于海洋起源的浅盐水体。主要区别在于碱度增加，以及随之而来的嗜碱性和耐碱性微生物的普遍存在，并且不存在嗜中性绿硫细菌群的代表。
