Laboratory of Microbiology, Department of Biology and Institute of Aquatic Ecology, University of Girona, Hospital 6, E-17071, Girona, Spain.
Photosynth Res. 1994 Jul;41(1):53-65. doi: 10.1007/BF02184145.
The effect of light quality on the selection of natural populations of Green Sulfur Bacteria (Chlorobiaceae) is considered to be a classic factor in the determination of their ecological niches. From the comparison among phototrophic bacterial populations of lakes, it is shown that brown and green pigmented groups of Chlorobiaceae have a differential distribution depending on depth. Statistical analyses prove that green species, which dominate at shallow oxic/anoxic boundaries, are correlated to light spectra enriched in long wavelengths, while brown ones are found when light spectra are enriched in the central region of the spectrum, as in deeper lake layers. Physiological experiments have been made withChlorobium limicola andC. phaeobacteroides cultures placed under different light quality conditions, in order to verify these hypotheses made on a field data basis. Results show that red and white light has more positive effects on the green bacterium than on the brown. Blue and green light illuminations have opposite consequences. Therefore, the effect of shallow depths and Chromatiaceae shading-which also increases the proportion of long wavelengths in light spectra-benefits the bacteriochlorophyll-based strategies of green species. On the other hand, the carotenoid-based strategies of brown ones are favored by the light climates usually dominant at greater depths. Thus, brown species are considered to be singular adaptations of Chlorobiaceae to depth, where bacteriochlorophyll light-harvesting is strongly limited by light quality.
光是影响绿硫细菌（绿菌科）自然种群选择的重要因素，这被认为是决定其生态位的经典因素之一。从湖泊中光养细菌种群的比较中可以看出，绿菌科中的棕色和绿色色素群体的分布存在差异，这取决于深度。统计分析证明，在浅氧化/缺氧边界占优势的绿色物种与长波长光光谱有关，而在光光谱富含光谱中心区域的情况下则存在棕色物种，如在较深的湖层中。为了验证基于野外数据提出的这些假设，已经对置于不同光质条件下的绿硫菌（Chlorobium limicola）和噬硫菌（C. phaeobacteroides）培养物进行了生理实验。结果表明，红光和白光对绿菌的影响比棕色菌更为积极。蓝光和绿光照射则有相反的后果。因此，浅深度和 Chromatiaceae 遮光的影响——这也增加了光光谱中长波长的比例——有利于基于细菌叶绿素的绿色物种策略。另一方面，棕色物种基于类胡萝卜素的策略则有利于在较深水域中通常占主导地位的光照条件。因此，棕色物种被认为是绿菌科对深度的独特适应，在深度条件下，细菌叶绿素的光捕获受到光质的强烈限制。
