Jonkers Henk M, Ludwig Rebecca, Wit Rutger, Pringault Olivier, Muyzer Gerard, Niemann Helge, Finke Niko, Beer Dirk
Max Planck Institute for Marine Microbiology, 28359 Bremen, Germany.
FEMS Microbiol Ecol. 2003 May 1;44(2):175-89. doi: 10.1016/S0168-6496(02)00464-6.
The benthic microbial mat community of the only permanent hypersaline natural inland lake of Western Europe, 'La Salada de Chiprana', northeastern Spain, was structurally and functionally analyzed. The ionic composition of the lake water is characterized by high concentrations of magnesium and sulfate, which were respectively 0.35 and 0.5 M at the time of sampling while the total salinity was 78 g l(-1). Community composition was analyzed by microscopy, high-performance liquid chromatography (HPLC) pigment analyses and by studying culturable bacteria from different functional groups. Therefore, denaturing gradient gel electrophoresis (DGGE) was applied on most probable number (MPN) dilution cultures. Microscopy revealed that a thin layer of Chloroflexus-like bacteria overlaid various cyanobacteria-dominated layers each characterized by different morphotypes. DGGE analysis of MPN dilution cultures from distinct mat layers showed that various phylotypes of anoxygenic phototrophic, aerobic heterotrophic, colorless sulfur-, and sulfate-reducing bacteria were present. The mats were furthermore functionally studied and attention was focussed on the relationship between oxygenic primary production and the flow of carbon through the microbial community. Microsensor techniques, porewater and sediment photopigment analysis were applied in order to estimate oxygenic photosynthetic rates, daily dynamics of (in)organic carbon porewater concentration and migration behavior of phototrophs. Chiprana microbial mats produced dissolved organic carbon (DOC) both during the day and night. It was estimated that 14% of the mats gross photosynthetic production and 49% of the mats net photosynthetic production diffused out of the mat in the form of low molecular mass fatty acids, although these compounds made up only 2% of the total DOC pool. The high flux of dissolved fatty acids from the microbial mat to the water column may explain why in this system Chloroflexus-like bacteria proliferate on top of the cyanobacterial layers since these photoheterotrophic bacteria grow preferably on organic phototrophic exudates. Furthermore it may also explain why high numbers of viable sulfate-reducing bacteria were found in the fully oxygenated sediment surface layers. These organisms apparently do not have to compete with aerobic heterotrophic community members due to the ample availability of organic substrates. Moreover, the high production of DOC strongly indicates that the mat community was nutrient limited in its growth. Photopigment analysis revealed furthermore that chlorophyll a (Chla) and three of its allomeres had a complementary depth distribution what suggests that the Chla allomeres are functional adaptations to differences in light quality and/or quantity and may be species specific.
对西班牙东北部“奇普拉纳盐湖”（La Salada de Chiprana）——西欧唯一的永久性超咸天然内陆湖的底栖微生物席群落进行了结构和功能分析。湖水的离子组成特点是镁和硫酸盐浓度高，采样时分别为0.35摩尔/升和0.5摩尔/升，而总盐度为78克/升。通过显微镜检查、高效液相色谱（HPLC）色素分析以及研究来自不同功能组的可培养细菌来分析群落组成。因此，对最可能数（MPN）稀释培养物应用了变性梯度凝胶电泳（DGGE）。显微镜检查显示，一层类似绿弯菌属的细菌覆盖在以不同形态类型为特征的各种蓝细菌主导层之上。对来自不同席层的MPN稀释培养物的DGGE分析表明，存在各种类型的无氧光合、好氧异养、无色硫还原和硫酸盐还原细菌。此外，对这些微生物席进行了功能研究，并将重点放在了有氧初级生产与碳在微生物群落中的流动之间的关系上。应用微传感器技术、孔隙水和沉积物光合色素分析来估计有氧光合速率、（有机）无机碳孔隙水浓度的日动态以及光合生物的迁移行为。奇普拉纳微生物席在白天和夜间都会产生溶解有机碳（DOC）。据估计，微生物席总光合产量的14%和净光合产量的49%以低分子质量脂肪酸的形式从微生物席中扩散出来，尽管这些化合物仅占总DOC库的2%。溶解脂肪酸从微生物席到水柱的高通量可能解释了为什么在这个系统中，类似绿弯菌属的细菌在蓝细菌层之上增殖，因为这些光异养细菌优先在有机光合渗出物上生长。此外，这也可能解释了为什么在完全有氧的沉积物表层中发现了大量有活力的硫酸盐还原细菌。由于有机底物充足，这些生物显然不必与好氧异养群落成员竞争。此外，DOC的高产量强烈表明微生物席群落的生长受到营养限制。光合色素分析还显示，叶绿素a（Chla）及其三种同分异构体具有互补的深度分布，这表明Chla同分异构体是对光质和/或光量差异的功能适应，可能具有物种特异性。
