Häusler Stefan, Weber Miriam, Siebert Christian, Holtappels Moritz, Noriega-Ortega Beatriz E, De Beer Dirk, Ionescu Danny
Max Planck Institute for Marine Microbiology, Bremen, Germany.
FEMS Microbiol Ecol. 2014 Dec;90(3):956-69. doi: 10.1111/1574-6941.12449. Epub 2014 Nov 17.
Abundant microbial mats, recently discovered in underwater freshwater springs in the hypersaline Dead Sea, are mostly dominated by sulfur-oxidizing bacteria. We investigated the source of sulfide and the activity of these communities. Isotopic analysis of sulfide and sulfate in the spring water showed a fractionation of 39-50‰ indicative of active sulfate reduction. Sulfate reduction rates (SRR) in the spring sediment (< 2.8 nmol cm(-3) day(-1)) are too low to account for the measured sulfide flux. Thus, sulfide from the springs, locally reduced salinity and O2 from the Dead Sea water are responsible for the abundant microbial biomass around the springs. The springs flow is highly variable and accordingly the local salinities. We speculate that the development of microbial mats dominated by either Sulfurimonas/Sulfurovum-like or Thiobacillus/Acidithiobacillus-like sulfide-oxidizing bacteria, results from different mean salinities in the microenvironment of the mats. SRR of up to 10 nmol cm(-3) day(-1) detected in the Dead Sea sediment are surprisingly higher than in the less saline springs. While this shows the presence of an extremely halophilic sulfate-reducing bacteria community in the Dead Sea sediments, it also suggests that extensive salinity fluctuations limit these communities in the springs due to increased energetic demands for osmoregulation.
最近在高盐度死海的水下淡水泉中发现了丰富的微生物垫，其中大多以硫氧化细菌为主。我们研究了硫化物的来源以及这些群落的活性。对泉水硫化物和硫酸盐的同位素分析显示分馏率为39 - 50‰，表明存在活跃的硫酸盐还原作用。泉水沉积物中的硫酸盐还原率（SRR）（< 2.8 nmol cm⁻³ 天⁻¹）过低，无法解释所测得的硫化物通量。因此，泉水中的硫化物、局部降低的盐度以及死海海水中的氧气，是泉周围丰富微生物生物量的成因。泉水流量变化很大，相应地局部盐度也变化很大。我们推测，以类似硫单胞菌属/硫卵菌属或类似硫杆菌属/嗜酸硫杆菌属的硫氧化细菌为主导的微生物垫的形成，是由于垫子微环境中不同的平均盐度所致。在死海沉积物中检测到的高达10 nmol cm⁻³ 天⁻¹ 的SRR，出人意料地高于盐度较低的泉水。这表明死海沉积物中存在一个极端嗜盐的硫酸盐还原细菌群落，但同时也表明，由于渗透调节所需能量增加，泉水中盐度的大幅波动限制了这些群落的生存。
