Hinck Susanne, Neu Thomas R, Lavik Gaute, Mussmann Marc, de Beer Dirk, Jonkers Henk M
Max Planck Institute for Marine Microbiology, Celsiusstr. 1, D-28359 Bremen, Germany.
Appl Environ Microbiol. 2007 Nov;73(21):7013-22. doi: 10.1128/AEM.00548-07. Epub 2007 Aug 31.
The aim of this study was to investigate the supposed vertical diel migration and the accompanying physiology of Beggiatoa bacteria from hypersaline microbial mats. We combined microsensor, stable-isotope, and molecular techniques to clarify the phylogeny and physiology of the most dominant species inhabiting mats of the natural hypersaline Lake Chiprana, Spain. The most dominant morphotype had a filament diameter of 6 to 8 microm and a length varying from 1 to >10 mm. Phylogenetic analysis by 16S rRNA gene comparison revealed that this type appeared to be most closely related (91% sequence identity) to the narrow (4-microm diameter) nonvacuolated marine strain MS-81-6. Stable-isotope analysis showed that the Lake Chiprana species could store nitrate intracellularly to 40 mM. The presence of large intracellular vacuoles was confirmed by fluorescein isothiocyanate staining and subsequent confocal microscopy. In illuminated mats, their highest abundance was found at a depth of 8 mm, where oxygen and sulfide co-occurred. However, in the dark, the highest Beggiatoa densities occurred at 7 mm, and the whole population was present in the anoxic zone of the mat. Our findings suggest that hypersaline Beggiatoa bacteria oxidize sulfide with oxygen under light conditions and with internally stored nitrate under dark conditions. It was concluded that nitrate storage by Beggiatoa is an optimal strategy to both occupy the suboxic zones in sulfidic sediments and survive the dark periods in phototrophic mats.
本研究的目的是调查来自高盐度微生物席的贝氏硫菌假定的垂直昼夜迁移及其伴随的生理学特征。我们结合了微传感器、稳定同位素和分子技术，以阐明栖息于西班牙天然高盐湖奇普拉纳湖湖底微生物席中最优势物种的系统发育和生理学特征。最优势的形态类型，其丝状体直径为6至8微米，长度从1毫米到超过10毫米不等。通过16S rRNA基因比较进行的系统发育分析表明，该类型似乎与狭窄的（直径4微米）无液泡海洋菌株MS - 81 - 6关系最为密切（序列同一性为91%）。稳定同位素分析表明，奇普拉纳湖的该物种能够在细胞内储存高达40 mM的硝酸盐。异硫氰酸荧光素染色及随后的共聚焦显微镜检查证实了细胞内存在大液泡。在有光照的微生物席中，它们在8毫米深度处丰度最高，此处氧气和硫化物同时存在。然而，在黑暗中，贝氏硫菌的最高密度出现在7毫米处，且整个种群都存在于微生物席的缺氧区。我们的研究结果表明，高盐度的贝氏硫菌在光照条件下利用氧气氧化硫化物，在黑暗条件下利用细胞内储存的硝酸盐进行氧化。得出的结论是，贝氏硫菌储存硝酸盐是占据含硫沉积物亚缺氧区并在光合微生物席的黑暗时期存活下来的最佳策略。
