Yeager Chris M, Kornosky Jennifer L, Housman David C, Grote Edmund E, Belnap Jayne, Kuske Cheryl R
Biosciences Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.
Appl Environ Microbiol. 2004 Feb;70(2):973-83. doi: 10.1128/AEM.70.2.973-983.2004.
The objective of this study was to characterize the community structure and activity of N2-fixing microorganisms in mature and poorly developed biological soil crusts from both the Colorado Plateau and Chihuahuan Desert. Nitrogenase activity was approximately 10 and 2.5 times higher in mature crusts than in poorly developed crusts at the Colorado Plateau site and Chihuahuan Desert site, respectively. Analysis of nifH sequences by clone sequencing and the terminal restriction fragment length polymorphism technique indicated that the crust diazotrophic community was 80 to 90% heterocystous cyanobacteria most closely related to Nostoc spp. and that the composition of N2-fixing species did not vary significantly between the poorly developed and mature crusts at either site. In contrast, the abundance of nifH sequences was approximately 7.5 times greater (per microgram of total DNA) in mature crusts than in poorly developed crusts at a given site as measured by quantitative PCR. 16S rRNA gene clone sequencing and microscopic analysis of the cyanobacterial community within both crust types demonstrated a transition from a Microcoleus vaginatus-dominated, poorly developed crust to mature crusts harboring a greater percentage of Nostoc and Scytonema spp. We hypothesize that ecological factors, such as soil instability and water stress, may constrain the growth of N2-fixing microorganisms at our study sites and that the transition to a mature, nitrogen-producing crust initially requires bioengineering of the surface microenvironment by Microcoleus vaginatus.
本研究的目的是描述来自科罗拉多高原和奇瓦瓦沙漠的成熟和发育不良的生物土壤结皮中固氮微生物的群落结构和活性。在科罗拉多高原站点和奇瓦瓦沙漠站点，成熟结皮中的固氮酶活性分别比发育不良的结皮高约10倍和2.5倍。通过克隆测序和末端限制性片段长度多态性技术对nifH序列进行分析表明，结皮中的固氮群落有80%至90%是与念珠藻属关系最密切的异形胞蓝细菌，并且在两个站点中，发育不良的结皮和成熟结皮之间固氮物种的组成没有显著差异。相比之下，通过定量PCR测量，在给定站点的成熟结皮中，nifH序列的丰度（每微克总DNA）比发育不良的结皮大约高7.5倍。对两种结皮类型中的蓝细菌群落进行16S rRNA基因克隆测序和显微镜分析表明，从以鞘丝藻为主的发育不良结皮向含有更高比例念珠藻属和席藻属的成熟结皮转变。我们推测，诸如土壤不稳定和水分胁迫等生态因素可能会限制我们研究站点中固氮微生物的生长，并且向成熟的产氮结皮的转变最初需要鞘丝藻对表面微环境进行生物工程改造。
