Vargas-Gastélum Lluvia, Romero-Olivares Adriana L, Escalante Ana E, Rocha-Olivares Axayácatl, Brizuela Carlos, Riquelme Meritxell
Department of Microbiology, Center for Scientific Research and Higher Education of Ensenada (CICESE), Ctra. Ensenada-Tijuana No. 3918, Ensenada, Baja California, 22860, Mexico.
Department of Ecology and Evolutionary Biology, University of California-Irvine, 321 Steinhaus Hall, Irvine, CA 92697, USA.
FEMS Microbiol Ecol. 2015 May;91(5). doi: 10.1093/femsec/fiv044. Epub 2015 Apr 14.
Fungi play fundamental ecological roles in terrestrial ecosystems. However, their distribution and diversity remain poorly described in natural communities, particularly in arid and semi-arid ecosystems. In order to identify environmental factors determining fungal community structure in these systems, we assessed their diversity in conjunction with soil physicochemical characteristics in a semi-arid ecosystem in Baja California, Mexico, endemic for Coccidioidomycosis (Valley Fever). Two different microhabitats, burrows (influenced by rodent activity) and topsoil, were compared in winter and summer. Using a metagenomic approach, the ITS1 region of nuclear ribosomal DNA was used as barcode. A total of 1940 Operational Taxonomic Units (OTUs) were identified from 362 332 ITS1 sequences obtained by 454 pyrosequencing. Differences in fungal composition between seasons were clearly identified. Moreover, differences in composition between microhabitats were mainly correlated to significant differences in environmental factors, such as moisture and clay content in topsoil samples, and temperature and electrical conductivity in burrow samples. Overall, the fungal community structure (dominated by Ascomycota and Basidiomycota) was less variable between seasons in burrow than in topsoil samples. Coccidioides spp. went undetected by pyrosequencing. However, a nested PCR approach revealed its higher prevalence in burrows.
真菌在陆地生态系统中发挥着重要的生态作用。然而，在自然群落中，尤其是在干旱和半干旱生态系统中，它们的分布和多样性仍鲜为人知。为了确定决定这些系统中真菌群落结构的环境因素，我们结合墨西哥下加利福尼亚州一个半干旱生态系统（球孢子菌病（谷热）的地方病流行区）的土壤理化特性，评估了真菌的多样性。在冬季和夏季比较了两种不同的微生境，即洞穴（受啮齿动物活动影响）和表土。采用宏基因组学方法，将核糖体DNA的ITS1区域用作条形码。通过454焦磷酸测序从362332条ITS1序列中总共鉴定出1940个操作分类单元（OTU）。明确识别出了不同季节真菌组成的差异。此外，微生境之间的组成差异主要与环境因素的显著差异相关，如表土样品中的湿度和粘土含量，以及洞穴样品中的温度和电导率。总体而言，洞穴中真菌群落结构（以子囊菌门和担子菌门为主）在不同季节间的变化小于表土样品。通过焦磷酸测序未检测到球孢子菌属。然而，一种巢式PCR方法显示其在洞穴中的患病率较高。
