Mehda Smail, Muñoz-Martín M Ángeles, Oustani Mabrouka, Hamdi-Aïssa Baelhadj, Perona Elvira, Mateo Pilar
Departamento de Biología, Facultad de Ciencias, Universidad Autónoma de Madrid, 28049 Madrid, Spain.
Laboratory of Biogeochemistry of Desert Areas, University of Ouargla, 30000 Ouargla, Algeria.
Microorganisms. 2021 Feb 25;9(3):487. doi: 10.3390/microorganisms9030487.
The Sahara Desert is characterized by extreme environmental conditions, which are a unique challenge for life. Cyanobacteria are key players in the colonization of bare soils and form assemblages with other microorganisms in the top millimetres, establishing biological soil crusts (biocrusts) that cover most soil surfaces in deserts, which have important roles in the functioning of drylands. However, knowledge of biocrusts from these extreme environments is limited. Therefore, to study cyanobacterial community composition in biocrusts from the Sahara Desert, we utilized a combination of methodologies in which taxonomic assignation, for next-generation sequencing of soil samples, was based on phylogenetic analysis (16S rRNA gene) in parallel with morphological identification of cyanobacteria in natural samples and isolates from certain locations. Two close locations that differed in microenvironmental conditions were analysed. One was a dry salt lake (a "chott"), and the other was an extension of sandy, slightly saline soil. Differences in cyanobacterial composition between the sites were found, with a clear dominance of spp. in the less saline site, while the chott presented a high abundance of heterocystous cyanobacteria as well as the filamentous non-heterocystous sp. and the unicellular cf. . The cyanobacteria found in our study area, such as and sp., are also widely distributed in other geographic locations around the world, where the conditions are less severe. Our results, therefore, indicated that some cyanobacteria can cope with polyextreme conditions, as confirmed by bioassays, and can be considered extremotolerant, being able to live in a wide range of conditions.
撒哈拉沙漠的环境条件极为恶劣，这对生命构成了独特的挑战。蓝细菌是裸土定殖过程中的关键参与者，它们在表层几毫米内与其他微生物形成群落，形成生物土壤结皮（生物结皮），覆盖了沙漠中的大部分土壤表面，在旱地生态系统功能中发挥着重要作用。然而，对于这些极端环境下生物结皮的了解还很有限。因此，为了研究撒哈拉沙漠生物结皮中的蓝细菌群落组成，我们采用了多种方法相结合的方式，其中土壤样本的下一代测序分类归属基于系统发育分析（16S rRNA基因），同时对自然样本和特定地点分离株中的蓝细菌进行形态学鉴定。我们分析了两个微环境条件不同但距离相近的地点。一个是干涸的盐湖（“盐沼”），另一个是沙质、微咸土壤的延伸区域。研究发现，两个地点的蓝细菌组成存在差异，在盐分较低的地点， 属明显占优势，而在盐沼中，异形胞蓝细菌以及丝状非异形胞 属和单细胞类 大量存在。我们研究区域中发现的蓝细菌，如 和 属，在世界其他条件没那么恶劣的地理位置也广泛分布。因此，我们的结果表明，一些蓝细菌能够应对多种极端条件，生物测定也证实了这一点，它们可被视为极端耐受型，能够在广泛的条件下生存。
