沙漠环境具有寡营养、极端干旱、太阳辐射强、昼夜温差大等特点，这些严酷的环境压力是对生命的挑战，也是生命进化的动力。地嗜皮菌科放线菌是一类高GC含量的革兰氏染色阳性菌，被称作为环境中的先锋生物。在沙漠环境压力胁迫下，地嗜皮菌科放线菌必然进化形成一套独特的适应机制，其生态学意义及其应用潜力值得深入研究。一直以来，受制于微生物纯培养技术，未能收集到足够的地嗜皮菌科放线菌纯培养物供系统性研究，以至于对地嗜皮菌科放线菌的研究仅止步于对零星菌株的观察和实验。

本研究选择巴丹吉林沙漠和古尔班通古特沙漠这两大典型沙漠环境作为研究对象，分别从不同的微生态环境采集沙漠土样品，首先应用高通量测序方法探测各不同微环境中微生物多样性和丰富度情况，通过构建网络共现图，分析微生物群落结构特征，着重探测地嗜皮菌科放线菌在沙漠环境的分布特征，并以此为指导，优化菌种分离培养方案，分离获得地嗜皮菌科放线菌，再结合Biolog表型芯片实验，收集菌株的表型特征。

将采集自古尔班通古特沙漠的44份土壤样品按微生态环境分成8组，进行高通量测序分析，拼接后去冗余共得到389321条reads。使用Usearch对序列进行OTU聚类分析，共检测到归属于27门575属的微生物类群，其中归属于地嗜皮菌科的reads共有6494条，占比为1.67%，从8种不同的微环境中均检测到了地嗜皮菌科放线菌成员。以高通量测序分析为基础构建的网络共现图提示：在沙漠环境中，地嗜皮菌科放线菌是核心菌群，是沙漠环境的特色微生物类群；地嗜皮菌科放线菌与沙漠环境其他核心菌群间的互作关系比较复杂，可能对部分微生物的定植起着积极作用。

根据高通量测序分析结果提示，我们应用纯培养手段对巴丹吉林沙漠40份样品和古尔班通古特沙漠44份样品进行菌种分离培养。从巴丹吉林沙漠环境共分离纯化得到归属于细菌域5门90属的505株纯培养物，从古尔班通古特沙漠分离得到归属于细菌域3门76属的361株纯培养物。从上述84份沙漠环境样品中共得到地嗜皮菌科菌株16株。

地嗜皮菌科放线菌菌株，表型芯片实验结果显示: 1）在碳源同化方面，地嗜皮菌科放线菌的碳源利用谱较广，来源于沙漠环境的全部实验菌株能够同化多糖（葡聚糖），91.7%的实验菌株能够同化醋酸，75%的菌株能够同化吐温40等酯类物质。所测试中的71种碳源中，只有D-蜜二糖，β-甲酰-D-葡萄糖苷、3-甲酰葡萄糖、L-丙氨酸、L-组氨酸和D-葡糖二酸等碳源没有被任何一株菌株利用。菌株对碳源的同化情况和菌株的分类学地位的相关性较其与生态环境相关性更为明显。2）地嗜皮菌科放线菌在对氮源和磷硫元素的同化方面，表现出和菌株的生态环境及其分类学地位之间均无明显相关性。

综合菌株的表型和基因型特征实验结果，我们确定了来源于沙漠环境的菌株CPCC 205119^T、CPCC 205215和CPCC 205251的分类学地位。这3株菌属于贫养杆菌属的同一个新物种，以菌株CPCC 205119^T为典型菌株，将这个新物种命名为沙漠贫养杆菌。

本研究系统探索了沙漠环境地嗜皮菌科放线菌的多样性，收集了地嗜皮菌科放线菌的生物学特征，也初步从基因组层面上分析了地嗜皮菌科放线菌抗逆特性的遗传物质基础。

The desert environment is characterized by oligotrophic, extreme drought, strong solar radiation, and huge temperature fluctuations between day and night. These severe environmental pressures are not only a challenge to life, but also a driving force for life evolution. As a kind of gram-staining-positive bacteria with high GC content, members of the family Geodermatophilaceae are regarded as pioneer organisms in the desert environment. Under the stress of desert environment, the strains of Geodermatophilaceae may have evolved into some unique adaptive mechanisms. For a long time, due to the restriction of microbial cultivation techniques, insufficient pure cultures of the family Geodermatophilaceae have been collected for systematic research, so that the research on the family Geodermatophilaceae has been limited to the observation on the sporadic strains.

In this study, we collected desert soil samples from different ecological environments from two typical deserts in China, Badain Jaran desert and Gurbantunggut Desert. Firstly, the high-throughput sequencing method was used to detect the microbial diversity and abundance in different micro-environments. The microbial community structure characteristics were analyzed by construction of co-occurrence network map, focusing on detection of the distribution properties of the family Geodermatophilaceae in the desert environment, based on which optimized the isolation methods on microbial pure cultures, to collect Geodermatophilaceae strains. Subsequently, the phenotypic characteristics of Geodermatophilaceae strains were collected using the Biolog phenotype microarrays experiments.

The 44 soil samples collected from Gurbantunggut Desert were pooled into 8 groups according to micro-environments, and high-throughput sequencing analysis was performed. After splicings, 389,321 reads were obtained. Usearch was used to perform OTU clustering analysis of sequences, and a total of microbial groups belonging to of 575 genera of 27 phyla were detected. There were 6494 reads, accounting for 1.67%, belonging to the family Geodermatophilaceae. As a result, members of the family Geodermatophilaceae were detected in 8 different micro-environments. The co-occurrence network based on high-throughput sequencing analysis indicated that the actinomycetes of the family Geodermatophilaceae were the core flora and the specific microbial group in the desert environment. The interaction between the family Geodermatophilaceae and other core bacteria in the desert environment is complex. Members of the family Geodermatophilaceae may play a positive role in the colonization of some other microorganisms.

According to the results of high-throughput sequencing we selected, 40 samples from Badain Jaran desert and 44 samples from Gurbantunggut Desert for microbe isolation by pure culture method. As a result, 505 strains belonging to 90 genera of 5 phylum in bacterial domain were isolated and purified from badan Jaran desert, and 361 strains belonging to 76 genera of 3 phylum in bacterial domain were isolated from Gurbantunggut Desert. Among them, 16 strains of the family Geodermatophilaceae were obtained from 84 desert samples.

Phenotypic microarray test results showed that: 1) The carbon source utilization spectrum of the family Geodermatophilaceae was wide. All of the tested strains from desert environment could assimilate polysaccharides (dextrin), 91.7% of the tested strains were able to assimilate acetic acid and 75% of strains could assimilate ester compounds such as Tween 40. Among the 71 carbon sources tested, only 3-methyl-glucose, D-melibiose, D-saccharic acid, L-alanine, L-histidine and β-methyl-D-glucoside were not utilized by any of the strains. The correlation between the strains’ assimilation of carbon sources and their taxonomic status of strains was more obvious than that with the corresponding ecology. 2) In terms of assimilation of nitrogen source, phosphorus source and sulfur source, the family Geodermatophilaceae showed no obvious correlation between the assimilation of with the ecological environment and taxonomic status of the strain.

The taxonomic status of strains CPCC 205119^T, CPCC 205215 and CPCC 205251 collected from desert were comfirmed by combining the phenotype and genotype characteristics. These three strains represent a new species of the genus Modestobacter, which is named as Modestobacter deserti, with strain CPCC 205119^T as the typical strain.

In this study, we systematically analyzed the diversity of Geodermatophilaceae in the desert environment, collected the biological characteristics of strains in the family Geodermatophilaceae, and preliminarily analyzed the genetic basis of the tress resistance characteristics of strains in the family Geodermatophilaceae from the level of genome.