Feng Wen

Understanding how cultivation conditions influence the recovery of microbial diversity is critical for interpreting cultivation-derived communities in relation to in situ microbial ecology, particularly in nutrient-limited environments such as desert soils. In this study, we investigated how an oligotrophic nutrient gradient shapes cultivation outcomes and enrichment-derived bacterial community structure in soils from the Taklimakan Desert. Three enrichment treatments representing decreasing nutrient availability—standard low-nutrient medium (R2A), diluted medium (DR2A), and sterile water—were used to compare enrichment-derived communities with the original soil microbiome. Amplicon sequencing revealed that cultivation substantially altered community composition and reduced both taxonomic richness and diversity relative to the original soil. Across enrichment treatments, bacterial communities were dominated by a limited number of taxa, whereas the original soil contained a broader range of low-abundance lineages. Within the enrichment system, variation in nutrient supply influenced the relative abundance of specific taxa, with differential responses observed at the genus level. In contrast, beta diversity analysis showed only limited separation among enrichment treatments, and co-occurrence network analysis indicated generally simple and weakly connected community structures across all conditions. Overall, our results demonstrate that cultivation represents the primary selective force shaping enrichment-derived bacterial communities, while nutrient supply intensity acts as a secondary modulator of taxon-specific enrichment. These findings highlight the importance of incorporating nutrient gradients into cultivation strategies to improve ecological interpretation and facilitate the recovery of oligotrophy-associated microorganisms from desert soils.

A total of 304 bacterial strains were isolated from the Taklamakan Desert. Through screening, strain TRM82367 exhibited potent insecticidal activity against cotton aphids (Aphis gossypii) and was identified as Bacillus velezensis. To explore the primary insecticidal active components of this strain, lipopeptide substances in the fermentation broth were extracted via hydrochloric acid precipitation. The main active components were analyzed using activity-guided fractionation combined with liquid chromatography–mass spectrometry (LC-MS). Our results demonstrated that Bacillus velezensis TRM82367 possessed strong lethal activity against cotton aphids. The crude extract obtained by means of hydrochloric acid precipitation and methanol dissolution showed high insecticidal efficacy. At concentrations of 100, 150, 200, 250, 300, 400, and 500 mg/L, the 48 h corrected mortality rates of cotton aphids were 25.14%, 38.05%, 50.09%, 53.03%, 57.96%, 74.68%, and 88.67%, respectively. The toxicity regression equation was Y = 2.47X − 5.72, with a median lethal concentration (LC₅₀) of 207.616 mg/L and a 95% lethal concentration (LC₉₅) of 1004.673 mg/L. After separation by an ODS chromatographic column and identification by means of mass spectrometry, the main active components were confirmed to be C₁₂–C₁₆ surfactin homologs.

Lop Nur, an extremely arid environment, harbors unique microbial resources and represents a potential reservoir for novel bioactive substances. With antibiotic resistance becoming an increasing global concern, the resistance traits of microorganisms in extreme habitats and their potential association with antibacterial activity remain poorly understood. This study aimed to investigate the diversity of soil microorganisms in Lop Nur, their resistance to norfloxacin, kanamycin, and amoxicillin, and their inhibitory activity against common pathogenic bacteria, thereby providing a scientific basis for the discovery of new antibacterial candidates. Surface soils from three sampling points in Lop Nur were inoculated onto Gao’s No.1 and LB media supplemented with different antibiotic regimens (single, pairwise, and triple combinations). Isolates were identified by 16S rRNA gene sequencing, their antibiotic resistance was assessed using the disk diffusion method, and antibacterial activity was evaluated using the agar well diffusion method. A total of 120 microorganisms were isolated, belonging to six phyla and nine genera, including 10 potential new species. The control group yielded the highest diversity (35 strains), whereas only 4 strains were recovered under triple-antibiotic treatment, demonstrating the strong selective effect of antibiotic stress. Resistance profiling showed that 88.14% of strains were resistant to amoxicillin, 64.71% to norfloxacin, and 60.68% to kanamycin, with multidrug resistance being widespread. Eleven strains exhibited antibacterial activity against five pathogens, including Staphylococcus aureus (maximum inhibition zone 53.51 mm), and nine of these strains also displayed antibiotic resistance, suggesting a potential association between resistance and antibacterial activity. Microorganisms isolated from Lop Nur displayed extensive resistance and notable antibacterial activity. Antibiotic stress strongly influenced the cultivable microbial isolates, facilitating the recovery of resistant strains with antibacterial potential. These findings provide a valuable reference for exploring microbial resources in extreme environments and highlight the potential link between antibiotic resistance and antibacterial activity.

The cotton aphid Aphis gossypii poses a global, serious threat to cotton yield and quality. Although chemical pesticides are effective, pollution and resistance are increasingly prominent, making development of new biopesticides a priority in the context of green agricultural development. Given that reports on the activity of surfactins against A. gossypii are limited, here, 107 Bacillus strains isolated from the extreme environment of the Chinese Taklamakan Desert were screened for insecticidal activity against A. gossypii using the leaf-dip method. Active strains were characterized by morphological observation, 16S rRNA gene sequencing, and phylogenetic analysis. Secondary metabolite synthesis genes were identified by whole-genome sequencing and antiSMASH analysis. B. australimaris strain TRM82479 showed 75.00% 48-h mortality against A. gossypii. An antiSMASH analysis showed that this strain has several gene clusters associated with the synthesis of nonribosomal peptide (NRP) fengycin and lichenysin lipopeptide analogs; therefore, we isolated and characterized its NRPs. A surfactin was the primary insecticidal substance, with an aqueous LC50 of 0.857 mg/mL and LC95 of 4.350 mg/mL. This study not only provides new strain resources for A. gossypii control, but also demonstrates the potential of surfactin as a biopesticide, which will lay a foundation for its future agricultural application.

Although the Taklimakan Desert lacks the necessary nutrients and conditions to support an extensive ecosystem, it is a treasure trove of extremophile resources with special structures and functions. We analyzed the bacterial communities using oligotrophic medium and velvet cloth replicate combined with an extended culture duration. We isolated numerous uncultured microorganisms and rare microorganisms belonging to genera not often isolated or recently described, such as Aliihoeflea, Halodurantibacterium, and Indioceanicola. A total of 669 strains were isolated from the soil of the Taklimakan Desert, which were classified into 5 phyla, 7 classes, 25 orders, 42 families, 83 genera, and 379 species. Among them, 148 strains were potential new species. Our data show that even when working with samples from extreme environments, simple approaches are still useful for cultivating stubborn microbes. Through comparing the isolation effects of different nutrient levels on microbial diversity and abundance, the results show that reducing the nutrient level of the medium was more conducive to improving the culturability of microorganisms in low-nutrient environments, while the high-nutrient medium was more suitable for the isolation of dominant fast-growing strains. This study helps to better reflect the diversity of microbial resources and lays a foundation for the further research and utilization of soil microbial resources in the Taklimakan Desert.