Caves are considered to be extreme and challenging environments. It is believed that the ability of microorganisms to produce secondary metabolites enhances their survivability and adaptiveness in the energy-starved cave environment. Unfortunately, information on the genetic potential for the production of secondary metabolites, such as polyketides and nonribosomal peptides, is limited. In the present study, we aimed to identify and characterize genes responsible for the production of secondary metabolites in the microbial community of one of the deepest caves in the world, Krubera-Voronja Cave (43.4184 N 40.3083 E, Western Caucasus). The analysed sample materials included sediments, drinkable water from underground camps, soil and clay from the cave walls, speleothems and coloured spots from the cave walls. The type II polyketide synthases (PKSs) ketosynthases α and β and the adenylation domains of nonribosomal peptide synthetases (NRPSs) were investigated using a metagenomic approach. Taxonomic diversity analysis showed that most PKS sequences could be attributed to Actinobacteria followed by unclassified bacteria and Acidobacteria, while the NRPS sequences were more taxonomically diverse and could be assigned to Proteobacteria, Actinobacteria, Cyanobacteria, Firmicutes, Chloroflexi, etc. Only three putative metabolites could be predicted: an angucycline group polyketide, a massetolide A-like cyclic lipopeptide and a surfactin-like lipopeptide. The absolute majority of PKS and NRPS sequences showed low similarity with the sequences of the reference biosynthetic pathways, suggesting that these sequences could be involved in the production of novel secondary metabolites.

洞穴被认为是极端且具有挑战性的环境。据信，微生物产生次级代谢产物的能力增强了它们在能量匮乏的洞穴环境中的生存能力和适应性。不幸的是，关于产生次级代谢产物如聚酮化合物和非核糖体肽的遗传潜力的信息有限。在本研究中，我们旨在鉴定和表征负责在世界上最深的洞穴之一，Krubera-Voronja洞穴（43.4184 N 40.3083 E，西高加索）的微生物群落中产生次级代谢产物的基因。分析的样品材料包括沉积物，地下营地的饮用水，洞穴壁上的土壤和黏土，鞘脂和洞穴壁上的有色斑点。使用宏基因组学方法研究了II型聚酮化合物合酶（PKSs）酮合酶α和β以及非核糖体肽合成酶（NRPSs）的腺苷酸化域。分类学多样性分析表明，大多数PKS序列可归因于放线菌紧随其后是未分类的细菌和酸性菌，而NRPS序列在分类学上更具多样性，并且可以归类为变形杆菌，放线菌，蓝藻，硬毛菌，绿屈挠菌等。只能预测三种假定的代谢产物：环磷酰胺基聚酮化合物，马赛屈内酯A-如环状脂肽和表面活性素样脂肽。绝对大多数的PKS和NRPS序列与参考生物合成途径的序列显示出较低的相似性，表明这些序列可能与新型次生代谢产物的产生有关。