漳江口红树林沉积物可培养细菌多样性、产酶潜力及优势芽孢杆菌特征

Cultivable bacterial diversity, enzyme-producing capacity, and characteristics of dominant Bacillus sensu lato in mangrove sediments from the Zhangjiang Estuary

摘要:

目的 解析漳江口红树林沉积物中可培养细菌的多样性格局与产酶能力，重点探究其中优势芽孢杆菌类群的分布特征及其环境驱动机制。方法 采用稀释涂布法分离细菌，基于16S rRNA基因测序进行鉴定；利用平板法检测8种胞外酶活性。结果 共分离获得1 392株菌株，隶属于4门97属，其中芽孢杆菌类群为绝对优势群(占比57.8%)。初筛发现263株(18.9%)潜在新分类单元，多集中于芽孢杆菌(Bacillus)及喜盐芽孢杆菌(Halobacillus)等属。统计分析表明，可培养细菌整体Shannon多样性在核心区和出海口均显著高于入海口(P<0.05)，群落结构存在显著空间差异(P<0.05)，主要受盐度及金属离子驱动；而芽孢杆菌群落结构在空间上相对稳定，主要受pH及碳氮营养因子影响。酶活筛选显示，分离菌株在蛋白酶(64.2%)与脂酶(52.6%)上的阳性率最高；芽孢杆菌类群在多种酶类上的阳性率均高于群落平均水平，显示出广谱代谢潜力。结论 漳江口红树林沉积物蕴藏着丰富的可培养细菌资源。除优势的芽孢杆菌外，假单胞菌门和拟杆菌门是维持群落多样性的关键组分。芽孢杆菌类群凭借其高生态稳定性与多底物降解能力，与其他类群共同驱动红树林沉积物的元素循环。

Abstract:

Objective To characterize the cultivable bacterial diversity patterns and extracellular enzyme-producing capacity in mangrove sediments from the Zhangjiang Estuary, with a particular focus on the distribution of dominant Bacillus sensu lato and the environmental factors shaping their assemblages.Methods Bacterial isolates were obtained by dilution plating. Taxonomic identification was performed by 16S rRNA gene sequencing. Plate-based assays were used to evaluate the activities of eight extracellular enzymes.Results In total, 1 392 isolates were obtained, representing 97 genera of 4 phyla. Bacillus sensu lato constituted the dominant assemblage (57.8%). Preliminary screening suggested 263 isolates (18.9%) as putative novel taxa, largely concentrated in Bacillus and allied genera such as Halobacillus. The Shannon diversity of cultivable bacteria was higher in the core mangrove zone and at the estuarine outlet than at the inlet (P<0.05), and the community composition differed among sites (P<0.05), being mainly associated with salinity and metal ions. By contrast, the community structure of Bacillus sensu lato was comparatively stable across space and was primarily associated with pH and carbon-nitrogen nutrient variables. Enzyme screening showed the highest positive rates for proteases (64.2%) and lipases (52.6%). Isolates affiliated with Bacillus sensu lato displayed higher positive rates than the overall community across multiple enzymes, indicating broad metabolic potential.Conclusion Mangrove sediments from the Zhangjiang Estuary harbor abundant cultivable bacterial resources. In addition to the dominant Bacillus-related taxa, Pseudomonadota and Bacteroidota appear to be key components underpinning overall community diversity. The high ecological stability and multi-substrate degradation capacity of Bacillus sensu lato, together with other bacterial groups, contribute to element cycling in mangrove sediments.