Effects of Bacillus licheniformis on the bacterial communities in shrimp zero-water exchange aquaculture system

The effects of Bacillus licheniformis on immune response, disease resistance, and nutrition for the Penaeus vannamei have been extensively studied, but little is known about the effects in intestinal and environmental microbial communities under the zero-water exchange aquaculture system. The effect of Bacillus licheniformis can probably be achieved by influencing the bacterial community of intestinal and environmental. To test this hypothesis, we used 16S rRNA gene amplicon sequencing to investigate both intestinal and environmental bacterial composition in shrimp zero-water exchange aquaculture system after add Bacillus licheniformis to feed or water applied. First of all, shrimp intestinal microbiota had a close correlation to the ambient microbiota in the zero-water exchange aquaculture system. The main phylum is Planctomycetes and Proteobacteria, but their proportion differs greatly in different environments. Then there was significant impact on the abundance of Chlamydia in the intestine and water after adding Bacillus licheniformis to water or feed; while at the genus level, it significantly changes the abundance of Planctomicrobium and Pir4_lineage in the intestinal and sediment. Finally, the results showed that the addition of Bacillus licheniformis to feed and water changed the related pathways, for example, Digestive System, but the change trend was opposite. These above results may be helpful to comprehensively understand the changes in shrimp intestines and environment after Bacillus licheniformis is added through feed and water in the zero-water exchange aquaculture system, thereby providing basic information for choosing the right probiotics and how to add them to sustain shrimp health.

目前针对地衣芽孢杆菌（Bacillus licheniformis）对凡纳滨对虾（Penaeus vannamei）免疫应答、抗病性及营养状况的影响已开展大量研究，但零换水养殖系统下其对肠道与环境微生物群落的影响却鲜有报道。推测地衣芽孢杆菌的调控效应可能通过改变肠道与环境中的细菌群落实现。为验证该假说，本研究采用16S rRNA基因扩增子测序技术，探究在饲料或水体中添加地衣芽孢杆菌后，凡纳滨对虾零换水养殖系统内肠道与环境细菌的组成特征。首先，零换水养殖系统中凡纳滨对虾肠道菌群与环境菌群存在显著相关性；群落优势菌门为浮霉菌门（Planctomycetes）和变形菌门（Proteobacteria），但二者在不同生境中的占比差异显著。其次，向水体或饲料中添加地衣芽孢杆菌后，肠道与水体中衣原体（Chlamydia）的丰度均发生显著改变；在属水平上，肠道与沉积物中的Planctomicrobium及Pir4_lineage的丰度也出现显著变化。最后，研究结果显示，分别向饲料与水体中添加地衣芽孢杆菌，均会对肠道菌群的代谢通路产生调控作用，例如消化系统相关通路，但二者的调控趋势恰好相反。上述研究结果有助于全面解析零换水养殖系统中，通过饲料与水体途径添加地衣芽孢杆菌后凡纳滨对虾肠道及养殖环境的微生物群落变化，可为筛选适宜益生菌及确定其施用方式以维持对虾健康提供基础数据支撑。