Intestinal microbial diversity in domestic honey bees and evaluation of their probiotic properties

As populations of managed honey bees in various regions increase in comparison to wild colonies, there is a need to ensure that threats to bee health and survival in all environments are countered. One of the more direct methods of approaching bee health is through dietary means and as such, we investigated the intestinal microbial diversity in the gut of honey bees in order to identify strains with probiotic potential. Honey bees were fed with several feeds including Feedbee, Megabee, sugar syrup 60% (w/v), Yangbongnonghyup (YBNH), and Test A, to monitor the culture-dependent and culture-independent microbial diversity. In the culture-dependent study, most isolates belonged to Apilactobacillus (24.1%), Fructobacillus (21.8%), and Bacillus (15.4%) at the genus level. Culture-independent results showed that Bacillota and Pseudomonadota were the most abundant groups (99%) among the gut bacteria, while other bacteria showed a lower percentage than 0.1%. Next, the hydrolytic enzymes (α-amylase, protease, and cellulase) and antibacterial and antioxidant activities of the isolated strains were evaluated to examine their applicability as potential probiotics for honey bees. The selected strains showing three hydrolytic enzyme activities were used to determine their antibacterial activity against Paenibacillus larvae. Bacillus subtilis MBLB2796 showed the highest α-amylase (1.24 ± 0.06 U/mL) and cellulase (0.24 ± 0.01 U/mL) activities while B. tequilensis MBLB2834 exhibited the highest protease activity (0.15 ± 0.03 mU/mL) and the highest antioxidant activity (71.0 ± 3.8%). This study suggests that honey bee gut-originated isolates are prime candidates for use as probiotics in honey bees.

伴随各地区养殖蜜蜂种群数量相较野生蜂群持续攀升，亟需有效防控各类环境中威胁蜜蜂健康与生存的风险因素。其中较为直接的干预路径之一为膳食调控手段，为此本研究针对蜜蜂肠道微生物多样性展开探究，以期筛选出具备益生菌开发潜力的菌株。
实验中，蜜蜂被饲喂Feedbee、Megabee、60%（w/v）蔗糖溶液、Yangbongnonghyup（YBNH）以及试验组A（Test A）等多种饲料，以此开展依赖培养与不依赖培养两种方式的肠道微生物多样性监测。在依赖培养的分析中，属水平下多数分离菌株归属于Api乳杆菌属（Apilactobacillus，24.1%）、果糖杆菌属（Fructobacillus，21.8%）与芽孢杆菌属（Bacillus，15.4%）。不依赖培养的测序结果显示，厚壁菌门（Bacillota）与假单胞菌门（Pseudomonadota）为肠道菌群中丰度最高的两个类群，总占比达99%，其余细菌类群占比均低于0.1%。
随后，本研究对分离得到的菌株进行了水解酶（α-淀粉酶、蛋白酶与纤维素酶）活性、抗菌活性与抗氧化活性的检测，以评估其作为蜜蜂潜在益生菌的应用价值。选取同时具备三种水解酶活性的菌株，测定其对幼虫芽孢杆菌（Paenibacillus larvae）的抗菌活性。枯草芽孢杆菌（Bacillus subtilis）MBLB2796的α-淀粉酶活性（1.24±0.06 U/mL）与纤维素酶活性（0.24±0.01 U/mL）均为最高；而特基拉芽孢杆菌（B. tequilensis）MBLB2834则展现出最高的蛋白酶活性（0.15±0.03 mU/mL）与抗氧化活性（71.0±3.8%）。
本研究证实，源自蜜蜂肠道的分离菌株可作为蜜蜂益生菌制剂的优质候选菌株。