Secondary metabolites of bacteria associated with honey bees were evaluated as part of an investigation on their potentiality for apiary health. Low molecular weight compounds released into culture filtrates by the four bacterial isolates taken from surface of healthy honey bees were analyzed using time-of-flight mass spectrometry. Only one low molecular weight compound was found in the culture filtrate of each isolate. Bacillus thuringiensis, Bifidobacterium asteroides and Acetobacteraceae bacterium, released into culture filtrates platynecine, a pyrrolizidine alkaloid of plant origin, which, until now, had never been reported as produced by bacteria. Lactobacillus kunkeei produced a 3,5-dinitropyridine, of unknown biological action never associated so far to bacteria. The highest relative concentration of platynecine was detected in B. thuringiensis (100%), B. asteroides and A. bacterium showed a concentration above 50% and below 25% that concentration. An in vitro assay on the potential for controlling the parasitic mite Varroa destructor by the culture filtrates of the three platynecine-producing bacteria was performed. Varroa mite mortality was proportional to the platynecine relative concentration into culture filtrate. Although miticidal activity of B. thuringiensis might be associated to other toxic proteins produced by this species, B. asteroides toxicity toward V. destructor along with the other findings of this study support the hypothesis that platynecine plays a direct or an indirect role in controlling varroa. Findings of this study suggest that secondary metabolites released by honey bee-associated bacteria represent a source of natural compounds to be considered in the challenge for counteracting the colony decline.

中文翻译：

---

蜜蜂相关细菌产生的次生代谢物对养蜂场健康的影响：Platynecine 的潜在活性

对与蜜蜂相关的细菌的次级代谢产物进行了评估，作为对其养蜂场健康潜力的调查的一部分。使用飞行时间质谱法分析了从健康蜜蜂表面提取的四种细菌分离物释放到培养滤液中的低分子量化合物。在每种分离物的培养滤液中仅发现一种低分子量化合物。苏云金芽孢杆菌、星形双歧杆菌和醋杆菌科细菌释放到培养物滤液中的扁桃碱是一种植物来源的吡咯里西啶生物碱，迄今为止，从未有报道称其由细菌产生。Lactobacillus kunkeei 产生一种 3,5-二硝基吡啶，其生物学作用未知，迄今为止从未与细菌相关联。在 B. thuringiensis (100%)、B. asteroides 和 A. 细菌显示浓度高于 50% 和低于 25%。对三种产生桔梗的细菌的培养滤液控制寄生螨瓦螨的潜力进行了体外试验。瓦螨死亡率与进入培养滤液中的柏油辛相对浓度成正比。虽然 B. thuringiensis 的杀螨活性可能与该物种产生的其他有毒蛋白质有关，但 B. asteroides 对 V. destructor 的毒性以及本研究的其他发现支持了以下假设：platynecine 在控制瓦螨中起直接或间接作用.