1Centro de Investigación en Estructuras Microscópicas (CIEMIC), Universidad de Costa Rica, 11501-2060 San José, Costa Rica.
2Centro de Investigación en Contaminación Ambiental (CICA), Universidad de Costa Rica, 11501-2060 San José, Costa Rica.
Microbiology (Reading). 2019 Mar;165(3):292-301. doi: 10.1099/mic.0.000754. Epub 2019 Jan 24.
Many insects have been associated with actinobacteria in protective symbiosis where antimicrobial metabolites inhibit host pathogens. However, the microbiota of neotropical insects such as the stingless-bee Tetragonisca angustula is poorly explored. T. angustula is a meliponid bee widely distributed in Latin America, its honey is traditionally exploited because of its ethno-pharmacological properties and its antimicrobial activity has been demonstrated. Also, the well-structured nest of this species allows exploration of the microbiota of its different components. Even though Streptomyces spp. have been cultured from stingless-bees, little is known about their role in this insect-microbe relationship. In this study, we examined the association between culturable actinobacteria and T. angustula, and evaluated the isolates' potential as antimicrobial producers. We isolated 51 actinobacteria from adult bees and different substrates of the hive of T. angustula (pollen and honey storage, garbage pellets and cerumen). We then performed a 16S rRNA phylogenetic analysis that clusters the bacteria to previously described lineages of host-associated Streptomyces. In addition, all the isolates were classified according to their antibacterial activity against human pathogens, measured by a growth inhibition test based on diffusion in agar. More than 50 % of our isolates exhibit antimicrobial activity, mainly to Gram-positive bacteria and fungi and only two against Gram-negative bacteria. Additionally, we obtained electron micrographs of adult bees with what appears to be patches of hyphae with Streptomyces-like cell morphology on their body surface. Our results suggest that T. angustula possibly uptakes and transfers actinobacteria from the environment, acting as vectors for these potentially beneficial organisms. This research provides new insights regarding the microbiota associated with T. angustula and justify future studies exploring the full diversity of the microbial community associated with the hive and the possible exchange of microbes with the crops they pollinate.
许多昆虫与放线菌形成保护性共生关系，其中抗菌代谢物抑制宿主病原体。然而，新热带地区昆虫（如无刺蜜蜂 Tetragonisca angustula）的微生物群尚未得到充分探索。T. angustula 是一种广泛分布于拉丁美洲的蜜蜂，其蜂蜜因其民族药理学特性而被传统利用，并且其抗菌活性已得到证实。此外，该物种结构良好的巢穴允许探索其不同组成部分的微生物群。尽管已经从无刺蜜蜂中培养出了链霉菌属细菌，但它们在这种昆虫-微生物关系中的作用知之甚少。在这项研究中，我们研究了可培养放线菌与 T. angustula 的关联，并评估了分离株作为抗菌剂产生的潜力。我们从成年蜜蜂和 T. angustula 蜂巢的不同基质（花粉和蜂蜜储存、垃圾球和耳垢）中分离出 51 株放线菌。然后，我们进行了 16S rRNA 系统发育分析，将细菌聚类到先前描述的与宿主相关的链霉菌谱系中。此外，根据基于琼脂扩散的生长抑制试验，所有分离株均根据其对人类病原体的抗菌活性进行了分类。我们的分离株中有超过 50%表现出抗菌活性，主要针对革兰氏阳性菌和真菌，只有两种对革兰氏阴性菌有效。此外，我们还获得了成年蜜蜂的电子显微镜照片，其表面似乎有带有链霉菌样细胞形态的菌丝斑。我们的结果表明，T. angustula 可能从环境中摄取并转移放线菌，充当这些潜在有益生物的载体。这项研究为与 T. angustula 相关的微生物群提供了新的见解，并证明了未来探索与蜂巢相关的微生物群落的全部多样性以及与它们授粉的作物交换微生物的可能性的研究是合理的。
