Peral-Aranega Ezequiel, Saati-Santamaría Zaki, Ayuso-Calles Miguel, Kostovčík Martin, Veselská Tereza, Švec Karel, Rivas Raúl, Kolařik Miroslav, García-Fraile Paula
Microbiology and Genetics Department, Universidad de Salamanca, Salamanca, 37007, Spain.
Institute for Agribiotechnology Research (CIALE), Salamanca, 37185, Spain.
Environ Microbiome. 2023 Jun 9;18(1):53. doi: 10.1186/s40793-023-00510-z.
Ips typographus (European spruce bark beetle) is the most destructive pest of spruce forests in Europe. As for other animals, it has been proposed that the microbiome plays important roles in the biology of bark beetles. About the bacteriome, there still are many uncertainties regarding the taxonomical composition, insect-bacteriome interactions, and their potential roles in the beetle ecology. Here, we aim to deep into the ecological functions and taxonomical composition of I. typographus associated bacteria.
We assessed the metabolic potential of a collection of isolates obtained from different life stages of I. typographus beetles. All strains showed the capacity to hydrolyse one or more complex polysaccharides into simpler molecules, which may provide an additional carbon source to its host. Also, 83.9% of the strains isolated showed antagonistic effect against one or more entomopathogenic fungi, which could assist the beetle in its fight against this pathogenic threat. Using culture-dependent and -independent techniques, we present a taxonomical analysis of the bacteriome associated with the I. typographus beetle during its different life stages. We have observed an evolution of its bacteriome, which is diverse at the larval phase, substantially diminished in pupae, greater in the teneral adult phase, and similar to that of the larval stage in mature adults. Our results suggest that taxa belonging to the Erwiniaceae family, and the Pseudoxanthomonas and Pseudomonas genera, as well as an undescribed genus within the Enterobactereaceae family, are part of the core microbiome and may perform vital roles in maintaining beetle fitness.
Our results indicate that isolates within the bacteriome of I. typographus beetle have the metabolic potential to increase beetle fitness by proving additional and assimilable carbon sources for the beetle, and by antagonizing fungi entomopathogens. Furthermore, we observed that isolates from adult beetles are more likely to have these capacities but those obtained from larvae showed strongest antifungal activity. Our taxonomical analysis showed that Erwinia typographi, Pseudomonas bohemica, and Pseudomonas typographi species along with Pseudoxanthomonas genus, and putative new taxa belonging to the Erwiniaceae and Enterobacterales group are repeatedly present within the bacteriome of I. typographus beetles, indicating that these species might be part of the core microbiome. In addition to Pseudomonas and Erwinia group, Staphylococcus, Acinetobacter, Curtobacterium, Streptomyces, and Bacillus genera seem to also have interesting metabolic capacities but are present in a lower frequency. Future studies involving bacterial-insect interactions or analysing other potential roles would provide more insights into the bacteriome capacity to be beneficial to the beetle.
云杉八齿小蠹（欧洲云杉树皮甲虫）是欧洲云杉林最具破坏性的害虫。与其他动物一样，有人提出微生物群在树皮甲虫的生物学特性中发挥着重要作用。关于细菌群落，在分类组成、昆虫与细菌群落的相互作用及其在甲虫生态学中的潜在作用方面仍存在许多不确定性。在这里，我们旨在深入研究云杉八齿小蠹相关细菌的生态功能和分类组成。
我们评估了从云杉八齿小蠹不同生命阶段分离得到的一系列菌株的代谢潜力。所有菌株都显示出将一种或多种复杂多糖水解为更简单分子的能力，这可能为其宿主提供额外的碳源。此外，分离得到的83.9%的菌株对一种或多种昆虫病原真菌具有拮抗作用，这可以帮助甲虫对抗这种致病威胁。使用依赖培养和不依赖培养的技术，我们对云杉八齿小蠹在其不同生命阶段的细菌群落进行了分类分析。我们观察到其细菌群落的演变，在幼虫阶段多样，在蛹期大幅减少，在 teneral 成虫阶段较多，在成熟成虫阶段与幼虫阶段相似。我们的结果表明，属于欧文氏菌科、假黄单胞菌属和假单胞菌属的分类群，以及肠杆菌科内一个未描述的属，是核心微生物群的一部分，可能在维持甲虫健康方面发挥重要作用。
我们的结果表明，云杉八齿小蠹细菌群落中的分离菌株具有代谢潜力，通过为甲虫提供额外的可同化碳源以及拮抗昆虫病原真菌来提高甲虫的健康水平。此外，我们观察到从成虫分离得到的菌株更有可能具有这些能力，但从幼虫分离得到的菌株显示出最强的抗真菌活性。我们的分类分析表明，云杉欧文氏菌、波希米亚假单胞菌和云杉假单胞菌物种以及假黄单胞菌属，以及属于欧文氏菌科和肠杆菌目的假定新分类群在云杉八齿小蠹的细菌群落中反复出现，表明这些物种可能是核心微生物群的一部分。除了假单胞菌和欧文氏菌属外，葡萄球菌属、不动杆菌属、短小杆菌属、链霉菌属和芽孢杆菌属似乎也具有有趣的代谢能力，但出现频率较低。未来涉及细菌与昆虫相互作用或分析其他潜在作用的研究将为细菌群落对甲虫有益的能力提供更多见解。
