Institute of Applied Ecology, Fujian Agriculture and Forestry University, Fuzhou, China.
PLoS One. 2013 Jul 19;8(7):e68852. doi: 10.1371/journal.pone.0068852. Print 2013.
Insect midgut microbiota is important in host nutrition, development and immune response. Recent studies indicate possible links between insect gut microbiota and resistance to biological and chemical toxins. Studies of this phenomenon and symbionts in general have been hampered by difficulties in culture-based approach. In the present study, DNA sequencing was used to examine the midgut microbiota of diamondback moth (DBM), Plutella xylostella (L.), a destructive pest that attacks cruciferous crops worldwide. Its ability to develop resistance to many types of synthetic insecticide and even Bacillus thuringiensis toxins makes it an important species to study.
METHODOLOGY/PRINCIPAL FINDINGS: Bacteria of the DBM larval midgut in a susceptible and two insecticide (chlorpyrifos and fipronil) resistant lines were examined by Illumina sequencing sampled from an insect generation that was not exposed to insecticide. This revealed that more than 97% of the bacteria were from three orders: Enterobacteriales, Vibrionales and Lactobacillales. Both insecticide-resistant lines had more Lactobacillales and the much scarcer taxa Pseudomonadales and Xanthomonadales with fewer Enterobacteriales compared with the susceptible strain. Consistent with this, a second study observed an increase in the proportion of Lactobacillales in the midgut of DBM individuals from a generation treated with insecticides.
CONCLUSIONS/SIGNIFICANCE: This is the first report of high-throughput DNA sequencing of the entire microbiota of DBM. It reveals differences related to inter- and intra-generational exposure to insecticides. Differences in the midgut microbiota among susceptible and insecticide-resistant lines are independent of insecticide exposure in the sampled generations. While this is consistent with the hypothesis that Lactobacillales or other scarcer taxa play a role in conferring DBM insecticide resistance, further studies are necessary to rule out other possibilities. Findings constitute the basis for future molecular work on the functions of insect midgut microbiota taxa and their possible role in conferring host resistance to toxins.
昆虫中肠微生物群在宿主营养、发育和免疫反应中很重要。最近的研究表明，昆虫肠道微生物群与对生物和化学毒素的抗性之间可能存在联系。由于基于培养的方法存在困难，对这种现象和共生体的研究一直受到阻碍。在本研究中，我们使用 DNA 测序技术研究了小菜蛾（Plutella xylostella）幼虫中肠微生物群，小菜蛾是一种全球性的十字花科作物害虫。它对多种类型的合成杀虫剂甚至苏云金芽孢杆菌毒素产生抗性的能力使其成为一种重要的研究物种。
方法/主要发现：对易感性和两种杀虫剂（毒死蜱和氟虫腈）抗性品系的小菜蛾幼虫中肠细菌进行了 Illumina 测序，这些品系取自未接触杀虫剂的昆虫一代。结果表明，超过 97%的细菌来自三个菌目：肠杆菌目、弧菌目和乳杆菌目。与敏感株相比，两种杀虫剂抗性品系的乳杆菌目数量更多，而非常罕见的假单胞菌目和黄单胞菌目数量更少。与这一结果一致的是，第二项研究观察到，在经过杀虫剂处理的一代小菜蛾个体中，中肠乳杆菌目比例增加。
结论/意义：这是小菜蛾整个微生物组高通量 DNA 测序的首次报道。它揭示了与世代间和世代内接触杀虫剂相关的差异。易感性和杀虫剂抗性品系中肠微生物群的差异与采样世代中接触杀虫剂无关。虽然这与乳杆菌目或其他罕见类群在赋予小菜蛾抗虫性方面发挥作用的假设一致，但仍需要进一步研究来排除其他可能性。这些发现为未来研究昆虫中肠微生物群类群的功能及其在赋予宿主对毒素抗性方面的可能作用奠定了基础。
