一项研究报告说，一种寄生蜂的幼虫使用杀菌剂对它们的美洲蟑螂宿主进行消毒。Gudrun Herzner及其同事分析了美洲蟑螂的外表面和内部组织，并且确定了它们含有粘质沙雷氏菌（Serratia marcescens）和其他病原体。这组作者然后分析了寄生蜂扁头泥蜂（Ampulex compressa）的幼虫分泌的液滴，结果发现了这种液滴含有强大的杀菌剂，能保护宿主不受粘质沙雷氏菌和其他细菌与真菌的侵害。这种天然消毒剂是有用处的，因为这种蜂的雌性成虫在把一枚卵粘在这种蟑螂的腿上之前，会蜇这种蟑螂并且把它们拖到一个隐蔽的地点。在大约7天之后，孵化出的幼虫运动到这种蟑螂体内并以它的内脏为食。在几乎完整地吃掉这种蟑螂之后，这种幼虫会在蟑螂尸体内化作一个茧，然后变成一只蜂。此前的研究已经确定了一种来自这种幼虫的物质micromolide可能作为一种有潜力的抗结核药物。其他研究也已经发现了另外的一些昆虫——诸如埋葬甲虫——能够对它们的幼虫的宿主进行消毒。这组作者说，人类因此不是唯一一种试图应对与被污染的食物来源相关的问题的生物。(生物谷Bioon.com)
doi: 10.1073/pnas.1213384110
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Larvae of the parasitoid wasp Ampulex compressa sanitize their host, the American cockroach, with a blend of antimicrobials
Gudrun Herznera,1, Anja Schlechta, Veronika Dollhofera, Christopher Parzefalla, Klaus Harrarb, Andreas Kreuzerb, Ludwig Pilslb, and Joachim Rutherc
Food resources contaminated with spoilage or pathogenic microorganisms pose severe problems to all higher organisms. Here, we describe a food-hygienic strategy of the emerald cockroach wasp Ampulex compressa. The wasp larvae develop on and inside the American cockroach Periplaneta americana, a host that can harbor various putrefactive microbes, as well as human and insect pathogens. From P. americana, we isolated the Gram-negative bacterium Serratia marcescens, which is a potent entomopathogen that can rapidly kill insect larvae. It is also known as a food contaminant and as an opportunistic human pathogen. Using behavioral observations and chemical analyses, we demonstrated that A. compressa larvae impregnate their cockroach hosts from inside with large amounts of an oral secretion containing a blend of γ-lactones and isocoumarins with (R)-(-)-mellein [(R)-(-)-3,4-diydro-8-hydroxy-3-methylisocoumarin] and micromolide [(4R,9Z)-octadec-9-en-4-olide] as dominant components. We fractionated hexane extracts of the secretion and investigated the antimicrobial properties of the fraction containing the lactones and isocoumarins, as well as of synthetic (R)-(-)-mellein and micromolide, against S. marcescens and a Gram-positive bacterium, Staphylococcus hyicus, in broth microdilution assays. The test fraction inhibited growth of both tested bacteria. The activity of the fraction against S. marcescens was explained by (R)-(-)-mellein alone, and the activity against S. hyicus was explained by the combined action of (R)-(-)-mellein and micromolide. Our data suggest that the specific combination of antimicrobials in the larval secretion provides an effective frontline defense against the unpredictable spectrum of microbes that A. compressa larvae may encounter during their development inside their cockroach hosts.
