Genta Fernando A, Dillon Rod J, Terra Walter R, Ferreira Clélia
Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, C.P. 26077, São Paulo, SP 05513-970, Brazil.
J Insect Physiol. 2006 Jun;52(6):593-601. doi: 10.1016/j.jinsphys.2006.02.007. Epub 2006 Feb 28.
Tenebrio molitor larvae were successfully reared free of cultivatable gut lumen bacteria, yeasts and fungi using two approaches; aseptic rearing from surface sterilized eggs and by feeding larvae with antibiotic-containing food. Insects were reared on a rich-nutrient complete diet or a nutrient-poor refractory diet. A comparison of digestive enzyme activities in germ free and conventional insects containing a gut microbiota did not reveal gross differences in enzymes that degrade cell walls from bacteria (lysozyme), fungi (chitinase and laminarinase) and plants (cellulase and licheninase). This suggested that microbial-derived enzymes are not an essential component of the digestive process in this insect. However, more detailed analysis of T. molitor midgut proteins using an electrophoretic separation approach showed that some digestive enzymes were absent and others were newly expressed in microbiota-free larvae. Larvae reared in antibiotic-containing refractory wheat bran diet performed poorly in comparison with controls. The addition of saligenin, the aglycone of the plant glucoside salicin, has more deleterious effects on microbiota-free larvae than on the conventionally reared larvae, suggesting a detoxifying role of midgut microbiota. Analysis of the volatile organic compounds released from the faecal pellets of the larvae shows key differences in the profiles from conventionally reared and aseptically reared larvae. Pentadecene is a semiochemical commonly found in other beetle species. Here we demonstrate the absence of pentadecene from aseptically reared larvae in contrast to its presence in conventionally reared larvae. The results are discussed in the light of the hypothesis that microbial products play subtle roles in the life of the insect, they are involved in the digestion of refractory food, detoxification of secondary plant compounds and modify the volatile profiles of the insect host.
利用两种方法成功培育出无可培养肠道腔细菌、酵母和真菌的黄粉虫幼虫；一种是从表面消毒的卵进行无菌饲养，另一种是用含抗生素的食物喂养幼虫。昆虫饲养在营养丰富的完全饲料或营养贫乏的难消化饲料上。对无菌昆虫和含有肠道微生物群的传统昆虫的消化酶活性进行比较，未发现降解细菌细胞壁（溶菌酶）、真菌细胞壁（几丁质酶和海带多糖酶）和植物细胞壁（纤维素酶和地衣多糖酶）的酶存在显著差异。这表明微生物衍生的酶不是这种昆虫消化过程的必需组成部分。然而，使用电泳分离方法对黄粉虫中肠蛋白质进行更详细的分析表明，一些消化酶在无菌幼虫中不存在，而其他消化酶则是新表达的。与对照组相比，在含抗生素的难消化麦麸饲料中饲养的幼虫表现不佳。植物糖苷水杨苷的苷元水杨醇的添加，对无菌幼虫的有害影响比对传统饲养幼虫的更大，这表明中肠微生物群具有解毒作用。对幼虫粪便颗粒释放的挥发性有机化合物的分析表明，传统饲养和无菌饲养幼虫的挥发性有机化合物谱存在关键差异。十五碳烯是在其他甲虫物种中常见的一种信息素。在这里，我们证明无菌饲养的幼虫中不存在十五碳烯，而传统饲养的幼虫中存在十五碳烯。根据微生物产物在昆虫生命中发挥微妙作用的假设对结果进行了讨论，这些作用包括参与难消化食物的消化、次生植物化合物的解毒以及改变昆虫宿主的挥发性特征。
