de Vries E J, Breeuwer J A, Jacobs G, Mollema C
Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, Kruislaan 320, Amsterdam, 1098 SM, The Netherlands.
J Invertebr Pathol. 2001 Feb;77(2):120-8. doi: 10.1006/jipa.2001.5009.
Associations between insects and gut bacteria are ubiquitous. It is possible to make a distinction between permanent associations (called symbiosis), in which the same type of bacteria is present in more than one generation of the insect, and transient associations. Transient bacteria are ingested together with food but do not settle in the insect gut in such a way that they will be passed on to the next generation. In this study, we describe the permanent association between Western flower thrips (Frankliniella occidentalis), a polyphagous insect species that is a major pest worldwide, and one type of gut bacteria. On the basis of direct microscopic observations and counts of bacteria, it was found that thrips from the populations studied contained large numbers of bacteria in their hindgut. Bacteria were isolated from their host and grown on 10 different agar media. The number of bacteria isolated on agar media equaled the number of direct counts. All isolates had the same colony morphology. On the basis of their 16S rDNA sequence these bacteria were identified as Enterobacteriaceae, closely related to Escherichia coli. Isolates tested with API 20E biochemical tests were Erwinia species. This was the only type of bacteria found in all thrips individuals on any of the 10 different agar media. Universal primers, which would potentially pick up DNA from any bacterium present in the insect, were applied on crude DNA extracts from thrips with bacteria. We only found 16S rDNA sequences similar to those of the isolated thrips gut bacteria. The same type of bacteria was present in all life stages of the thrips and was found to persist in the thrips populations for at least 2 years (more than 50 generations).
昆虫与肠道细菌之间的关联无处不在。可以区分永久性关联（称为共生）和短暂性关联，前者指同一类型的细菌在昆虫的不止一代中存在。短暂性细菌与食物一起被摄入，但不会以能传递给下一代的方式在昆虫肠道中定居。在本研究中，我们描述了西花蓟马（Frankliniella occidentalis）——一种多食性昆虫物种，也是全球主要害虫——与一种肠道细菌之间的永久性关联。基于对细菌的直接显微镜观察和计数，发现所研究种群的蓟马后肠中含有大量细菌。从其宿主中分离出细菌，并在10种不同的琼脂培养基上培养。在琼脂培养基上分离出的细菌数量与直接计数的数量相等。所有分离株具有相同的菌落形态。基于其16S rDNA序列，这些细菌被鉴定为肠杆菌科，与大肠杆菌密切相关。用API 20E生化试验检测的分离株为欧文氏菌属。这是在10种不同琼脂培养基上的所有蓟马个体中发现的唯一一种细菌类型。将可能从昆虫中存在的任何细菌中获取DNA的通用引物应用于带有细菌的蓟马的粗DNA提取物。我们只发现了与分离出的蓟马肠道细菌的16S rDNA序列相似的序列。同一种细菌存在于蓟马的所有生命阶段，并在蓟马种群中持续存在至少2年（超过50代）。
