The gut of the agricultural pest Ceratitis capitata hosts a varied community of bacteria, mainly Enterobacteriaceae, that were implicated in several processes that increase the fitness of the insect. In this study, we investigated the antagonistic activity in vitro of Klebsiella oxytoca strains isolated in the 1990s from the alimentary tract of wild medflies collected from different varieties of fruit trees at diverse localities. Assays were carried out against reference strains (representative of Gram-negative and -positive bacterial species) of the American Type Culture Collection (ATCC). Eight Klebsiella, out of 11, expressed a killing activity against Escherichia coli ATCC 23739, and Enterobacter cloacae ATCC 13047; among the eight strains, at least one showed activity against Salmonella typhimurium ATCC 23853. Genomic DNA derived from all Klebsiella strains was then subjected to PCR amplification using specific primer pairs designed from each of the four bacteriocin (KlebB, C, D, CCL) sequences found so far in Klebsiella. KlebD primer pairs were the only to produce a single product for all strains expressing the killing phenotype in vitro. One of the amplicons was cloned and sequenced; the DNA sequence shows 93% identity with a plasmid-carried colicin-D gene of a strain of Klebsiella michiganensis, and 86% identity with the sequence encoding for the klebicin D activity protein in K. oxytoca. Our work provides the first evidence that dominant symbiotic bacteria associated with wild medfly populations express a killing phenotype that may mediate inter and intraspecies competition among bacterial populations in the insect gut in vivo.

中文翻译：

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与野生地中海果蝇种群相关的优势共生细菌揭示了一种类似细菌素的杀灭表型：一项“冷例”研究

农业害虫的肠道头孢菌素拥有不同的细菌群落，主要是肠杆菌科，它们与增加昆虫适应性的几个过程有关。在这项研究中，我们研究了拮抗作用体外的产酸克雷伯菌1990 年代从不同地区不同品种果树采集的野生地中海果蝇消化道中分离出的菌株。针对美国典型培养物保藏中心 (ATCC) 的参考菌株（代表革兰氏阴性和阳性细菌物种）进行了测定。八克雷伯氏菌, 在 11 人中, 表达了针对大肠杆菌ATCC 23739 和阴沟肠杆菌ATCC 13047；在八种菌株中，至少有一种表现出抗鼠伤寒沙门氏菌ATCC 23853. 源自所有基因的基因组 DNA克雷伯氏菌然后使用从迄今为止在克雷伯氏菌. KlebD 引物对是唯一为所有表达杀伤表型的菌株产生单一产品的产品体外. 其中一个扩增子被克隆和测序；该DNA序列与一株携带质粒的大肠杆菌素-D基因有93%的同一性。密歇根克雷伯氏菌, 与编码 klebicin D 活性蛋白的序列有 86% 的同一性K. oxytoca. 我们的工作提供了第一个证据表明与野生地中海果蝇种群相关的优势共生细菌表达了一种杀死表型，该表型可能介导昆虫肠道中细菌种群之间的种间和种内竞争体内.