分離自截切小黃瓜之菌株Enterobacter sp. FS08特性分析

Abstract

微生物引起的食品腐敗導致食品的感官分數和營養價值下降。細菌中的趨化泳動行為與特定化合物的降解有關。然而，泳動行為是否涉及食品腐敗尚無相關研究佐證。在目前有關於小黃瓜菌相的分析與研究中，實驗室利用全長16S rDNA定序之方式，發現腸桿菌屬(Enterobacter)為普遍存在於小黃瓜中的菌屬之一，此外分離及挑選來自小黃瓜的其中一菌株，命名為Enterobacter sp. FS08，全基因體定序 (Whole genome sequencing, WGS) 鑑定結果與National Center for Biotechnology Information (NCBI)資料庫中Enterobacter mori 08-091、Enterobacter cloacae WP8-W19—CRE-02相似。初期實驗結果發現Enterobacter sp. FS08與其他小黃瓜分離株相比，具有更高的泳動速率。這個結果暗示 Enterobacter sp. FS08 的泳動行為或許與它在小黃瓜表成為優勢菌株有關。因此，本研究的目的為探討Enterobacter sp. FS08的泳動能力與截切小黃瓜中特定成分之間的關聯，並同時了解菌株是否有良好的壓力適應性，以了解菌株是否有提高生存能力的特性，也幫助推測菌株與生鮮小黃瓜之間的關聯。結果顯示，Enterobacter sp. FS08不僅在15℃下表現出游泳能力，而且對小黃瓜基質、葡萄糖和蘋果酸也表現出顯著的趨化泳動反應，還能在7.5%的鹽濃度下生長，已和中等嗜鹽菌相當。而泳動和趨化性的表現可以透過一些WGS分析出之基因來解釋，例如具有化學趨化物質受體(chemoreceptor)的tsr、trg基因與鞭毛合成的相關基因fliE。未來則可進一步探討Enterobacter sp. FS08之泳動與小黃瓜腐敗的關聯性。瞭解微生物行為之相關機制後有助於未來開發延長生鮮產品保存期限之策略。

Food spoilage caused by bacteria leads to poor sensory and nutritional quality. Chemotactic swimming behavior in bacteria is related to the degradation toward specific compounds. However, the link between the swimming behavior and food spoilage is unclear. In the current study, I studied cucumber microbiota and found that Enterobacter is one of common genera existing in cucumber, defined by full length 16S rDNA amplicon sequencing method. I selected and isolated one of the Enterobacter strains from cucumber, named Enterobacter sp. FS08, whose genome was analyzed by whole genome sequencing (WGS). The WGS result showed that Enterobacter sp. FS08 was similar to Enterobacter mori 08-091 and Enterobacter cloacae WP8-W19—CRE-02 in NCBI database. Furthermore, the Enterobacter sp. FS08 with flagella displayed higher rate of swimming motility compared to other isolates from cucumbers. Therefore, the goal of this study was to characterize the link between the strain and cucumber. The correlation between specific compositions in cucumber and Enterobacter sp. FS08 was determined and the stress tolerance of this strain was evaluated. The result showed that Enterobacter sp. FS08 not only exhibits swimming ability at 15℃, but also displays markedly positive chemotactic swimming response to the cucumber matrix, glucose and malic acid. Enterobacter sp. FS08 can grow in 7.5% NaCl environment, which is in the range of moderate halophile. The observed phenotypes could be explained by the presence of genes related to chemoreceptors, such as tsr and trg and flagellar biosynthesis, e.g., flhA based on the WGS results. Further studies are required to delineate the relationship between swimming of Enterobacter sp. FS08 and the spoilage of fresh-cut cucumbers. Better understanding of the microbial behavior paves the way for extending the shelf life and controlling the quality of fresh-cut products in the future.