大黄鱼源气单胞菌的分离鉴定及致腐表型

为鉴别大黄鱼腐败菌气单胞菌的致腐能力,采用生理生化和分子方法(16S r RNA)鉴定冷藏大黄鱼货架期终点不产H2S的菌株。分析菌株在体外培养条件下的生长、胞外酶活性、三甲胺(TMA)和生物胺形成的腐败表型,将菌株接种在灭菌鱼汁中测定其致腐能力。结果显示,分离株AE03和AE04在0~37°C及0~60的盐度下生长良好,在4和25°C条件下AE03菌株的生长速率显著高于AE04菌株。2株细菌不产H2S,能还原氧化三甲胺(TMAO),分解尿素和液化明胶,氧化酶、赖氨酸、鸟氨酸脱羧酶、精氨酸水解酶等都呈阳性,能利用葡萄糖。结合16S r RNA鉴定发现分离株AE03为杀鲑气单胞菌,AE04为软体动物气单胞菌。在体外培养中,2种气单胞菌均能产生蛋白酶、形成TMA和生物被膜,其中AE03菌株生成各指标的能力高于AE04菌株,同时AE03菌株还具有脂酶活性,产生生物胺,其中尸胺含量较高。气单胞菌AE03在灭菌鱼汁中产生的挥发性盐基氮(TVB-N)显著高于AE04。通过紫色杆菌CV026和根癌农杆菌A136 2种报告菌检测发现,2株气单胞菌是高丝氨酸内酯(AHLs)产生菌,其中AE03菌株产生的AHLs含量显著高于AE04菌株。研究表明,杀鲑气单胞菌AE03为冷藏大黄鱼的强致腐菌,且能分泌高含量的AHLs,研究为从群体感应角度阐明气单胞菌的致腐机理奠定了良好的基础。

Spoilage phenotypic characterization and identification of Aeromonas isolated from spoiled Larimichthys crocea

To identify the spoilage potential of two Aeromonas strains isolated from the spoiled Larimichthys crocea, we identified the isolates that did not produce H2S by biochemical characterization and 16S rRNA. All of the isolates were able to grow aerobically from 4 ℃ to 37 ℃, survived below 60 salinity, and could reduce trimethylamine N-Oxide to trimethylamine (TMA). Biochemical characterization and phylogenetic tree analysis of 16S rRNA gene showed that AE03 and AE04 belonged to A. salmonicida and A. molluscorum, repectively. The isolate AE03 showed the faster growth rate than AE04 on the growth curves at 4 ℃ and 25 ℃, and exhibited the higher production of biogenic amine, TMA, and extracellular enzyme activity in vitro. In sterile fish juice, the total volatile basic nitrogen (TVB-N) value of AE03 was also significantly higher than that of AE04. Furthermore, two isolates could produce AHLs by C. violaceum CV026 and A. tumefaciens A136 biosensor detecting system, and AHLs activity in AE03 was higher than that in AE04.Thus, it was found that AE03 (A. salmonicida) was a strong spoiler in deterioration of L. crocea at refrigerated storage, and produced higher AHLs activtiy. The present study provided a good foundation to clarify the mechanism of spoilage of Aeromonas from the point of quorum sensing.