培养温度对腐败希瓦氏菌DSM6067生长动力学及细胞膜理化特性的影响

低温是保障水产品质量安全的重要方法,然而仍有部分耐冷菌能适应低温环境,继续生长繁殖并最终导致水产品腐败变质。为了解不同培养温度对腐败希瓦氏菌生长动力学参数及细胞膜理化特性变化的影响,以水产品中典型的耐冷腐败微生物腐败希瓦氏菌模式菌株DSM6067为研究对象,对细菌的生长情况、细胞膜脂肪酸组成、膜蛋白含量、细胞微观结构和细胞膜流动性进行分析。结果表明,腐败希瓦氏菌模式菌株DSM6067分别在30,10℃和4℃培养条件下经3.35,25.94 h和122.03 h的延滞期后进入对数生长期;腐败希瓦氏菌虽在低温环境下培养增速较为缓慢,但能够适应低温环境继续生长。腐败希瓦氏菌在相应培养温度下的对数生长中期,30℃条件下细菌细胞膜不饱和脂肪酸总量仅43.36%,其中C16:1(棕榈油酸)为26.62%,而4℃培养下细菌细胞膜不饱和脂肪酸总量为51.04%,其中单不饱和脂肪酸C16:1含量高达46.66%,低温培养下细菌细胞膜中C16:1含量显著增加;细菌细胞膜蛋白表达量随培养温度的降低而有所上升;腐败希瓦氏菌微观结构观察显示,低温培养下的细菌细胞膜较为平滑,胞内空泡较少,细胞体积略大;在低温适应过程中,细菌细胞膜流动性增强。腐败希瓦氏菌细胞膜理化特性所产生的变化为细菌更好地适应低温环境生长提供了一定的物质基础。

Effects of Culture Temperature on the Growth Parameters of Shewanella putrefaciens DSM6067 and Its Membrane Physic-chemical Properties

Low temperature is an important method to ensure the quality and safety of aquatic products, but some cold tolerant bacteria can still survive and proliferate in the low temperature environment, and eventually lead to deterioration of aquatic products. In order to understand the effects of temperature on the growth kinetic parameters and membrane physicochemical properties of Shewanella putrefaciens, which is a typical cold resistant microorganism found in aquatic products, the growth curve and growth kinetic parameters of Shewanella putrefaciens DSM6067 strain, as well as the fatty acid composition, protein content, fluidity, and microstructure of its cell membrane were studied. It was found that the lag phase of the strain cultured at 30 ℃, 10 ℃, and 4 ℃ were 3.35 h, 25.94 h and 122.03 h respectively. Although the growth rate of Shewanella putrefaciens was slower in low temperature environment, it could still proliferate continually. According to the fatty acids compositions of cell membrane at the mid of exponential phase, the total contents of unsaturated fatty acids in bacteria cultured at 4 ℃ was 51.04%, while that of strains cultured at 30 ℃ was as low as 43.36%. Among them, the monounsaturated fatty acid(palmitic acid) C16:1 increased the most significantly from26.62% at 30 ℃ to 46.66% at 4 ℃. The protein content of membrane also increased slightly as the temperature decreased. The fluidity of cell membrane was low initially when the strain was incubated at low temperature, but increased in the latter culture period. The TEM results showed that smoother cell membrane, smaller vacuolation and bigger cell size in strains cultured at low temperatures. The changes of physic-chemical properties should be responsible for Shewanella putrefaciens strains to survive and grow at low temperatures.