环境因子对大黄鱼腐败希瓦氏菌生长影响的计数法分析

Effect of Environmental Factors on Growth of Shewanella putrefaciens Based on Different Counting Methods

摘要:

以分离于腐败大黄鱼中的腐败希瓦氏菌为对象，采用平板计数法和浊度法分析不同pH值、NaCl浓度和温度下的生长情况，运用修正的Gompertz方程拟合生长曲线，用决定系数、准确度、精确度、残差平方和及平方根误差评价拟合优度，比较分析2种计数法下环境因子对生长界限和动力学参数的影响。结果表明，在3~8℃，pH值6.0及NaCl质量分数3.5%时不生长；2种计数法下生长动力学参数最大比生长速率(μmax)和代时差异不显著(p>0.05)，而迟滞期(λ)和最大细胞密度差异显著(p<0.05)；环境因子对生长动力学参数有显著影响，温度和NaCl浓度对代时影响较大，温度越高或NaCl浓度越低，代时越短；在3~25℃，温度越高，μmax越大，增速为（0.0143±0.0032）h-1/℃，温度越高，λ越小，平板计数法下其降速约1.5h/℃，而在8~15℃，浊度法下λ降速约2.5h/℃；平板计数法下μmax的变化受NaCl浓度及pH值影响较大，λ变化无明显规律，而浊度法下μmax的变化受NaCl浓度和pH值影响不明显，λ变化较明显。因此2种计数法均可对腐败希瓦氏菌生长/非生长作出有效判断，环境因子强度较大时浊度法相比平板技数法迟滞期与最大细胞密度误差较大。

Abstract:

The Shewanella separated from corruption large yellow croaker was used as research object. The growth data of Shewanella putrefaciens under different pH values, NaCl concentrations and temperatures was obtained by using viable count and optical density methods, and the Gompertz model was built. Effect of environmental factors on growth kinetic parameters was compared and analyzed. Results showed that Shewanella putrefaciens could not grow at pH value of 6.0 and NaCl concentration of 3.5% during 3~8℃. The differences of maximum specific growth rate (μmax) and generation time were not significant (p>0.05), but the differences of lag phase (λ) and the most probable density (M) were significant (p<0.05). Environmental factors had significant effect on the growth kinetic parameters.High temperature or low NaCl concentration resulted in short generation time. When temperature was 3~25℃, high temperature resulted in large μmax. The increase rate of μmax was (0.0143±0.0032)h-1/℃.When temperature was high, λ would be short. The λ was decreased at a rate of 1.5h/℃ by using viable count method, while during 8~15℃, it was decreased approximately at a speed of 2.5h/℃ by optical density method. The μmax was influenced significantly by NaCl concentration and pH value, while lag time showed no significant changes by viable count method. Using optical density method, changes of μmaxwere affected unsignificantly by NaCl concentration and pH value, while changes of λ were apparent. Thus, both of the two counting methods could judge the growth/nongrowth state of Shewanella, and the estimation errors of λ and M were increased by harsh environments when using optical density methods.