Mellefont L A, McMeekin T A, Ross T
Centre for Food Safety and Quality, School of Agricultural Science, University of Tasmania, GPO Box 252-54, Hobart 7001, Tasmania, Australia.
Int J Food Microbiol. 2003 Jun 25;83(3):281-93. doi: 10.1016/s0168-1605(02)00377-x.
The effects of osmotic environment and inoculum history on lag times were examined. Abrupt osmotic shifts of cultures were found to induce lag phases in a variety of foodborne bacteria. Relative lag times (RLT; the ratio of lag time to generation time) were used to differentiate the effects of the shift from those of the outgrowth environment. In general, osmotic downshifts induced larger RLTs than equivalent upshifts. An observed reduction in RLT at very low a(w), however, was unexpected. For an osmotic downshift, differences were observed in the RLT response of the Gram-negative and -positive strains tested. RLTs were usually extended for Gram-negative organisms as conditions became less favourable for growth. In comparison, RLT remained relatively unaffected for Gram-positive organisms. The observations reported in this study demonstrate that lag time can be understood in terms of the amount of work to be done to adjust to new environmental conditions and the rate at which that work is done, and are consistent with known strategies for osmoregulation employed by the various organisms studied.
研究了渗透环境和接种物历史对延迟期的影响。发现培养物的突然渗透变化会在多种食源细菌中诱导延迟期。使用相对延迟时间（RLT；延迟时间与世代时间的比率）来区分转移效应与生长环境效应。一般来说，渗透向下转移比等效的向上转移诱导更大的RLT。然而，在非常低的a(w)下观察到的RLT降低是出乎意料的。对于渗透向下转移，在所测试的革兰氏阴性和阳性菌株的RLT反应中观察到差异。随着条件变得对生长不利，革兰氏阴性菌的RLT通常会延长。相比之下，革兰氏阳性菌的RLT相对不受影响。本研究报告的观察结果表明，延迟期可以根据适应新环境条件所需完成的工作量以及完成该工作的速率来理解，并且与所研究的各种生物体采用的已知渗透调节策略一致。
