Kluyver Centre for Genomics of Industrial Fermentation, P.O. Box 5057, 2600 GA, Delft, The Netherlands.
Environ Microbiol. 2013 Aug;15(8):2319-32. doi: 10.1111/1462-2920.12104. Epub 2013 Mar 5.
This paper describes the metabolic adaptation of Lactococcus lactis during the transition from a growing to a non-growing state using retentostat cultivation. Under retentostat cultivation, the specific growth rate decreased from 0.025 h(-1) to 0.0001 h(-1) in 42 days, while doubling time increased to more than 260 days. Viability of the overall culture was maintained above 90% but included approximately 20% damaged cells, which had lost their colony forming capacity on solid media. Although culture biomass and viability had reached a steady-state after 14 days of retentostat cultivation, the morphology of the cells changed from coccus-to-rod shape at later stages of retentostat cultivation, by which the cell's surface to volume ratio was estimated to increase 2.4-fold. Furthermore, the metabolic patterns switched between homolactic and mixed-acid fermentation during the retentostat cultivation. Retentostat cultivation enabled the calculation of accurate substrate- and energy-related maintenance coefficients and biomass yields under non-growing conditions, which were in good agreement with those calculated by extrapolation from chemostat cultivations at high dilution rates. In this study, we illustrate how retentostat cultivation allows decoupling of growth and non-growth associated processes in L. lactis, enabling the analysis of quantitative physiological responses of this bacterium to near zero-specific growth rates.
本文描述了嗜热链球菌在连续培养过程中从生长状态到非生长状态的代谢适应。在连续培养过程中，比生长速率从 0.025 h(-1) 降低至 0.0001 h(-1)，倍增时间增加到 260 天以上。整个培养物的存活率保持在 90%以上，但其中约有 20%的受损细胞失去了在固体培养基上形成菌落的能力。尽管连续培养 14 天后培养物生物量和存活率达到了稳定状态，但细胞形态在连续培养的后期从球菌变为杆状，由此估计细胞的表面积与体积比增加了 2.4 倍。此外，在连续培养过程中代谢模式在同质乳酸发酵和混合酸发酵之间切换。连续培养使我们能够在非生长条件下计算出准确的基质和能量相关维持系数和生物量产率，与通过高稀释率恒化培养外推计算出的值吻合良好。在本研究中，我们说明了连续培养如何使嗜热链球菌的生长和非生长相关过程解耦，从而能够分析该细菌对接近零比生长速率的定量生理响应。
