Ercan Onur, Wels Michiel, Smid Eddy J, Kleerebezem Michiel
Kluyver Centre for Genomics of Industrial Fermentation, Delft, The Netherlands Top Institute Food and Nutrition, Wageningen, The Netherlands Laboratory of Microbiology, Wageningen University, Wageningen, The Netherlands NIZO Food Research, Ede, The Netherlands.
Top Institute Food and Nutrition, Wageningen, The Netherlands NIZO Food Research, Ede, The Netherlands.
Appl Environ Microbiol. 2015 Jan;81(1):320-31. doi: 10.1128/AEM.02484-14. Epub 2014 Oct 24.
This paper describes the molecular and metabolic adaptations of Lactococcus lactis during the transition from a growing to a near-zero growth state by using carbon-limited retentostat cultivation. Transcriptomic analyses revealed that metabolic patterns shifted between lactic- and mixed-acid fermentations during retentostat cultivation, which appeared to be controlled at the level of transcription of the corresponding pyruvate dissipation-encoding genes. During retentostat cultivation, cells continued to consume several amino acids but also produced specific amino acids, which may derive from the conversion of glycolytic intermediates. We identify a novel motif containing CTGTCAG in the upstream regions of several genes related to amino acid conversion, which we propose to be the target site for CodY in L. lactis KF147. Finally, under extremely low carbon availability, carbon catabolite repression was progressively relieved and alternative catabolic functions were found to be highly expressed, which was confirmed by enhanced initial acidification rates on various sugars in cells obtained from near-zero-growth cultures. The present integrated transcriptome and metabolite (amino acids and previously reported fermentation end products) study provides molecular understanding of the adaptation of L. lactis to conditions supporting low growth rates and expands our earlier analysis of the quantitative physiology of this bacterium at near-zero growth rates toward gene regulation patterns involved in zero-growth adaptation.
本文描述了乳酸乳球菌在从生长状态转变为接近零生长状态的过程中的分子和代谢适应性，采用碳限制恒化器培养法。转录组分析表明，在恒化器培养过程中，代谢模式在乳酸发酵和混合酸发酵之间转变，这似乎在相应的丙酮酸消耗编码基因的转录水平上受到控制。在恒化器培养过程中，细胞继续消耗几种氨基酸，但也产生特定的氨基酸，这些氨基酸可能来自糖酵解中间产物的转化。我们在几个与氨基酸转化相关的基因的上游区域鉴定出一个含有CTGTCAG的新基序，我们认为它是乳酸乳球菌KF147中CodY的靶位点。最后，在极低的碳可用性下，碳分解代谢物阻遏逐渐解除，发现替代分解代谢功能高度表达，这通过从接近零生长的培养物中获得的细胞对各种糖的初始酸化速率增强得到证实。目前的综合转录组和代谢物（氨基酸和先前报道的发酵终产物）研究提供了对乳酸乳球菌适应低生长速率条件的分子理解，并将我们早期对该细菌在接近零生长速率下的定量生理学分析扩展到涉及零生长适应的基因调控模式。
