Del Rio Beatriz, Linares Daniel, Ladero Victor, Redruello Begoña, Fernandez Maria, Martin Maria Cruz, Alvarez Miguel A
Instituto de Productos Lácteos de Asturias, IPLA-CSIC, Paseo Rio Linares s/n, 33300 Villaviciosa, Spain.
Instituto de Productos Lácteos de Asturias, IPLA-CSIC, Paseo Rio Linares s/n, 33300 Villaviciosa, Spain.
Int J Food Microbiol. 2016 Nov 7;236:83-9. doi: 10.1016/j.ijfoodmicro.2016.07.021. Epub 2016 Jul 15.
Lactococcus lactis subsp. cremoris CECT 8666 is a lactic acid bacterium that synthesizes the biogenic amine putrescine from agmatine via the agmatine deiminase (AGDI) pathway. The AGDI genes cluster includes aguR. This encodes a transmembrane protein that functions as a one-component signal transduction system, the job of which is to sense the agmatine concentration of the medium and accordingly regulate the transcription of the catabolic operon aguBDAC. The latter encodes the proteins necessary for agmatine uptake and its conversion into putrescine. This work reports the effect of extracellular pH on putrescine biosynthesis and on the genetic regulation of the AGDI pathway. Increased putrescine biosynthesis was detected at acidic pH (pH5) compared to neutral pH. Acidic pH induced the transcription of the catabolic operon via the activation of the aguBDAC promoter PaguB. However, the external pH had no significant effect on the activity of the aguR promoter PaguR, or on the transcription of the aguR gene. The transcriptional activation of the AGDI pathway was also found to require a lower agmatine concentration at pH5 than at neutral pH. Finally, the following of the AGDI pathway counteracted the acidification of the cytoplasm under acidic external conditions, suggesting it to provide protection against acid stress.
乳酸乳球菌乳脂亚种CECT 8666是一种乳酸菌，它通过胍丁胺脱亚氨酶（AGDI）途径从胍丁胺合成生物胺腐胺。AGDI基因簇包括aguR。该基因编码一种跨膜蛋白，其作为单组分信号转导系统发挥作用，其作用是感知培养基中的胍丁胺浓度，并相应地调节分解代谢操纵子aguBDAC的转录。后者编码胍丁胺摄取及其转化为腐胺所需的蛋白质。这项工作报道了细胞外pH对腐胺生物合成以及AGDI途径的基因调控的影响。与中性pH相比，在酸性pH（pH5）下检测到腐胺生物合成增加。酸性pH通过激活aguBDAC启动子PaguB诱导分解代谢操纵子的转录。然而，外部pH对aguR启动子PaguR的活性或aguR基因的转录没有显著影响。还发现AGDI途径的转录激活在pH5时比在中性pH时需要更低的胍丁胺浓度。最后，AGDI途径的运行抵消了酸性外部条件下细胞质中的酸化作用，表明它能提供抗酸应激保护。
