title: Putrescine biosynthesis in Lactococcus lactis is transcriptionally activated at acidic pH and counteracts acidification of the cytosol.
abstract: 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.
authors.affiliation: Instituto de Productos Lácteos de Asturias, IPLA-CSIC, Paseo Rio Linares s/n, 33300 Villaviciosa, Spain. Electronic address: beadelrio@ipla.csic.es.
authors.forename: Beatriz
authors.initials: B
authors.lastname: Del Rio
authors.affiliation: Instituto de Productos Lácteos de Asturias, IPLA-CSIC, Paseo Rio Linares s/n, 33300 Villaviciosa, Spain.
authors.forename: Daniel
authors.initials: D
authors.lastname: Linares
authors.affiliation: Instituto de Productos Lácteos de Asturias, IPLA-CSIC, Paseo Rio Linares s/n, 33300 Villaviciosa, Spain.
authors.forename: Victor
authors.initials: V
authors.lastname: Ladero
authors.affiliation: Instituto de Productos Lácteos de Asturias, IPLA-CSIC, Paseo Rio Linares s/n, 33300 Villaviciosa, Spain.
authors.forename: Begoña
authors.initials: B
authors.lastname: Redruello
authors.affiliation: Instituto de Productos Lácteos de Asturias, IPLA-CSIC, Paseo Rio Linares s/n, 33300 Villaviciosa, Spain.
authors.forename: Maria
authors.initials: M
authors.lastname: Fernandez
authors.affiliation: Instituto de Productos Lácteos de Asturias, IPLA-CSIC, Paseo Rio Linares s/n, 33300 Villaviciosa, Spain.
authors.forename: Maria Cruz
authors.initials: MC
authors.lastname: Martin
authors.affiliation: Instituto de Productos Lácteos de Asturias, IPLA-CSIC, Paseo Rio Linares s/n, 33300 Villaviciosa, Spain.
authors.forename: Miguel A
authors.initials: MA
authors.lastname: Alvarez
mesh_terms: D000143:Acids / Q000378:metabolism; D000376:Agmatine / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D003600:Cytosol / Q000737:chemistry / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D006706:Homeostasis; D006863:Hydrogen-Ion Concentration; D006867:Hydrolases / Q000235:genetics / Q000378:metabolism; D013294:Lactococcus lactis / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D009876:Operon; D011700:Putrescine / Q000096:biosynthesis*; D014158:Transcription, Genetic
chemical_list: D000143:Acids; D001426:Bacterial Proteins; D000376:Agmatine; D006867:Hydrolases; C019626:agmatine deiminase; D011700:Putrescine
keywords: AGDI cluster; Acid stress; Biogenic amines; Lactococcus lactis; Putrescine; pH induction