title: Molecular adaptation of Lactobacillus plantarum WCFS1 to gallic acid revealed by genome-scale transcriptomic signature and physiological analysis.
abstract: BACKGROUND
  Gallic acid (GA) is a model hydroxybenzoic acid that occurs esterified in the lignocellulosic biomass of higher plants. GA displays relevant biological activities including anticancer properties. Owing to its antimicrobial and cellulase-inhibiting activities, GA also imposes constraints to the fermentability of lignocellulosic hydrolysates. In depth-knowledge of the mechanisms used by tolerant microorganisms to adapt to hydroxybenzoic acids would be a step forward to improve the bioavailability of GA or select/engineer production hosts with improved metabolic traits for the bioconversion of pretreated lignocellulosic biomass.
  
  
  RESULTS
  Whole genome transcriptional profiling using DNA microarrays was used to characterize the molecular response of Lactobacillus plantarum WCFS1 to GA. Expression levels of 14 and 40 genes were differentially regulated at 1.5 and 15 mM GA, respectively. The transcriptomic analysis identified a marked induction of genes with confirmed or related roles to gastrointestinal survival, the repression of genes coding for certain ABC-type transporters and modulation of genes involved in the control of intracellular ammonia levels, among other responses. Most notably, a core set of genes dedicated to produce GA from polyphenols (tanB Lp ), decarboxylate GA to pyrogallol (lpdB, lpdC and lpdD) and transport functions (lp_2943) was highly overexpressed at both GA concentrations. Correspondingly, resting cells of strain WCFS1 induced by GA, but not their non-induced controls, produced pyrogallol. Gene expression and organization of genes involved in GA metabolism suggested a chemiosmotic mechanism of energy generation. Resting cells of L. plantarum induced by GA generated a membrane potential and a pH gradient across the membrane immediately upon addition of GA. Altogether, transcriptome profiling correlated with physiological observations indicating that a proton motive force could be generated during GA metabolism as a result of electrogenic GA uptake coupled with proton consumption by the intracellular gallate decarboxylase.
  
  
  CONCLUSIONS
  The combination of transcriptome and physiological analyses revealed versatile molecular mechanisms involved in the adaptation of L. plantarum to GA. These data provide a platform to improve the survival of Lactobacillus in the gut. Our data may also guide the selection/engineering of microorganisms that better tolerate phenolic inhibitors present in pretreated lignocellulosic feedstocks.
authors.affiliation: Laboratorio de Biotecnología Bacteriana, Instituto de Ciencia y Tecnología de los Alimentos y Nutrición (ICTAN-CSIC), Madrid, Spain. imreveron@ictan.csic.es.
authors.forename: Inés
authors.initials: I
authors.lastname: Reverón
authors.affiliation: Laboratorio de Biotecnología Bacteriana, Instituto de Ciencia y Tecnología de los Alimentos y Nutrición (ICTAN-CSIC), Madrid, Spain. blanca.r@ictan.csic.es.
authors.forename: Blanca
authors.initials: B
authors.lastname: de las Rivas
authors.affiliation: Centro de Investigaciones Biológicas (CIB-CSIC), Madrid, Spain. ruth.m.r@cib.csic.es.
authors.forename: Ruth
authors.initials: R
authors.lastname: Matesanz
authors.affiliation: Laboratorio de Biotecnología Bacteriana, Instituto de Ciencia y Tecnología de los Alimentos y Nutrición (ICTAN-CSIC), Madrid, Spain. rmunoz@ictan.csic.es.
authors.forename: Rosario
authors.initials: R
authors.lastname: Muñoz
authors.affiliation: Laboratorio de Biotecnología Bacteriana, Instituto de Ciencia y Tecnología de los Alimentos y Nutrición (ICTAN-CSIC), Madrid, Spain. fxlopez@ictan.csic.es.
authors.forename: Félix
authors.initials: F
authors.lastname: López de Felipe
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000235:genetics / Q000378:metabolism; D000222:Adaptation, Physiological / Q000187:drug effects*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D050260:Carbohydrate Metabolism / Q000187:drug effects; D005707:Gallic Acid / Q000378:metabolism / Q000494:pharmacology*; D020869:Gene Expression Profiling; D016680:Genome, Bacterial; D048191:Lactiplantibacillus plantarum / Q000235:genetics* / Q000378:metabolism; D020411:Oligonucleotide Array Sequence Analysis; D011748:Pyrogallol / Q000378:metabolism; D060888:Real-Time Polymerase Chain Reaction; D059467:Transcriptome / Q000187:drug effects*
chemical_list: D018528:ATP-Binding Cassette Transporters; D001426:Bacterial Proteins; D011748:Pyrogallol; D005707:Gallic Acid