Article

Sensing and Adaptation to Low pH Mediated by Inducible Amino Acid Decarboxylases in Salmonella

Laboratoire de Chimie Bactérienne, Institut de Microbiologie de la Méditerranée, CNRS (UPR-CNRS 9043), Marseille, France.
PLoS ONE (Impact Factor: 3.53). 07/2011; 6(7):e22397. DOI: 10.1371/journal.pone.0022397
Source: PubMed

ABSTRACT During the course of infection, Salmonella enterica serovar Typhimurium must successively survive the harsh acid stress of the stomach and multiply into a mild acidic compartment within macrophages. Inducible amino acid decarboxylases are known to promote adaptation to acidic environments. Three low pH inducible amino acid decarboxylases were annotated in the genome of S. Typhimurium, AdiA, CadA and SpeF, which are specific for arginine, lysine and ornithine, respectively. In this study, we characterized and compared the contributions of those enzymes in response to acidic challenges. Individual mutants as well as a strain deleted for the three genes were tested for their ability (i) to survive an extreme acid shock, (ii) to grow at mild acidic pH and (iii) to infect the mouse animal model. We showed that the lysine decarboxylase CadA had the broadest range of activity since it both had the capacity to promote survival at pH 2.3 and growth at pH 4.5. The arginine decarboxylase AdiA was the most performant in protecting S. Typhimurium from a shock at pH 2.3 and the ornithine decarboxylase SpeF conferred the best growth advantage under anaerobiosis conditions at pH 4.5. We developed a GFP-based gene reporter to monitor the pH of the environment as perceived by S. Typhimurium. Results showed that activities of the lysine and ornithine decarboxylases at mild acidic pH did modify the local surrounding of S. Typhimurium both in culture medium and in macrophages. Finally, we tested the contribution of decarboxylases to virulence and found that these enzymes were dispensable for S. Typhimurium virulence during systemic infection. In the light of this result, we examined the genomes of Salmonella spp. normally responsible of systemic infection and observed that the genes encoding these enzymes were not well conserved, supporting the idea that these enzymes may be not required during systemic infection.

0 Followers
 · 
125 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: a b s t r a c t During the course of infection, Salmonella must successively survive the harsh acid stress of the stomach and multiply into a mild acidic compartment within macrophages. Inducible amino acid decarboxylases are known to promote adaptation to acidic environments, as lysine decarboxylation to cadaverine. The idea of Salmonella defenses responses could be employed in systems as polydiacetylene (PDA) to detect this pathogen so important to public health system. Beside that PDA is an important substance because of the unique optical property; that undergoes a colorimetric transitions by various external stimuli. Therefore 10,12-pentacosadyinoic acid (PCDA)/Sphingomyelin(SPH)/Cholesterol(CHO)/Lysine system was tested to determine the colorimetric response induced by Salmonella choleraesuis. PCDA/SPH/CHO/ Lysine vesicles showed a colour change even in low S. choleraesuis concentration present in laboratory conditions and in chicken meat. Thus, this work showed a PCDA/SPH/CHO/Lysine vesicle application to simplify routine analyses in food industry, as chicken meat industry.
    Food Chemistry 08/2014; Food Chemistry(172):428-432. DOI:10.1016/j.foodchem.2014.09.055 · 3.26 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The antimicrobial action of the curing agent sodium nitrite (NaNO2), which is added as a preservative to raw meat products, depends on its conversion to nitric oxide and other reactive nitrogen species under acidic conditions. In this study, we applied RNA-sequencing to analyze the acidified NaNO2 shock and adaptive response of Salmonella Typhimurium, a frequent contaminant in raw meat, considering parameters relevant for the production of raw-cured sausages. Upon a 10 minute exposure to 150 mg/l NaNO2 in LB pH 5.5 acidified with lactic acid, genes involved in nitrosative stress protection together with several other stress related genes were induced. To the contrary, genes involved in translation, transcription, replication and motility were down-regulated. Induction of stress tolerance and reduction of cell proliferation obviously promote survival under harsh acidified NaNO2 stress. The subsequent adaptive response was characterized by up-regulation of NsrR-regulated genes and iron-uptake systems and down-regulation of genes involved in anaerobic respiratory pathways. Strikingly, amino acid decarboxylase systems, which contribute to acid tolerance, displayed increased transcript levels in response to acidified NaNO2. The induction of systems known to be involved in acid resistance indicates a nitrite mediated increase of acid stress. Deletion of cadA, which encodes lysine decarboxylase, resulted in increased sensitivity to acidified NaNO2. Intracellular pH-measurements using a pH-sensitive GFP variant showed that the cytoplasmic pH of S. Typhimurium in LB medium pH 5.5 is decreased upon addition of NaNO2. This study provides the first evidence that intracellular acidification is an additional antibacterial mode of action of acidified NaNO2.
    Applied and Environmental Microbiology 08/2014; 80(20). DOI:10.1128/AEM.01696-14 · 3.95 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The human-pathogenic bacterium Salmonella enterica adjusts and adapts to different environments while attempting colonization. In the course of infection nutrient availabilities change drastically. New techniques, "-omics" data and subsequent integration by systems biology improve our understanding of these changes. We review changes in metabolism focusing on amino acid and carbohydrate metabolism. Furthermore, the adaptation process is associated with the activation of genes of the Salmonella pathogenicity islands (SPIs). Anti-infective strategies have to take these insights into account and include metabolic and other strategies. Salmonella infections will remain a challenge for infection biology.
    Frontiers in Cellular and Infection Microbiology 01/2015; 4:191. DOI:10.3389/fcimb.2014.00191 · 2.62 Impact Factor

Full-text (3 Sources)

Download
79 Downloads
Available from
Jun 2, 2014