Lactobacillus plantarum response to inorganic carbon concentrations: PyrR2-dependent and -independent transcription regulation of genes involved in arginine and nucleotide metabolism

Abstract

Lactobacillus plantarum susbp. plantarum is a capnophilic Gram-positive heterotroph with optimal growth in 4 % CO 2 -enriched air. At low inorganic carbon (C i ) concentrations, the pyr genes encoding the enzymes of the pyrimidine biosynthetic pathway were overexpressed, in agreement with a previous study showing that these genes are regulated at the transcription level in response to C i via a PyrR 2 -mediated mechanism. A previous study of high-CO 2 -requiring (HCR) mutants revealed an unknown genetic link between arginine regulation and C i -dependent nutritional needs. To better understand L. plantarum's adaptation to C i availability, additional C iresponsive genes were sought in the arginine biosynthetic pathway (arg and car genes) using slot-blot hybridization and a proteomic differential 2D gel electrophoresis (DIGE) global approach. Besides the nine pyr-encoded proteins, 16 new Icr (inorganic-carbon-regulated) proteins accumulated differentially in response to C i availability, suggesting that the C i response involves several metabolic pathways and adaptation processes. Among these Icr proteins only argininosuccinate lyase, encoded by argH, was involved in arginine biosynthesis. Three proteins involved in the purine biosynthetic pathway and nucleotide conversion, adenylate kinase (Adk), GMP synthase (GuaA), and IMP dehydrogenase (GuaB), accumulated differentially in response to changes in C i levels. Expression of the Icr protein-encoding genes argH and guaB was regulated at the transcription level or by RNA stability in response to C i availability, as previously demonstrated for the pyr genes. However, PyrR 2 was not essential for the C i -regulated transcription of argH and guaB, demonstrating that PyrR 2 modulates only a subset of C i -regulated genes. These results suggest that the C i response may involve at least two regulatory mechanisms in L. plantarum.

The MerR/NmlR Family Transcription Factor of Streptococcus pneumoniae Responds to Carbonyl Stress and Modulates Hydrogen Peroxide Production

“…The link between CarAB activity and hydrogen peroxide production in pneumococci is unclear; however, it should be noted that one of the products of the CarAB-catalyzed reaction (P i ) is a required substrate for SpxB. The major product of CarAB activity, car- (4). Regulation of carB in S. pneumoniae has not been studied, but in other organisms carB expression has been shown to be influenced by both pyrimidine and arginine availability, as well as the intracellular inorganic carbon concentration (CO 2 /bicarbonate) (4,5).…”

Isolation and characterization of a CO2-tolerant Lactobacillus strain from Crystal Geyser, Utah, U.S.A.

“…SFAs, for example, pack together much more tightly than MUFAs, which would be consistent with a decrease in cell size under high PCO 2 . Such responses have been documented for temperature, pH, hydrostatic pressure, and osmotic stresses but not for CO 2 (To and Etzel, 1997;De Vries et al, 2006;Bringel et al, 2008).…”

“…CO 2 enriched environments for cultured Lactobacilli are between 4 and 25% CO 2 (0.004-0.025 MPa) (Song et al, 2007;Bringel et al, 2008;Arioli et al, 2009). In contrast, CG-1 can grow at 1.0 MPa, or 40 times the CO 2 utilized by L. plantarum.…”

“…Many Lactobacilli are defined as capnophilic and fermentative, growing syntrophically with CO 2 and acidproducing organisms (Bringel et al, 2008). CO 2 enriched environments for cultured Lactobacilli are between 4 and 25% CO 2 (0.004-0.025 MPa) (Song et al, 2007;Bringel et al, 2008;Arioli et al, 2009).…”

“…They are phylogenetically diverse, perform a variety of metabolic activities, and share very little evolutionary relationship to each other (Song et al, 2007;Bringel et al, 2008;Arioli et al, 2009). Capnophiles have been isolated from a variety of habitats including plants, mammalian cavities, wastewater, and animal rumens (Ballestra et al, 1996;Bringel et al, 2008;Ueda et al, 2008;Arioli et al, 2009).…”