Regulation of the Arginine Deiminase System by ArgR2 Interferes with Arginine Metabolism and Fitness of Streptococcus pneumoniae

Abstract

Streptococcus pneumoniae is auxotrophic for arginine, and molecular analysis of the pneumococcal genome showed that the gene encoding an arginine-ornithine antiporter (ArcD) is organized in a cluster together with the arcABC genes encoding the arginine deiminase system (ADS) of pneumococci. The ADS consists of the arginine deiminase (AD), the catabolic ornithine carbamoyltransferase (cOCT), and the carbamate kinase (CK). Pneumococcal genomes contain three ArgR-type regulators (ArgR1, ArgR2, and AhrC) that are supposed to be involved in the regulation of arginine metabolism. Here, we identified ArgR2 of TIGR4 as the regulator of the ADS and ArcD. ArgR2 binds to promoter sequences of the arc operon, and the deficiency of ArgR2 in TIGR4 abrogates expression of the ADS, including the arginine-ornithine antiporter ArcD. Intranasal infection of mice and real-time bioimaging revealed that deletion of the arcABCDT genes attenuates TIGR4. However, the acute-pneumonia model and coinfection experiments indicated that the arginine-ornithine antiporter ArcD is essential to maintain fitness, while the deficiency of ADS enzymes has a minor impact on pneumococcal fitness under in vivo conditions. Strikingly, argR2 mutant TIGR4 outcompeted the wild type in the respiratory tract, suggesting an increase in fitness and further regulatory functions of ArgR2. In contrast to TIGR4, other pneumococci, such as D39, lacking expression of ArgR2, constitutively express the ADS with a truncated nonfunctional AD. On the basis of these results, we propose that the arginine-ornithine antiporter is essential to maintain pneumococcal fitness and that the genes of the ADS cluster are positively regulated in a strain-specific manner by ArgR2.

Low Concentrations of Nitric Oxide Modulate Streptococcus pneumoniae Biofilm Metabolism and Antibiotic Tolerance

“…Abrupt changes in arginine concentrations were recently shown to induce differential transcription of Ͼ450 genes in Streptococcus gordonii, many of which were involved in adhesion and biofilm development (45). Furthermore, the difference in the effect of NO on two of the strains of pneumococcus used in our experiments is consistent with D39 and serotype 14 having variable disruptions in the arginine regulators ArgR1 and ArgR2 (43,44).…”

“…Regulation of S. pneumoniae arginine metabolism appears to be distinct from that of other bacteria and involves the regulators ArgR1, ArgR2, and AhrC (43,44). ArgR1 is a transcriptional regulator of the arginine deiminase system (ADS), consisting of arginine deiminase (encoded by arcA), ornithine carbamoyltransferase (arcB), and carbamate kinase (arcC), which mediate arginine acquisition and virulence in pneumococci.…”

Acquired resistance to innate immune clearance promotes Klebsiella pneumoniae ST258 pulmonary infection

“…Selective metabolic advantage is provided by arcD in the evolution of P. aeruginosa in the cystic fibrosis lung (39,40) as well as in Streptococcus spp. infections (41,42). To rigorously test the role of arcD in the pathogenesis of pneumonia, the construction of an arcD mutant would be optimal.…”

Convergent evolution of the arginine deiminase pathway: the ArcD and ArcE arginine/ornithine exchangers

“…The product of the arcE gene is a membrane protein with no significant homology with ArcD transporters based on amino acid sequence and, accordingly, is found in a different transporter family (basic amino acid antiporter family ArcD, TC 2.A.118). Deletion of the arcE gene in S. pneumoniae resulted in reduced ADI pathway activity (Schulz et al., ) and arginine uptake (Gupta et al., ), strongly suggesting that the arcE gene product is the L‐arginine/L‐ornithine exchanger in S. pneumoniae .…”