Streptococcus pneumoniae folate biosynthesis responds to environmental CO2 levels.
Although carbon dioxide (CO2) is known to be essential for Streptococcus pneumoniae growth, it is poorly understood how this respiratory tract pathogen adapts to the large changes in environmental CO2 levels it encounters during transmission, host colonization, and disease. To identify the molecular mechanisms that facilitate pneumococcal growth under CO2-poor conditions, we generated a random S. pneumoniae R6 mariner transposon mutant library representing mutations in 1,538 different genes and exposed it to CO2-poor ambient air. With Tn-seq, we found mutations in two genes that were involved in S. pneumoniae adaptation to changes in CO2 availability. The gene pca, encoding pneumococcal carbonic anhydrase (PCA), was absolutely essential for S. pneumoniae growth under CO2-poor conditions. PCA catalyzes the reversible hydration of endogenous CO2 to bicarbonate (HCO3(-)) and was previously demonstrated to facilitate HCO3(-)-dependent fatty acid biosynthesis. The gene folC that encodes the dihydrofolate/folylpolyglutamate synthase was required at the initial phase of bacterial growth under CO2-poor culture conditions. FolC compensated for the growth-phase-dependent decrease in S. pneumoniae intracellular long-chain (n > 3) polyglutamyl folate levels, which was most pronounced under CO2-poor growth conditions. In conclusion, S. pneumoniae adaptation to changes in CO2 availability involves the retention of endogenous CO2 and the preservation of intracellular long-chain polyglutamyl folate pools.
Laboratory of Pediatric Infectious Diseases, Radboud University Medical Center, Nijmegen, The Netherlands. p.j.burghout@gmail.com
Peter
P
Burghout
Aldert
A
Zomer
Christa E
CE
van der Gaast-de Jongh
Eva M
EM
Janssen-Megens
Kees-Jan
KJ
Françoijs
Hendrik G
HG
Stunnenberg
Peter W M
PW
Hermans
D002245:Carbon Dioxide / Q000378:metabolism*; D002256:Carbonic Anhydrases / Q000235:genetics / Q000378:metabolism; D004251:DNA Transposable Elements; D005492:Folic Acid / Q000096:biosynthesis*; D055786:Gene Knockout Techniques; D016254:Mutagenesis, Insertional; D010453:Peptide Synthases / Q000235:genetics / Q000378:metabolism; D013296:Streptococcus pneumoniae / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism*
D004251:DNA Transposable Elements; D002245:Carbon Dioxide; D005492:Folic Acid; D002256:Carbonic Anhydrases; D010453:Peptide Synthases; C023103:folylpolyglutamate synthetase