Role for Ferredoxin:NAD(P)H Oxidoreductase (FprA) in Sulfate Assimilation and Siderophore Biosynthesis in Pseudomonads

Abstract

bPyridine-2,6-bis(thiocarboxylate) (PDTC), produced by certain pseudomonads, is a sulfur-containing siderophore that binds iron, as well as a wide range of transition metals, and it affects the net hydrolysis of the environmental contaminant carbon tetrachloride. The pathway of PDTC biosynthesis has not been defined. Here, we performed a transposon screen of Pseudomonas putida DSM 3601 to identify genes necessary for PDTC production (Pdt phenotype). Transposon insertions within genes for sulfate assimilation (cysD, cysNC, and cysG [cobA2]) dominated the collection of Pdt mutations. In addition, two insertions were within the gene for the LysR-type transcriptional activator FinR (PP1637). Phenotypic characterization indicated that finR mutants were cysteine bradytrophs. The Pdt phenotype of finR mutants could be complemented by the known target of FinR regulation, fprA (encoding ferredoxin:NADP ؉ oxidoreductase), or by Escherichia coli cysJI (encoding sulfite reductase). These data indicate that fprA is necessary for effective sulfate assimilation by P. putida and that the effect of finR mutation on PDTC production was due to deficient expression of fprA and sulfite reduction. fprA expression in both P. putida and P. aeruginosa was found to be regulated by FinR, but in a manner dependent upon reduced sulfur sources, implicating FinR in sulfur regulatory physiology. The genes and phenotypes identified in this study indicated a strong dependence upon intracellular reduced sulfur/ cysteine for PDTC biosynthesis and that pseudomonads utilize sulfite reduction enzymology distinct from that of E. coli and possibly similar to that of chloroplasts and other proteobacteria.

NADPH-generating systems in bacteria and archaea

“…In non-photosynthetic tissues and organisms, FNRs participate in the electron transfer chains of various other metabolic processes such as nitrogen fixation, sulfate assimilation, isoprenoid biosynthesis, osmotic and oxidative stress responses, and iron-sulfur cluster biogenesis (Arakaki et al, 1997 ; Krapp et al, 2002 ; Seeber et al, 2005 ; Giro et al, 2006 ; Lee et al, 2007b ; Balconi et al, 2009 ; Tang et al, 2010 ; Lewis et al, 2013 ). However, in contrast to the FNRs involved in photosynthesis, the physiological direction of FNRs involved in these processes is toward the production of Fd red .…”

The FinR-regulated essential gene fprA, encoding ferredoxin NADP+ reductase: Roles in superoxide-mediated stress protection and virulence of Pseudomonas aeruginosa

“…For example, in an iron storage complex, the [Fe-S] cluster of bacterioferritin-associated ferredoxin (Bdf) transfers electrons to the heme in bacterioferritin (BfrB) and promotes the release of Fe 2+ from BfrB by mediating electrons from FprA to BfrB [ 30 ]. Moreover, roles for FprA in sulfate assimilation and siderophore biosynthesis in pseudomonads have been characterized [ 31 ]. The expression of fprB could be induced by exposure to oxidative stress in an [Fe-S] biogenesis regulator IscR-dependent manner [ 29 ].…”

“…The physiological function of P . aeruginosa FprA remains mysterious due to unsuccessful construction of the fprA mutant [ 31 , 32 ]. This observation raised the possibility that the activity of FprA is essential for bacterial viability.…”

Thermococcus kodakarensis : the key to affordable biohydrogen production

“…In non-photosynthetic tissues and organisms, FNRs participate in the electron transfer chains of various other metabolic processes such as nitrogen fixation, sulfate assimilation, isoprenoid biosynthesis, osmotic and oxidative stress responses, and iron-sulfur cluster biogenesis [395][396][397][398][399][400][401][402]. However, in contrast to the FNRs involved in photosynthesis, the physiological direction of FNRs involved in these processes is toward the production of Fd red .…”