title: The metabolic impact of extracellular nitrite on aerobic metabolism of Paracoccus denitrificans.
abstract: Nitrite, in equilibrium with free nitrous acid (FNA), can inhibit both aerobic and anaerobic growth of microbial communities through bactericidal activities that have considerable potential for control of microbial growth in a range of water systems. There has been much focus on the effect of nitrite/FNA on anaerobic metabolism and so, to enhance understanding of the metabolic impact of nitrite/FNA on aerobic metabolism, a study was undertaken with a model denitrifying bacterium Paracoccus denitrificans PD1222. Extracellular nitrite inhibits aerobic growth of P. denitrificans in a pH-dependent manner that is likely to be a result of both nitrite and free nitrous acid (pKa= 3.25) and subsequent reactive nitrogen oxides generated from the intracellular passage of FNA into P. denitrificans. Increased expression of a gene encoding a flavohemoglobin protein (Fhp) (Pden_1689) was observed in response to extracellular nitrite. Construction and analysis of a deletion mutant established Fhp to be involved in endowing nitrite/FNA resistance at high extracellular nitrite concentrations. Global transcriptional analysis confirmed nitrite-dependent expression of fhp and indicated that P. denitrificans expressed a number of stress response systems associated with protein, DNA and lipid repair. It is therefore suggested that nitrite causes a pH-dependent stress response that is due to the production of associated reactive nitrogen species, such as nitric oxide from the internalisation of FNA.
authors.affiliation: School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich, NR4 7TJ, UK.
authors.forename: K R
authors.initials: KR
authors.lastname: Hartop
authors.affiliation: School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich, NR4 7TJ, UK.
authors.forename: M J
authors.initials: MJ
authors.lastname: Sullivan
authors.affiliation: School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich, NR4 7TJ, UK.
authors.forename: G
authors.initials: G
authors.lastname: Giannopoulos
authors.affiliation: School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich, NR4 7TJ, UK.
authors.forename: A J
authors.initials: AJ
authors.lastname: Gates
authors.affiliation: Advanced Water Management Centre (AWMC), University of Queensland, St Lucia, Brisbane, QLD, 4072, Australia.
authors.forename: P L
authors.initials: PL
authors.lastname: Bond
authors.affiliation: Advanced Water Management Centre (AWMC), University of Queensland, St Lucia, Brisbane, QLD, 4072, Australia.
authors.forename: Z
authors.initials: Z
authors.lastname: Yuan
authors.affiliation: School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich, NR4 7TJ, UK.
authors.forename: T A
authors.initials: TA
authors.lastname: Clarke
authors.affiliation: School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich, NR4 7TJ, UK.
authors.forename: G
authors.initials: G
authors.lastname: Rowley
authors.affiliation: School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich, NR4 7TJ, UK. Electronic address: d.richardson@uea.ac.uk.
authors.forename: D J
authors.initials: DJ
authors.lastname: Richardson
mesh_terms: D058440:Denitrification; D009569:Nitric Oxide / Q000378:metabolism; D009573:Nitrites / Q000378:metabolism*; D010084:Oxidation-Reduction; D010231:Paracoccus denitrificans
chemical_list: D009573:Nitrites; D009569:Nitric Oxide
keywords: Denitrification; Flavohemoglobin; Free nitrous acid; Nitric oxide; Nitrite; Nitrosative stress; Paracoccus denitrificans; Reactive nitrogen species