title: Do globins in microaerophilic Campylobacter jejuni confer nitrosative stress tolerance under oxygen limitation?
abstract: The microaerophilic pathogen Campylobacter jejuni possesses inducible systems for resisting NO. Two globins--Cgb (a single-domain globin) and Ctb (a truncated globin)--are up-regulated in response to NO via the positively acting transcription factor NssR. Our aims were to determine whether these oxygen-binding globins also function in severely oxygen-limited environments, as in the host. At growth-limiting oxygen transfer rates, bacteria were more S-nitrosoglutathione (GSNO) sensitive, irrespective of the presence of Cgb, Ctb, or NssR. Pregrowth of cells with GSNO enhanced GSNO resistance, even in nssR and cgb mutants, but transcriptomic profiling of oxygen-limited, NO-exposed cells failed to reveal the NssR regulon. Nevertheless, globin expression in an Escherichia coli mutant lacking the NO-detoxifying flavohemoglobin Hmp showed that Cgb and Ctb consume NO aerobically or anoxically and offer some protection to respiratory inhibition by NO. The constitutively expressed nitrite reductase NrfA does not provide resistance under oxygen-limited conditions. We, therefore, hypothesize that, although Cgb and NrfA can detoxify NO, even anoxically, they are neither up-regulated nor functional under physiologically relevant oxygen-limited conditions and, second, responses to NO do not stem from trancriptional regulation.
authors: Department of Molecular Biology and Biotechnology, The University of Sheffield, Sheffield, UK.
authors: Carlos
authors: C
authors: Avila-Ramirez
authors: Mariana
authors: M
authors: Tinajero-Trejo
authors: Kelly S
authors: KS
authors: Davidge
authors: Claire E
authors: CE
authors: Monk
authors: David J
authors: DJ
authors: Kelly
authors: Robert K
authors: RK
authors: Poole
mesh_terms: D000222:Adaptation, Physiological; D000693:Anaerobiosis; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism / Q000502:physiology; D016123:Campylobacter jejuni / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D005914:Globins / Q000235:genetics* / Q000378:metabolism / Q000502:physiology; D009569:Nitric Oxide / Q000378:metabolism*; D026361:Reactive Nitrogen Species / Q000378:metabolism; D018085:Regulon; D026422:S-Nitrosoglutathione / Q000378:metabolism; D013312:Stress, Physiological; D059467:Transcriptome; D015854:Up-Regulation
chemical_list: D001426:Bacterial Proteins; D026361:Reactive Nitrogen Species; D009569:Nitric Oxide; D026422:S-Nitrosoglutathione; D005914:Globins