title: PerR acts as a switch for oxygen tolerance in the strict anaerobe Clostridium acetobutylicum.
abstract: Clostridia belong to those bacteria which are considered as obligate anaerobe, e.g. oxygen is harmful or lethal to these bacteria. Nevertheless, it is known that they can survive limited exposure to air, and often eliminate oxygen or reactive derivatives via NAD(P)H-dependent reduction. This system does apparently contribute to survival after oxidative stress, but is insufficient to establish long-term tolerance of aerobic conditions. Here we show that manipulation of the regulatory mechanism of this defence mechanism can trigger aerotolerance in the obligate anaerobe Clostridium acetobutylicum. Deletion of a peroxide repressor (PerR)-homologous protein resulted in prolonged aerotolerance, limited growth under aerobic conditions and rapid consumption of oxygen from an aerobic environment. The mutant strain also revealed higher resistance to H2O2 and activities of NADH-dependent scavenging of H2O2 and organic peroxides in cell-free extracts increased by at least one order of magnitude. Several genes encoding the putative enzymes were upregulated and identified as members of the clostridial PerR regulon, including the heat shock protein Hsp21, a reverse rubrerythrin which was massively produced and became the most abundant protein in the absence of PerR. This multifunctional protein is proposed to play the crucial role in the oxidative stress defence.
authors.affiliation: Division of Microbiology, Institute of Biological Sciences, University of Rostock, Albert-Einstein-Str. 3, D-18051 Rostock, Germany.
authors.forename: Falk
authors.initials: F
authors.lastname: Hillmann
authors.forename: Ralf-Jörg
authors.initials: RJ
authors.lastname: Fischer
authors.forename: Florence
authors.initials: F
authors.lastname: Saint-Prix
authors.forename: Laurence
authors.initials: L
authors.lastname: Girbal
authors.forename: Hubert
authors.initials: H
authors.lastname: Bahl
mesh_terms: D000332:Aerobiosis / Q000235:genetics; D000693:Anaerobiosis / Q000235:genetics; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D046969:Clostridium acetobutylicum / Q000187:drug effects / Q000235:genetics*; D017353:Gene Deletion; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D006861:Hydrogen Peroxide / Q000494:pharmacology; D018384:Oxidative Stress / Q000235:genetics*; D010100:Oxygen / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D018085:Regulon; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D017382:Reactive Oxygen Species; D012097:Repressor Proteins; D014157:Transcription Factors; C122138:peroxide repressor proteins; D006861:Hydrogen Peroxide; D010100:Oxygen