title: Comparison of genes required for H2O2 resistance in Streptococcus gordonii and Streptococcus sanguinis.
abstract: Hydrogen peroxide (H2O2) is produced by several members of the genus Streptococcus mainly through the pyruvate oxidase SpxB under aerobic growth conditions. The acute toxic nature of H2O2 raises the interesting question of how streptococci cope with intrinsically produced H2O2, which subsequently accumulates in the microenvironment and threatens the closely surrounding population. Here, we investigate the H2O2 susceptibility of oral Streptococcus gordonii and Streptococcus sanguinis and elucidate potential mechanisms of how they protect themselves from the deleterious effect of H2O2. Both organisms are considered primary colonizers and occupy the same intraoral niche making them potential targets for H2O2 produced by other species. We demonstrate that S. gordonii produces relatively more H2O2 and has a greater ability for resistance to H2O2 stress. Functional studies show that, unlike in Streptococcus pneumoniae, H2O2 resistance is not dependent on a functional SpxB and confirms the important role of the ferritin-like DNA-binding protein Dps. However, the observed increased H2O2 resistance of S. gordonii over S. sanguinis is likely to be caused by an oxidative stress protection machinery present even under anaerobic conditions, while S. sanguinis requires a longer period of time for adaptation. The ability to produce more H2O2 and be more resistant to H2O2 might aid S. gordonii in the competitive oral biofilm environment, since it is lower in abundance yet manages to survive quite efficiently in the oral biofilm.
authors.affiliation: Department of Surgical Oncology, The First Hospital of China Medical University, Shenyang, PR China.|Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA.
authors.forename: Yifan
authors.initials: Y
authors.lastname: Xu
authors.affiliation: Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA.
authors.forename: Andreas
authors.initials: A
authors.lastname: Itzek
authors.affiliation: College of Dentistry, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA.|Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA.
authors.forename: Jens
authors.initials: J
authors.lastname: Kreth
mesh_terms: D004361:Drug Tolerance; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D006861:Hydrogen Peroxide / Q000378:metabolism / Q000633:toxicity*; D018384:Oxidative Stress; D054773:Streptococcus gordonii / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism*; D013296:Streptococcus pneumoniae / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism*; D013312:Stress, Physiological
chemical_list: D006861:Hydrogen Peroxide