title: NapB in excess inhibits growth of Shewanella oneidensis by dissipating electrons of the quinol pool.
abstract: Shewanella, a group of ubiquitous bacteria renowned for respiratory versatility, thrive in environments where various electron acceptors (EAs) of different chemical and physiological characteristics coexist. Despite being extensively studied, we still know surprisingly little about strategies by which multiple EAs and their interaction define ecophysiology of these bacteria. Previously, we showed that nitrite inhibits growth of the genus representative Shewanella oneidensis on fumarate and presumably some other CymA (quinol dehydrogenase)-dependent EAs by reducing cAMP production, which in turn leads to lowered expression of nitrite and fumarate reductases. In this study, we demonstrated that inhibition of fumarate growth by nitrite is also attributable to overproduction of NapB, the cytochrome c subunit of nitrate reductase. Further investigations revealed that excessive NapB per se inhibits growth on all EAs tested, including oxygen. When overproduced, NapB acts as an electron shuttle to dissipate electrons of the quinol pool, likely to extracellullar EAs, because the Mtr system, the major electron transport pathway for extracellular electron transport, is implicated. The study not only sheds light on mechanisms by which certain EAs, especially toxic ones, impact the bacterial ecophysiology, but also provides new insights into how electron shuttle c-type cytochromes regulate multi-branched respiratory networks.
authors.affiliation: Institute of Microbiology and College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, 310058, China.
authors.forename: Miao
authors.initials: M
authors.lastname: Jin
authors.affiliation: Institute of Microbiology and College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, 310058, China.
authors.forename: Qianyun
authors.initials: Q
authors.lastname: Zhang
authors.affiliation: Institute of Microbiology and College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, 310058, China.
authors.forename: Yijuan
authors.initials: Y
authors.lastname: Sun
authors.affiliation: Institute of Microbiology and College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, 310058, China.
authors.forename: Haichun
authors.initials: H
authors.lastname: Gao
mesh_terms: D045263:Cytochromes a1 / Q000235:genetics*; D003575:Cytochromes c1 / Q000235:genetics*; D004579:Electron Transport / Q000187:drug effects; D004583:Electrons; D005650:Fumarates / Q000737:chemistry / Q000378:metabolism; D006873:Hydroquinones / Q000737:chemistry / Q000378:metabolism; D009565:Nitrate Reductases / Q000235:genetics*; D009573:Nitrites / Q000633:toxicity; D010084:Oxidation-Reduction / Q000187:drug effects*; D020592:Shewanella / Q000187:drug effects / Q000235:genetics* / Q000254:growth & development
chemical_list: D005650:Fumarates; D006873:Hydroquinones; D009573:Nitrites; D045263:Cytochromes a1; D003575:Cytochromes c1; D009565:Nitrate Reductases; C054690:nitrate reductase (cytochrome); C031927:hydroquinone