Genetic and Biochemical Analysis of Anaerobic Respiration in <named-content content-type="genus-species">Bacteroides fragilis</named-content> and Its Importance <italic toggle="yes">In Vivo</italic>

ABSTRACT In bacteria, the respiratory pathways that drive molecular transport and ATP synthesis include a variety of enzyme complexes that utilize different electron donors and acceptors. This property allows them to vary the efficiency of energy conservation and to generate different types of elect...

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Autores principales:	Takeshi Ito, Rene Gallegos, Leigh M. Matano, Nicole L. Butler, Noam Hantman, Matthew Kaili, Michael J. Coyne, Laurie E. Comstock, Michael H. Malamy, Blanca Barquera
Formato:	article
Lenguaje:	EN
Publicado:	American Society for Microbiology 2020
Materias:	Bacteroides fragilis respiration NQR gut microbiota Microbiology QR1-502
Acceso en línea:	https://doaj.org/article/12244fa6b43343798eb241ea4fed69c0
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spelling	oai:doaj.org-article:12244fa6b43343798eb241ea4fed69c02021-11-15T15:56:58ZGenetic and Biochemical Analysis of Anaerobic Respiration in <named-content content-type="genus-species">Bacteroides fragilis</named-content> and Its Importance <italic toggle="yes">In Vivo</italic>10.1128/mBio.03238-192150-7511https://doaj.org/article/12244fa6b43343798eb241ea4fed69c02020-02-01T00:00:00Zhttps://journals.asm.org/doi/10.1128/mBio.03238-19https://doaj.org/toc/2150-7511ABSTRACT In bacteria, the respiratory pathways that drive molecular transport and ATP synthesis include a variety of enzyme complexes that utilize different electron donors and acceptors. This property allows them to vary the efficiency of energy conservation and to generate different types of electrochemical gradients (H+ or Na+). We know little about the respiratory pathways in Bacteroides species, which are abundant in the human gut, and whether they have a simple or a branched pathway. Here, we combined genetics, enzyme activity measurements, and mammalian gut colonization assays to better understand the first committed step in respiration, the transfer of electrons from NADH to quinone. We found that a model gut Bacteroides species, Bacteroides fragilis, has all three types of putative NADH dehydrogenases that typically transfer electrons from the highly reducing molecule NADH to quinone. Analyses of NADH oxidation and quinone reduction in wild-type and deletion mutants showed that two of these enzymes, Na+-pumping NADH:quinone oxidoreductase (NQR) and NADH dehydrogenase II (NDH2), have NADH dehydrogenase activity, whereas H+-pumping NADH:ubiquinone oxidoreductase (NUO) does not. Under anaerobic conditions, NQR contributes more than 65% of the NADH:quinone oxidoreductase activity. When grown in rich medium, none of the single deletion mutants had a significant growth defect; however, the double Δnqr Δndh2 mutant, which lacked almost all NADH:quinone oxidoreductase activity, had a significantly increased doubling time. Despite unaltered in vitro growth, the single nqr deletion mutant was unable to competitively colonize the gnotobiotic mouse gut, confirming the importance of NQR to respiration in B. fragilis and the overall importance of respiration to this abundant gut symbiont. IMPORTANCE Bacteroides species are abundant in the human intestine and provide numerous beneficial properties to their hosts. The ability of Bacteroides species to convert host and dietary glycans and polysaccharides to energy is paramount to their success in the human gut. We know a great deal about the molecules that these bacteria extract from the human gut but much less about how they convert those molecules into energy. Here, we show that B. fragilis has a complex respiratory pathway with two different enzymes that transfer electrons from NADH to quinone and a third enzyme complex that may use an electron donor other than NADH. Although fermentation has generally been believed to be the main mechanism of energy generation in Bacteroides, we found that a mutant lacking one of the NADH:quinone oxidoreductases was unable to compete with the wild type in the mammalian gut, revealing the importance of respiration to these abundant gut symbionts.Takeshi ItoRene GallegosLeigh M. MatanoNicole L. ButlerNoam HantmanMatthew KailiMichael J. CoyneLaurie E. ComstockMichael H. MalamyBlanca BarqueraAmerican Society for MicrobiologyarticleBacteroides fragilisrespirationNQRgut microbiotaMicrobiologyQR1-502ENmBio, Vol 11, Iss 1 (2020)
institution	DOAJ
collection	DOAJ
language	EN
topic	Bacteroides fragilis respiration NQR gut microbiota Microbiology QR1-502
spellingShingle	Bacteroides fragilis respiration NQR gut microbiota Microbiology QR1-502 Takeshi Ito Rene Gallegos Leigh M. Matano Nicole L. Butler Noam Hantman Matthew Kaili Michael J. Coyne Laurie E. Comstock Michael H. Malamy Blanca Barquera Genetic and Biochemical Analysis of Anaerobic Respiration in <named-content content-type="genus-species">Bacteroides fragilis</named-content> and Its Importance <italic toggle="yes">In Vivo</italic>
description	ABSTRACT In bacteria, the respiratory pathways that drive molecular transport and ATP synthesis include a variety of enzyme complexes that utilize different electron donors and acceptors. This property allows them to vary the efficiency of energy conservation and to generate different types of electrochemical gradients (H+ or Na+). We know little about the respiratory pathways in Bacteroides species, which are abundant in the human gut, and whether they have a simple or a branched pathway. Here, we combined genetics, enzyme activity measurements, and mammalian gut colonization assays to better understand the first committed step in respiration, the transfer of electrons from NADH to quinone. We found that a model gut Bacteroides species, Bacteroides fragilis, has all three types of putative NADH dehydrogenases that typically transfer electrons from the highly reducing molecule NADH to quinone. Analyses of NADH oxidation and quinone reduction in wild-type and deletion mutants showed that two of these enzymes, Na+-pumping NADH:quinone oxidoreductase (NQR) and NADH dehydrogenase II (NDH2), have NADH dehydrogenase activity, whereas H+-pumping NADH:ubiquinone oxidoreductase (NUO) does not. Under anaerobic conditions, NQR contributes more than 65% of the NADH:quinone oxidoreductase activity. When grown in rich medium, none of the single deletion mutants had a significant growth defect; however, the double Δnqr Δndh2 mutant, which lacked almost all NADH:quinone oxidoreductase activity, had a significantly increased doubling time. Despite unaltered in vitro growth, the single nqr deletion mutant was unable to competitively colonize the gnotobiotic mouse gut, confirming the importance of NQR to respiration in B. fragilis and the overall importance of respiration to this abundant gut symbiont. IMPORTANCE Bacteroides species are abundant in the human intestine and provide numerous beneficial properties to their hosts. The ability of Bacteroides species to convert host and dietary glycans and polysaccharides to energy is paramount to their success in the human gut. We know a great deal about the molecules that these bacteria extract from the human gut but much less about how they convert those molecules into energy. Here, we show that B. fragilis has a complex respiratory pathway with two different enzymes that transfer electrons from NADH to quinone and a third enzyme complex that may use an electron donor other than NADH. Although fermentation has generally been believed to be the main mechanism of energy generation in Bacteroides, we found that a mutant lacking one of the NADH:quinone oxidoreductases was unable to compete with the wild type in the mammalian gut, revealing the importance of respiration to these abundant gut symbionts.
format	article
author	Takeshi Ito Rene Gallegos Leigh M. Matano Nicole L. Butler Noam Hantman Matthew Kaili Michael J. Coyne Laurie E. Comstock Michael H. Malamy Blanca Barquera
author_facet	Takeshi Ito Rene Gallegos Leigh M. Matano Nicole L. Butler Noam Hantman Matthew Kaili Michael J. Coyne Laurie E. Comstock Michael H. Malamy Blanca Barquera
author_sort	Takeshi Ito
title	Genetic and Biochemical Analysis of Anaerobic Respiration in <named-content content-type="genus-species">Bacteroides fragilis</named-content> and Its Importance <italic toggle="yes">In Vivo</italic>
title_short	Genetic and Biochemical Analysis of Anaerobic Respiration in <named-content content-type="genus-species">Bacteroides fragilis</named-content> and Its Importance <italic toggle="yes">In Vivo</italic>
title_full	Genetic and Biochemical Analysis of Anaerobic Respiration in <named-content content-type="genus-species">Bacteroides fragilis</named-content> and Its Importance <italic toggle="yes">In Vivo</italic>
title_fullStr	Genetic and Biochemical Analysis of Anaerobic Respiration in <named-content content-type="genus-species">Bacteroides fragilis</named-content> and Its Importance <italic toggle="yes">In Vivo</italic>
title_full_unstemmed	Genetic and Biochemical Analysis of Anaerobic Respiration in <named-content content-type="genus-species">Bacteroides fragilis</named-content> and Its Importance <italic toggle="yes">In Vivo</italic>
title_sort	genetic and biochemical analysis of anaerobic respiration in <named-content content-type="genus-species">bacteroides fragilis</named-content> and its importance <italic toggle="yes">in vivo</italic>
publisher	American Society for Microbiology
publishDate	2020
url	https://doaj.org/article/12244fa6b43343798eb241ea4fed69c0
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Genetic and Biochemical Analysis of Anaerobic Respiration in <named-content content-type="genus-species">Bacteroides fragilis</named-content> and Its Importance <italic toggle="yes">In Vivo</italic>

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