Nitrate and nitrite transport in bacteria

Moir, James; Wood, Nicholas

doi:10.1007/pl00000849

Cited by 156 publications

(138 citation statements)

References 43 publications

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“…The genomic structure of R. solanacearum's nitrate assimilation network is unique to a subset of Betaproteobacteria. Genomic analysis suggests R. solanacearum has two assimilatory nitrate uptake systems, encoded by nasFED and narK3 (26,27). The nasFED operon, predicted to encode the typical assimilatory nitrate transporter, is atypically distant from the metabolic operon, suggesting a relatively recent genomic rearrangement (27).…”

Section: Resultsmentioning

confidence: 99%

Nitrate Assimilation Contributes to Ralstonia solanacearum Root Attachment, Stem Colonization, and Virulence

Dalsing

Allen

2013

Journal of Bacteriology

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Ralstonia solanacearum, an economically important plant pathogen, must attach, grow, and produce virulence factors to colonize plant xylem vessels and cause disease. Little is known about the bacterial metabolism that drives these processes. Nitrate is present in both tomato xylem fluid and agricultural soils, and the bacterium's gene expression profile suggests that it assimilates nitrate during pathogenesis. A nasA mutant, which lacks the gene encoding the catalytic subunit of R. solanacearum's sole assimilatory nitrate reductase, did not grow on nitrate as a sole nitrogen source. This nasA mutant exhibited reduced virulence and delayed stem colonization after soil soak inoculation of tomato plants. The nasA virulence defect was more severe following a period of soil survival between hosts. Unexpectedly, once bacteria reached xylem tissue, nitrate assimilation was dispensable for growth, virulence, and competitive fitness. However, nasA-dependent nitrate assimilation was required for normal production of extracellular polysaccharide (EPS), a major virulence factor. Quantitative analyses revealed that EPS production was significantly influenced by nitrate assimilation when nitrate was not required for growth. The plant colonization delay of the nasA mutant was externally complemented by coinoculation with wild-type bacteria but not by coinoculation with an EPS-deficient epsB mutant. The nasA mutant and epsB mutant did not attach to tomato roots as well as wild-type strain UW551. However, adding either wild-type cells or cell-free EPS improved the root attachment of these mutants. These data collectively suggest that nitrate assimilation promotes R. solanacearum virulence by enhancing root attachment, the initial stage of infection, possibly by modulating EPS production.

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Section: Resultsmentioning

confidence: 99%

Nitrate Assimilation Contributes to Ralstonia solanacearum Root Attachment, Stem Colonization, and Virulence

Dalsing

Allen

2013

Journal of Bacteriology

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“…The NarG-rich communities also showed a high number of nitrate/nitrite antiporters (NarK), which import nitrate into the cytoplasm and export nitrite from it ( Fig. 5) (40). This result showed that different sponge communities use analogous pathways for denitrification, although it is not clear why these preferences for NarG or NapA exist.…”

Section: Functional Annotation Reveals Shared Genomic Signatures In Smentioning

confidence: 98%

Functional equivalence and evolutionary convergence in complex communities of microbial sponge symbionts

Fan

Reynolds

Liu

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

340

476

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Microorganisms often form symbiotic relationships with eukaryotes, and the complexity of these relationships can range from those with one single dominant symbiont to associations with hundreds of symbiont species. Microbial symbionts occupying equivalent niches in different eukaryotic hosts may share functional aspects, and convergent genome evolution has been reported for simple symbiont systems in insects. However, for complex symbiont communities, it is largely unknown how prevalent functional equivalence is and whether equivalent functions are conducted by evolutionarily convergent mechanisms. Sponges represent an evolutionarily divergent group of species with common physiological and ecological traits. They also host complex communities of microbial symbionts and thus are the ideal model to test whether functional equivalence and evolutionary convergence exist in complex symbiont communities across phylogenetically divergent hosts. Here we use a sampling design to determine the phylogenetic and functional profiles of microbial communities associated with six sponge species. We identify common functions in the six microbiomes, demonstrating the existence of functional equivalence. These core functions are consistent with our current understanding of the biological and ecological roles of sponge-associated microorganisms and also provide insight into symbiont functions. Importantly, core functions also are provided in each sponge species by analogous enzymes and biosynthetic pathways. Moreover, the abundance of elements involved in horizontal gene transfer suggests their key roles in the genomic evolution of symbionts. Our data thus demonstrate evolutionary convergence in complex symbiont communities and reveal the details and mechanisms that underpin the process.

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“…For further reduction, nitrite will now be actively transported to the periplasm, where it is reduced to NO by Nir. Both processes, export to the periplasm and nitrite reduction rate, are controlled via activity of a NarK-type transporter protein (Moir and Wood, 2001;Zumft, 1997) and Nir activity, respectively. A stable equilibrium between both reactions (i.e., the rates k 3 and k 5 ) could theoretically explain the constant isotope offset: if the fraction of exported vs. reduced nitrite remains constant, the same holds for the fraction of substrate versus the original concentration resulting in a constant value for ln(f ).…”

Section: Fractionation During Nitrite Processing?mentioning

confidence: 99%

Nitrogen isotope dynamics and fractionation during sedimentary denitrification in Boknis Eck, Baltic Sea

Dähnke

Thamdrup

2013

Biogeosciences

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The global marine nitrogen cycle is constrained by nitrogen fixation as a source of reactive nitrogen, and denitrification or anammox on the sink side. These processes with their respective isotope effects set the marine nitrate N-15-isotope value (delta N-15) to a relatively constant average of 5 parts per thousand. This value can be used to better assess the magnitude of these sources and sink terms, but the underlying assumption is that sedimentary denitrification and anammox, processes responsible for approximately one-third of global nitrogen removal, have little to no isotope effect on nitrate in the water column. We investigated the isotope fractionation in sediment incubations, measuring net denitrification and nitrogen and oxygen stable isotope fractionation in surface sediments from the coastal Baltic Sea (Boknis Eck, northern Germany), a site with seasonal hypoxia and dynamic nitrogen turnover. Sediment denitrification was fast, and regardless of current paradigms assuming little fractionation during sediment denitrification, we measured fractionation factors of 18.9 parts per thousand for nitrogen and 15.8 parts per thousand for oxygen in nitrate. While the input of nitrate to the water column remains speculative, these results challenge the current view of fractionation during sedimentary denitrification and imply that nitrogen budget calculations may need to consider this variability, as both preferential uptake of light nitrate and release of the remaining heavy fraction can significantly alter water column nitrate isotope values at the sediment-water interface

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Nitrate and nitrite transport in bacteria

Cited by 156 publications

References 43 publications

Nitrate Assimilation Contributes to Ralstonia solanacearum Root Attachment, Stem Colonization, and Virulence

Nitrate Assimilation Contributes to Ralstonia solanacearum Root Attachment, Stem Colonization, and Virulence

Functional equivalence and evolutionary convergence in complex communities of microbial sponge symbionts

Nitrogen isotope dynamics and fractionation during sedimentary denitrification in Boknis Eck, Baltic Sea

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