Limits...
Identifying Potential Mechanisms Enabling Acidophily in the Ammonia-Oxidizing Archaeon "Candidatus Nitrosotalea devanaterra".

Lehtovirta-Morley LE, Sayavedra-Soto LA, Gallois N, Schouten S, Stein LY, Prosser JI, Nicol GW - Appl. Environ. Microbiol. (2016)

Bottom Line: Instead, the genome indicates that "Ca Nitrosotalea devanaterra" contains genes encoding both a predicted high-affinity substrate acquisition system and potential pH homeostasis mechanisms absent in neutrophilic AOA.Analysis of mRNA revealed that candidate genes encoding the proposed homeostasis mechanisms were all expressed during acidophilic growth, and lipid profiling by high-performance liquid chromatography-mass spectrometry (HPLC-MS) demonstrated that the membrane lipids of "Ca Nitrosotalea devanaterra" were not dominated by crenarchaeol, as found in neutrophilic AOA.This study for the first time describes a genome of an obligately acidophilic ammonia oxidizer and identifies potential mechanisms enabling this unique phenotype for future biochemical characterization.

View Article: PubMed Central - PubMed

Affiliation: Institute of Biological and Environmental Sciences, University of Aberdeen, Aberdeen, United Kingdom l.lehtovirta@abdn.ac.uk.

No MeSH data available.


Related in: MedlinePlus

Conceptual model of ammonia acquisition and oxidation mechanisms in “Ca. Nitrosotalea devanaterra.” The model is based on references 70 and 81 and work in this study.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4836417&req=5

Figure 6: Conceptual model of ammonia acquisition and oxidation mechanisms in “Ca. Nitrosotalea devanaterra.” The model is based on references 70 and 81 and work in this study.

Mentions: Acidophilic growth could be facilitated by high substrate affinity: the whole cells of the marine AOA “Candidatus Nitrosopumilus maritimus” have an apparent half-saturation constant, Km(NH3+NH4+), of 133 nM at pH 7.5 (2, 80), which is equivalent to ∼2 nM NH3 at pH 7.5. At pH 4, 133 nM (NH3+NH4+) is equivalent to ∼0.75 pM, and ammonia oxidation at pH 4 would therefore require a Km(NH3) for AMO in the picomolar range or a mechanism for generating high localized concentrations of ammonia. Import of NH4+ followed by diffusion of membrane-permeative NH3 into the pseudoperiplasm might generate local ammonia concentrations sufficiently high for oxidation (Fig. 6). NH4+, rather than NH3, is abundant at low pH, but oxidation of NH4+ by the AMO would necessitate substantial changes to the enzyme, which would likely be evident in AMO sequence comparisons.


Identifying Potential Mechanisms Enabling Acidophily in the Ammonia-Oxidizing Archaeon "Candidatus Nitrosotalea devanaterra".

Lehtovirta-Morley LE, Sayavedra-Soto LA, Gallois N, Schouten S, Stein LY, Prosser JI, Nicol GW - Appl. Environ. Microbiol. (2016)

Conceptual model of ammonia acquisition and oxidation mechanisms in “Ca. Nitrosotalea devanaterra.” The model is based on references 70 and 81 and work in this study.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4836417&req=5

Figure 6: Conceptual model of ammonia acquisition and oxidation mechanisms in “Ca. Nitrosotalea devanaterra.” The model is based on references 70 and 81 and work in this study.
Mentions: Acidophilic growth could be facilitated by high substrate affinity: the whole cells of the marine AOA “Candidatus Nitrosopumilus maritimus” have an apparent half-saturation constant, Km(NH3+NH4+), of 133 nM at pH 7.5 (2, 80), which is equivalent to ∼2 nM NH3 at pH 7.5. At pH 4, 133 nM (NH3+NH4+) is equivalent to ∼0.75 pM, and ammonia oxidation at pH 4 would therefore require a Km(NH3) for AMO in the picomolar range or a mechanism for generating high localized concentrations of ammonia. Import of NH4+ followed by diffusion of membrane-permeative NH3 into the pseudoperiplasm might generate local ammonia concentrations sufficiently high for oxidation (Fig. 6). NH4+, rather than NH3, is abundant at low pH, but oxidation of NH4+ by the AMO would necessitate substantial changes to the enzyme, which would likely be evident in AMO sequence comparisons.

Bottom Line: Instead, the genome indicates that "Ca Nitrosotalea devanaterra" contains genes encoding both a predicted high-affinity substrate acquisition system and potential pH homeostasis mechanisms absent in neutrophilic AOA.Analysis of mRNA revealed that candidate genes encoding the proposed homeostasis mechanisms were all expressed during acidophilic growth, and lipid profiling by high-performance liquid chromatography-mass spectrometry (HPLC-MS) demonstrated that the membrane lipids of "Ca Nitrosotalea devanaterra" were not dominated by crenarchaeol, as found in neutrophilic AOA.This study for the first time describes a genome of an obligately acidophilic ammonia oxidizer and identifies potential mechanisms enabling this unique phenotype for future biochemical characterization.

View Article: PubMed Central - PubMed

Affiliation: Institute of Biological and Environmental Sciences, University of Aberdeen, Aberdeen, United Kingdom l.lehtovirta@abdn.ac.uk.

No MeSH data available.


Related in: MedlinePlus