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Ammonia as the driving factor for aerobic ammonia oxidizers

Ghimire, Sabita
http://orcid.org/0000-0003-4528-8848
http://rave.ohiolink.edu/etdc/view?acc_num=miami16891208612541

Abstract Details

2023, Doctor of Philosophy, Miami University, Microbiology.
Ammonia-oxidizing bacteria (AOB), ammonia-oxidizing archaea (AOA) and complete ammonia oxidizers (comammox) comprise aerobic ammonia oxidizers (AO). Here, we present the ammonium concentration as a determinant of the distribution of ammonia-oxidizers. The ecophysiology of comammox enrichment Cmx-BO4 was characterized by growing it in different ammonium concentrations, pH, light and nitrite concentrations. Cmx-BO4 oxidized up to 3 mM ammonium, with the highest growth rate at 10 M ammonium. The comammox enrichment oxidized ammonium through pH 6 to 8 and was inhibited by blue and white light. Cmx-BO4 oxidized nitrite in presence of ammonium but did not oxidize nitrite only. The genomic characterization of comammox strain Nitrospira sp. BO4 in the comammox enrichment Cmx-BO4 was performed through metagenomic sequencing. The metagenome assembled genome (MAG) of Nitrospira sp. BO4 possessed genes for ammonia and nitrite oxidation. The MAG, however, lacked genes for assimilatory nitrite reduction and nitrite transporters, corresponding to the inability of the culture to consume nitrite as the nitrogen source. Comammox Nitrospira sp. BO4 was competed for ammonium against AOA Nitrosoarchaeum sp. BO1 to investigate if the two oligotrophic AO had niche differentiation or if they co-existed in nature. Cmx-BO4 and AOA-BO1 have Nitrosopira sp. BO4 and Nitrosoarchaeum sp. BO1 as the AO respectively. Nitrospira sp. BO4 outcompeted Nitrospira sp. BO1 at all three tested ammonium concentrations (<10-, 50- and 500 M). Comammox may have an advantage over AOA at ammonium limited environments and the AOA may occupy microniches devoid of comammox to be able to coexist in oligotrophic environments. The effect of elevated ammonium availability was investigated to characterize the toxic effects of high ammonium concentration on Nitrosomonas sp. Is79 and N. eutropha. We cultivated both cultures at low, intermediate and high ammonium concentrations to investigate the effect of ammonium concentrations on gene expression. Overall, the activity and growth of AO depends on the ammonium concentration. The concentration of ammonium is a factor determining the distribution of AO in nature.
Annette Bollmann, Dr. (Advisor)
126 p.
Microbiology
Aerobic ammonia oxidizers, ammonium concentration, complete ammonia oxidizers (comammox), ammonia-oxidizing archaea (AOA), ammonia-oxidizing bacteria (AOB), Environmental factors

Recommended Citations

Citations

  • Ghimire, S. (2023). Ammonia as the driving factor for aerobic ammonia oxidizers [Doctoral dissertation, Miami University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=miami16891208612541

    APA Style (7th edition)

  • Ghimire, Sabita. Ammonia as the driving factor for aerobic ammonia oxidizers . 2023. Miami University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=miami16891208612541.

    MLA Style (8th edition)

  • Ghimire, Sabita. "Ammonia as the driving factor for aerobic ammonia oxidizers ." Doctoral dissertation, Miami University, 2023. http://rave.ohiolink.edu/etdc/view?acc_num=miami16891208612541

    Chicago Manual of Style (17th edition)

miami16891208612541
299
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This open access ETD is published by Miami University and OhioLINK.