Progress 10/01/13 to 09/30/17
Outputs
Target Audience: Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?One postgraduate student graduated in 2017 with a PhD and several undergraduate students worked on this project. How have the results been disseminated to communities of interest?Results were disseminated through national and international scientific meetings, website reports, and professional journal articles. What do you plan to do during the next reporting period to accomplish the goals?
Nothing Reported
Impacts
What was accomplished under these goals?
Phosphite is the most energetically favorable biological electron donor known, but only one organism capable of growing by phosphite oxidation has been previously identified. As part of our studies we described a novel phosphite-oxidizing bacterium that can grow with carbon dioxide (CO2) as its sole electron acceptor and proposed a metabolic model by which inorganic carbon is assimilated via the reductive glycine pathway to make new biomass. Although the reductive glycine pathway has previously been described as a "synthetic" carbonfixation pathway, to our knowledge, this study provides the first evidence that it may actually function as a natural autotrophic pathway involved in carbon sequestration. Our results suggest that phosphite may serve as a driver of microbial growth and carbon fixation in energy-limited environments, especially in aphotic environments lacking alternative terminal electron acceptors.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2017
Citation:
IA Figueroa, et al. (2017)Metagenomics-guided analysis of microbial chemolithoautotrophic phosphite oxidation yields evidence of a seventh natural CO2 fixation pathway. Proceedings of the National Academy of Sciences 115 (1), E92-E101
IA Figueroa, JD Coates (2017) Microbial phosphite oxidation and its potential role in the global phosphorus and carbon cycles. Advances in applied microbiology 98, 93-117
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Progress 10/01/15 to 09/30/16
Outputs
Target Audience:Academic scientists and environmental engineers Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?
Nothing Reported
How have the results been disseminated to communities of interest?Through poster presentation at national and international scientific conferences. What do you plan to do during the next reporting period to accomplish the goals?Complete the metagenomic analysis of the DPO community
Impacts
What was accomplished under these goals?
Dissimilatory phosphite oxidation (DPO) is a microbial process by which phosphite (HPO32-) is oxidized to phosphate (PO43-) in order to provide energy for cell growth. Only one organism capable of DPO has been described and little is known about the environmental relevance of this metabolism. This study sought to expand our understanding of this process by enriching for novel organisms capable of DPO in wastewater treatment sludge. Active enrichments with carbon dioxide as the sole electron acceptor showed a decrease in phosphite with a concomitant increase in phosphate over a period of 29 weeks, which was not seen in killed controls. Phosphite oxidation was coupled to cellular growth and was enhanced by rumen fluid addition, while molybdate and sulfite were inhibitory. Unexpectedly, and in contrast to the only known organism capable of DPO, phosphite-oxidizing enrichments were incapable of reducing sulfate. Community analysis revealed significant changes in the microbial population associated with phosphite presence and identified a single bacterial OTU whose abundance strongly correlated with phosphite oxidation. Phylogenetic analysis indicated that this OTU belonged to a candidate order within the Deltaprotobacteria with no known cultured isolates. This study provides new insights into DPO and the unusual microorganisms with this capacity.
Publications
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Progress 10/01/14 to 09/30/15
Outputs
Target Audience:Microbiology study and scientists working in the area of environmental sciences. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?This project has allowed the training of one graduate student and 3 undergraduate students. How have the results been disseminated to communities of interest?The results have been deissemniated at professional microbiology meetings. A manuscript is currently in preparation for publication in a high profile scientific journal. What do you plan to do during the next reporting period to accomplish the goals?We plan to complete a metagenomic study to verify the identity of the key organisms repsonisble for phosphite oxidation in the enriched community.
Impacts
What was accomplished under these goals?
Dissimilatory phosphite oxidation (DPO) is a microbial process by which phosphite (HPO32-) is oxidized to phosphate (HPO42-) in order to provide energy for cell growth. Only one organism capable of DPO has been isolated to date and little is known about the biochemical mechanism or the genes involved in the metabolism. Our study sought to expand our understanding of this process by enriching for novel organisms capable of DPO. Sludge samples from an anaerobic wastewater digester were incubated in triplicate at 37oC in bicarbonate buffered freshwater medium under an 80:20 N2/CO2 headspace. Enrichments to which phosphite was added as the sole electron donor showed a decrease in the concentration of phosphite over a period of 29 weeks with a concomitant increase in the concentration of phosphate. No decrease in phosphite or accumulation of phosphate was observed in heat-killed controls. DNA samples were taken at 0, 20, and 29 weeks from the phosphite-oxidizing cultures as well as from controls to which no electron donor was added. The 16S rRNA genes were amplified from these samples and sequenced on an Illumina MiSeq platform. Sequencing reads were then analyzed using the MOTHUR software package in order to determine the taxonomic compositions of the different microbial communities. Hierarchical clustering analysis using PRIMER6 statistical software confirmed that the communities clustered together by treatment. A similarity percentage analysis using a 10% cutoff yielded 7 OTUs that had significantly higher abundance under phosphite-oxidizing conditions, 3 of which were identified at the genus level as Desulfomonile, Thermovirga, and Anaerobaculum. Of these, the Desulfomonile was of particular interest because it appeared to be enriched more than 1,000 fold compared to the no donor control based on the number of 16S reads. Efforts are currently underway to obtain this organism in pure culture.
Publications
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2015
Citation:
*1. (D). Figueroa, I. and Coates, J.D. (2015). 16S Community Analysis of Dissimilatory Phosphite-Oxidizing Microbial Enrichments from a Mesophilic Anaerobic Wastewater Digester. American Society for Microbiology General Meeting. New Orleans, LA. May 2015.
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Progress 10/01/13 to 09/30/14
Outputs
Target Audience: Target Audiences in this period included highschool students, undergraduate students, graduate students, undergraduate students, and professional environmental scientists. Knowledge dissemination included formal classroom instruction, laboratory instruction, summer internships, and poster presentation at professional meetings. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided? This project has provided insight into a novel metabolism responsible for phosphorous turnover in anaerobic environments. It has provided graduate training at the bench and intellectually for one graduate student and and internship for a visiting summer undergraduate student. How have the results been disseminated to communities of interest? Presentations at international meetings What do you plan to do during the next reporting period to accomplish the goals? More completely investigate the diversity of organisms capable of this metabolism and investigate the underlying biochemical and genetic mechanisms involved.
Impacts
What was accomplished under these goals?
Desulfotignum phosphitoxidans, strain FiPS-3 is currently the only isolated organism capable of using phosphite (HPO3) as an electron donor for growth. This process is known as dissimilatory phosphite oxidation (DPO) and leads to the accumulation of inorganic phosphate in the medium. Previous studies have shown that DPO can be coupled to either sulfate reduction or homoacetogenesis under anaerobic conditions. Here we provide evidence that FiPS-3 can also grow by coupling phosphite oxidation to aerobic respiration under microaerophilic conditions. Results Although FiPS-3 has been previously described as a strict anaerobe, its genome contains genes characteristic of aerobic organisms, such as catalase-peroxidase, superoxide dismutase, and cytochrome c oxidase. However, early attempts to grow the bacterium in well-aerated culture tubes were unsuccessful. Growth was observed only when FiPS-3 was grown in sealed anaerobic tubes to which small volumes of air were added. Interestingly, the growth rates of cells were similar under microaerophilic and sulfate reducing conditions, even though aerobic growth is more thermodynamically favorable. Together with the lack of growth observed in well-aerated cultures, this indicates that FiPS-3 grows poorly under aerobic conditions and cannot tolerate high oxygen concentrations. Conclusions The ability of FiPS-3 to grow at all by aerobic respiration is noteworthy, since this capability is rare among sulfate reducers. To our knowledge, this is also the first study to document an organism capable of growing by aerobic phosphite oxidation. This metabolic reaction has the greatest potential difference of any known biological redox process, but it remains unclear how much of this available energy FiPS-3 is able to harness for growth. Further study is needed in order to elucidate the biochemical mechanisms and the genetic requirements underlying this metabolism.
Publications
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2013
Citation:
Figueroa, I. and Coates, J. (2014). Dissimilatory phosphite oxidation coupled to aerobic respiration by the sulfate reducer Desulfotignum phosphitoxidans, strain FiPS-3 under microaerophilic conditions.Abstracts of the Annual General Meeting of the American Society for Microbiology, Boston MA
Figueroa, I. and Coates, J. (2013). Insights from the genome of the dissimilatory phosphite oxidizer Desulfotignum phosphitoxidans, strain FiPS-3. Abstracts of the Annual General Meeting of the American Society for Microbiology, Denver Co.
Zhu, H., Carlson,H., Ajo-Franklin, J., Hubbard, C., and Coates, J.D. (2013) Altering Petrology In Oil Reservoirs Through Microbial Authigenic Mineral Formation. Abstracts of the Annual General Meeting of the American Society for Microbiology, Denver Co.
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