1
|
Nikeleit V, Maisch M, Byrne JM, Harwood C, Kappler A, Bryce C. Phototrophic Fe(II) oxidation by Rhodopseudomonas palustris TIE-1 in organic and Fe(II)-rich conditions. Environ Microbiol 2024; 26:e16608. [PMID: 38504412 DOI: 10.1111/1462-2920.16608] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2023] [Accepted: 02/28/2024] [Indexed: 03/21/2024]
Abstract
Rhodopseudomonas palustris TIE-1 grows photoautotrophically with Fe(II) as an electron donor and photoheterotrophically with a variety of organic substrates. However, it is unclear whether R. palustris TIE-1 conducts Fe(II) oxidation in conditions where organic substrates and Fe(II) are available simultaneously. In addition, the effect of organic co-substrates on Fe(II) oxidation rates or the identity of Fe(III) minerals formed is unknown. We incubated R. palustris TIE-1 with 2 mM Fe(II), amended with 0.6 mM organic co-substrate, and in the presence/absence of CO2 . We found that in the absence of CO2 , only the organic co-substrates acetate, lactate and pyruvate, but not Fe(II), were consumed. When CO2 was present, Fe(II) and all organic substrates were consumed. Acetate, butyrate and pyruvate were consumed before Fe(II) oxidation commenced, whereas lactate and glucose were consumed at the same time as Fe(II) oxidation proceeded. Lactate, pyruvate and glucose increased the Fe(II) oxidation rate significantly (by up to threefold in the case of lactate). 57 Fe Mössbauer spectroscopy revealed that short-range ordered Fe(III) oxyhydroxides were formed under all conditions. This study demonstrates phototrophic Fe(II) oxidation proceeds even in the presence of organic compounds, and that the simultaneous oxidation of organic substrates can stimulate Fe(II) oxidation.
Collapse
Affiliation(s)
- Verena Nikeleit
- Department of Geoscience, University of Tübingen, Tübingen, Germany
| | - Markus Maisch
- Department of Geoscience, University of Tübingen, Tübingen, Germany
| | - James M Byrne
- School of Earth Sciences, University of Bristol, Bristol, UK
| | - Caroline Harwood
- Department of Microbiology, University of Washington, Seattle, Washington, USA
| | - Andreas Kappler
- Department of Geoscience, University of Tübingen, Tübingen, Germany
- Cluster of Excellence: EXC 2124: Controlling Microbes to Fight Infections, Tübingen, Germany
| | - Casey Bryce
- School of Earth Sciences, University of Bristol, Bristol, UK
| |
Collapse
|
2
|
Shaikh S, Rashid N, Onwusogh U, McKay G, Mackey H. Effect of nutrients deficiency on biofilm formation and single cell protein production with a purple non-sulphur bacteria enriched culture. Biofilm 2023; 5:100098. [PMID: 36588982 PMCID: PMC9794892 DOI: 10.1016/j.bioflm.2022.100098] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2022] [Revised: 11/27/2022] [Accepted: 12/03/2022] [Indexed: 12/23/2022] Open
Abstract
Purple non-sulphur bacteria (PNSB) are of interest for biorefinery applications to create biomolecules, but their production cost is expensive due to substrate and biomass separation costs. This research has utilized fuel synthesis wastewater (FSW) as a low-cost carbon-rich substrate to produce single-cell protein (SCP) and examines PNSB biofilm formation using this substrate to achieve a more efficient biomass-liquid separation. In this study, PNSB were grown in Ca, Mg, S, P, and N-deficient media using green shade as biofilm support material. Among these nutrient conditions, only N-deficient and control (nutrient-sufficient) conditions showed biofilm formation. Although total biomass growth of the control was 1.5 times that of the N-deficient condition and highest overall, the total biofilm-biomass in the N-deficient condition was 2.5 times greater than the control, comprising 49% of total biomass produced. Total protein content was similar between these four biomass samples, ranging from 35.0 ± 0.2% to 37.2 ± 0.0%. The highest protein content of 44.7 ± 1.3% occurred in the Mg-deficient condition (suspended biomass only) but suffered from a low growth rate. Overall, nutrient sufficient conditions are optimal for overall protein productivity and dominated by suspended growth, but where fixed growth systems are desired for cost-effective harvesting, N-deficient conditions provide an effective means to maximize biofilm production without sacrificing protein content.
Collapse
Affiliation(s)
- S. Shaikh
- Division of Sustainable Development, College of Science and Engineering, Hamad Bin Khalifa University, Qatar Foundation, Doha, Qatar
| | - N. Rashid
- Division of Sustainable Development, College of Science and Engineering, Hamad Bin Khalifa University, Qatar Foundation, Doha, Qatar
| | - U. Onwusogh
- Qatar Shell Research and Technology Centre, Tech 1, Qatar Science and Technology Park, Doha, Qatar
| | - G. McKay
- Division of Sustainable Development, College of Science and Engineering, Hamad Bin Khalifa University, Qatar Foundation, Doha, Qatar
| | - H.R. Mackey
- Division of Sustainable Development, College of Science and Engineering, Hamad Bin Khalifa University, Qatar Foundation, Doha, Qatar
- Department of Civil and Natural Resources Engineering, University of Canterbury, Private Bag 4800, Christchurch, 8140, New Zealand
| |
Collapse
|
3
|
Li L, Liu Z, Meng D, Liu Y, Liu T, Jiang C, Yin H. Sequence similarity network and protein structure prediction offer insights into the evolution of microbial pathways for ferrous iron oxidation. mSystems 2023; 8:e0072023. [PMID: 37768051 PMCID: PMC10654088 DOI: 10.1128/msystems.00720-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2023] [Accepted: 08/09/2023] [Indexed: 09/29/2023] Open
Abstract
IMPORTANCE Microbial Fe(II) oxidation is a crucial process that harnesses and converts the energy available in Fe, contributing significantly to global element cycling. However, there are still many aspects of this process that remain unexplored. In this study, we utilized a combination of comparative genomics, sequence similarity network analysis, and artificial intelligence-driven structure modeling methods to address the lack of structural information on Fe(II) oxidation proteins and offer a comprehensive perspective on the evolution of Fe(II) oxidation pathways. Our findings suggest that several microbial Fe(II) oxidation pathways currently known may have originated within classes Gammaproteobacteria and Betaproteobacteria.
Collapse
Affiliation(s)
- Liangzhi Li
- School of Minerals Processing and Bioengineering, Central South University, Changsha, China
- Key Laboratory of Biometallurgy of Ministry of Education, Central South University, Changsha, China
| | - Zhenghua Liu
- School of Minerals Processing and Bioengineering, Central South University, Changsha, China
- Key Laboratory of Biometallurgy of Ministry of Education, Central South University, Changsha, China
| | - Delong Meng
- School of Minerals Processing and Bioengineering, Central South University, Changsha, China
- Key Laboratory of Biometallurgy of Ministry of Education, Central South University, Changsha, China
| | - Yongjun Liu
- Hunan Tobacco Science Institute, Changsha, China
| | - Tianbo Liu
- Hunan Tobacco Science Institute, Changsha, China
| | - Chengying Jiang
- University of Chinese Academy of Sciences, Beijing, China
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China
| | - Huaqun Yin
- School of Minerals Processing and Bioengineering, Central South University, Changsha, China
- Key Laboratory of Biometallurgy of Ministry of Education, Central South University, Changsha, China
| |
Collapse
|
4
|
Nalvothula R, Challa S, Peddireddy V, Merugu R, Rudra MPP, Alataway A, Dewidar AZ, Elansary HO. Isolation, Molecular Identification and Amino Acid Profiling of Single-Cell-Protein-Producing Phototrophic Bacteria Isolated from Oil-Contaminated Soil Samples. Molecules 2022; 27:molecules27196265. [PMID: 36234802 PMCID: PMC9572994 DOI: 10.3390/molecules27196265] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2022] [Revised: 08/20/2022] [Accepted: 09/07/2022] [Indexed: 11/16/2022] Open
Abstract
In the current study, soil samples were gathered from different places where petrol and diesel filling stations were located for isolation of photosynthetic bacteria under anaerobic conditions using the paraffin wax-overlay pour plate method with Biebl and Pfennig’s medium. The three isolated strains were named Rhodopseudomonas palustris SMR 001 (Mallapur), Rhodopseudomonas palustris NR MPPR (Nacahram) and Rhodopseudomonas faecalis N Raju MPPR (Karolbagh). The morphologies of the bacteria were examined with a scanning electron microscope (SEM). The phylogenetic relationship between R. palustris strains was examined by means of 16S rRNA gene sequence analysis using NCBI-BLAST search and a phylogenetic tree. The sequenced data for R. palustris were deposited with the National Centre for Biotechnology Research (NCBI). The total amino acids produced by the isolated bacteria were determined by HPLC. A total of 14 amino acids and their derivatives were produced by the R. palustris SMR 001 strain. Among these, carnosine was found in the highest concentration (8553.2 ng/mL), followed by isoleucine (1818.044 ng/mL) and anserine (109.5 ng/mL), while R. palustris NR MPPR was found to produce 12 amino acids. Thirteen amino acids and their derivatives were found to be produced from R. faecalis N Raju MPPR, for which the concentration of carnosine (21601.056 ng/mL) was found to be the highest, followed by isoleucine (2032.6 ng/mL) and anserine (227.4 ng/mL). These microbes can be explored for the scaling up of the process, along with biohydrogen and single cell protein production.
Collapse
Affiliation(s)
- Raju Nalvothula
- Department of Biochemistry, Osmania University, Hyderabad 500007, India
| | - Surekha Challa
- Department of Biochemistry and Bioinformatics, GSS, GITAM, A P., Gandhinagar 530045, India
| | - Vidyullatha Peddireddy
- Department of Nutrition Biology, School of Interdisciplinary & Applied Sciences, Central University of Haryana, Jant-Pali, Mahendergarh 123031, India
| | - Ramchander Merugu
- Department of Biochemistry, Mahatma Gandhi University, Nalgonda 508254, India
- Correspondence: (R.M.); (M.P.P.R.)
| | - M. P. Pratap Rudra
- Department of Biochemistry, Osmania University, Hyderabad 500007, India
- Correspondence: (R.M.); (M.P.P.R.)
| | - Abed Alataway
- Prince Sultan Bin Abdulaziz International Prize for Water Chair, Prince Sultan Institute for Environmental, Water and Desert Research, King Saud University, Riyadh 11451, Saudi Arabia
| | - Ahmed Z. Dewidar
- Prince Sultan Bin Abdulaziz International Prize for Water Chair, Prince Sultan Institute for Environmental, Water and Desert Research, King Saud University, Riyadh 11451, Saudi Arabia
- Department of Agricultural Engineering, College of Food and Agriculture Sciences, King Saud University, Riyadh 11451, Saudi Arabia
| | - Hosam O. Elansary
- Prince Sultan Bin Abdulaziz International Prize for Water Chair, Prince Sultan Institute for Environmental, Water and Desert Research, King Saud University, Riyadh 11451, Saudi Arabia
- Plant Production Department, College of Food and Agricultural Sciences, King Saud University, P.O. Box 2455, Riyadh 11451, Saudi Arabia
- Department of Geography, Environmental Management, and Energy Studies, University of Johannesburg, APK Campus, Johannesburg 2006, South Africa
| |
Collapse
|
5
|
Haas NW, Jain A, Hying Z, Arif SJ, Niehaus TD, Gralnick JA, Fixen KR. PioABC-Dependent Fe(II) Oxidation during Photoheterotrophic Growth on an Oxidized Carbon Substrate Increases Growth Yield. Appl Environ Microbiol 2022; 88:e0097422. [PMID: 35862670 PMCID: PMC9361825 DOI: 10.1128/aem.00974-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2022] [Accepted: 06/29/2022] [Indexed: 01/21/2023] Open
Abstract
Microorganisms that carry out Fe(II) oxidation play a major role in biogeochemical cycling of iron in environments with low oxygen. Fe(II) oxidation has been largely studied in the context of autotrophy. Here, we show that the anoxygenic phototroph, Rhodopseudomonas palustris CGA010, carries out Fe(II) oxidation during photoheterotrophic growth with an oxidized carbon source, malate, leading to an increase in cell yield and allowing more carbon to be directed to cell biomass. We probed the regulatory basis for this by transcriptome sequencing (RNA-seq) and found that the expression levels of the known pioABC Fe(II) oxidation genes in R. palustris depended on the redox-sensing two-component system, RegSR, and the oxidation state of the carbon source provided to cells. This provides the first mechanistic demonstration of mixotrophic growth involving reducing power generated from both Fe(II) oxidation and carbon assimilation. IMPORTANCE The simultaneous use of carbon and reduced metals such as Fe(II) by bacteria is thought to be widespread in aquatic environments, and a mechanistic description of this process could improve our understanding of biogeochemical cycles. Anoxygenic phototrophic bacteria like Rhodopseudomonas palustris typically use light for energy and organic compounds as both a carbon and an electron source. They can also use CO2 for carbon by carbon dioxide fixation when electron-rich compounds like H2, thiosulfate, and Fe(II) are provided as electron donors. Here, we show that Fe(II) oxidation can be used in another context to promote higher growth yields of R. palustris when the oxidized carbon compound malate is provided. We further established the regulatory mechanism underpinning this observation.
Collapse
Affiliation(s)
- Nicholas W. Haas
- BioTechnology Institute and Department of Plant and Microbial Biology, University of Minnesota, St. Paul, Minnesota, USA
| | - Abhiney Jain
- BioTechnology Institute and Department of Plant and Microbial Biology, University of Minnesota, St. Paul, Minnesota, USA
| | - Zachary Hying
- BioTechnology Institute and Department of Plant and Microbial Biology, University of Minnesota, St. Paul, Minnesota, USA
| | - Sabrina J. Arif
- Department of Genetics, Cell Biology, and Development, University of Minnesota, Minneapolis, Minnesota, USA
| | - Thomas D. Niehaus
- BioTechnology Institute and Department of Plant and Microbial Biology, University of Minnesota, St. Paul, Minnesota, USA
| | - Jeffrey A. Gralnick
- BioTechnology Institute and Department of Plant and Microbial Biology, University of Minnesota, St. Paul, Minnesota, USA
| | - Kathryn R. Fixen
- BioTechnology Institute and Department of Plant and Microbial Biology, University of Minnesota, St. Paul, Minnesota, USA
| |
Collapse
|
6
|
Cai C, Ni G, Xia J, Zhang X, Zheng Y, He B, Marcellin E, Li W, Pu J, Yuan Z, Hu S. Response of the Anaerobic Methanotrophic Archaeon Candidatus " Methanoperedens nitroreducens" to the Long-Term Ferrihydrite Amendment. Front Microbiol 2022; 13:799859. [PMID: 35509320 PMCID: PMC9058156 DOI: 10.3389/fmicb.2022.799859] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2021] [Accepted: 03/10/2022] [Indexed: 11/30/2022] Open
Abstract
Anaerobic methanotrophic (ANME) archaea can drive anaerobic oxidation of methane (AOM) using solid iron or manganese oxides as the electron acceptors, hypothetically via direct extracellular electron transfer (EET). This study investigated the response of Candidatus "Methanoperedens nitroreducens TS" (type strain), an ANME archaeon previously characterized to perform nitrate-dependent AOM, to an Fe(III)-amended condition over a prolonged period. Simultaneous consumption of methane and production of dissolved Fe(II) were observed for more than 500 days in the presence of Ca. "M. nitroreducens TS," indicating that this archaeon can carry out Fe(III)-dependent AOM for a long period. Ca. "M. nitroreducens TS" possesses multiple multiheme c-type cytochromes (MHCs), suggesting that it may have the capability to reduce Fe(III) via EET. Intriguingly, most of these MHCs are orthologous to those identified in Candidatus "Methanoperedens ferrireducens," an Fe(III)-reducing ANME archaeon. In contrast, the population of Ca. "M. nitroreducens TS" declined and was eventually replaced by Ca. "M. ferrireducens," implying niche differentiation between these two ANME archaea in the environment.
Collapse
Affiliation(s)
- Chen Cai
- CAS Key Laboratory of Urban Pollutant Conversion, Department of Environmental Science and Engineering, University of Science and Technology of China, Hefei, China
- Australian Centre for Water and Environmental Biotechnology, The University of Queensland, St Lucia, QLD, Australia
| | - Gaofeng Ni
- Australian Centre for Water and Environmental Biotechnology, The University of Queensland, St Lucia, QLD, Australia
| | - Jun Xia
- Australian Centre for Water and Environmental Biotechnology, The University of Queensland, St Lucia, QLD, Australia
| | - Xueqin Zhang
- Australian Centre for Water and Environmental Biotechnology, The University of Queensland, St Lucia, QLD, Australia
| | - Yue Zheng
- State Key Laboratory of Marine Environmental Science, College of the Environment and Ecology, Xiamen University, Xiamen, China
| | - Bingqing He
- Australian Centre for Water and Environmental Biotechnology, The University of Queensland, St Lucia, QLD, Australia
- Australian Institute for Bioengineering and Nanotechnology, The University of Queensland, St Lucia, QLD, Australia
| | - Esteban Marcellin
- Australian Institute for Bioengineering and Nanotechnology, The University of Queensland, St Lucia, QLD, Australia
| | - Weiwei Li
- Australian Centre for Water and Environmental Biotechnology, The University of Queensland, St Lucia, QLD, Australia
- State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing University, Chongqing, China
| | - Jiaoyang Pu
- Australian Centre for Water and Environmental Biotechnology, The University of Queensland, St Lucia, QLD, Australia
| | - Zhiguo Yuan
- Australian Centre for Water and Environmental Biotechnology, The University of Queensland, St Lucia, QLD, Australia
| | - Shihu Hu
- Australian Centre for Water and Environmental Biotechnology, The University of Queensland, St Lucia, QLD, Australia
| |
Collapse
|
7
|
Land use influences stream bacterial communities in lowland tropical watersheds. Sci Rep 2021; 11:21752. [PMID: 34741067 PMCID: PMC8571290 DOI: 10.1038/s41598-021-01193-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2021] [Accepted: 10/18/2021] [Indexed: 01/04/2023] Open
Abstract
Land use is known to affect water quality yet the impact it has on aquatic microbial communities in tropical systems is poorly understood. We used 16S metabarcoding to assess the impact of land use on bacterial communities in the water column of four streams in central Panama. Each stream was influenced by a common Neotropical land use: mature forest, secondary forest, silvopasture and traditional cattle pasture. Bacterial community diversity and composition were significantly influenced by nearby land uses. Streams bordered by forests had higher phylogenetic diversity (Faith’s PD) and similar community structure (based on weighted UniFrac distance), whereas the stream surrounded by traditional cattle pasture had lower diversity and unique bacterial communities. The silvopasture stream showed strong seasonal shifts, with communities similar to forested catchments during the wet seasons and cattle pasture during dry seasons. We demonstrate that natural forest regrowth and targeted management, such as maintaining and restoring riparian corridors, benefit stream-water microbiomes in tropical landscapes and can provide a rapid and efficient approach to balancing agricultural activities and water quality protection.
Collapse
|
8
|
Single Cell Protein: A Potential Substitute in Human and Animal Nutrition. SUSTAINABILITY 2021. [DOI: 10.3390/su13169284] [Citation(s) in RCA: 29] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Single cell protein (SCP) is the first product of the fermentation process and has proven to be a good protein alternative. Food competition is becoming more intense as the world’s population continues to grow. Soon, SCP may be able to compensate for a protein deficit. Various global businesses are focusing on SCP production, and the scope of its application is expanding as time and knowledge increases. High quantities of SCP can be produced by microorganisms, such as algae, yeast, fungi and bacteria, due to their fast development rate and the significant level of protein in their chemical structure. Beside proteins, SCP contains carbohydrates, nucleic acids, lipids, minerals, vitamins and several important amino acids. SCP has been an effective substitute for more expensive protein sources such as fish and soybean products. In conclusion, SCP can easily replace traditional protein sources in human and animal feed without detrimental effects. Potential substrate candidates and optimization strategies for SCP production have been extensively studied. This review article focuses on the various aspects of SCP, from its production, using different substrates, player microorganisms and nutritional benefits, to its economic aspects.
Collapse
|
9
|
Lee J, Mahandra H, Hein GA, Ramsay J, Ghahreman A. Toward Sustainable Solution for Biooxidation of Waste and Refractory Materials Using Neutrophilic and Alkaliphilic Microorganisms—A Review. ACS APPLIED BIO MATERIALS 2021; 4:2274-2292. [DOI: 10.1021/acsabm.0c01582] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Affiliation(s)
- Jung Lee
- Hydrometallurgy and Environment Laboratory, Robert M. Buchan Department of Mining, Queen’s University, 25 Union Street, Kingston, Ontario K7L 3N6, Canada
| | - Harshit Mahandra
- Hydrometallurgy and Environment Laboratory, Robert M. Buchan Department of Mining, Queen’s University, 25 Union Street, Kingston, Ontario K7L 3N6, Canada
| | - Guillermo Alvial Hein
- Hydrometallurgy and Environment Laboratory, Robert M. Buchan Department of Mining, Queen’s University, 25 Union Street, Kingston, Ontario K7L 3N6, Canada
| | - Juliana Ramsay
- Department of Chemical Engineering, Queen’s University, 19 Division Street, Kingston, Ontario K7L 3N6, Canada
| | - Ahmad Ghahreman
- Hydrometallurgy and Environment Laboratory, Robert M. Buchan Department of Mining, Queen’s University, 25 Union Street, Kingston, Ontario K7L 3N6, Canada
| |
Collapse
|
10
|
Unchartered waters: the unintended impacts of residual chlorine on water quality and biofilms. NPJ Biofilms Microbiomes 2020; 6:34. [PMID: 32978404 PMCID: PMC7519676 DOI: 10.1038/s41522-020-00144-w] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2020] [Accepted: 08/25/2020] [Indexed: 02/08/2023] Open
Abstract
Disinfection residuals in drinking water protect water quality and public heath by limiting planktonic microbial regrowth during distribution. However, we do not consider the consequences and selective pressures of such residuals on the ubiquitous biofilms that persist on the vast internal surface area of drinking water distribution systems. Using a full scale experimental facility, integrated analyses were applied to determine the physical, chemical and biological impacts of different free chlorine regimes on biofilm characteristics (composition, structure and microbiome) and water quality. Unexpectedly, higher free chlorine concentrations resulted in greater water quality degredation, observable as elevated inorganic loading and greater discolouration (a major cause of water quality complaints and a mask for other failures). High-chlorine concentrations also reduced biofilm cell concentrations but selected for a distinct biofilm bacterial community and inorganic composition, presenting unique risks. The results challenge the assumption that a measurable free chlorine residual necessarily assures drinking water safety.
Collapse
|
11
|
Cojean ANY, Lehmann MF, Robertson EK, Thamdrup B, Zopfi J. Controls of H 2S, Fe 2 +, and Mn 2 + on Microbial NO 3 --Reducing Processes in Sediments of an Eutrophic Lake. Front Microbiol 2020; 11:1158. [PMID: 32612583 PMCID: PMC7308436 DOI: 10.3389/fmicb.2020.01158] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2020] [Accepted: 05/06/2020] [Indexed: 11/18/2022] Open
Abstract
Understanding the biogeochemical controls on the partitioning between nitrogen (N) removal through denitrification and anaerobic ammonium oxidation (anammox), and N recycling via dissimilatory nitrate (NO3 -) reduction to ammonium (DNRA) is crucial for constraining lacustrine N budgets. Besides organic carbon, inorganic compounds may serve as electron donors for NO3 - reduction, yet the significance of lithotrophic NO3 - reduction in the environment is still poorly understood. Conducting incubation experiments with additions of 15N-labeled compounds and reduced inorganic substrates (H2S, Fe2+, Mn2+), we assessed the role of alternative electron donors in regulating the partitioning between the different NO3 --reducing processes in ferruginous surface sediments of Lake Lugano, Switzerland. In sediment slurry incubations without added inorganic substrates, denitrification and DNRA were the dominant NO3 --reducing pathways, with DNRA contributing between 31 and 46% to the total NO3 - reduction. The contribution of anammox was less than 1%. Denitrification rates were stimulated by low to moderate additions of ferrous iron (Fe2+ ≤ 258 μM) but almost completely suppressed at higher levels (≥1300 μM). Conversely, DNRA was stimulated only at higher Fe2+ concentrations. Dissolved sulfide (H2S, i.e., sum of H2S, HS- and S2-) concentrations up to ∼80 μM, strongly stimulated denitrification, but did not affect DNRA significantly. At higher H2S levels (≥125 μM), both processes were inhibited. We were unable to find clear evidence for Mn2+-supported lithotrophic NO3 - reduction. However, at high concentrations (∼500 μM), Mn2+ additions inhibited NO3 - reduction, while it did not affect the balance between the two NO3 - reduction pathways. Our results provide experimental evidence for chemolithotrophic denitrification or DNRA with Fe2+ and H2S in the Lake Lugano sediments, and demonstrate that all tested potential electron donors, despite the beneficial effect at low concentrations of some of them, can inhibit NO3 - reduction at high concentration levels. Our findings thus imply that the concentration of inorganic electron donors in lake sediments can act as an important regulator of both benthic denitrification and DNRA rates, and suggest that they can exert an important control on the relative partitioning between microbial N removal and N retention in lakes.
Collapse
Affiliation(s)
- Adeline N. Y. Cojean
- Department of Environmental Sciences, Aquatic and Stable Isotope Biogeochemistry, University of Basel, Basel, Switzerland
| | - Moritz F. Lehmann
- Department of Environmental Sciences, Aquatic and Stable Isotope Biogeochemistry, University of Basel, Basel, Switzerland
| | | | - Bo Thamdrup
- Department of Biology and Nordic Center for Earth Evolution, University of Southern Denmark, Odense, Denmark
| | - Jakob Zopfi
- Department of Environmental Sciences, Aquatic and Stable Isotope Biogeochemistry, University of Basel, Basel, Switzerland
| |
Collapse
|
12
|
Bennett BD, Gralnick JA. Mechanisms of toxicity by and resistance to ferrous iron in anaerobic systems. Free Radic Biol Med 2019; 140:167-171. [PMID: 31251977 DOI: 10.1016/j.freeradbiomed.2019.06.027] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/05/2018] [Revised: 06/13/2019] [Accepted: 06/23/2019] [Indexed: 12/24/2022]
Abstract
Iron is an essential element for nearly all life on Earth, primarily for its value as a redox active cofactor. Iron exists predominantly in two biologically relevant redox states: ferric iron, the oxidized state (Fe3+), and ferrous iron, the reduced state (Fe2+). Fe2+ is well known to facilitate electron transfer reactions that can lead to the generation of reactive oxygen species. Less is known about why iron is toxic to cells in the absence of oxygen, yet this phenomenon is critically important for our understanding of life on early Earth and in iron-rich ecosystems today. In this brief review, we will highlight our current understanding of anaerobic Fe2+ toxicity, focusing on molecular mechanistic studies in several model systems.
Collapse
Affiliation(s)
- B D Bennett
- Pacific Biosciences Research Center, University of Hawai‛i at Mānoa, Honolulu, HI, 96813, USA
| | - J A Gralnick
- BioTechnology Institute and Department of Plant and Microbial Biology, University of Minnesota - Twin Cities, St. Paul, MN, 55108, USA.
| |
Collapse
|
13
|
Zhou GW, Yang XR, Rønn R, Su JQ, Cui L, Zheng BX, Zhu YG. Metabolic Inactivity and Re-awakening of a Nitrate Reduction Dependent Iron(II)-Oxidizing Bacterium Bacillus ferrooxidans. Front Microbiol 2019; 10:1494. [PMID: 31333611 PMCID: PMC6617468 DOI: 10.3389/fmicb.2019.01494] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2019] [Accepted: 06/14/2019] [Indexed: 11/13/2022] Open
Abstract
Microorganisms capable of anaerobic nitrate-dependent Fe(II) (ferrous iron) oxidation (ANDFO) contribute significantly to iron and nitrogen cycling in various environments. However, lab efforts in continuous cultivation of ANDFO strains suffer from loss of activity when ferrous iron is used as sole electron donor. Here, we used a novel strain of nitrate-dependent Fe(II)-oxidizing bacterium Bacillus ferroxidians as a model and focused on the physiological activity of cells during ANDFO. It was shown that B. ferrooxidans entered a metabolically inactive state during ANDFO. B. ferrooxidans exhibited nitrate reduction coupled with Fe(II) oxidation, and the activity gradually declined and was hardly detected after 48-h incubation. Propidium monoazide (PMA) assisted 16S rRNA gene real-time PCR suggested that a large number of B. ferrooxidans cells were alive during incubation. However, 2H(D)-isotope based Raman analysis indicated that the cells were metabolically inactive after 120-h of ANDFO. These inactive cells re-awakened in R2A medium and were capable of growth and reproduction, which was consistent with results in Raman analysis. Scanning electron microscopy (SEM) observation and x-ray diffraction (XRD) revealed the formation of Fe minerals in close proximity of cells in the Fe(II)-oxidizing medium after Fe(II) oxidation. Overall, our results demonstrated that continued ANDFO can induce a metabolically inactive state in B. ferrooxidans, which was responsible for the loss of activity during ANDFO. This study provides an insight into the ANDFO process and its contribution to iron and nitrogen cycling in the environments.
Collapse
Affiliation(s)
- Guo-Wei Zhou
- Key Laboratory of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen, China.,State Key Laboratory of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, China
| | - Xiao-Ru Yang
- Key Laboratory of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen, China
| | - Regin Rønn
- Department of Biology, University of Copenhagen, Copenhagen, Denmark
| | - Jian-Qiang Su
- Key Laboratory of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen, China
| | - Li Cui
- Key Laboratory of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen, China
| | - Bang-Xiao Zheng
- Faculty of Biological and Environmental Sciences, University of Helsinki, Lahti, Finland
| | - Yong-Guan Zhu
- Key Laboratory of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen, China.,State Key Laboratory of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, China.,College of Advanced Agricultural Sciences, University of Chinese Academy of Sciences, Beijing, China
| |
Collapse
|
14
|
Phan VTH, Bernier-Latmani R, Tisserand D, Bardelli F, Le Pape P, Frutschi M, Gehin A, Couture RM, Charlet L. As release under the microbial sulfate reduction during redox oscillations in the upper Mekong delta aquifers, Vietnam: A mechanistic study. THE SCIENCE OF THE TOTAL ENVIRONMENT 2019; 663:718-730. [PMID: 30731417 DOI: 10.1016/j.scitotenv.2019.01.219] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/22/2018] [Revised: 12/14/2018] [Accepted: 01/18/2019] [Indexed: 06/09/2023]
Abstract
The impact of seasonal fluctuations linked to monsoon and irrigation generates redox oscillations in the subsurface, influencing the release of arsenic (As) in aquifers. Here, the biogeochemical control on As mobility was investigated in batch experiments using redox cycling bioreactors and As- and SO42--amended sediment. Redox potential (Eh) oscillations between anoxic (-300-0 mV) and oxic condition (0-500 mV) were implemented by automatically modulating an admixture of N2/CO2 or compressed air. A carbon source (cellobiose, a monomer of cellulose) was added at the beginning of each reducing cycle to stimulate the metabolism of the native microbial community. Results show that successive redox cycles can decrease arsenic mobility by up to 92% during reducing conditions. Anoxic conditions drive mainly the conversion of soluble As(V) to As(III) in contrast to oxic conditions. Phylogenetic analyses of 16S rRNA amplified from the sediments revealed the presence of sulfate and iron - reducing bacteria, confirming that sulfate and iron reduction are key factors for As immobilization from the aqueous phase. As and S K-edge X-ray absorption spectroscopy suggested the association of Fe-(oxyhydr)oxides and the importance of pyrite (FeS2(s)), rather than poorly ordered mackinawite (FeS(s)), for As sequestration under oxidizing and reducing conditions, respectively. Finally, these findings suggest a role for elemental sulfur in mediating aqueous thioarsenates formation in As-contaminated groundwater of the Mekong delta.
Collapse
Affiliation(s)
- Van T H Phan
- University Grenoble Alps, CNRS, IRD, IFSTTAR, Institut des Sciences de la Terre (ISTerre), 38000 Grenoble, France; Ho Chi Minh City University of Technology (HCMUT), Vietnam National University - Ho Chi Minh City (VNU-HCM), 268 Ly Thuong Kiet, District 10, Ho Chi Minh City, Viet Nam.
| | - Rizlan Bernier-Latmani
- Ecole Polytechnique Fédérale de Lausanne (EPFL), Environmental Microbiology Laboratory (EML), EPFL-ENAC-IIE-EML, Station 6, CH-1015 Lausanne, Switzerland
| | - Delphine Tisserand
- University Grenoble Alps, CNRS, IRD, IFSTTAR, Institut des Sciences de la Terre (ISTerre), 38000 Grenoble, France
| | | | - Pierre Le Pape
- Institut de Mineralogie, de Physique des Materiaux et de Cosmochimie (IMPMC), UMR 7590 CNRS-UPMC-IRD-MNHN, 4 place Jussieu, 75252 Paris cedex 05, France
| | - Manon Frutschi
- Ecole Polytechnique Fédérale de Lausanne (EPFL), Environmental Microbiology Laboratory (EML), EPFL-ENAC-IIE-EML, Station 6, CH-1015 Lausanne, Switzerland
| | - Antoine Gehin
- University Grenoble Alps, CNRS, IRD, IFSTTAR, Institut des Sciences de la Terre (ISTerre), 38000 Grenoble, France
| | - Raoul-Marie Couture
- Département de Chimie, Université Laval, 1045 Avenue de la Médecine, Québec, QC G1V 0A6, Canada
| | - Laurent Charlet
- University Grenoble Alps, CNRS, IRD, IFSTTAR, Institut des Sciences de la Terre (ISTerre), 38000 Grenoble, France
| |
Collapse
|
15
|
Bryce C, Blackwell N, Schmidt C, Otte J, Huang YM, Kleindienst S, Tomaszewski E, Schad M, Warter V, Peng C, Byrne JM, Kappler A. Microbial anaerobic Fe(II) oxidation - Ecology, mechanisms and environmental implications. Environ Microbiol 2018; 20:3462-3483. [DOI: 10.1111/1462-2920.14328] [Citation(s) in RCA: 104] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2018] [Revised: 06/15/2018] [Accepted: 06/16/2018] [Indexed: 11/30/2022]
Affiliation(s)
- Casey Bryce
- Geomicrobiology; University of Tübingen; Tübingen Germany
| | - Nia Blackwell
- Geomicrobiology; University of Tübingen; Tübingen Germany
| | | | - Julia Otte
- Geomicrobiology; University of Tübingen; Tübingen Germany
| | - Yu-Ming Huang
- Geomicrobiology; University of Tübingen; Tübingen Germany
| | | | | | - Manuel Schad
- Geomicrobiology; University of Tübingen; Tübingen Germany
| | - Viola Warter
- Geomicrobiology; University of Tübingen; Tübingen Germany
| | - Chao Peng
- Geomicrobiology; University of Tübingen; Tübingen Germany
| | - James M. Byrne
- Geomicrobiology; University of Tübingen; Tübingen Germany
| | - Andreas Kappler
- Geomicrobiology; University of Tübingen; Tübingen Germany
- Center for Geomicrobiology, Department of Bioscience; Aarhus University; Aarhus Denmark
| |
Collapse
|
16
|
Singh VK, Singh AL, Singh R, Kumar A. Iron oxidizing bacteria: insights on diversity, mechanism of iron oxidation and role in management of metal pollution. ACTA ACUST UNITED AC 2018. [DOI: 10.1007/s42398-018-0024-0] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
|
17
|
Proteome Response of a Metabolically Flexible Anoxygenic Phototroph to Fe(II) Oxidation. Appl Environ Microbiol 2018; 84:AEM.01166-18. [PMID: 29915106 DOI: 10.1128/aem.01166-18] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2018] [Accepted: 06/07/2018] [Indexed: 11/20/2022] Open
Abstract
The oxidation of Fe(II) by anoxygenic photosynthetic bacteria was likely a key contributor to Earth's biosphere prior to the evolution of oxygenic photosynthesis and is still found in a diverse range of modern environments. All known phototrophic Fe(II) oxidizers can utilize a wide range of substrates, thus making them very metabolically flexible. However, the underlying adaptations required to oxidize Fe(II), a potential stressor, are not completely understood. We used a combination of quantitative proteomics and cryogenic transmission electron microscopy (cryo-TEM) to compare cells of Rhodopseudomonas palustris TIE-1 grown photoautotrophically with Fe(II) or H2 and photoheterotrophically with acetate. We observed unique proteome profiles for each condition, with differences primarily driven by carbon source. However, these differences were not related to carbon fixation but to growth and light harvesting processes, such as pigment synthesis. Cryo-TEM showed stunted development of photosynthetic membranes in photoautotrophic cultures. Growth on Fe(II) was characterized by a response typical of iron homeostasis, which included an increased abundance of proteins required for metal efflux (particularly copper) and decreased abundance of iron import proteins, including siderophore receptors, with no evidence of further stressors, such as oxidative damage. This study suggests that the main challenge facing anoxygenic phototrophic Fe(II) oxidizers comes from growth limitations imposed by autotrophy, and, once this challenge is overcome, iron stress can be mitigated using iron management mechanisms common to diverse bacteria (e.g., by control of iron influx and efflux).IMPORTANCE The cycling of iron between redox states leads to the precipitation and dissolution of minerals, which can in turn impact other major biogeochemical cycles, such as those of carbon, nitrogen, phosphorus and sulfur. Anoxygenic phototrophs are one of the few drivers of Fe(II) oxidation in anoxic environments and are thought to contribute significantly to iron cycling in both modern and ancient environments. These organisms thrive at high Fe(II) concentrations, yet the adaptations required to tolerate the stresses associated with this are unclear. Despite the general consensus that high Fe(II) concentrations pose numerous stresses on these organisms, our study of the large-scale proteome response of a model anoxygenic phototroph to Fe(II) oxidation demonstrates that common iron homeostasis strategies are adequate to manage this. The bulk of the proteome response is not driven by adaptations to Fe(II) stress but to adaptations required to utilize an inorganic carbon source. Such a global overview of the adaptation of these organisms to Fe(II) oxidation provides valuable insights into the physiology of these biogeochemically important organisms and suggests that Fe(II) oxidation may not pose as many challenges to anoxygenic phototrophs as previously thought.
Collapse
|
18
|
Camacho A, Walter XA, Picazo A, Zopfi J. Photoferrotrophy: Remains of an Ancient Photosynthesis in Modern Environments. Front Microbiol 2017; 8:323. [PMID: 28377745 PMCID: PMC5359306 DOI: 10.3389/fmicb.2017.00323] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2016] [Accepted: 02/15/2017] [Indexed: 11/13/2022] Open
Abstract
Photoferrotrophy, the process by which inorganic carbon is fixed into organic matter using light as an energy source and reduced iron [Fe(II)] as an electron donor, has been proposed as one of the oldest photoautotrophic metabolisms on Earth. Under the iron-rich (ferruginous) but sulfide poor conditions dominating the Archean ocean, this type of metabolism could have accounted for most of the primary production in the photic zone. Here we review the current knowledge of biogeochemical, microbial and phylogenetic aspects of photoferrotrophy, and evaluate the ecological significance of this process in ancient and modern environments. From the ferruginous conditions that prevailed during most of the Archean, the ancient ocean evolved toward euxinic (anoxic and sulfide rich) conditions and, finally, much after the advent of oxygenic photosynthesis, to a predominantly oxic environment. Under these new conditions photoferrotrophs lost importance as primary producers, and now photoferrotrophy remains as a vestige of a formerly relevant photosynthetic process. Apart from the geological record and other biogeochemical markers, modern environments resembling the redox conditions of these ancient oceans can offer insights into the past significance of photoferrotrophy and help to explain how this metabolism operated as an important source of organic carbon for the early biosphere. Iron-rich meromictic (permanently stratified) lakes can be considered as modern analogs of the ancient Archean ocean, as they present anoxic ferruginous water columns where light can still be available at the chemocline, thus offering suitable niches for photoferrotrophs. A few bacterial strains of purple bacteria as well as of green sulfur bacteria have been shown to possess photoferrotrophic capacities, and hence, could thrive in these modern Archean ocean analogs. Studies addressing the occurrence and the biogeochemical significance of photoferrotrophy in ferruginous environments have been conducted so far in lakes Matano, Pavin, La Cruz, and the Kabuno Bay of Lake Kivu. To date, only in the latter two lakes a biogeochemical role of photoferrotrophs has been confirmed. In this review we critically summarize the current knowledge on iron-driven photosynthesis, as a remains of ancient Earth biogeochemistry.
Collapse
Affiliation(s)
- Antonio Camacho
- Cavanilles Institute for Biodiversity and Evolutionary Biology, University of ValenciaBurjassot, Spain
| | - Xavier A. Walter
- Bristol BioEnergy Centre, Bristol Robotics Laboratory, University of the West of EnglandBristol, UK
| | - Antonio Picazo
- Cavanilles Institute for Biodiversity and Evolutionary Biology, University of ValenciaBurjassot, Spain
| | - Jakob Zopfi
- Aquatic and Stable Isotope Biogeochemistry, Department of Environmental Sciences, University of BaselBasel, Switzerland
| |
Collapse
|
19
|
Klueglein N, Picardal F, Zedda M, Zwiener C, Kappler A. Oxidation of Fe(II)-EDTA by nitrite and by two nitrate-reducing Fe(II)-oxidizing Acidovorax strains. GEOBIOLOGY 2015; 13:198-207. [PMID: 25612223 DOI: 10.1111/gbi.12125] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/16/2014] [Accepted: 12/29/2014] [Indexed: 06/04/2023]
Abstract
The enzymatic oxidation of Fe(II) by nitrate-reducing bacteria was first suggested about two decades ago. It has since been found that most strains are mixotrophic and need an additional organic co-substrate for complete and prolonged Fe(II) oxidation. Research during the last few years has tried to determine to what extent the observed Fe(II) oxidation is driven enzymatically, or abiotically by nitrite produced during heterotrophic denitrification. A recent study reported that nitrite was not able to oxidize Fe(II)-EDTA abiotically, but the addition of the mixotrophic nitrate-reducing Fe(II)-oxidizer, Acidovorax sp. strain 2AN, led to Fe(II) oxidation (Chakraborty & Picardal, 2013). This, along with other results of that study, was used to argue that Fe(II) oxidation in strain 2AN was enzymatically catalyzed. However, the absence of abiotic Fe(II)-EDTA oxidation by nitrite reported in that study contrasts with previously published data. We have repeated the abiotic and biotic experiments and observed rapid abiotic oxidation of Fe(II)-EDTA by nitrite, resulting in the formation of Fe(III)-EDTA and the green Fe(II)-EDTA-NO complex. Additionally, we found that cultivating the Acidovorax strains BoFeN1 and 2AN with 10 mM nitrate, 5 mm acetate, and approximately 10 mM Fe(II)-EDTA resulted only in incomplete Fe(II)-EDTA oxidation of 47-71%. Cultures of strain BoFeN1 turned green (due to the presence of Fe(II)-EDTA-NO) and the green color persisted over the course of the experiments, whereas strain 2AN was able to further oxidize the Fe(II)-EDTA-NO complex. Our work shows that the two used Acidovorax strains behave very differently in their ability to deal with toxic effects of Fe-EDTA species and the further reduction of the Fe(II)-EDTA-NO nitrosyl complex. Although the enzymatic oxidation of Fe(II) cannot be ruled out, this study underlines the importance of nitrite in nitrate-reducing Fe(II)- and Fe(II)-EDTA-oxidizing cultures and demonstrates that Fe(II)-EDTA cannot be used to demonstrate unequivocally the enzymatic oxidation of Fe(II) by mixotrophic Fe(II)-oxidizers.
Collapse
Affiliation(s)
- N Klueglein
- Geomicrobiology, Center for Applied Geosciences, University of Tuebingen, Tuebingen, Germany
| | | | | | | | | |
Collapse
|
20
|
The ferrous iron-responsive BqsRS two-component system activates genes that promote cationic stress tolerance. mBio 2015; 6:e02549. [PMID: 25714721 PMCID: PMC4358008 DOI: 10.1128/mbio.02549-14] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
UNLABELLED The physiological resistance of pathogens to antimicrobial treatment is a severe problem in the context of chronic infections. For example, the mucus-filled lungs of cystic fibrosis (CF) patients are readily colonized by diverse antibiotic-resistant microorganisms, including Pseudomonas aeruginosa. Previously, we showed that bioavailable ferrous iron [Fe(II)] is present in CF sputum at all stages of infection and constitutes a significant portion of the iron pool at advanced stages of lung function decline [R. C. Hunter et al., mBio 4(4):e00557-13, 2013]. P. aeruginosa, a dominant CF pathogen, senses Fe(II) using a two-component signal transduction system, BqsRS, which is transcriptionally active in CF sputum [R. C. Hunter et al., mBio 4(4):e00557-13, 2013; N. N. Kreamer, J. C. Wilks, J. J. Marlow, M. L. Coleman, and D. K. Newman, J Bacteriol 194:1195-1204, 2012]. Here, we show that an RExxE motif in BqsS is required for BqsRS activation. Once Fe(II) is sensed, BqsR binds a tandem repeat DNA sequence, activating transcription. The BqsR regulon--defined through iterative bioinformatic predictions and experimental validation--includes several genes whose products are known to drive antibiotic resistance to aminoglycosides and polymyxins. Among them are genes encoding predicted determinants of polyamine transport and biosynthesis. Compared to the wild type, bqsS and bqsR deletion mutants are sensitive to high levels of Fe(II), produce less spermidine in high Fe(II), and are more sensitive to tobramycin and polymyxin B but not arsenate, chromate, or cefsulodin. BqsRS thus mediates a physiological response to Fe(II) that guards the cell against positively charged molecules but not negatively charged stressors. These results suggest Fe(II) is an important environmental signal that, via BqsRS, bolsters tolerance of a variety of cationic stressors, including clinically important antimicrobial agents. IMPORTANCE Clearing chronic infections is challenging due to the physiological resistance of opportunistic pathogens to antibiotics. Effective treatments are hindered by a lack of understanding of how these organisms survive in situ. Fe(II) is typically present at micromolar levels in soils and sedimentary habitats, as well as in CF sputum. All P. aeruginosa strains possess a two-component system, BqsRS, that specifically senses extracellular Fe(II) at low micromolar concentrations. Our work shows that BqsRS protects the cell against cationic perturbations to the cell envelope as well as low pH and reduction potential (Eh), conditions under which Fe(2+) is stable. Fe(II) can thus be understood as a proxy for a broader environmental state; the cellular response to its detection may help rationalize the resistance of P. aeruginosa to clinically important cationic antibiotics. This finding demonstrates the importance of considering environmental chemistry when exploring mechanisms of microbial survival in habitats that include the human body.
Collapse
|
21
|
Park S, Kim DH, Lee JH, Hur HG. Sphaerotilus natans encrusted with nanoball-shaped Fe(III) oxide minerals formed by nitrate-reducing mixotrophic Fe(II) oxidation. FEMS Microbiol Ecol 2014; 90:68-77. [PMID: 24965827 PMCID: PMC4262009 DOI: 10.1111/1574-6941.12372] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2014] [Revised: 06/18/2014] [Accepted: 06/19/2014] [Indexed: 11/30/2022] Open
Abstract
Ferrous iron has been known to function as an electron source for iron-oxidizing microorganisms in both anoxic and oxic environments. A diversity of bacteria has been known to oxidize both soluble and solid-phase Fe(II) forms coupled to the reduction of nitrate. Here, we show for the first time Fe(II) oxidation by Sphaerotilus natans strain DSM 6575T under mixotrophic condition. Sphaerotilus natans has been known to form a sheath structure enclosing long chains of rod-shaped cells, resulting in a thick biofilm formation under oxic conditions. Here, we also demonstrate that strain DSM 6575T grows mixotrophically with pyruvate, Fe(II) as electron donors and nitrate as an electron acceptor and single cells of strain DSM 6575T are dominant under anoxic conditions. Furthermore, strain DSM 6575T forms nanoball-shaped amorphous Fe(III) oxide minerals encrusting on the cell surfaces through the mixotrophic iron oxidation reaction under anoxic conditions. We propose that cell encrustation results from the indirect Fe(II) oxidation by biogenic nitrite during nitrate reduction and that causes the bacterial morphological change to individual rod-shaped single cells from filamentous sheath structures. This study extends the group of existing microorganisms capable of mixotrophic Fe(II) oxidation by a new strain, S. natans strain DSM 6575T, and could contribute to biogeochemical cycles of Fe and N in the environment.
Collapse
Affiliation(s)
- Sunhwa Park
- School of Environmental Science and Engineering, Gwangju Institute of Science and Technology, Gwangju, Korea
| | | | | | | |
Collapse
|
22
|
Schmid G, Zeitvogel F, Hao L, Ingino P, Floetenmeyer M, Stierhof YD, Schroeppel B, Burkhardt CJ, Kappler A, Obst M. 3-D analysis of bacterial cell-(iron)mineral aggregates formed during Fe(II) oxidation by the nitrate-reducing Acidovorax sp. strain BoFeN1 using complementary microscopy tomography approaches. GEOBIOLOGY 2014; 12:340-361. [PMID: 24828365 DOI: 10.1111/gbi.12088] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2013] [Accepted: 04/08/2014] [Indexed: 06/03/2023]
Abstract
The formation of cell-(iron)mineral aggregates as a consequence of bacterial iron oxidation is an environmentally widespread process with a number of implications for processes such as sorption and coprecipitation of contaminants and nutrients. Whereas the overall appearance of such aggregates is easily accessible using 2-D microscopy techniques, the 3-D and internal structure remain obscure. In this study, we examined the 3-D structure of cell-(iron)mineral aggregates formed during Fe(II) oxidation by the nitrate-reducing Acidovorax sp. strain BoFeN1 using a combination of advanced 3-D microscopy techniques. We obtained 3-D structural and chemical information on different cellular encrustation patterns at high spatial resolution (4-200 nm, depending on the method): more specifically, (1) cells free of iron minerals, (2) periplasm filled with iron minerals, (3) spike- or platelet-shaped iron mineral structures, (4) bulky structures on the cell surface, (5) extracellular iron mineral shell structures, (6) cells with iron mineral filled cytoplasm, and (7) agglomerations of extracellular globular structures. In addition to structural information, chemical nanotomography suggests a dominant role of extracellular polymeric substances (EPS) in controlling the formation of cell-(iron)mineral aggregates. Furthermore, samples in their hydrated state showed cell-(iron)mineral aggregates in pristine conditions free of preparation (i.e., drying/dehydration) artifacts. All these results were obtained using 3-D microscopy techniques such as focused ion beam (FIB)/scanning electron microscopy (SEM) tomography, transmission electron microscopy (TEM) tomography, scanning transmission (soft) X-ray microscopy (STXM) tomography, and confocal laser scanning microscopy (CLSM). It turned out that, due to the various different contrast mechanisms of the individual approaches, and due to the required sample preparation steps, only the combination of these techniques was able to provide a comprehensive understanding of structure and composition of the various Fe-precipitates and their association with bacterial cells and EPS.
Collapse
Affiliation(s)
- G Schmid
- Center for Applied Geoscience, University of Tuebingen, Tuebingen, Germany
| | | | | | | | | | | | | | | | | | | |
Collapse
|
23
|
Dubinina GA, Sorokina AY. Neutrophilic lithotrophic iron-oxidizing prokaryotes and their role in the biogeochemical processes of the iron cycle. Microbiology (Reading) 2014. [DOI: 10.1134/s0026261714020052] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
|
24
|
Grégoire DS, Poulain AJ. A little bit of light goes a long way: the role of phototrophs on mercury cycling. Metallomics 2014; 6:396-407. [DOI: 10.1039/c3mt00312d] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
|
25
|
Potential role of nitrite for abiotic Fe(II) oxidation and cell encrustation during nitrate reduction by denitrifying bacteria. Appl Environ Microbiol 2013; 80:1051-61. [PMID: 24271182 DOI: 10.1128/aem.03277-13] [Citation(s) in RCA: 98] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Microorganisms have been observed to oxidize Fe(II) at neutral pH under anoxic and microoxic conditions. While most of the mixotrophic nitrate-reducing Fe(II)-oxidizing bacteria become encrusted with Fe(III)-rich minerals, photoautotrophic and microaerophilic Fe(II) oxidizers avoid cell encrustation. The Fe(II) oxidation mechanisms and the reasons for encrustation remain largely unresolved. Here we used cultivation-based methods and electron microscopy to compare two previously described nitrate-reducing Fe(II) oxidizers ( Acidovorax sp. strain BoFeN1 and Pseudogulbenkiania sp. strain 2002) and two heterotrophic nitrate reducers (Paracoccus denitrificans ATCC 19367 and P. denitrificans Pd 1222). All four strains oxidized ∼8 mM Fe(II) within 5 days in the presence of 5 mM acetate and accumulated nitrite (maximum concentrations of 0.8 to 1.0 mM) in the culture media. Iron(III) minerals, mainly goethite, formed and precipitated extracellularly in close proximity to the cell surface. Interestingly, mineral formation was also observed within the periplasm and cytoplasm; intracellular mineralization is expected to be physiologically disadvantageous, yet acetate consumption continued to be observed even at an advanced stage of Fe(II) oxidation. Extracellular polymeric substances (EPS) were detected by lectin staining with fluorescence microscopy, particularly in the presence of Fe(II), suggesting that EPS production is a response to Fe(II) toxicity or a strategy to decrease encrustation. Based on the data presented here, we propose a nitrite-driven, indirect mechanism of cell encrustation whereby nitrite forms during heterotrophic denitrification and abiotically oxidizes Fe(II). This work adds to the known assemblage of Fe(II)-oxidizing bacteria in nature and complicates our ability to delineate microbial Fe(II) oxidation in ancient microbes preserved as fossils in the geological record.
Collapse
|
26
|
Bird LJ, Coleman ML, Newman DK. Iron and copper act synergistically to delay anaerobic growth of bacteria. Appl Environ Microbiol 2013; 79:3619-27. [PMID: 23563938 PMCID: PMC3675935 DOI: 10.1128/aem.03944-12] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2013] [Accepted: 03/27/2013] [Indexed: 11/20/2022] Open
Abstract
Transition metals are known to cause toxic effects through their interaction with oxygen, but toxicity under anoxic conditions is poorly understood. Here we investigated the effects of iron (Fe) and copper (Cu) on the anaerobic growth and gene expression of the purple phototrophic bacterium Rhodopseudomonas palustris TIE-1. We found that Fe(II) and Cu(II) act synergistically to delay anaerobic growth at environmentally relevant metal concentrations. Cu(I) and Cu(II) had similar effects both alone and in the presence of ascorbate, a Cu(II) reductant, indicating that reduction of Cu(II) to Cu(I) by Fe(II) is not sufficient to explain the growth inhibition. Addition of Cu(II) increased the toxicity of Co(II) and Ni(II); in contrast, Ni(II) toxicity was diminished in the presence of Fe(II). The synergistic anaerobic toxicity of Fe(II) and Cu(II) was also observed for Escherichia coli MG1655, Shewanella oneidensis MR-1, and Rhodobacter capsulatus SB1003. Gene expression analyses for R. palustris identified three regulatory genes that respond to Cu(II) and not to Fe(II): homologs of cueR and cusR, two known proteobacterial copper homeostasis regulators, and csoR, a copper regulator recently identified in Mycobacterium tuberculosis. Two P-type ATPase efflux pumps, along with an F(o)F(1) ATP synthase, were also upregulated by Cu(II) but not by Fe(II). An Escherichia coli mutant deficient in copA, cus, and cueO showed a smaller synergistic effect, indicating that iron might interfere with one or more of the copper homeostasis systems. Our results suggest that interactive effects of transition metals on microbial physiology may be widespread under anoxic conditions, although the molecular mechanisms remain to be more fully elucidated.
Collapse
Affiliation(s)
- Lina J. Bird
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
- Divisions of Biology and Geological and Planetary Sciences, Howard Hughes Medical Institute at the California Institute of Technology, Pasadena, California, USA
| | - Maureen L. Coleman
- Divisions of Biology and Geological and Planetary Sciences, Howard Hughes Medical Institute at the California Institute of Technology, Pasadena, California, USA
| | - Dianne K. Newman
- Divisions of Biology and Geological and Planetary Sciences, Howard Hughes Medical Institute at the California Institute of Technology, Pasadena, California, USA
| |
Collapse
|
27
|
Fe(II) oxidation is an innate capability of nitrate-reducing bacteria that involves abiotic and biotic reactions. J Bacteriol 2013; 195:3260-8. [PMID: 23687275 DOI: 10.1128/jb.00058-13] [Citation(s) in RCA: 80] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Phylogenetically diverse species of bacteria can catalyze the oxidation of ferrous iron [Fe(II)] coupled to nitrate (NO(3)(-)) reduction, often referred to as nitrate-dependent iron oxidation (NDFO). Very little is known about the biochemistry of NDFO, and though growth benefits have been observed, mineral encrustations and nitrite accumulation likely limit growth. Acidovorax ebreus, like other species in the Acidovorax genus, is proficient at catalyzing NDFO. Our results suggest that the induction of specific Fe(II) oxidoreductase proteins is not required for NDFO. No upregulated periplasmic or outer membrane redox-active proteins, like those involved in Fe(II) oxidation by acidophilic iron oxidizers or anaerobic photoferrotrophs, were observed in proteomic experiments. We demonstrate that while "abiotic" extracellular reactions between Fe(II) and biogenic NO(2)(-)/NO can be involved in NDFO, intracellular reactions between Fe(II) and periplasmic components are essential to initiate extensive NDFO. We present evidence that an organic cosubstrate inhibits NDFO, likely by keeping periplasmic enzymes in their reduced state, stimulating metal efflux pumping, or both, and that growth during NDFO relies on the capacity of a nitrate-reducing bacterium to overcome the toxicity of Fe(II) and reactive nitrogen species. On the basis of our data and evidence in the literature, we postulate that all respiratory nitrate-reducing bacteria are innately capable of catalyzing NDFO. Our findings have implications for a mechanistic understanding of NDFO, the biogeochemical controls on anaerobic Fe(II) oxidation, and the production of NO(2)(-), NO, and N(2)O in the environment.
Collapse
|
28
|
Kopf S, Henny C, Newman DK. Ligand-enhanced abiotic iron oxidation and the effects of chemical versus biological iron cycling in anoxic environments. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2013; 47:2602-11. [PMID: 23402562 PMCID: PMC3604861 DOI: 10.1021/es3049459] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
This study introduces a newly isolated, genetically tractable bacterium ( Pseudogulbenkiania sp. strain MAI-1) and explores the extent to which its nitrate-dependent iron-oxidation activity is directly biologically catalyzed. Specifically, we focused on the role of iron chelating ligands in promoting chemical oxidation of Fe(II) by nitrite under anoxic conditions. Strong organic ligands such as nitrilotriacetate and citrate can substantially enhance chemical oxidation of Fe(II) by nitrite at circumneutral pH. We show that strain MAI-1 exhibits unambiguous biological Fe(II) oxidation despite a significant contribution (∼30-35%) from ligand-enhanced chemical oxidation. Our work with the model denitrifying strain Paracoccus denitrificans further shows that ligand-enhanced chemical oxidation of Fe(II) by microbially produced nitrite can be an important general side effect of biological denitrification. Our assessment of reaction rates derived from literature reports of anaerobic Fe(II) oxidation, both chemical and biological, highlights the potential competition and likely co-occurrence of chemical Fe(II) oxidation (mediated by microbial production of nitrite) and truly biological Fe(II) oxidation.
Collapse
Affiliation(s)
- Sebastian
H. Kopf
- Division
of Geologial and Planetary Sciences and Division of Biology, California Institute of Technology,
Pasadena, California, United States
| | - Cynthia Henny
- Research Center for
Limnology, LIPI, Cibinong, Indonesia
| | - Dianne K. Newman
- Division
of Geologial and Planetary Sciences and Division of Biology, California Institute of Technology,
Pasadena, California, United States
- Howard Hughes Medical
Institute, Pasadena, California, United States
- Phone: 626-395-3543. Fax: 626-395-4135. E-mail:
| |
Collapse
|
29
|
Zappa S, Bauer CE. Iron homeostasis in the Rhodobacter genus. ADVANCES IN BOTANICAL RESEARCH 2013; 66:10.1016/B978-0-12-397923-0.00010-2. [PMID: 24382933 PMCID: PMC3875232 DOI: 10.1016/b978-0-12-397923-0.00010-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Metals are utilized for a variety of critical cellular functions and are essential for survival. However cells are faced with the conundrum of needing metals coupled with e fact that some metals, iron in particular are toxic if present in excess. Maintaining metal homeostasis is therefore of critical importance to cells. In this review we have systematically analyzed sequenced genomes of three members of the Rhodobacter genus, R. capsulatus SB1003, R. sphaeroides 2.4.1 and R. ferroxidans SW2 to determine how these species undertake iron homeostasis. We focused our analysis on elemental ferrous and ferric iron uptake genes as well as genes involved in the utilization of iron from heme. We also discuss how Rhodobacter species manage iron toxicity through export and sequestration of iron. Finally we discuss the various putative strategies set up by these Rhodobacter species to regulate iron homeostasis and the potential novel means of regulation. Overall, this genomic analysis highlights surprisingly diverse features involved in iron homeostasis in the Rhodobacter genus.
Collapse
Affiliation(s)
- Sébastien Zappa
- Department of Molecular and Cellular Biochemistry, Indiana University, Simon Hall, 212 S Hawthorne Dr, Bloomington, IN 47405, U. S. A
| | - Carl E. Bauer
- Department of Molecular and Cellular Biochemistry, Indiana University, Simon Hall, 212 S Hawthorne Dr, Bloomington, IN 47405, U. S. A
| |
Collapse
|
30
|
Induction of nitrate-dependent Fe(II) oxidation by Fe(II) in Dechloromonas sp. strain UWNR4 and Acidovorax sp. strain 2AN. Appl Environ Microbiol 2012; 79:748-52. [PMID: 23144134 DOI: 10.1128/aem.02709-12] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We evaluated the inducibility of nitrate-dependent Fe(II)-EDTA oxidation (NDFO) in non-growth, chloramphenicol-amended, resting-cell suspensions of Dechloromonas sp. strain UWNR4 and Acidovorax sp. strain 2AN. Cells previously incubated with Fe(II)-EDTA oxidized ca. 6-fold more Fe(II)-EDTA than cells previously incubated with Fe(III)-EDTA. This is the first report of induction of NDFO by Fe(II).
Collapse
|
31
|
Ilbert M, Bonnefoy V. Insight into the evolution of the iron oxidation pathways. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2012; 1827:161-75. [PMID: 23044392 DOI: 10.1016/j.bbabio.2012.10.001] [Citation(s) in RCA: 192] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/03/2012] [Revised: 09/27/2012] [Accepted: 10/01/2012] [Indexed: 01/01/2023]
Abstract
Iron is a ubiquitous element in the universe. Ferrous iron (Fe(II)) was abundant in the primordial ocean until the oxygenation of the Earth's atmosphere led to its widespread oxidation and precipitation. This change of iron bioavailability likely put selective pressure on the evolution of life. This element is essential to most extant life forms and is an important cofactor in many redox-active proteins involved in a number of vital pathways. In addition, iron plays a central role in many environments as an energy source for some microorganisms. This review is focused on Fe(II) oxidation. The fact that the ability to oxidize Fe(II) is widely distributed in Bacteria and Archaea and in a number of quite different biotopes suggests that the dissimilatory Fe(II) oxidation is an ancient energy metabolism. Based on what is known today about Fe(II) oxidation pathways, we propose that they arose independently more than once in evolution and evolved convergently. The iron paleochemistry, the phylogeny, the physiology of the iron oxidizers, and the nature of the cofactors of the redox proteins involved in these pathways suggest a possible scenario for the timescale in which each type of Fe(II) oxidation pathways evolved. The nitrate dependent anoxic iron oxidizers are likely the most ancient iron oxidizers. We suggest that the phototrophic anoxic iron oxidizers arose in surface waters after the Archaea/Bacteria-split but before the Great Oxidation Event. The neutrophilic oxic iron oxidizers possibly appeared in microaerobic marine environments prior to the Great Oxidation Event while the acidophilic ones emerged likely after the advent of atmospheric O(2). This article is part of a Special Issue entitled: The evolutionary aspects of bioenergetic systems.
Collapse
Affiliation(s)
- Marianne Ilbert
- Aix-Marseille Université, CNRS, BIP UMR7281,13009, Marseille, France.
| | | |
Collapse
|
32
|
Melton ED, Schmidt C, Kappler A. Microbial Iron(II) Oxidation in Littoral Freshwater Lake Sediment: The Potential for Competition between Phototrophic vs. Nitrate-Reducing Iron(II)-Oxidizers. Front Microbiol 2012; 3:197. [PMID: 22666221 PMCID: PMC3364526 DOI: 10.3389/fmicb.2012.00197] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2011] [Accepted: 05/14/2012] [Indexed: 11/13/2022] Open
Abstract
The distribution of neutrophilic microbial iron oxidation is mainly determined by local gradients of oxygen, light, nitrate and ferrous iron. In the anoxic top part of littoral freshwater lake sediment, nitrate-reducing and phototrophic Fe(II)-oxidizers compete for the same e− donor; reduced iron. It is not yet understood how these microbes co-exist in the sediment and what role they play in the Fe cycle. We show that both metabolic types of anaerobic Fe(II)-oxidizing microorganisms are present in the same sediment layer directly beneath the oxic-anoxic sediment interface. The photoferrotrophic most probable number counted 3.4·105 cells·g−1 and the autotrophic and mixotrophic nitrate-reducing Fe(II)-oxidizers totaled 1.8·104 and 4.5·104 cells·g−1 dry weight sediment, respectively. To distinguish between the two microbial Fe(II) oxidation processes and assess their individual contribution to the sedimentary Fe cycle, littoral lake sediment was incubated in microcosm experiments. Nitrate-reducing Fe(II)-oxidizing bacteria exhibited a higher maximum Fe(II) oxidation rate per cell, in both pure cultures and microcosms, than photoferrotrophs. In microcosms, photoferrotrophs instantly started oxidizing Fe(II), whilst nitrate-reducing Fe(II)-oxidizers showed a significant lag-phase during which they probably use organics as e− donor before initiating Fe(II) oxidation. This suggests that they will be outcompeted by phototrophic Fe(II)-oxidizers during optimal light conditions; as phototrophs deplete Fe(II) before nitrate-reducing Fe(II)-oxidizers start Fe(II) oxidation. Thus, the co-existence of the two anaerobic Fe(II)-oxidizers may be possible due to a niche space separation in time by the day-night cycle, where nitrate-reducing Fe(II)-oxidizers oxidize Fe(II) during darkness and phototrophs play a dominant role in Fe(II) oxidation during daylight. Furthermore, metabolic flexibility of Fe(II)-oxidizing microbes may play a paramount role in the conservation of the sedimentary Fe cycle.
Collapse
Affiliation(s)
- E D Melton
- Geomicrobiology, Centre for Applied Geosciences, University of Tübingen Tübingen, Germany
| | | | | |
Collapse
|
33
|
Abstract
This study investigates the role iron oxidation plays in the purple non-sulfur bacterium Rhodobacter capsulatus SB1003. This organism is unable to grow photoautotrophically on unchelated ferrous iron [Fe(II)] despite its ability to oxidize chelated Fe(II). This apparent paradox was partly resolved by the discovery that SB1003 can grow photoheterotrophically on the photochemical breakdown products of certain ferric iron-ligand complexes, yet whether it could concomitantly benefit from the oxidation of Fe(II) to fix CO(2) was unknown. Here, we examine carbon fixation by stable isotope labeling of the inorganic carbon pool in cultures growing phototrophically on acetate with and without Fe(II). We show that R. capsulatus SB1003, an organism formally thought incapable of phototrophic growth on Fe(II), can actually harness the reducing power of this substrate and grow photomixotrophically, deriving carbon both from organic sources and from fixation of inorganic carbon. This suggests the possibility of a wider occurrence of photoferrotrophy than previously assumed.
Collapse
Affiliation(s)
| | - Dianne K. Newman
- Division of Geological and Planetary Sciences, Pasadena, CA 91125
- Division of Biological Sciences, California Institute of Technology, Pasadena, CA 91125
- Howard Hughes Medical Institute, Pasadena, CA 91125
| |
Collapse
|
34
|
Abundance, distribution, and activity of Fe(II)-oxidizing and Fe(III)-reducing microorganisms in hypersaline sediments of Lake Kasin, southern Russia. Appl Environ Microbiol 2012; 78:4386-99. [PMID: 22504804 DOI: 10.1128/aem.07637-11] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The extreme osmotic conditions prevailing in hypersaline environments result in decreasing metabolic diversity with increasing salinity. Various microbial metabolisms have been shown to occur even at high salinity, including photosynthesis as well as sulfate and nitrate reduction. However, information about anaerobic microbial iron metabolism in hypersaline environments is scarce. We studied the phylogenetic diversity, distribution, and metabolic activity of iron(II)-oxidizing and iron(III)-reducing Bacteria and Archaea in pH-neutral, iron-rich salt lake sediments (Lake Kasin, southern Russia; salinity, 348.6 g liter(-1)) using a combination of culture-dependent and -independent techniques. 16S rRNA gene clone libraries for Bacteria and Archaea revealed a microbial community composition typical for hypersaline sediments. Most-probable-number counts confirmed the presence of 4.26 × 10(2) to 8.32 × 10(3) iron(II)-oxidizing Bacteria and 4.16 × 10(2) to 2.13 × 10(3) iron(III)-reducing microorganisms per gram dry sediment. Microbial iron(III) reduction was detected in the presence of 5 M NaCl, extending the natural habitat boundaries for this important microbial process. Quantitative real-time PCR showed that 16S rRNA gene copy numbers of total Bacteria, total Archaea, and species dominating the iron(III)-reducing enrichment cultures (relatives of Halobaculum gomorrense, Desulfosporosinus lacus, and members of the Bacilli) were highest in an iron oxide-rich sediment layer. Combined with the presented geochemical and mineralogical data, our findings suggest the presence of an active microbial iron cycle at salt concentrations close to the solubility limit of NaCl.
Collapse
|
35
|
Carlson HK, Clark IC, Melnyk RA, Coates JD. Toward a mechanistic understanding of anaerobic nitrate-dependent iron oxidation: balancing electron uptake and detoxification. Front Microbiol 2012; 3:57. [PMID: 22363331 PMCID: PMC3282478 DOI: 10.3389/fmicb.2012.00057] [Citation(s) in RCA: 74] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2011] [Accepted: 02/02/2012] [Indexed: 11/25/2022] Open
Abstract
The anaerobic oxidation of Fe(II) by subsurface microorganisms is an important part of biogeochemical cycling in the environment, but the biochemical mechanisms used to couple iron oxidation to nitrate respiration are not well understood. Based on our own work and the evidence available in the literature, we propose a mechanistic model for anaerobic nitrate-dependent iron oxidation. We suggest that anaerobic iron-oxidizing microorganisms likely exist along a continuum including: (1) bacteria that inadvertently oxidize Fe(II) by abiotic or biotic reactions with enzymes or chemical intermediates in their metabolic pathways (e.g., denitrification) and suffer from toxicity or energetic penalty, (2) Fe(II) tolerant bacteria that gain little or no growth benefit from iron oxidation but can manage the toxic reactions, and (3) bacteria that efficiently accept electrons from Fe(II) to gain a growth advantage while preventing or mitigating the toxic reactions. Predictions of the proposed model are highlighted and experimental approaches are discussed.
Collapse
Affiliation(s)
- Hans K Carlson
- Department of Plant and Microbial Biology, University of California Berkeley Berkeley, CA, USA
| | | | | | | |
Collapse
|
36
|
Dang H, Chen R, Wang L, Shao S, Dai L, Ye Y, Guo L, Huang G, Klotz MG. Molecular characterization of putative biocorroding microbiota with a novel niche detection of Epsilon- and Zetaproteobacteria in Pacific Ocean coastal seawaters. Environ Microbiol 2011; 13:3059-74. [DOI: 10.1111/j.1462-2920.2011.02583.x] [Citation(s) in RCA: 89] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
|
37
|
Hedrich S, Schlömann M, Johnson DB. The iron-oxidizing proteobacteria. Microbiology (Reading) 2011; 157:1551-1564. [DOI: 10.1099/mic.0.045344-0] [Citation(s) in RCA: 400] [Impact Index Per Article: 30.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The ‘iron bacteria’ are a collection of morphologically and phylogenetically heterogeneous prokaryotes. They include some of the first micro-organisms to be observed and described, and continue to be the subject of a considerable body of fundamental and applied microbiological research. While species of iron-oxidizing bacteria can be found in many different phyla, most are affiliated with the Proteobacteria. The latter can be subdivided into four main physiological groups: (i) acidophilic, aerobic iron oxidizers; (ii) neutrophilic, aerobic iron oxidizers; (iii) neutrophilic, anaerobic (nitrate-dependent) iron oxidizers; and (iv) anaerobic photosynthetic iron oxidizers. Some species (mostly acidophiles) can reduce ferric iron as well as oxidize ferrous iron, depending on prevailing environmental conditions. This review describes what is currently known about the phylogenetic and physiological diversity of the iron-oxidizing proteobacteria, their significance in the environment (on the global and micro scales), and their increasing importance in biotechnology.
Collapse
Affiliation(s)
- Sabrina Hedrich
- Interdisciplinary Ecological Center, TU Bergakademie Freiberg, Leipziger Strasse 29, 09599 Freiberg, Germany
- School of Biological Sciences, College of Natural Sciences, Bangor University, Deiniol Road, Bangor LL57 2UW, UK
| | - Michael Schlömann
- Interdisciplinary Ecological Center, TU Bergakademie Freiberg, Leipziger Strasse 29, 09599 Freiberg, Germany
| | - D. Barrie Johnson
- School of Biological Sciences, College of Natural Sciences, Bangor University, Deiniol Road, Bangor LL57 2UW, UK
| |
Collapse
|
38
|
Bose A, Newman DK. Regulation of the phototrophic iron oxidation (pio) genes in Rhodopseudomonas palustris TIE-1 is mediated by the global regulator, FixK. Mol Microbiol 2010; 79:63-75. [PMID: 21166894 PMCID: PMC3050613 DOI: 10.1111/j.1365-2958.2010.07430.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The pioABC operon is required for phototrophic iron oxidative (photoferrotrophic) growth by the αproteobacterium Rhodopseudomonas palustris TIE-1. Expression analysis of this operon showed that it was transcribed and translated during anaerobic growth, upregulation being observed only under photoferrotrophic conditions. Very low levels of transcription were observed during aerobic growth, suggesting expression was induced by anoxia. The presence of two canonical FixK boxes upstream of the identified pioABC transcription start site implicated FixK as a likely regulator. To test this possibility, a δfixK mutant of R. palustris TIE-1 was assessed for pioABC expression. pioABC expression decreased dramatically in δfixK versus WT during photoferrotrophic growth, implying that FixK positively regulates its expression; coincidently, the onset of iron oxidation was prolonged in this mutant. In contrast, pioABC expression increased in δfixK under all non-photoferrotrophic conditions tested, suggesting the presence of additional levels of regulation. Purified FixK directly bound only the proximal FixK box in gel mobility-shift assays. Mutant expression analysis revealed that FixK regulates anaerobic phototrophic expression of other target genes with FixK binding sites in their promoters. This study shows that FixK regulates key iron metabolism genes in an αproteobacterium, pointing to a departure from the canonical Fur/Irr mode of regulation.
Collapse
Affiliation(s)
- Arpita Bose
- Department of Biology, Massachusetts Institute of Technology, Howard Hughes Medical Institute, 77 Massachusetts Ave., 68-380, Cambridge, MA 02139, USA
| | | |
Collapse
|
39
|
Bräuer SL, Adams C, Kranzler K, Murphy D, Xu M, Zuber P, Simon HM, Baptista AM, Tebo BM. Culturable Rhodobacter and Shewanella species are abundant in estuarine turbidity maxima of the Columbia River. Environ Microbiol 2010; 13:589-603. [PMID: 20977571 DOI: 10.1111/j.1462-2920.2010.02360.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Measurements of dissolved, ascorbate-reducible and total Mn by ICP-OES revealed significantly higher concentrations during estuarine turbidity maxima (ETM) events, compared with non-events in the Columbia River. Most probable number (MPN) counts of Mn-oxidizing or Mn-reducing heterotrophs were not statistically different from that of other heterotrophs (10³ -10⁴ cells ml⁻¹) when grown in defined media, but counts of Mn oxidizers were significantly lower in nutrient-rich medium (13 cells ml⁻¹). MPN counts of Mn oxidizers were also significantly lower on Mn(III)-pyrophosphate and glycerol (21 cells ml⁻¹). Large numbers of Rhodobacter spp. were cultured from dilutions of 10⁻² to 10⁻⁵, and many of these were capable of Mn(III) oxidation. Up to c. 30% of the colonies tested LBB positive, and all 77 of the successfully sequenced LBB positive colonies (of varying morphology) yielded sequences related to Rhodobacter spp. qPCR indicated that a cluster of Rhodobacter isolates and closely related strains (95-99% identity) represented approximately 1-3% of the total Bacteria, consistent with clone library results. Copy numbers of SSU rRNA genes for either Rhodobacter spp. or Bacteria were four to eightfold greater during ETM events compared with non-events. Strains of a Shewanella sp. were retrieved from the highest dilutions (10⁻⁵) of Mn reducers, and were also capable of Mn oxidation. The SSU rRNA gene sequences from these strains shared a high identity score (98%) with sequences obtained in clone libraries. Our results support previous findings that ETMs are zones with high microbial activity. Results indicated that Shewanella and Rhodobacter species were present in environmentally relevant concentrations, and further demonstrated that a large proportion of culturable bacteria, including Shewanella and Rhodobacter spp., were capable of Mn cycling in vitro.
Collapse
Affiliation(s)
- S L Bräuer
- Department of Biology, Appalachian State University, Boone, NC 28608, USA.
| | | | | | | | | | | | | | | | | |
Collapse
|
40
|
Affiliation(s)
- Dianne K. Newman
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02142, USA
| |
Collapse
|