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Liu H, Liu T, Chen S, Liu X, Li N, Huang T, Ma B, Liu X, Pan S, Zhang H. Biogeochemical cycles of iron: Processes, mechanisms, and environmental implications. THE SCIENCE OF THE TOTAL ENVIRONMENT 2024; 951:175722. [PMID: 39187081 DOI: 10.1016/j.scitotenv.2024.175722] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/02/2024] [Revised: 07/29/2024] [Accepted: 08/08/2024] [Indexed: 08/28/2024]
Abstract
The iron (Fe) biogeochemical cycle is critical for abiotic and biological environmental processes that overlap spatially and may compete with each other. The development of modern molecular biology technologies promoted the understanding of the electron transport mechanisms of Fe-cycling-related microorganisms. Recent studies have revealed a novel pathway for microaerophilic ferrous iron (Fe(II))-oxidizers in extracellular Fe(II) oxidation. In addition, OmcS, OmcZ, and OmcE nanowires on the cell surface have been shown to promote electron transfer between microorganisms and their environment. These processes affect the fate of pollutants in directly or indirectly ways, such as greenhouse gas emissions. In this review, these advances and the environmental implications of the Fe cycle process were discussed, with a particular focus on the mechanisms of intracellular or extracellular electron transport in microorganisms.
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Affiliation(s)
- Huan Liu
- Collaborative Innovation Center of Water Pollution Control and Water Quality Security Assurance of Shaanxi Province, Xi'an University of Architecture and Technology, Xi'an 710055, China; Shaanxi Provincial Field Scientific Observation and Research Station of Water Quality in Qinling Mountains, Xi'an University of Architecture and Technology, Xi'an 710055, China; School of Environmental and Municipal Engineering, Xi'an University of Architecture and Technology, Xi'an 710055, China
| | - Tao Liu
- Collaborative Innovation Center of Water Pollution Control and Water Quality Security Assurance of Shaanxi Province, Xi'an University of Architecture and Technology, Xi'an 710055, China; Shaanxi Provincial Field Scientific Observation and Research Station of Water Quality in Qinling Mountains, Xi'an University of Architecture and Technology, Xi'an 710055, China; School of Environmental and Municipal Engineering, Xi'an University of Architecture and Technology, Xi'an 710055, China
| | - Shengnan Chen
- Collaborative Innovation Center of Water Pollution Control and Water Quality Security Assurance of Shaanxi Province, Xi'an University of Architecture and Technology, Xi'an 710055, China; Shaanxi Provincial Field Scientific Observation and Research Station of Water Quality in Qinling Mountains, Xi'an University of Architecture and Technology, Xi'an 710055, China; School of Environmental and Municipal Engineering, Xi'an University of Architecture and Technology, Xi'an 710055, China
| | - Xiaoyan Liu
- Collaborative Innovation Center of Water Pollution Control and Water Quality Security Assurance of Shaanxi Province, Xi'an University of Architecture and Technology, Xi'an 710055, China; Shaanxi Provincial Field Scientific Observation and Research Station of Water Quality in Qinling Mountains, Xi'an University of Architecture and Technology, Xi'an 710055, China; School of Environmental and Municipal Engineering, Xi'an University of Architecture and Technology, Xi'an 710055, China
| | - Nan Li
- Collaborative Innovation Center of Water Pollution Control and Water Quality Security Assurance of Shaanxi Province, Xi'an University of Architecture and Technology, Xi'an 710055, China; Shaanxi Provincial Field Scientific Observation and Research Station of Water Quality in Qinling Mountains, Xi'an University of Architecture and Technology, Xi'an 710055, China; School of Environmental and Municipal Engineering, Xi'an University of Architecture and Technology, Xi'an 710055, China.
| | - Tinglin Huang
- Collaborative Innovation Center of Water Pollution Control and Water Quality Security Assurance of Shaanxi Province, Xi'an University of Architecture and Technology, Xi'an 710055, China; Shaanxi Provincial Field Scientific Observation and Research Station of Water Quality in Qinling Mountains, Xi'an University of Architecture and Technology, Xi'an 710055, China; School of Environmental and Municipal Engineering, Xi'an University of Architecture and Technology, Xi'an 710055, China
| | - Ben Ma
- Collaborative Innovation Center of Water Pollution Control and Water Quality Security Assurance of Shaanxi Province, Xi'an University of Architecture and Technology, Xi'an 710055, China; Shaanxi Provincial Field Scientific Observation and Research Station of Water Quality in Qinling Mountains, Xi'an University of Architecture and Technology, Xi'an 710055, China; School of Environmental and Municipal Engineering, Xi'an University of Architecture and Technology, Xi'an 710055, China
| | - Xiang Liu
- Collaborative Innovation Center of Water Pollution Control and Water Quality Security Assurance of Shaanxi Province, Xi'an University of Architecture and Technology, Xi'an 710055, China; Shaanxi Provincial Field Scientific Observation and Research Station of Water Quality in Qinling Mountains, Xi'an University of Architecture and Technology, Xi'an 710055, China; School of Environmental and Municipal Engineering, Xi'an University of Architecture and Technology, Xi'an 710055, China
| | - Sixuan Pan
- Collaborative Innovation Center of Water Pollution Control and Water Quality Security Assurance of Shaanxi Province, Xi'an University of Architecture and Technology, Xi'an 710055, China; Shaanxi Provincial Field Scientific Observation and Research Station of Water Quality in Qinling Mountains, Xi'an University of Architecture and Technology, Xi'an 710055, China; School of Environmental and Municipal Engineering, Xi'an University of Architecture and Technology, Xi'an 710055, China
| | - Haihan Zhang
- Collaborative Innovation Center of Water Pollution Control and Water Quality Security Assurance of Shaanxi Province, Xi'an University of Architecture and Technology, Xi'an 710055, China; Shaanxi Provincial Field Scientific Observation and Research Station of Water Quality in Qinling Mountains, Xi'an University of Architecture and Technology, Xi'an 710055, China; School of Environmental and Municipal Engineering, Xi'an University of Architecture and Technology, Xi'an 710055, China.
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Brooks CN, Field EK. Microbial community response to hydrocarbon exposure in iron oxide mats: an environmental study. Front Microbiol 2024; 15:1388973. [PMID: 38800754 PMCID: PMC11116660 DOI: 10.3389/fmicb.2024.1388973] [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: 02/20/2024] [Accepted: 04/16/2024] [Indexed: 05/29/2024] Open
Abstract
Hydrocarbon pollution is a widespread issue in both groundwater and surface-water systems; however, research on remediation at the interface of these two systems is limited. This interface is the oxic-anoxic boundary, where hydrocarbon pollutant from contaminated groundwaters flows into surface waters and iron mats are formed by microaerophilic iron-oxidizing bacteria. Iron mats are highly chemically adsorptive and host a diverse community of microbes. To elucidate the effect of hydrocarbon exposure on iron mat geochemistry and microbial community structure and function, we sampled iron mats both upstream and downstream from a leaking underground storage tank. Hydrocarbon-exposed iron mats had significantly higher concentrations of oxidized iron and significantly lower dissolved organic carbon and total dissolved phosphate than unexposed iron mats. A strong negative correlation between dissolved phosphate and benzene was observed in the hydrocarbon-exposed iron mats and water samples. There were positive correlations between iron and other hydrocarbons with benzene in the hydrocarbon-exposed iron mats, which was unique from water samples. The hydrocarbon-exposed iron mats represented two types, flocculent and seep, which had significantly different concentrations of iron, hydrocarbons, and phosphate, indicating that iron mat is also an important context in studies of freshwater mats. Using constrained ordination, we found the best predictors for community structure to be dissolved oxygen, pH, and benzene. Alpha diversity and evenness were significantly lower in hydrocarbon-exposed iron mats than unexposed mats. Using 16S rDNA amplicon sequences, we found evidence of three putative nitrate-reducing iron-oxidizing taxa in microaerophile-dominated iron mats (Azospira, Paracoccus, and Thermomonas). 16S rDNA amplicons also indicated the presence of taxa that are associated with hydrocarbon degradation. Benzene remediation-associated genes were found using metagenomic analysis both in exposed and unexposed iron mats. Furthermore, the results indicated that season (summer vs. spring) exacerbates the negative effect of hydrocarbon exposure on community diversity and evenness and led to the increased abundance of numerous OTUs. This study represents the first of its kind to attempt to understand how contaminant exposure, specifically hydrocarbons, influences the geochemistry and microbial community of freshwater iron mats and further develops our understanding of hydrocarbon remediation at the land-water interface.
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Affiliation(s)
- Chequita N. Brooks
- Department of Biology, East Carolina University, Greenville, NC, United States
- Louisiana Universities Marine Consortium, Chauvin, LA, United States
| | - Erin K. Field
- Department of Biology, East Carolina University, Greenville, NC, United States
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Eshun LE, Coker VS, Shaw S, Lloyd JR. Strategies for optimizing biovivianite production using dissimilatory Fe(III)-reducing bacteria. ENVIRONMENTAL RESEARCH 2024; 242:117667. [PMID: 37980994 DOI: 10.1016/j.envres.2023.117667] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/13/2023] [Revised: 11/06/2023] [Accepted: 11/13/2023] [Indexed: 11/21/2023]
Abstract
Vivianite (Fe3(PO4)2·8H2O), a sink for phosphorus, is a key mineralization product formed during the microbial reduction of phosphate-containing Fe(III) minerals in natural systems, and also in wastewater treatment where Fe(III)-minerals are used to remove phosphate. As biovivianite is a potentially useful Fe and P fertiliser, there is much interest in harnessing microbial biovivianite synthesis for circular economy applications. In this study, we investigated the factors that influence the formation of microbially-synthesized vivianite (biovivianite) under laboratory batch systems including the presence and absence of phosphate and electron shuttle, the buffer system, pH, and the type of Fe(III)-reducing bacteria (comparing Geobacter sulfurreducens and Shewanella putrefaciens). The rate of Fe(II) production, and its interactions with the residual Fe(III) and other oxyanions (e.g., phosphate and carbonate) were the main factors that controlled the rate and extent of biovivianite formation. Higher concentrations of phosphate (e.g., P/Fe = 1) in the presence of an electron shuttle, at an initial pH between 6 and 7, were needed for optimal biovivianite formation. Green rust, a key intermediate in biovivianite production, could be detected as an endpoint alongside vivianite and metavivianite (Fe2+Fe3+2(PO4)2.(OH)2.6H2O), in treatments with G. sulfurreducens and S. putrefaciens. However, XRD indicated that vivianite abundance was higher in experiments containing G. sulfurreducens, where it dominated. This study, therefore, shows that vivianite formation can be controlled to optimize yield during microbial processing of phosphate-loaded Fe(III) materials generated from water treatment processes.
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Affiliation(s)
- Lordina E Eshun
- University of Manchester, Department of Earth and Environmental Sciences, Geomicrobiology Group, Williamson Building, M13 9QQ, Oxford Road, Manchester, UK.
| | - Victoria S Coker
- University of Manchester, Department of Earth and Environmental Sciences, Geomicrobiology Group, Williamson Building, M13 9QQ, Oxford Road, Manchester, UK.
| | - Samuel Shaw
- University of Manchester, Department of Earth and Environmental Sciences, Geomicrobiology Group, Williamson Building, M13 9QQ, Oxford Road, Manchester, UK.
| | - Jonathan R Lloyd
- University of Manchester, Department of Earth and Environmental Sciences, Geomicrobiology Group, Williamson Building, M13 9QQ, Oxford Road, Manchester, UK.
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Xiong R, Li Y, Gao X, Li N, Lou R, Saeed L, Huang J. Effects of a long-term operation wetland for wastewater treatment on the spatial pattern and function of microbial communities in groundwater. ENVIRONMENTAL RESEARCH 2023; 228:115929. [PMID: 37072080 DOI: 10.1016/j.envres.2023.115929] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/19/2023] [Revised: 04/12/2023] [Accepted: 04/15/2023] [Indexed: 05/16/2023]
Abstract
Constructed wetlands have been used globally for wastewater treatment owing to low energy inputs and operating costs. However, the impact of their long-term operation on groundwater microbial communities is still unclear. This study aims to investigate the effects and further reveal the linkage between a large-scale surface flow constructed wetland (in operation for 14 years) and groundwater. Changes in the characteristics of groundwater microbial communities and their potential influencing factors were studied based on hydrochemical analysis, Illumina MiSeq sequencing, and multivariate statistical analysis methods. Results show that the long-term operation wetland significantly elevated groundwater nutrient levels and increased the risk of ammonia nitrogen pollution compared to background values. An apparent heterogeneity of microbial communities exhibited in the vertical direction and a similarity in the horizontal direction. Wetland operations substantially altered the structure of microbial communities at 3, 5, and 12 m depths, particularly a reduced abundance of denitrifying and chemoheterotrophic functional genera. The formation and evolution of groundwater microbial community structure mainly subjected to the contributions of dissolved oxygen (33.70%), total nitrogen (21.40%), dissolved organic carbon (11.09%), and pH (10.60%) variations resulted from the wetland operation and largely differed in depths. A combined effect of these factors on the groundwater should be concerned for such a long-term running wetland system. This study provides a new insight into the responses of groundwater microbial community structure driving by wetland operation and a better understanding of corresponding variation of microbial-based geochemical processes.
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Affiliation(s)
- Rongwei Xiong
- Key Laboratory of Integrated Regulation and Resource Development on Shallow Lakes of Ministry of Education, College of Environment, Hohai University, Nanjing, 210098, PR China
| | - Yong Li
- Key Laboratory of Integrated Regulation and Resource Development on Shallow Lakes of Ministry of Education, College of Environment, Hohai University, Nanjing, 210098, PR China; National Engineering Research Center of Water Resources Efficient Utilization and Engineering Safety, Hohai University, Nanjing, 210098, PR China.
| | - Xiufang Gao
- College of Resources and Environment, Yangtze University, Wuhan, 430100, PR China; Engineering Research Center of Ecology and Agricultural Use of Wetland, Ministry of Education, Jingzhou, 434025, PR China
| | - Na Li
- Key Laboratory of Integrated Regulation and Resource Development on Shallow Lakes of Ministry of Education, College of Environment, Hohai University, Nanjing, 210098, PR China
| | - Ruitao Lou
- Key Laboratory of Integrated Regulation and Resource Development on Shallow Lakes of Ministry of Education, College of Environment, Hohai University, Nanjing, 210098, PR China
| | - Laraib Saeed
- Key Laboratory of Integrated Regulation and Resource Development on Shallow Lakes of Ministry of Education, College of Environment, Hohai University, Nanjing, 210098, PR China
| | - Jinquan Huang
- Department of Soil and Water Conservation, Yangtze River Scientific Research Institute, Wuhan, 430010, PR China
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Shao S, Zhong J, Wang C, Pan D, Wu X. Performance of simultaneous nitrification-denitrification and denitrifying phosphorus and manganese removal by driving a single-stage moving bed biofilm reactor based on manganese redox cycling. BIORESOURCE TECHNOLOGY 2022; 362:127846. [PMID: 36031132 DOI: 10.1016/j.biortech.2022.127846] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/29/2022] [Revised: 08/17/2022] [Accepted: 08/22/2022] [Indexed: 06/15/2023]
Abstract
Simultaneous removal of NH4+-N, NO3--N, COD, and P by manganese redox cycling in nutrient wastewater was established with a single-stage moving bed biofilm reactor (MBBR) under low C/N ratio. When sodium succinate replaced the conventional denitrifying carbon source, removal efficiencies of TN, NO3--N, NH4+-N, TP, and Mn2+ were 65.13 %, 79.63 %, 92.79 %, 51.57 %, and 68.10 %, respectively. Based on modified Stover-Kincannon model, 11.03 and 10.05 mg TN·L-1·h-1 of Umax values were obtained with sodium acetate and sodium succinate as substrates. Extracellular polymeric substances were used to evaluate the characteristics of biofilm, and microbial community of biofilm was identified. Transformation processes of NO3--N, NH4+-N, Mn2+, and P were investigated, suggesting that the main functional groups (e.g., CO, Mn-O, and CN bonds) participated in N, P, and Mn2+ removal, and MnO2 was the main component of biogenic manganese oxides. This study provides a new strategy for nutrients removal by Mn2+ driven MBBR.
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Affiliation(s)
- Sicheng Shao
- College of Resources and Environment, Anhui Agricultural University, Key Laboratory of Agri-food Safety of Anhui Province, Hefei 230036, PR China
| | - Jinfeng Zhong
- College of Resources and Environment, Anhui Agricultural University, Key Laboratory of Agri-food Safety of Anhui Province, Hefei 230036, PR China
| | - Chunxiao Wang
- College of Resources and Environment, Anhui Agricultural University, Key Laboratory of Agri-food Safety of Anhui Province, Hefei 230036, PR China
| | - Dandan Pan
- College of Resources and Environment, Anhui Agricultural University, Key Laboratory of Agri-food Safety of Anhui Province, Hefei 230036, PR China
| | - Xiangwei Wu
- College of Resources and Environment, Anhui Agricultural University, Key Laboratory of Agri-food Safety of Anhui Province, Hefei 230036, PR China.
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ThomasArrigo LK, Notini L, Shuster J, Nydegger T, Vontobel S, Fischer S, Kappler A, Kretzschmar R. Mineral characterization and composition of Fe-rich flocs from wetlands of Iceland: Implications for Fe, C and trace element export. THE SCIENCE OF THE TOTAL ENVIRONMENT 2022; 816:151567. [PMID: 34762956 DOI: 10.1016/j.scitotenv.2021.151567] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/25/2021] [Revised: 11/05/2021] [Accepted: 11/05/2021] [Indexed: 05/26/2023]
Abstract
In freshwater wetlands, redox interfaces characterized by circumneutral pH, steep gradients in O2, and a continual supply of Fe(II) form ecological niches favorable to microaerophilic iron(II) oxidizing bacteria (FeOB) and the formation of flocs; associations of (a)biotic mineral phases, microorganisms, and (microbially-derived) organic matter. On the volcanic island of Iceland, wetlands are replenished with Fe-rich surface-, ground- and springwater. Combined with extensive drainage of lowland wetlands, which forms artificial redox gradients, accumulations of bright orange (a)biotically-derived Fe-rich flocs are common features of Icelandic wetlands. These loosely consolidated flocs are easily mobilized, and, considering the proximity of Iceland's lowland wetlands to the coast, are likely to contribute to the suspended sediment load transported to coastal waters. To date, however, little is known regarding (Fe) mineral and elemental composition of the flocs. In this study, flocs from wetlands (n = 16) across Iceland were analyzed using X-ray diffraction and spectroscopic techniques (X-ray absorption and 57Fe Mössbauer) combined with chemical extractions and (electron) microscopy to comprehensively characterize floc mineral, elemental, and structural composition. All flocs were rich in Fe (229-414 mg/g), and floc Fe minerals comprised primarily ferrihydrite and nano-crystalline lepidocrocite, with a single floc sample containing nano-crystalline goethite. Floc mineralogy also included Fe in clay minerals and appreciable poorly-crystalline aluminosilicates, most likely allophane and/or imogolite. Microscopy images revealed that floc (bio)organics largely comprised mineral encrusted microbially-derived components (i.e. sheaths, stalks, and EPS) indicative of common FeOB Leptothrix spp. and Gallionella spp. Trace element contents in the flocs were in the low μg/g range, however nearly all trace elements were extracted with hydroxylamine hydrochloride. This finding suggests that the (a)biotic reductive dissolution of floc Fe minerals, plausibly driven by exposure to the varied geochemical conditions of coastal waters following floc mobilization, could lead to the release of associated trace elements. Thus, the flocs should be considered vectors for transport of Fe, organic carbon, and trace elements from Icelandic wetlands to coastal waters.
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Affiliation(s)
- Laurel K ThomasArrigo
- Soil Chemistry Group, Institute of Biogeochemistry and Pollutant Dynamics, Department of Environmental Systems Science, ETH Zurich, Universitätstrasse 16, CHN, CH-8092 Zürich, Switzerland.
| | - Luiza Notini
- Soil Chemistry Group, Institute of Biogeochemistry and Pollutant Dynamics, Department of Environmental Systems Science, ETH Zurich, Universitätstrasse 16, CHN, CH-8092 Zürich, Switzerland
| | - Jeremiah Shuster
- Tübingen Structural Microscopy Core Facility, Centre for Applied Geosciences (ZAG), University of Tübingen, Schnarrenbergstrasse 94-96, D-72076 Tübingen, Germany
| | - Tabea Nydegger
- Soil Chemistry Group, Institute of Biogeochemistry and Pollutant Dynamics, Department of Environmental Systems Science, ETH Zurich, Universitätstrasse 16, CHN, CH-8092 Zürich, Switzerland
| | - Sophie Vontobel
- Soil Chemistry Group, Institute of Biogeochemistry and Pollutant Dynamics, Department of Environmental Systems Science, ETH Zurich, Universitätstrasse 16, CHN, CH-8092 Zürich, Switzerland
| | - Stefan Fischer
- Tübingen Structural Microscopy Core Facility, Centre for Applied Geosciences (ZAG), University of Tübingen, Schnarrenbergstrasse 94-96, D-72076 Tübingen, Germany
| | - Andreas Kappler
- Geomicrobiology Group, Centre for Applied Geosciences (ZAG), University of Tübingen, Schnarrenbergstrasse 94-96, D-72076 Tübingen, Germany
| | - Ruben Kretzschmar
- Soil Chemistry Group, Institute of Biogeochemistry and Pollutant Dynamics, Department of Environmental Systems Science, ETH Zurich, Universitätstrasse 16, CHN, CH-8092 Zürich, Switzerland
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Zastepa A, Miller TR, Watson LC, Kling H, Watson SB. Toxins and Other Bioactive Metabolites in Deep Chlorophyll Layers Containing the Cyanobacteria Planktothrix cf. isothrix in Two Georgian Bay Embayments, Lake Huron. Toxins (Basel) 2021; 13:445. [PMID: 34199141 PMCID: PMC8309927 DOI: 10.3390/toxins13070445] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2021] [Revised: 06/21/2021] [Accepted: 06/23/2021] [Indexed: 01/03/2023] Open
Abstract
The understanding of deep chlorophyll layers (DCLs) in the Great Lakes-largely reported as a mix of picoplankton and mixotrophic nanoflagellates-is predominantly based on studies of deep (>30 m), offshore locations. Here, we document and characterize nearshore DCLs from two meso-oligotrophic embayments, Twelve Mile Bay (TMB) and South Bay (SB), along eastern Georgian Bay, Lake Huron (Ontario, Canada) in 2014, 2015, and 2018. Both embayments showed the annual formation of DCLs, present as dense, thin, metalimnetic plates dominated by the large, potentially toxic, and bloom-forming cyanobacteria Planktothrix cf. isothrix. The contribution of P. cf. isothrix to the deep-living total biomass (TB) increased as thermal stratification progressed over the ice-free season, reaching 40% in TMB (0.6 mg/L at 9.5 m) and 65% in South Bay (3.5 mg/L at 7.5 m) in 2015. The euphotic zone in each embayment extended down past the mixed layer, into the nutrient-enriched hypoxic hypolimnia, consistent with other studies of similar systems with DCLs. The co-occurrence of the metal-oxidizing bacteria Leptothrix spp. and bactivorous flagellates within the metalimnetic DCLs suggests that the microbial loop plays an important role in recycling nutrients within these layers, particularly phosphate (PO4) and iron (Fe). Samples taken through the water column in both embayments showed measurable concentrations of the cyanobacterial toxins microcystins (max. 0.4 µg/L) and the other bioactive metabolites anabaenopeptins (max. ~7 µg/L) and cyanopeptolins (max. 1 ng/L), along with the corresponding genes (max. in 2018). These oligopeptides are known to act as metabolic inhibitors (e.g., in chemical defence against grazers, parasites) and allow a competitive advantage. In TMB, the 2018 peaks in these oligopeptides and genes coincided with the P. cf. isothrix DCLs, suggesting this species as the main source. Our data indicate that intersecting physicochemical gradients of light and nutrient-enriched hypoxic hypolimnia are key factors in supporting DCLs in TMB and SB. Microbial activity and allelopathy may also influence DCL community structure and function, and require further investigation, particularly related to the dominance of potentially toxigenic species such as P. cf. isothrix.
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Affiliation(s)
- Arthur Zastepa
- Environment and Climate Change Canada, Canada Centre for Inland Waters, 867 Lakeshore Road, Burlington, ON L7S 1A1, Canada;
| | - Todd R. Miller
- Joseph J. Zilber School of Public Health, University of Wisconsin-Milwaukee, Milwaukee, WI 53211, USA;
| | - L. Cynthia Watson
- Environment and Climate Change Canada, Canada Centre for Inland Waters, 867 Lakeshore Road, Burlington, ON L7S 1A1, Canada;
| | - Hedy Kling
- Algal Taxonomy and Ecology Inc., P.O. Box 761, Stony Mountain, MB R0C 3A0, Canada;
| | - Susan B. Watson
- School of Graduate Studies, Environmental and Life Sciences, Trent University, Peterborough, ON K9L 0G2, Canada;
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Kunoh T, Yamamoto T, Sugimoto S, Ono E, Nomura N, Utada AS. Leptothrix cholodnii Response to Nutrient Limitation. Front Microbiol 2021; 12:691563. [PMID: 34248917 PMCID: PMC8264430 DOI: 10.3389/fmicb.2021.691563] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2021] [Accepted: 05/27/2021] [Indexed: 11/13/2022] Open
Abstract
Microorganisms are widely utilized for the treatment of wastewater in activated sludge systems. However, the uncontrolled growth of filamentous bacteria leads to bulking and adversely affects wastewater treatment efficiency. To clarify the nutrient requirements for filament formation, we track the growth of a filamentous bacterium, Leptothrix cholodnii SP-6 in different nutrient-limited conditions using a high aspect-ratio microfluidic chamber to follow cell-chain elongation and sheath formation. We find that limitations in Na+, K+, and Fe2+ yield no observable changes in the elongation of cell chains and sheath formation, whereas limitations of C, N, P, or vitamins lead to more pronounced changes in filament morphology; here we observe the appearance of partially empty filaments with wide intercellular gaps. We observe more dramatic differences when SP-6 cells are transferred to media lacking Mg2+ and Ca2+. Loss of Mg2+ results in cell autolysis, while removal of Ca2+ results in the catastrophic disintegration of the filaments. By simultaneously limiting both carbon and Ca2+ sources, we are able to stimulate planktonic cell generation. These findings paint a detailed picture of the ecophysiology of Leptothrix, which may lead to improved control over the unchecked growth of deleterious filamentous bacteria in water purification systems.
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Affiliation(s)
- Tatsuki Kunoh
- Faculty of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Japan
| | - Tatsuya Yamamoto
- Faculty of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Japan
| | - Shinya Sugimoto
- Department of Bacteriology, Jikei Center for Biofilm Research and Technology, The Jikei University School of Medicine, Minato-ku, Japan
| | - Erika Ono
- School of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Japan
| | - Nobuhiko Nomura
- Faculty of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Japan.,Microbiology Research Center for Sustainability, University of Tsukuba, Tsukuba, Japan
| | - Andrew S Utada
- Faculty of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Japan.,Microbiology Research Center for Sustainability, University of Tsukuba, Tsukuba, Japan
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Abstract
Freshwater iron mats are dynamic geochemical environments with broad ecological diversity, primarily formed by the iron-oxidizing bacteria. The community features functional groups involved in biogeochemical cycles for iron, sulfur, carbon, and nitrogen. Despite this complexity, iron mat communities provide an excellent model system for exploring microbial ecological interactions and ecological theories in situ Syntrophies and competition between the functional groups in iron mats, how they connect cycles, and the maintenance of these communities by taxons outside bacteria (the eukaryota, archaea, and viruses) have been largely unstudied. Here, we review what is currently known about freshwater iron mat communities, the taxa that reside there, and the interactions between these organisms, and we propose ways in which future studies may uncover exciting new discoveries. For example, the archaea in these mats may play a greater role than previously thought as they are diverse and widespread in iron mats based on 16S rRNA genes and include methanogenic taxa. Studies with a holistic view of the iron mat community members focusing on their diverse interactions will expand our understanding of community functions, such as those involved in pollution removal. To begin addressing questions regarding the fundamental interactions and to identify the conditions in which they occur, more laboratory culturing techniques and coculture studies, more network and keystone species analyses, and the expansion of studies to more freshwater iron mat systems are necessary. Increasingly accessible bioinformatic, geochemical, and culturing tools now open avenues to address the questions that we pose herein.
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Affiliation(s)
- Chequita N Brooks
- Department of Biology, East Carolina University, Greenville, North Carolina, USA
| | - Erin K Field
- Department of Biology, East Carolina University, Greenville, North Carolina, USA
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