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Mo W, Wang H, Wang J, Wang Y, Liu Y, Luo Y, He M, Cheng S, Mei H, He J, Su J. Advances in Research on Bacterial Oxidation of Mn(II): A Visualized Bibliometric Analysis Based on CiteSpace. Microorganisms 2024; 12:1611. [PMID: 39203453 PMCID: PMC11356483 DOI: 10.3390/microorganisms12081611] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2024] [Revised: 08/03/2024] [Accepted: 08/05/2024] [Indexed: 09/03/2024] Open
Abstract
Manganese (Mn) pollution poses a serious threat to the health of animals, plants, and humans. The microbial-mediated Mn(II) removal method has received widespread attention because of its rapid growth, high efficiency, and economy. Mn(II)-oxidizing bacteria can oxidize toxic soluble Mn(II) into non-toxic Mn(III/IV) oxides, which can further participate in the transformation of other heavy metals and organic pollutants, playing a crucial role in environmental remediation. This study aims to conduct a bibliometric analysis of research papers on bacterial Mn(II) oxidation using CiteSpace, and to explore the research hotspots and developmental trends within this field between 2008 and 2023. A series of visualized knowledge map analyses were conducted with 469 screened SCI research papers regarding annual publication quantity, author groups and their countries and regions, journal categories, publishing institutions, and keywords. China, the USA, and Japan published the most significant number of research papers on the research of bacterial Mn(II) oxidation. Research hotspots of bacterial Mn(II) oxidation mainly focused on the species and distributions of Mn(II)-oxidizing bacteria, the influencing factors of Mn(II) oxidation, the mechanisms of Mn(II) oxidation, and their applications in environment. This bibliometric analysis provides a comprehensive visualized knowledge map to quickly understand the current advancements, research hotspots, and academic frontiers in bacterial Mn(II) oxidation.
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Affiliation(s)
- Wentao Mo
- Hubei Key Laboratory of Regional Development and Environmental Response, Faculty of Resources and Environmental Science, Hubei University, Wuhan 430062, China; (W.M.); (H.W.); (J.W.); (Y.W.); (Y.L.); (Y.L.); (M.H.); (S.C.); (H.M.)
| | - Hang Wang
- Hubei Key Laboratory of Regional Development and Environmental Response, Faculty of Resources and Environmental Science, Hubei University, Wuhan 430062, China; (W.M.); (H.W.); (J.W.); (Y.W.); (Y.L.); (Y.L.); (M.H.); (S.C.); (H.M.)
| | - Jianghan Wang
- Hubei Key Laboratory of Regional Development and Environmental Response, Faculty of Resources and Environmental Science, Hubei University, Wuhan 430062, China; (W.M.); (H.W.); (J.W.); (Y.W.); (Y.L.); (Y.L.); (M.H.); (S.C.); (H.M.)
| | - Yue Wang
- Hubei Key Laboratory of Regional Development and Environmental Response, Faculty of Resources and Environmental Science, Hubei University, Wuhan 430062, China; (W.M.); (H.W.); (J.W.); (Y.W.); (Y.L.); (Y.L.); (M.H.); (S.C.); (H.M.)
| | - Yunfei Liu
- Hubei Key Laboratory of Regional Development and Environmental Response, Faculty of Resources and Environmental Science, Hubei University, Wuhan 430062, China; (W.M.); (H.W.); (J.W.); (Y.W.); (Y.L.); (Y.L.); (M.H.); (S.C.); (H.M.)
| | - Yi Luo
- Hubei Key Laboratory of Regional Development and Environmental Response, Faculty of Resources and Environmental Science, Hubei University, Wuhan 430062, China; (W.M.); (H.W.); (J.W.); (Y.W.); (Y.L.); (Y.L.); (M.H.); (S.C.); (H.M.)
| | - Minghui He
- Hubei Key Laboratory of Regional Development and Environmental Response, Faculty of Resources and Environmental Science, Hubei University, Wuhan 430062, China; (W.M.); (H.W.); (J.W.); (Y.W.); (Y.L.); (Y.L.); (M.H.); (S.C.); (H.M.)
| | - Shuang Cheng
- Hubei Key Laboratory of Regional Development and Environmental Response, Faculty of Resources and Environmental Science, Hubei University, Wuhan 430062, China; (W.M.); (H.W.); (J.W.); (Y.W.); (Y.L.); (Y.L.); (M.H.); (S.C.); (H.M.)
| | - Huiting Mei
- Hubei Key Laboratory of Regional Development and Environmental Response, Faculty of Resources and Environmental Science, Hubei University, Wuhan 430062, China; (W.M.); (H.W.); (J.W.); (Y.W.); (Y.L.); (Y.L.); (M.H.); (S.C.); (H.M.)
| | - Jin He
- National Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural University, Wuhan 430062, China;
| | - Jianmei Su
- Hubei Key Laboratory of Regional Development and Environmental Response, Faculty of Resources and Environmental Science, Hubei University, Wuhan 430062, China; (W.M.); (H.W.); (J.W.); (Y.W.); (Y.L.); (Y.L.); (M.H.); (S.C.); (H.M.)
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Kunoh T, Yamamoto T, Ono E, Sugimoto S, Takabe K, Takeda M, Utada AS, Nomura N. Identification of lthB, a Gene Encoding a Putative Glycosyltransferase Family 8 Protein Required for Leptothrix Sheath Formation. Appl Environ Microbiol 2023; 89:e0191922. [PMID: 36951572 PMCID: PMC10132092 DOI: 10.1128/aem.01919-22] [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: 12/01/2022] [Accepted: 02/20/2023] [Indexed: 03/24/2023] Open
Abstract
The bacterium Leptothrix cholodnii generates cell chains encased in sheaths that are composed of woven nanofibrils. The nanofibrils are mainly composed of glycoconjugate repeats, and several glycosyltransferases (GTs) are required for its biosynthesis. However, only one GT (LthA) has been identified to date. In this study, we screened spontaneous variants of L. cholodnii SP6 to find those that form smooth colonies, which is one of the characteristics of sheathless variants. Genomic DNA sequencing of an isolated variant revealed an insertion in the locus Lcho_0972, which encodes a putative GT family 8 protein. We thus designated this protein LthB and characterized it using deletion mutants and antibodies. LthB localized adjacent to the cell envelope. ΔlthB cell chains were nanofibril free and thus sheathless, indicating that LthB is involved in nanofibril biosynthesis. Unlike the ΔlthA mutant and the wild-type strain, which often generate planktonic cells, most ΔlthB organisms presented as long cell chains under static conditions, resulting in deficient pellicle formation, which requires motile planktonic cells. These results imply that sheaths are not required for elongation of cell chains. Finally, calcium depletion, which induces cell chain breakage due to sheath loss, abrogated the expression of LthA, but not LthB, suggesting that these GTs cooperatively participate in glycoconjugate biosynthesis under different signaling controls. IMPORTANCE In recent years, the regulation of cell chain elongation of filamentous bacteria via extracellular signals has attracted attention as a potential strategy to prevent clogging of water distribution systems and filamentous bulking of activated sludge in industrial settings. However, a fundamental understanding of the ecology of filamentous bacteria remains elusive. Since sheath formation is associated with cell chain elongation in most of these bacteria, the molecular mechanisms underlying nanofibril sheath formation, including the intracellular signaling cascade in response to extracellular stimuli, must be elucidated. Here, we isolated a sheathless variant of L. cholodnii SP6 and thus identified a novel glycosyltransferase, LthB. Although mutants with deletions of lthA, encoding another GT, and lthB were both defective for nanofibril formation, they exhibited different phenotypes of cell chain elongation and pellicle formation. Moreover, LthA expression, but not LthB expression, was influenced by extracellular calcium, which is known to affect nanofibril formation, indicating the functional diversities of LthA and LthB. Such molecular insights are critical for a better understanding of ecology of filamentous bacteria, which, in turn, can be used to improve strategies to control filamentous bacteria in industrial facilities.
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Affiliation(s)
- Tatsuki Kunoh
- Faculty of Life and Environmental Sciences, University of Tsukuba, Ibaraki, Japan
| | - Tatsuya Yamamoto
- Faculty of Life and Environmental Sciences, University of Tsukuba, Ibaraki, Japan
| | - Erika Ono
- Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Ibaraki, Japan
| | - Shinya Sugimoto
- Department of Bacteriology, The Jikei University School of Medicine, Tokyo, Japan
- Jikei Center for Biofilm Science and Technology, The Jikei University School of Medicine, Tokyo, Japan
| | - Kyosuke Takabe
- Faculty of Life and Environmental Sciences, University of Tsukuba, Ibaraki, Japan
| | - Minoru Takeda
- Division of Materials Science and Chemical Engineering, Faculty of Engineering, Yokohama National University, Yokohama, Kanagawa, Japan
| | - Andrew S. Utada
- Faculty of Life and Environmental Sciences, University of Tsukuba, Ibaraki, Japan
- Microbiology Research Center for Sustainability, University of Tsukuba, Tsukuba, Ibaraki, Japan
| | - Nobuhiko Nomura
- Faculty of Life and Environmental Sciences, University of Tsukuba, Ibaraki, Japan
- Microbiology Research Center for Sustainability, University of Tsukuba, Tsukuba, Ibaraki, Japan
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Porous Pellicle Formation of a Filamentous Bacterium, Leptothrix. Appl Environ Microbiol 2022; 88:e0134122. [PMID: 36416549 PMCID: PMC9746318 DOI: 10.1128/aem.01341-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
The bacterium Leptothrix cholodnii generates filaments encased in a sheath comprised of woven nanofibrils. In static liquid culture, L. cholodnii moves toward the air-liquid interface, where it forms porous pellicles. Observations of aggregation at the interface reveal that clusters consisting of only a few bacteria primarily grow by netting free cells. These growing clusters hierarchically enlarge through the random docking of other small clusters. We find that the bacteria swim using their polar flagellum toward the interface, where their sheath assists them in intertwining with others and thereby promotes the formation of small clusters. In contrast, sheathless hydrophobic mutant cells get stuck to the interface. We find that the nanofibril sheath is vital for robust pellicle formation as it lowers cell surface hydrophobicity by 60%, thereby reducing their adsorption and enabling cells to move toward and stick together at the air-liquid interface. IMPORTANCE Efficient and sustainable management of water resources is becoming a fundamental issue for supporting growing populations and for developing economic activity. Fundamental to this management is the treatment of wastewater. Microorganisms are the active component of activated sludge that is employed in the biodegradation process of many wastewater treatment facilities. However, uncontrolled growth of filamentous bacteria such as Sphaerotilus often results in filamentous bulking, lowering the efficiency of water treatment systems. To prevent this undesirable condition, strategies based on a fundamental understanding of the ecology of filamentous bacteria are required. Although the filamentous bacterium Leptothrix cholodnii, which is closely related to Sphaerotilus, is a minor inhabitant of activated sludge, its complete genome sequence is known, making gene manipulation relatively easy. Moreover, L. cholodnii generates porous pellicles under static conditions, which may be a characteristic of filamentous bulking. We show that both swimming motility and nanofibril-mediated air-liquid interface attachment are required for porous pellicle formation. These insights are critical for a better understanding of the characteristics of filamentous bulking and might improve strategies to control activated sludge.
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Development of a Targeted Gene Disruption System in the Poly(Ethylene Terephthalate)-Degrading Bacterium Ideonella sakaiensis and Its Applications to PETase and MHETase Genes. Appl Environ Microbiol 2021; 87:e0002021. [PMID: 34260304 DOI: 10.1128/aem.00020-21] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Poly(ethylene terephthalate) (PET) is a commonly used synthetic plastic; however, its nonbiodegradability results in a large amount of waste accumulation that has a negative impact on the environment. Recently, a PET-degrading bacterium, Ideonella sakaiensis 201-F6 strain, was isolated, and the enzymes involved in PET digestion, PET hydrolase (PETase), and mono(2-hydroxyethyl) terephthalic acid (MHET) hydrolase (MHETase) were identified. Despite the great potentials of I. sakaiensis in bioremediation and biorecycling, approaches to studying this bacterium remain limited. In this study, to enable the functional analysis of PETase and MHETase genes in vivo, we have developed a gene disruption system in I. sakaiensis. The pT18mobsacB-based disruption vector harboring directly connected 5'- and 3'-flanking regions of the target gene for homologous recombination was introduced into I. sakaiensis cells via conjugation. First, we deleted the orotidine 5'-phosphate decarboxylase gene (pyrF) from the genome of the wild-type strain, producing the ΔpyrF strain with 5-fluoroorotic acid (5-FOA) resistance. Next, using the ΔpyrF strain as a parent strain and pyrF as a counterselection marker, we disrupted the genes for PETase and MHETase. The growth of both Δpetase and Δmhetase strains on terephthalic acid (TPA; one of the PET hydrolytic products) was comparable to that of the parent strain. However, these mutant strains dramatically decreased the growth level on PET to that on a no-carbon source. Moreover, the Δpetase strain completely abolished PET degradation capacity. These results demonstrate that PETase and MHETase are essential for I. sakaiensis metabolism of PET. IMPORTANCE The poly(ethylene terephthalate) (PET)-degrading bacterium Ideonella sakaiensis possesses two unique enzymes able to serve in PET hydrolysis. PET hydrolase (PETase) hydrolyzes PET into mono(2-hydroxyethyl) terephthalic acid (MHET), and MHET hydrolase (MHETase) hydrolyzes MHET into terephthalic acid (TPA) and ethylene glycol (EG). These enzymes have attracted global attention, as they have potential to be used for bioconversion of PET. Compared to many in vitro studies, including biochemical and crystal structure analyses, few in vivo studies have been reported. Here, we developed a targeted gene disruption system in I. sakaiensis, which was then applied for constructing Δpetase and Δmhetase strains. Growth of these disruptants revealed that PETase is the sole enzyme responsible for PET degradation in I. sakaiensis, while PETase and MHETase play essential roles in its PET assimilation.
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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
The importance of manganese in the physiology of marine microbes, the biogeochemistry of the ocean and the health of microbial communities of past and present is emerging. Manganese is distributed widely throughout the global ocean, taking the form of an essential antioxidant (Mn2+), a potent oxidant (Mn3+) and strong adsorbent (Mn oxides) sequestering disproportionately high levels of trace metals and nutrients in comparison to the surrounding seawater. Manganese is, in fact, linked to nearly all other elemental cycles and intricately involved in the health, metabolism and function of the ocean's microbiome. Here, we briefly review the diversity of microbes and pathways responsible for the transformation of Mn within the three Mn pools and their distribution within the marine environment. Despite decades of interrogation, we still have much to learn about the players, mechanisms and consequences of the Mn cycle, and new and exciting discoveries are being made at a rapid rate. What is clear is the dynamic and ever-inspiring complexity of reactions involving Mn, and the acknowledgement that microorganisms are the catalytic engine driving the Mn cycle.
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Affiliation(s)
- Colleen M Hansel
- Woods Hole Oceanographic Institution, Woods Hole, MA, United States.
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