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Zhang M, Li X, Lin L, Shi J, Luan H, Li B. Cell-free hemoglobin and hemin catalyzing triclosan oxidative coupling in plasma: A novel exogenous phenolic pollutants coupling pathway. ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY 2024; 282:116708. [PMID: 39018736 DOI: 10.1016/j.ecoenv.2024.116708] [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: 01/28/2024] [Revised: 07/04/2024] [Accepted: 07/07/2024] [Indexed: 07/19/2024]
Abstract
Previous studies reported that hemoprotein CYP450 catalyzed triclosan coupling is an "uncommon" metabolic pathway that may enhance toxicity, raising concerns about its environmental and health impacts. Hemoglobin, a notable hemoprotein, can catalyze endogenous phenolic amino acid tyrosine coupling reactions. Our study explored the feasibility of these coupling reactions for exogenous phenolic pollutants in plasma. Both hemoglobin and hemin were found to catalyze triclosan coupling in the presence of H₂O₂. This resulted in the formation of five diTCS-2 H, two diTCS-Cl-3 H, and twelve triTCS-4 H in phosphate buffer, with a total of nineteen triclosan coupling products monitored using LC-QTOF. In plasma, five diTCS-2 H, two diTCS-Cl-3 H, and two triTCS-4 H were detected in hemoglobin-catalyzed reactions. Hemin showed a weaker catalytic effect on triclosan transformation compared to hemoglobin, likely due to hemin dimerization and oxidative degradation by H₂O₂, which limits its catalytic efficiency. Triclosan transformation in the human plasma-like medium still occurs with high H₂O₂, despite the presence of antioxidant proteins that typically inhibit such transformations. In plasma, free H₂O₂ was depleted within 40 minutes when 800 µM H₂O₂ was added, suggesting a rapid consumption of H₂O₂ in these reactions. Antioxidative species, or hemoglobin/hemin scavengers such as bovine serum albumin, may inhibit but not completely terminate the triclosan coupling reactions. Previous studies reported that diTCS-2 H showed higher hydrophobicity and greater endocrine-disrupting effects compared to triclosan, which further underscores the potential health risks. This study indicates that hemoglobin and heme in human plasma might significantly contribute to phenolic coupling reactions, potentially increasing health risks.
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Affiliation(s)
- Mengtao Zhang
- Institute of Environment and Ecology, Tsinghua Shenzhen International Graduate School, Tsinghua University, Shenzhen 518055, China
| | - Xiaoyan Li
- Institute of Environment and Ecology, Tsinghua Shenzhen International Graduate School, Tsinghua University, Shenzhen 518055, China
| | - Lin Lin
- Institute of Environment and Ecology, Tsinghua Shenzhen International Graduate School, Tsinghua University, Shenzhen 518055, China
| | - Jianghong Shi
- State Environmental Protection Key Lahoratory of Integrated Surface Water-Groundwater Pollution Control, School of Environmental Science and Engineering, Southern University of Science and Technology, Shenzhen 518055, China
| | - Hemi Luan
- School of Biomedical and Pharmaceutical Sciences, Guangdong University of Technology, Guangzhou, Guangdong 510006, China
| | - Bing Li
- Institute of Environment and Ecology, Tsinghua Shenzhen International Graduate School, Tsinghua University, Shenzhen 518055, China.
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Liu Q, Zhou K, Liu Y, Zhang Y, Chen W, Tang S. Exploring the potential applications of amphiphilic carbon dots based nanocomposite hydrogel in liquid chromatographic separations. Anal Chim Acta 2024; 1299:342445. [PMID: 38499423 DOI: 10.1016/j.aca.2024.342445] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2023] [Revised: 01/29/2024] [Accepted: 03/01/2024] [Indexed: 03/20/2024]
Abstract
BACKGROUND Due to their excellent stability, low toxicity, flexible modification and adjustable functionality, carbon dots (CDs) have a promising application prospect in the field of chromatographic stationary phases. Hydrogels are new functional polymer materials with three-dimensional network structure that have excellent hydrophilicity, high porosity and unique mechanical properties, which are also good candidate materials for liquid chromatography. Nevertheless, a review of the literature reveals that CDs based nanocomposite hydrogels have not yet been reported as HPLC stationary phases. RESULTS In this work, amphiphilic CDs with multiple functional groups and polyacrylic acid hydrogel were grafted to the surface of silica gel by an in-situ polymerization method, and a CDs/polyacrylic acid nanocomposite hydrogel stationary phase (CDs/hydrogel@SiO2) was prepared. CDs act as the macroscopic cross-linking agents to form a cross-linked network with polyacrylic acid chains through physical cross-linking by hydrogen bonding and chemical cross-linking by amidation and esterification reactions, which not only improve the swelling property of the hydrogel but also increase its stability. Additionally, the introduction of CDs with multifunctional groups modulates the hydrophilic-hydrophobic balance of the hydrogel that also imparts good hydrophobicity to the composite hydrogel. Through the study of retention mechanism and influencing factors, it is certificate that the CDs/hydrogel@SiO2 has mixed-mode chromatographic performance. Furthermore, the CDs/hydrogel@SiO2 column shows great potential for the determination of organic contaminants in environmental water samples. SIGNIFICANCE This work confirms the potential application of CDs/hydrogel composite for the separation of various samples and provides the possibility of developing CDs based nanocomposite hydrogel in the field of liquid chromatography. Introducing CDs into hydrogel can open up a new way for nanocomposite hydrogels to be used in HPLC, which expands the advance of hydrogel and CDs in separation field.
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Affiliation(s)
- Qiaoling Liu
- School of Chemistry and Environmental Engineering, Hubei Key Laboratory of Novel Reactor and Green Chemical Technology, Key Laboratory of Green Chemical Process of Ministry of Education, Wuhan Institute of Technology, Wuhan 430205, China
| | - Kunming Zhou
- School of Chemistry and Environmental Engineering, Hubei Key Laboratory of Novel Reactor and Green Chemical Technology, Key Laboratory of Green Chemical Process of Ministry of Education, Wuhan Institute of Technology, Wuhan 430205, China
| | - Yanjuan Liu
- School of Pharmacy, Linyi University, Shuangling Road, Linyi 276000, Shandong, China
| | - Yuefei Zhang
- School of Chemistry and Environmental Engineering, Hubei Key Laboratory of Novel Reactor and Green Chemical Technology, Key Laboratory of Green Chemical Process of Ministry of Education, Wuhan Institute of Technology, Wuhan 430205, China
| | - Wei Chen
- School of Chemistry and Environmental Engineering, Hubei Key Laboratory of Novel Reactor and Green Chemical Technology, Key Laboratory of Green Chemical Process of Ministry of Education, Wuhan Institute of Technology, Wuhan 430205, China
| | - Sheng Tang
- School of Chemistry and Environmental Engineering, Hubei Key Laboratory of Novel Reactor and Green Chemical Technology, Key Laboratory of Green Chemical Process of Ministry of Education, Wuhan Institute of Technology, Wuhan 430205, China.
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Zhang J, Liang Q, Mu D, Lian F, Gong Y, Ye M, Chen G, Ye Y, Du Z. Cultivating the uncultured: Harnessing the "sandwich agar plate" approach to isolate heme-dependent bacteria from marine sediment. MLIFE 2024; 3:143-155. [PMID: 38827516 PMCID: PMC11139205 DOI: 10.1002/mlf2.12093] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/12/2023] [Revised: 09/18/2023] [Accepted: 10/10/2023] [Indexed: 06/04/2024]
Abstract
In the classical microbial isolation technique, the isolation process inevitably destroys all microbial interactions and thus makes it difficult to culture the many microorganisms that rely on these interactions for survival. In this study, we designed a simple coculture technique named the "sandwich agar plate method," which maintains microbial interactions throughout the isolation and pure culture processes. The total yield of uncultured species in sandwich agar plates based on eight helper strains was almost 10-fold that of the control group. Many uncultured species displayed commensal lifestyles. Further study found that heme was the growth-promoting factor of some marine commensal bacteria. Subsequent genomic analysis revealed that heme auxotrophies were common in various biotopes and prevalent in many uncultured microbial taxa. Moreover, our study supported that the survival strategies of heme auxotrophy in different habitats varied considerably. These findings highlight that cocultivation based on the "sandwich agar plate method" could be developed and used to isolate more uncultured bacteria.
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Affiliation(s)
- Jing Zhang
- State Key Laboratory of Microbial Technology, Institute of Microbial TechnologyShandong UniversityQingdaoChina
- Marine CollegeShandong UniversityWeihaiChina
| | | | - Da‐Shuai Mu
- State Key Laboratory of Microbial Technology, Institute of Microbial TechnologyShandong UniversityQingdaoChina
- Marine CollegeShandong UniversityWeihaiChina
- Shandong University‐Weihai Research Institute of Industrial TechnologyWeihaiChina
| | | | - Ya Gong
- State Key Laboratory of Microbial Technology, Institute of Microbial TechnologyShandong UniversityQingdaoChina
- Marine CollegeShandong UniversityWeihaiChina
| | - Mengqi Ye
- State Key Laboratory of Microbial Technology, Institute of Microbial TechnologyShandong UniversityQingdaoChina
- Marine CollegeShandong UniversityWeihaiChina
| | - Guan‐Jun Chen
- State Key Laboratory of Microbial Technology, Institute of Microbial TechnologyShandong UniversityQingdaoChina
- Marine CollegeShandong UniversityWeihaiChina
| | - Yuqi Ye
- Marine CollegeShandong UniversityWeihaiChina
| | - Zong‐Jun Du
- State Key Laboratory of Microbial Technology, Institute of Microbial TechnologyShandong UniversityQingdaoChina
- Marine CollegeShandong UniversityWeihaiChina
- Shandong University‐Weihai Research Institute of Industrial TechnologyWeihaiChina
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Elsabbagh S, Landau M, Gross H, Schultz A, Schultz JE. Heme b inhibits class III adenylyl cyclases. Cell Signal 2023; 103:110568. [PMID: 36565898 DOI: 10.1016/j.cellsig.2022.110568] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2022] [Revised: 12/12/2022] [Accepted: 12/19/2022] [Indexed: 12/24/2022]
Abstract
Acidic lipid extracts from mouse liver, kidney, heart, brain, and lung inhibited human pseudoheterodimeric adenylyl cyclases (hACs) expressed in HEK293 cells. Using an acidic lipid extract from bovine lung, a combined MS- and bioassay-guided fractionation identified heme b as inhibitor of membrane-bound ACs. IC50 concentrations were 8-12 μM for the hAC isoforms. Hemopexin and bacterial hemophore attenuated heme b inhibition of hAC5. Structurally related compounds, such as hematin, protoporphyrin IX, and biliverdin, were significantly less effective. Monomeric bacterial class III ACs (mycobacterial ACs Rv1625c; Rv3645; Rv1264; cyanobacterial AC CyaG) were inhibited by heme b with similar efficiency. Surprisingly, structurally related chlorophyll a similarly inhibited hAC5. Heme b inhibited isoproterenol-stimulated cAMP accumulation in HEK293 cells. Using cortical membranes from mouse brain hemin efficiently and reversibly inhibited basal and Gsα-stimulated AC activity. The physiological relevance of heme b inhibition of the cAMP generating system in certain pathologies is discussed.
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Affiliation(s)
- Sherif Elsabbagh
- Pharmazeutisches Institut der Universität Tübingen, Tübingen, Germany
| | - Marius Landau
- Pharmazeutisches Institut der Universität Tübingen, Tübingen, Germany
| | - Harald Gross
- Pharmazeutisches Institut der Universität Tübingen, Tübingen, Germany
| | - Anita Schultz
- Pharmazeutisches Institut der Universität Tübingen, Tübingen, Germany
| | - Joachim E Schultz
- Pharmazeutisches Institut der Universität Tübingen, Tübingen, Germany.
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Zeng L, Xie W, Jiang L, Yao X, Li H, Shi B, Lei F. Fabrication and evaluation of dodecyl imide maleopimaric acid glycidyl methacrylate ester modified silica with multiple retention mechanisms for reversed phase liquid chromatography. J Chromatogr A 2023; 1689:463747. [PMID: 36621106 DOI: 10.1016/j.chroma.2022.463747] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2022] [Revised: 12/07/2022] [Accepted: 12/22/2022] [Indexed: 12/24/2022]
Abstract
As green, less toxic, and abundant ligands with rich functional groups, natural products are widely used in synthesis of chromatographic stationary phases. In this work, dodecyl imide maleopimaric acid glycidyl methacrylate ester (C12-MPAGN) was prepared from maleopimaric acid through the imidization and ring-opening based esterification reaction. By using "thiol-ene" click chemistry, it was chemically bonded to the silica and (3-mercaptopropyl) trimethoxysilane (γ-MPS) was used as the coupling agent to obtain dodecyl imide maleopimaric acid glycidyl methacrylate ester bonded silica stationary phase (Sil-C12-MPAGN). Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), scanning electron microscopies (SEM), and elemental analysis (EA) were utilized to verify that the Sil-C12-MPAGN stationary phase was successfully prepared with C12-MPAGN immobilized on the silica surface. In order to evaluate the chromatographic performance and retention mechanisms of the Sil-C12-MPAGN column and compared with C18 column, a variety of compounds were used, including stander mixture of Tanaka, alkylbenzenes, polycyclic aromatic hydrocarbons (PAHs), phenols and flavonoids. Based on these multiple interactions, including hydrophobic, hydrogen-bonding, and π-π interactions, high selectivity and superior separation performance were demonstrated by the Sil-C12-MPAGN column for probe molecules what had previously been mentioned. In addition, the quantitative determination of paclitaxel content in Yew bark extract was conducted with this column, which was found that the concentration was 83.67 mg/L, respectively. In short, the present study proposes a new strategy for introducing rosin to liquid chromatography with high selectivity and separation performance.
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Affiliation(s)
- Lei Zeng
- Key Laboratory of Chemistry and Engineering of Forest Products of State Ethnic Affairs Commission, Guangxi Key Laboratory of Chemistry and Engineering of Forest Products, Guangxi Collaborative Innovation Center for Chemistry and Engineering of Forest Products, School of Chemistry and Chemical Engineering, Guangxi Minzu University, Nanning, Guangxi 530006, China
| | - Wenbo Xie
- Key Laboratory of Chemistry and Engineering of Forest Products of State Ethnic Affairs Commission, Guangxi Key Laboratory of Chemistry and Engineering of Forest Products, Guangxi Collaborative Innovation Center for Chemistry and Engineering of Forest Products, School of Chemistry and Chemical Engineering, Guangxi Minzu University, Nanning, Guangxi 530006, China
| | - Lijuan Jiang
- Key Laboratory of Chemistry and Engineering of Forest Products of State Ethnic Affairs Commission, Guangxi Key Laboratory of Chemistry and Engineering of Forest Products, Guangxi Collaborative Innovation Center for Chemistry and Engineering of Forest Products, School of Chemistry and Chemical Engineering, Guangxi Minzu University, Nanning, Guangxi 530006, China
| | - Xingdong Yao
- Key Laboratory of Chemistry and Engineering of Forest Products of State Ethnic Affairs Commission, Guangxi Key Laboratory of Chemistry and Engineering of Forest Products, Guangxi Collaborative Innovation Center for Chemistry and Engineering of Forest Products, School of Chemistry and Chemical Engineering, Guangxi Minzu University, Nanning, Guangxi 530006, China
| | - Hao Li
- Key Laboratory of Chemistry and Engineering of Forest Products of State Ethnic Affairs Commission, Guangxi Key Laboratory of Chemistry and Engineering of Forest Products, Guangxi Collaborative Innovation Center for Chemistry and Engineering of Forest Products, School of Chemistry and Chemical Engineering, Guangxi Minzu University, Nanning, Guangxi 530006, China
| | - Boan Shi
- School of Chemical and Environmental Engineering, Hubei Minzu University, Enshi, Hubei 445000, China
| | - Fuhou Lei
- Key Laboratory of Chemistry and Engineering of Forest Products of State Ethnic Affairs Commission, Guangxi Key Laboratory of Chemistry and Engineering of Forest Products, Guangxi Collaborative Innovation Center for Chemistry and Engineering of Forest Products, School of Chemistry and Chemical Engineering, Guangxi Minzu University, Nanning, Guangxi 530006, China.
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OHKOUCHI N. A new era of isotope ecology: Nitrogen isotope ratio of amino acids as an approach for unraveling modern and ancient food web. PROCEEDINGS OF THE JAPAN ACADEMY. SERIES B, PHYSICAL AND BIOLOGICAL SCIENCES 2023; 99:131-154. [PMID: 37164681 PMCID: PMC10225296 DOI: 10.2183/pjab.99.009] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/05/2023] [Accepted: 04/03/2023] [Indexed: 05/12/2023]
Abstract
Food web research is rapidly expanding through study of natural fractional abundance of 15N in individual amino acids. This paper overviews the principles of this isotope approach, and from my perspective, reanalyzes applications, and further extends the discussion. It applies kinetic isotope effects that enriches 15N in certain amino acids associated with the metabolic processes, which was clearly demonstrated by observations of both natural ecosystem and laboratory experiments. In trophic processes 'trophic amino acids' such as glutamic acid that significantly enrich 15N, whereas 'source amino acids' such as phenylalanine and methionine show little 15N enrichment. Through various applications conducted over the years, the principles of the method have shown to operate well and disentangle complex food webs and relevant problems. Applications include food chain length estimate, nitrogen resource assessment, tracking fish migration, and reconstruction of paleodiet. With this approach, considerations of a wide range of classical issues have been reinvigorated, while in the same time, new challenging frontiers are emerging.
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Affiliation(s)
- Naohiko OHKOUCHI
- Biogeochemistry Research Center, Japan Agency for Marine-Earth Science and Technology, Yokosuka, Kanagawa, Japan
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7
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Du N, Zhang H, Wang J, Dong X, Li J, Wang K, Guan R. Fluorescent silicon nanoparticle–based quantitative hemin assay. Anal Bioanal Chem 2022; 414:8223-8232. [DOI: 10.1007/s00216-022-04386-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2022] [Revised: 10/10/2022] [Accepted: 10/13/2022] [Indexed: 11/01/2022]
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Hu X, Wang Y, Zuping X, Song P, Wang AJ, Qian Z, Yuan PX, Zhao T, Feng JJ. Novel Aggregation-Enhanced PEC Photosensitizer Based on Electrostatic Linkage of Ionic Liquid with Protoporphyrin IX for Ultrasensitive Detection of Molt-4 Cells. Anal Chem 2022; 94:3708-3717. [PMID: 35172575 DOI: 10.1021/acs.analchem.1c05578] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Nowadays, aggregation quenching of most organic photosensitizers in aqueous media seriously restricts analytical and biomedical applications of photoelectrochemical (PEC) sensors. In this work, an aggregation-enhanced PEC photosensitizer was prepared by electrostatically bonding protoporphyrin IX (PPIX) with an ionic liquid of 1-butyl-3-methylimidazole tetrafluoroborate ([BMIm][BF4]), termed as PPIX-[BMIm] for clarity. The resultant PPIX-[BMIm] showed weak photocurrent in pure dimethyl sulfoxide (DMSO, good solvent), while the PEC signals displayed a 44.1-fold enhancement in a water (poor solvent)/DMSO binary solvent with a water fraction (fw) of 90%. Such PEC-enhanced mechanism was critically studied by electrochemistry and density functional theory (DFT) calculation in some detail. Afterward, a label-free PEC cytosensor was built for ultrasensitive bioassay of acute lymphoblastic leukemia (molt-4) cells by electrodepositing Au nanoparticles (Au NPs) on the PPIX-[BMIm] aggregates and sequential assembly of protein tyrosine kinase (PTK) aptamer DNA (aptDNA). The resultant cytosensor showed a wide linear range (300 to 3 × 105 cells mL-1) with a limit of detection (LOD) as low as 63 cells mL-1. The aggregation-enhanced PEC performance offers a valuable and practical pathway for synthesis of advanced organic photosensitizer to explore its PEC applications in early diagnosis of tumors.
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Affiliation(s)
- Xiang Hu
- Key Laboratory of the Ministry of Education for Advanced Catalysis Materials, College of Chemistry and Life Sciences, College of Geography and Environmental Sciences, Zhejiang Normal University, Jinhua 321004, China
| | - Ying Wang
- Key Laboratory of the Ministry of Education for Advanced Catalysis Materials, College of Chemistry and Life Sciences, College of Geography and Environmental Sciences, Zhejiang Normal University, Jinhua 321004, China
| | - Xiong Zuping
- Key Laboratory of the Ministry of Education for Advanced Catalysis Materials, College of Chemistry and Life Sciences, College of Geography and Environmental Sciences, Zhejiang Normal University, Jinhua 321004, China
| | - Pei Song
- Affiliated Jinhua Hospital, Zhejiang University School of Medicine, Jinhua 321000, China
| | - Ai-Jun Wang
- Key Laboratory of the Ministry of Education for Advanced Catalysis Materials, College of Chemistry and Life Sciences, College of Geography and Environmental Sciences, Zhejiang Normal University, Jinhua 321004, China
| | - Zhaosheng Qian
- Key Laboratory of the Ministry of Education for Advanced Catalysis Materials, College of Chemistry and Life Sciences, College of Geography and Environmental Sciences, Zhejiang Normal University, Jinhua 321004, China
| | - Pei-Xin Yuan
- Key Laboratory of the Ministry of Education for Advanced Catalysis Materials, College of Chemistry and Life Sciences, College of Geography and Environmental Sciences, Zhejiang Normal University, Jinhua 321004, China
| | - Tiejun Zhao
- Key Laboratory of the Ministry of Education for Advanced Catalysis Materials, College of Chemistry and Life Sciences, College of Geography and Environmental Sciences, Zhejiang Normal University, Jinhua 321004, China
| | - Jiu-Ju Feng
- Key Laboratory of the Ministry of Education for Advanced Catalysis Materials, College of Chemistry and Life Sciences, College of Geography and Environmental Sciences, Zhejiang Normal University, Jinhua 321004, China
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Heme auxotrophy in abundant aquatic microbial lineages. Proc Natl Acad Sci U S A 2021; 118:2102750118. [PMID: 34785591 DOI: 10.1073/pnas.2102750118] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/11/2021] [Indexed: 01/22/2023] Open
Abstract
Heme, a porphyrin ring complexed with iron, is a metalloprosthetic group of numerous proteins involved in diverse metabolic and respiratory processes across all domains of life, and is thus considered essential for respiring organisms. Several microbial groups are known to lack the de novo heme biosynthetic pathway and therefore require exogenous heme from the environment. These heme auxotroph groups are largely limited to pathogens, symbionts, or microorganisms living in nutrient-replete conditions, whereas the complete absence of heme biosynthesis is extremely rare in free-living organisms. Here, we show that the acI lineage, a predominant and ubiquitous free-living bacterial group in freshwater habitats, is auxotrophic for heme, based on the experimental or genomic evidence. We found that two recently cultivated acI isolates require exogenous heme for their growth. One of the cultured acI isolates also exhibited auxotrophy for riboflavin. According to whole-genome analyses, all (n = 20) isolated acI strains lacked essential enzymes necessary for heme biosynthesis, indicating that heme auxotrophy is a conserved trait in this lineage. Analyses of >24,000 representative genomes for species clusters of the Genome Taxonomy Database revealed that heme auxotrophy is widespread across abundant but not-yet-cultivated microbial groups, including Patescibacteria, Marinisomatota (SAR406), Actinomarinales (OM1), and Marine groups IIb and III of Euryarchaeota Our findings indicate that heme auxotrophy is a more common phenomenon than previously thought, and may lead to use of heme as a growth factor to increase the cultured microbial diversity.
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