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Broniatowski M, Wydro P. Interactions of Brominated Flame Retardants with Membrane Models of Dehalogenating Bacteria: Langmuir Monolayer and Grazing Incidence X-ray Diffraction Studies. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2024; 40:10600-10614. [PMID: 38721840 PMCID: PMC11112749 DOI: 10.1021/acs.langmuir.4c00518] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/12/2024] [Revised: 04/24/2024] [Accepted: 04/29/2024] [Indexed: 05/22/2024]
Abstract
Brominated flame retardants (BFRs) are small organic molecules containing several bromine substituents added to plastics to limit their flammability. BFRs can constitute up to 30% of the weight of some plastics, which is why they are produced in large quantities. Along with plastic waste and microplastic particles, BFRs end up in the soil and can easily leach causing contamination. As polyhalogenated molecules, multiple BFRs were classified as persistent organic pollutants (POPs), meaning that their biodegradation in the soils is especially challenging. However, some anaerobic bacteria as Dehaloccocoides can dehalogenate BFRs, which is important in the bioremediation of contaminated soils. BFRs are hydrophobic, can accumulate in plasma membranes, and disturb their function. On the other hand, limited membrane accumulation is necessary for BFR dehalogenation. To study the BFR-membrane interaction, we created membrane models of soil dehalogenating bacteria and tested their interactions with seven legacy and novel BFRs most common in soils. Phospholipid Langmuir monolayers with appropriate composition were used as membrane models. These membranes were doped in the selected BFRs, and the incorporation of BFR molecules into the phospholipid matrix and also the effects of BFR presence on membrane physical properties and morphology were studied. It turned out that the seven BFRs differed significantly in their membrane affinity. For some, the incorporation was very limited, and others incorporated effectively and could affect membrane properties, while one of the tested molecules induced the formation of bilayer domains in the membranes. Thus, Langmuir monolayers can be effectively used for pretesting BFR membrane activity.
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Affiliation(s)
- Marcin Broniatowski
- Department
of Environmental Chemistry, Faculty of Chemistry, the Jagiellonian University in Kraków, ul. Gronostajowa 2, Kraków 30-387, Poland
| | - Paweł Wydro
- Department
of Physical Chemistry and Electrochemistry, Faculty of Chemistry, the Jagiellonian University in Kraków, ul. Gronostajowa 2, Kraków 30-387, Poland
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2
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Mitchison-Field LM, Belin BJ. Bacterial lipid biophysics and membrane organization. Curr Opin Microbiol 2023; 74:102315. [PMID: 37058914 PMCID: PMC10523990 DOI: 10.1016/j.mib.2023.102315] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2023] [Revised: 03/13/2023] [Accepted: 03/14/2023] [Indexed: 04/16/2023]
Abstract
The formation of lateral microdomains is emerging as a central organizing principle in bacterial membranes. These microdomains are targets of antibiotic development and have the potential to enhance natural product synthesis, but the rules governing their assembly are unclear. Previous studies have suggested that microdomain formation is promoted by lipid phase separation, particularly by cardiolipin (CL) and isoprenoid lipids, and there is strong evidence that CL biosynthesis is required for recruitment of membrane proteins to cell poles and division sites. New work demonstrates that additional bacterial lipids may mediate membrane protein localization and function, opening the field for mechanistic evaluation of lipid-driven membrane organization in vivo.
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Affiliation(s)
- Lorna My Mitchison-Field
- Department of Embryology, Carnegie Institution for Science, Baltimore, MD, USA; Department of Biology, Johns Hopkins University, Baltimore, MD, USA
| | - Brittany J Belin
- Department of Embryology, Carnegie Institution for Science, Baltimore, MD, USA; Department of Biology, Johns Hopkins University, Baltimore, MD, USA.
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3
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Brown B, Wilkins M, Saha R. Rhodopseudomonas palustris: A biotechnology chassis. Biotechnol Adv 2022; 60:108001. [PMID: 35680002 DOI: 10.1016/j.biotechadv.2022.108001] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2022] [Revised: 05/18/2022] [Accepted: 06/01/2022] [Indexed: 11/26/2022]
Abstract
Rhodopseudomonas palustris is an attractive option for biotechnical applications and industrial engineering due to its metabolic versatility and its ability to catabolize a wide variety of feedstocks and convert them to several high-value products. Given its adaptable metabolism, R. palustris has been studied and applied in an extensive variety of applications such as examining metabolic tradeoffs for environmental perturbations, biodegradation of aromatic compounds, environmental remediation, biofuel production, agricultural biostimulation, and bioelectricity production. This review provides a holistic summary of the commercial applications for R. palustris as a biotechnology chassis and suggests future perspectives for research and engineering.
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Affiliation(s)
- Brandi Brown
- Department of Biological Systems Engineering, University of Nebraska-Lincoln, Lincoln, NE 68583, USA
| | - Mark Wilkins
- Department of Biological Systems Engineering, University of Nebraska-Lincoln, Lincoln, NE 68583, USA; Industrial Agricultural Products Center, University of Nebraska-Lincoln, Lincoln, NE 68583, USA; Department of Food Science and Technology, University of Nebraska-Lincoln, Lincoln, NE 68588, USA
| | - Rajib Saha
- Department of Chemical and Biomolecular Engineering, University of Nebraska-Lincoln, Lincoln, NE 68588, USA.
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4
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Tookmanian EM, Belin BJ, Sáenz JP, Newman DK. The role of hopanoids in fortifying rhizobia against a changing climate. Environ Microbiol 2021; 23:2906-2918. [PMID: 33989442 DOI: 10.1111/1462-2920.15594] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2021] [Revised: 05/09/2021] [Accepted: 05/11/2021] [Indexed: 11/30/2022]
Abstract
Bacteria are a globally sustainable source of fixed nitrogen, which is essential for life and crucial for modern agriculture. Many nitrogen-fixing bacteria are agriculturally important, including bacteria known as rhizobia that participate in growth-promoting symbioses with legume plants throughout the world. To be effective symbionts, rhizobia must overcome multiple environmental challenges: from surviving in the soil, to transitioning to the plant environment, to maintaining high metabolic activity within root nodules. Climate change threatens to exacerbate these challenges, especially through fluctuations in soil water potential. Understanding how rhizobia cope with environmental stress is crucial for maintaining agricultural yields in the coming century. The bacterial outer membrane is the first line of defence against physical and chemical environmental stresses, and lipids play a crucial role in determining the robustness of the outer membrane. In particular, structural remodelling of lipid A and sterol-analogues known as hopanoids are instrumental in stress acclimation. Here, we discuss how the unique outer membrane lipid composition of rhizobia may underpin their resilience in the face of increasing osmotic stress expected due to climate change, illustrating the importance of studying microbial membranes and highlighting potential avenues towards more sustainable soil additives.
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Affiliation(s)
- Elise M Tookmanian
- Division of Chemistry & Chemical Engineering, California Institute of Technology, 1200 E California Blvd, Pasadena, CA, 91125, USA
| | - Brittany J Belin
- Department of Embryology, The Carnegie Institution for Science, 3520 San Martin Drive, Baltimore, MD, 21218, USA
| | - James P Sáenz
- B CUBE Center for Molecular Bioengineering, Tatzberg 41, Technische Universität Dresden, Dresden, 01307, Germany
| | - Dianne K Newman
- Division of Biology & Biological Engineering, California Institute of Technology, 1200 E California Blvd, Pasadena, CA, 91125, USA
- Division of Geology & Planetary Sciences, California Institute of Technology, 1200 E California Blvd, Pasadena, CA, 91125, USA
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5
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Molecular and isotopic evidence reveals the end-Triassic carbon isotope excursion is not from massive exogenous light carbon. Proc Natl Acad Sci U S A 2020; 117:30171-30178. [PMID: 33199627 DOI: 10.1073/pnas.1917661117] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The negative organic carbon isotope excursion (CIE) associated with the end-Triassic mass extinction (ETE) is conventionally interpreted as the result of a massive flux of isotopically light carbon from exogenous sources into the atmosphere (e.g., thermogenic methane and/or methane clathrate dissociation linked to the Central Atlantic Magmatic Province [CAMP]). Instead, we demonstrate that at its type locality in the Bristol Channel Basin (UK), the CIE was caused by a marine to nonmarine transition resulting from an abrupt relative sea level drop. Our biomarker and compound-specific carbon isotopic data show that the emergence of microbial mats, influenced by an influx of fresh to brackish water, provided isotopically light carbon to both organic and inorganic carbon pools in centimeter-scale water depths, leading to the negative CIE. Thus, the iconic CIE and the disappearance of marine biota at the type locality are the result of local environmental change and do not mark either the global extinction event or input of exogenous light carbon into the atmosphere. Instead, the main extinction phase occurs slightly later in marine strata, where it is coeval with terrestrial extinctions and ocean acidification driven by CAMP-induced increases in Pco2; these effects should not be conflated with the CIE. An abrupt sea-level fall observed in the Central European basins reflects the tectonic consequences of the initial CAMP emplacement, with broad implications for all extinction events related to large igneous provinces.
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6
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Belin BJ, Tookmanian EM, de Anda J, Wong GCL, Newman DK. Extended Hopanoid Loss Reduces Bacterial Motility and Surface Attachment and Leads to Heterogeneity in Root Nodule Growth Kinetics in a Bradyrhizobium-Aeschynomene Symbiosis. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2019; 32:1415-1428. [PMID: 31170026 PMCID: PMC7583662 DOI: 10.1094/mpmi-04-19-0111-r] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
Hopanoids are steroid-like bacterial lipids that enhance membrane rigidity and promote bacterial growth under diverse stresses. Hopanoid biosynthesis genes are conserved in nitrogen-fixing plant symbionts, and we previously found that the extended (C35) class of hopanoids in Bradyrhizobium diazoefficiens are required for efficient symbiotic nitrogen fixation in the tropical legume host Aeschynomene afraspera. Here, we demonstrate that the nitrogen-fixation defect conferred by extended hopanoid loss can be fully explained by a reduction in root nodule sizes rather than per-bacteroid nitrogen-fixation levels. Using a single-nodule tracking approach to quantify A. afraspera nodule development, we provide a quantitative model of root nodule development in this host, uncovering both the baseline growth parameters for wild-type nodules and a surprising heterogeneity of extended hopanoid mutant developmental phenotypes. These phenotypes include a delay in root nodule initiation and the presence of a subpopulation of nodules with slow growth rates and low final volumes, which are correlated with reduced motility and surface attachment in vitro and lower bacteroid densities in planta, respectively. This work provides a quantitative reference point for understanding the phenotypic diversity of ineffective symbionts in A. afraspera and identifies specific developmental stages affected by extended hopanoid loss for future mechanistic work.
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Affiliation(s)
- Brittany J. Belin
- Division of Biology & Bioengineering, California Institute of Technology, Pasadena, CA, U.S.A
| | - Elise M. Tookmanian
- Division of Chemistry & Chemical Engineering, California Institute of Technology
| | - Jaime de Anda
- Department of Bioengineering, Department of Chemistry and Biochemistry, and California NanoSystems Institute, University of California Los Angeles, Los Angeles, CA, U.S.A
| | - Gerard C. L. Wong
- Division of Geological & Planetary Sciences, California Institute of Technology
| | - Dianne K. Newman
- Division of Biology & Bioengineering, California Institute of Technology, Pasadena, CA, U.S.A
- Division of Geological & Planetary Sciences, California Institute of Technology
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7
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Neubauer C, Sessions AL, Booth IR, Bowen BP, Kopf SH, Newman DK, Dalleska NF. Towards measuring growth rates of pathogens during infections by D 2 O-labeling lipidomics. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2018; 32:2129-2140. [PMID: 30252972 DOI: 10.1002/rcm.8288] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/23/2018] [Revised: 08/10/2018] [Accepted: 09/18/2018] [Indexed: 06/08/2023]
Abstract
RATIONALE Microbial growth rate is an important physiological parameter that is challenging to measure in situ, partly because microbes grow slowly in many environments. Recently, it has been demonstrated that generation times of S. aureus in cystic fibrosis (CF) infections can be determined by D2 O-labeling of actively synthesized fatty acids. To improve species specificity and allow growth rate monitoring for a greater range of pathogens during the treatment of infections, it is desirable to accurately quantify trace incorporation of deuterium into phospholipids. METHODS Lipid extracts of D2 O-treated E. coli cultures were measured on liquid chromatography/electrospray ionization mass spectrometry (LC/ESI-MS) instruments equipped with time-of-flight (TOF) and orbitrap mass analyzers, and used for comparison with the analysis of fatty acids by isotope-ratio gas chromatography (GC)/MS. We then developed an approach to enable tracking of lipid labeling, by following the transition from stationary into exponential growth in pure cultures. Lastly, we applied D2 O-labeling lipidomics to clinical samples from CF patients with chronic lung infections. RESULTS Lipidomics facilitates deuterium quantification in lipids at levels that are useful for many labeling applications (>0.03 at% D). In the E. coli cultures, labeling dynamics of phospholipids depend largely on their acyl chains and between phospholipids we notice differences that are not obvious from absolute concentrations alone. For example, cyclopropyl-containing lipids reflect the regulation of cyclopropane fatty acid synthase, which is predominantly expressed at the beginning of stationary phase. The deuterium incorporation into a lipid that is specific for S. aureus in CF sputum indicates an average generation time of the pathogen on the order of one cell doubling per day. CONCLUSIONS This study demonstrates how trace level measurement of stable isotopes in intact lipids can be used to quantify lipid metabolism in pure cultures and provides guidelines that enable growth rate measurements in microbiome samples after incubation with a low percentage of D2 O.
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Affiliation(s)
- Cajetan Neubauer
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA, 91125, USA
- Division of Geological and Planetary Sciences, California Institute of Technology, CA, 91125, USA
| | - Alex L Sessions
- Division of Geological and Planetary Sciences, California Institute of Technology, CA, 91125, USA
| | - Ian R Booth
- Institute of Medical Sciences, University of Aberdeen, Aberdeen, AB25 2ZD, UK
| | | | - Sebastian H Kopf
- Department of Geological Sciences, University of Colorado, Boulder, CO, 80309, USA
| | - Dianne K Newman
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA, 91125, USA
- Division of Geological and Planetary Sciences, California Institute of Technology, CA, 91125, USA
| | - Nathan F Dalleska
- Environmental Analysis Center, California Institute of Technology, CA, 91125, USA
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8
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Belin BJ, Busset N, Giraud E, Molinaro A, Silipo A, Newman DK. Hopanoid lipids: from membranes to plant-bacteria interactions. Nat Rev Microbiol 2018; 16:304-315. [PMID: 29456243 PMCID: PMC6087623 DOI: 10.1038/nrmicro.2017.173] [Citation(s) in RCA: 96] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Lipid research represents a frontier for microbiology, as showcased by hopanoid lipids. Hopanoids, which resemble sterols and are found in the membranes of diverse bacteria, have left an extensive molecular fossil record. They were first discovered by petroleum geologists. Today, hopanoid-producing bacteria remain abundant in various ecosystems, such as the rhizosphere. Recently, great progress has been made in our understanding of hopanoid biosynthesis, facilitated in part by technical advances in lipid identification and quantification. A variety of genetically tractable, hopanoid-producing bacteria have been cultured, and tools to manipulate hopanoid biosynthesis and detect hopanoids are improving. However, we still have much to learn regarding how hopanoid production is regulated, how hopanoids act biophysically and biochemically, and how their production affects bacterial interactions with other organisms, such as plants. The study of hopanoids thus offers rich opportunities for discovery.
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Affiliation(s)
- Brittany J. Belin
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA, USA
| | - Nicolas Busset
- Institut de Recherche pour le Développement, LSTM, UMR IRD, SupAgro, INRA, University of Montpellier, CIRAD, France
| | - Eric Giraud
- Institut de Recherche pour le Développement, LSTM, UMR IRD, SupAgro, INRA, University of Montpellier, CIRAD, France
| | - Antonio Molinaro
- Department of Chemical Sciences, University of Naples Federico II, Napoli, Italy
| | - Alba Silipo
- Department of Chemical Sciences, University of Naples Federico II, Napoli, Italy
| | - Dianne K. Newman
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA, USA
- Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, USA
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9
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Damsté JSS, Rijpstra WIC, Dedysh SN, Foesel BU, Villanueva L. Pheno- and Genotyping of Hopanoid Production in Acidobacteria. Front Microbiol 2017; 8:968. [PMID: 28642737 PMCID: PMC5462960 DOI: 10.3389/fmicb.2017.00968] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2017] [Accepted: 05/15/2017] [Indexed: 11/28/2022] Open
Abstract
Hopanoids are pentacyclic triterpenoid lipids synthesized by different bacterial groups. Methylated hopanoids were believed to be exclusively synthesized by cyanobacteria and aerobic methanotrophs until the genes encoding for the methylation at the C-2 and C-3 position (hpnP and hpnR) were found to be widespread in the bacterial domain, invalidating their use as specific biomarkers. These genes have been detected in the genome of the Acidobacterium "Ca. Koribacter versatilis," but our knowledge of the synthesis of hopanoids and the presence of genes of their biosynthetic pathway in other member of the Acidobacteria is limited. We analyzed 38 different strains of seven Acidobacteria subdivisions (SDs 1, 3, 4, 6, 8, 10, and 23) for the presence of C30 hopenes and C30+ bacteriohopane polyols (BHPs) using the Rohmer reaction. BHPs and/or C30 hopenes were detected in all strains of SD1 and SD3 but not in SD4 (excepting Chloracidobacterium thermophilum), 6, 8, 10, and 23. This is in good agreement with the presence of genes required for hopanoid biosynthesis in the 31 available whole genomes of cultivated Acidobacteria. All genomes encode the enzymes involved in the non-mevalonate pathway ultimately leading to farnesyl diphosphate but only SD1 and 3 Acidobacteria and C. thermophilum encode all three enzymes required for the synthesis of squalene, its cyclization (shc), and addition and modification of the extended side chain (hpnG, hpnH, hpnI, hpnJ, hpnO). In almost all strains, only tetrafunctionalized BHPs were detected; three strains contained variable relative abundances (up to 45%) of pentafunctionalized BHPs. Only "Ca. K. versatilis" contained methylated hopanoids (i.e., 2,3-dimethyl bishomohopanol), although in low (<10%) amounts. These genes are not present in any other Acidobacterium, consistent with the absence of methylated BHPs in the other examined strains. These data are in agreement with the scattered occurrence of methylated BHPs in other bacterial phyla such as the Alpha-, Beta-, and Gammaproteobacteria and the Cyanobacteria, limiting their biomarker potential. Metagenomes of Acidobacteria were also examined for the presence of genes required for hopanoid biosynthesis. The complete pathway for BHP biosynthesis was evident in SD2 Acidobacteria and a group phylogenetically related to SD1 and SD3, in line with the limited occurrence of BHPs in acidobacterial cultures.
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Affiliation(s)
- Jaap S. Sinninghe Damsté
- Department of Marine Microbiology and Biogeochemistry, NIOZ Royal Netherlands Institute for Sea Research, Utrecht UniversityDen Burg, Netherlands
- Department of Earth Sciences, Geochemistry, Faculty of Geosciences, Utrecht UniversityUtrecht, Netherlands
| | - W. Irene C. Rijpstra
- Department of Marine Microbiology and Biogeochemistry, NIOZ Royal Netherlands Institute for Sea Research, Utrecht UniversityDen Burg, Netherlands
| | - Svetlana N. Dedysh
- S. N. Winogradsky Institute of Microbiology, Research Center of Biotechnology of Russian Academy of SciencesMoscow, Russia
| | - Bärbel U. Foesel
- Department of Microbial Ecology and Diversity Research, German Collection of Microorganisms and Cell Cultures (LG)Braunschweig, Germany
| | - Laura Villanueva
- Department of Marine Microbiology and Biogeochemistry, NIOZ Royal Netherlands Institute for Sea Research, Utrecht UniversityDen Burg, Netherlands
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Bradley AS, Swanson PK, Muller EEL, Bringel F, Caroll SM, Pearson A, Vuilleumier S, Marx CJ. Hopanoid-free Methylobacterium extorquens DM4 overproduces carotenoids and has widespread growth impairment. PLoS One 2017; 12:e0173323. [PMID: 28319163 PMCID: PMC5358736 DOI: 10.1371/journal.pone.0173323] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2016] [Accepted: 02/17/2017] [Indexed: 01/27/2023] Open
Abstract
Hopanoids are sterol-like membrane lipids widely used as geochemical proxies for bacteria. Currently, the physiological role of hopanoids is not well understood, and this represents one of the major limitations in interpreting the significance of their presence in ancient or contemporary sediments. Previous analyses of mutants lacking hopanoids in a range of bacteria have revealed a range of phenotypes under normal growth conditions, but with most having at least an increased sensitivity to toxins and osmotic stress. We employed hopanoid-free strains of Methylobacterium extorquens DM4, uncovering severe growth defects relative to the wild-type under many tested conditions, including normal growth conditions without additional stressors. Mutants overproduce carotenoids-the other major isoprenoid product of this strain-and show an altered fatty acid profile, pronounced flocculation in liquid media, and lower growth yields than for the wild-type strain. The flocculation phenotype can be mitigated by addition of cellulase to the medium, suggesting a link between the function of hopanoids and the secretion of cellulose in M. extorquens DM4. On solid media, colonies of the hopanoid-free mutant strain were smaller than wild-type, and were more sensitive to osmotic or pH stress, as well as to a variety of toxins. The results for M. extorquens DM4 are consistent with the hypothesis that hopanoids are important for membrane fluidity and lipid packing, but also indicate that the specific physiological processes that require hopanoids vary across bacterial lineages. Our work provides further support to emerging observations that the role of hopanoids in membrane robustness and barrier function may be important across lineages, possibly mediated through an interaction with lipid A in the outer membrane.
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Affiliation(s)
- Alexander S. Bradley
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, United States of America
- Department of Earth and Planetary Sciences, Washington University in St Louis, St Louis, MO, United States of America
| | - Paige K. Swanson
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, United States of America
| | - Emilie E. L. Muller
- Equipe Adaptations et interactions microbiennes, Université de Strasbourg, UMR 7156 UNISTRA–CNRS Génétique Moléculaire, Génomique, Microbiologie, Strasbourg, France
| | - Françoise Bringel
- Equipe Adaptations et interactions microbiennes, Université de Strasbourg, UMR 7156 UNISTRA–CNRS Génétique Moléculaire, Génomique, Microbiologie, Strasbourg, France
| | - Sean M. Caroll
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, United States of America
| | - Ann Pearson
- Department of Earth and Planetary Sciences, Harvard University, Cambridge, MA, United States of America
| | - Stéphane Vuilleumier
- Equipe Adaptations et interactions microbiennes, Université de Strasbourg, UMR 7156 UNISTRA–CNRS Génétique Moléculaire, Génomique, Microbiologie, Strasbourg, France
| | - Christopher J. Marx
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, United States of America
- Department of Biological Sciences, University of Idaho, Moscow, ID, United States of America
- Institute for Bioinformatics and Evolutionary Studies, University of Idaho, Moscow, ID, United States of America
- Center for Modeling Complex Interactions, University of Idaho, Moscow, ID, United States of America
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11
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Ricci JN, Morton R, Kulkarni G, Summers ML, Newman DK. Hopanoids play a role in stress tolerance and nutrient storage in the cyanobacterium Nostoc punctiforme. GEOBIOLOGY 2017; 15:173-183. [PMID: 27527874 DOI: 10.1111/gbi.12204] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/19/2016] [Accepted: 07/15/2016] [Indexed: 06/06/2023]
Abstract
Hopanes are abundant in ancient sedimentary rocks at discrete intervals in Earth history, yet interpreting their significance in the geologic record is complicated by our incomplete knowledge of what their progenitors, hopanoids, do in modern cells. To date, few studies have addressed the breadth of diversity of physiological functions of these lipids and whether those functions are conserved across the hopanoid-producing bacterial phyla. Here, we generated mutants in the filamentous cyanobacterium, Nostoc punctiforme, that are unable to make all hopanoids (shc) or 2-methylhopanoids (hpnP). While the absence of hopanoids impedes growth of vegetative cells at high temperature, the shc mutant grows faster at low temperature. This finding is consistent with hopanoids acting as membrane rigidifiers, a function shared by other hopanoid-producing phyla. Apart from impacting fitness under temperature stress, hopanoids are dispensable for vegetative cells under other stress conditions. However, hopanoids are required for stress tolerance in akinetes, a resting survival cell type. While 2-methylated hopanoids do not appear to contribute to any stress phenotype, total hopanoids and to a lesser extent 2-methylhopanoids were found to promote the formation of cyanophycin granules in akinetes. Finally, although hopanoids support symbiotic interactions between Alphaproteobacteria and plants, they do not appear to facilitate symbiosis between N. punctiforme and the hornwort Anthoceros punctatus. Collectively, these findings support interpreting hopanes as general environmental stress biomarkers. If hopanoid-mediated enhancement of nitrogen-rich storage products turns out to be a conserved phenomenon in other organisms, a better understanding of this relationship may help us parse the enrichment of 2-methylhopanes in the rock record during episodes of disrupted nutrient cycling.
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Affiliation(s)
- J N Ricci
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA, USA
| | - R Morton
- Department of Biology, California State University Northridge, Northridge, CA, USA
| | - G Kulkarni
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA, USA
| | - M L Summers
- Department of Biology, California State University Northridge, Northridge, CA, USA
| | - D K Newman
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA, USA
- Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, USA
- Howard Hughes Medical Institute, Pasadena, CA, USA
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12
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Abstract
The structure-function relationship for a family of antimicrobial peptides (AMPs) from the skin of Australian tree frogs is discussed and compared with that of peptide toxins from bee and Australian scorpion venoms. Although these membrane-active peptides induce a similar cellular fate by disrupting the lipid bilayer integrity, their lytic activity is achieved via different modes of action, which are investigated in relation to amino acid sequence, secondary structure, and membrane lipid composition. In order to better understand what structural features govern the interaction between peptides and lipid membranes, cell-penetrating peptides (CPPs), which translocate through the membrane without compromising its integrity, are also discussed. AMPs possess membrane lytic activities that are naturally designed to target the cellular membrane of pathogens or competitors. They are extremely diverse in amino acid composition and often show specificity against a particular strain of microbe. Since our antibiotic arsenal is declining precariously in the face of the rise in multiantibiotic resistance, AMPs increasingly are seen as a promising alternative. In an effort to understand their molecular mechanism, biophysical studies of a myriad of AMPs have been reported, yet no unifying mechanism has emerged, rendering difficult the rational design of drug leads. Similarly, a wide variety of cytotoxic peptides are found in venoms, the best known being melittin, yet again, predicting their activity based on a particular amino acid composition or secondary structure remains elusive. A common feature of these membrane-active peptides is their preference for the lipid environment. Indeed, they are mainly unstructured in solution and, in the presence of lipid membranes, quickly adsorb onto the surface, change their secondary structure, eventually insert into the hydrophobic core of the membrane bilayer, and finally disrupt the bilayer integrity. These steps define the molecular mechanism by which these membrane-active peptides lyse membranes. The last class of membrane-active peptides discussed are the CPPs, which translocate across the lipid bilayer without inducing severe disruption and have potential as drug vehicles. CPPs are typically highly charged and can show antimicrobial activity by targeting an intracellular target rather than via a direct membrane lytic mechanism. A critical aspect in the structure-function relationship of membrane-active peptides is their specific activity relative to the lipid membrane composition of the cell target. Cell membranes have a wide diversity of lipids, and those of eukaryotic and prokaryotic species differ greatly in composition and structure. The activity of AMPs from Australian tree frogs, toxins, and CPPs has been investigated within various lipid systems to assess whether a relationship between peptide and membrane composition could be identified. NMR spectroscopy techniques are being used to gain atomistic details of how these membrane-active peptides interact with model membranes and cells, and in particular, competitive assays demonstrate the difference between affinity and activity for a specific lipid environment. Overall, the interactions between these relatively small sized peptides and various lipid bilayers give insight into how these peptides function at the membrane interface.
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Affiliation(s)
- Marc-Antoine Sani
- School of Chemistry, Bio21
Institute, University of Melbourne, Melbourne, Victoria 3010, Australia
| | - Frances Separovic
- School of Chemistry, Bio21
Institute, University of Melbourne, Melbourne, Victoria 3010, Australia
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13
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Banta AB, Wei JH, Welander PV. A distinct pathway for tetrahymanol synthesis in bacteria. Proc Natl Acad Sci U S A 2015; 112:13478-83. [PMID: 26483502 PMCID: PMC4640766 DOI: 10.1073/pnas.1511482112] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Tetrahymanol is a polycyclic triterpenoid lipid first discovered in the ciliate Tetrahymena pyriformis whose potential diagenetic product, gammacerane, is often used as a biomarker for water column stratification in ancient ecosystems. Bacteria are also a potential source of tetrahymanol, but neither the distribution of this lipid in extant bacteria nor the significance of bacterial tetrahymanol synthesis for interpreting gammacerane biosignatures is known. Here we couple comparative genomics with genetic and lipid analyses to link a protein of unknown function to tetrahymanol synthesis in bacteria. This tetrahymanol synthase (Ths) is found in a variety of bacterial genomes, including aerobic methanotrophs, nitrite-oxidizers, and sulfate-reducers, and in a subset of aquatic and terrestrial metagenomes. Thus, the potential to produce tetrahymanol is more widespread in the bacterial domain than previously thought. However, Ths is not encoded in any eukaryotic genomes, nor is it homologous to eukaryotic squalene-tetrahymanol cyclase, which catalyzes the cyclization of squalene directly to tetrahymanol. Rather, heterologous expression studies suggest that bacteria couple the cyclization of squalene to a hopene molecule by squalene-hopene cyclase with a subsequent Ths-dependent ring expansion to form tetrahymanol. Thus, bacteria and eukaryotes have evolved distinct biochemical mechanisms for producing tetrahymanol.
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Affiliation(s)
- Amy B Banta
- Department of Earth System Science, Stanford University, Stanford, CA 94305
| | - Jeremy H Wei
- Department of Earth System Science, Stanford University, Stanford, CA 94305
| | - Paula V Welander
- Department of Earth System Science, Stanford University, Stanford, CA 94305
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14
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Kulkarni G, Busset N, Molinaro A, Gargani D, Chaintreuil C, Silipo A, Giraud E, Newman DK. Specific hopanoid classes differentially affect free-living and symbiotic states of Bradyrhizobium diazoefficiens. mBio 2015. [PMID: 26489859 DOI: 10.1128/mbio.01251-1215] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/02/2023] Open
Abstract
UNLABELLED A better understanding of how bacteria resist stresses encountered during the progression of plant-microbe symbioses will advance our ability to stimulate plant growth. Here, we show that the symbiotic system comprising the nitrogen-fixing bacterium Bradyrhizobium diazoefficiens and the legume Aeschynomene afraspera requires hopanoid production for optimal fitness. While methylated (2Me) hopanoids contribute to growth under plant-cell-like microaerobic and acidic conditions in the free-living state, they are dispensable during symbiosis. In contrast, synthesis of extended (C35) hopanoids is required for growth microaerobically and under various stress conditions (high temperature, low pH, high osmolarity, bile salts, oxidative stress, and antimicrobial peptides) in the free-living state and also during symbiosis. These defects might be due to a less rigid membrane resulting from the absence of free or lipidA-bound C35 hopanoids or the accumulation of the C30 hopanoid diploptene. Our results also show that C35 hopanoids are necessary for symbiosis only with the host Aeschynomene afraspera but not with soybean. This difference is likely related to the presence of cysteine-rich antimicrobial peptides in Aeschynomene nodules that induce drastic modification in bacterial morphology and physiology. The study of hopanoid mutants in plant symbionts thus provides an opportunity to gain insight into host-microbe interactions during later stages of symbiotic progression, as well as the microenvironmental conditions for which hopanoids provide a fitness advantage. IMPORTANCE Because bradyrhizobia provide fixed nitrogen to plants, this work has potential agronomical implications. An understanding of how hopanoids facilitate bacterial survival in soils and plant hosts may aid the engineering of more robust agronomic strains, especially relevant in regions that are becoming warmer and saline due to climate change. Moreover, this work has geobiological relevance: hopanes, molecular fossils of hopanoids, are enriched in ancient sedimentary rocks at discrete intervals in Earth history. This is the first study to uncover roles for 2Me- and C35 hopanoids in the context of an ecological niche that captures many of the stressful environmental conditions thought to be important during (2Me)-hopane deposition. Though much remains to be done to determine whether the conditions present within the plant host are shared with niches of relevance to the rock record, our findings represent an important step toward identifying conserved mechanisms whereby hopanoids contribute to fitness.
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Affiliation(s)
- Gargi Kulkarni
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, California, USA
| | - Nicolas Busset
- IRD, Laboratoire des Symbioses Tropicales et Méditerranéennes (LSTM), UMR IRD/SupAgro/INRA/UM2/CIRAD, Montpellier, France
| | - Antonio Molinaro
- Dipartimento di Scienze Chimiche, Università di Napoli Federico II, Naples, Italy
| | | | - Clemence Chaintreuil
- IRD, Laboratoire des Symbioses Tropicales et Méditerranéennes (LSTM), UMR IRD/SupAgro/INRA/UM2/CIRAD, Montpellier, France
| | - Alba Silipo
- Dipartimento di Scienze Chimiche, Università di Napoli Federico II, Naples, Italy
| | - Eric Giraud
- IRD, Laboratoire des Symbioses Tropicales et Méditerranéennes (LSTM), UMR IRD/SupAgro/INRA/UM2/CIRAD, Montpellier, France
| | - Dianne K Newman
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, California, USA Howard Hughes Medical Institute, Pasadena, California, USA Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA
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15
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Kulkarni G, Busset N, Molinaro A, Gargani D, Chaintreuil C, Silipo A, Giraud E, Newman DK. Specific hopanoid classes differentially affect free-living and symbiotic states of Bradyrhizobium diazoefficiens. mBio 2015; 6:e01251-15. [PMID: 26489859 PMCID: PMC4620461 DOI: 10.1128/mbio.01251-15] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2015] [Accepted: 09/17/2015] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED A better understanding of how bacteria resist stresses encountered during the progression of plant-microbe symbioses will advance our ability to stimulate plant growth. Here, we show that the symbiotic system comprising the nitrogen-fixing bacterium Bradyrhizobium diazoefficiens and the legume Aeschynomene afraspera requires hopanoid production for optimal fitness. While methylated (2Me) hopanoids contribute to growth under plant-cell-like microaerobic and acidic conditions in the free-living state, they are dispensable during symbiosis. In contrast, synthesis of extended (C35) hopanoids is required for growth microaerobically and under various stress conditions (high temperature, low pH, high osmolarity, bile salts, oxidative stress, and antimicrobial peptides) in the free-living state and also during symbiosis. These defects might be due to a less rigid membrane resulting from the absence of free or lipidA-bound C35 hopanoids or the accumulation of the C30 hopanoid diploptene. Our results also show that C35 hopanoids are necessary for symbiosis only with the host Aeschynomene afraspera but not with soybean. This difference is likely related to the presence of cysteine-rich antimicrobial peptides in Aeschynomene nodules that induce drastic modification in bacterial morphology and physiology. The study of hopanoid mutants in plant symbionts thus provides an opportunity to gain insight into host-microbe interactions during later stages of symbiotic progression, as well as the microenvironmental conditions for which hopanoids provide a fitness advantage. IMPORTANCE Because bradyrhizobia provide fixed nitrogen to plants, this work has potential agronomical implications. An understanding of how hopanoids facilitate bacterial survival in soils and plant hosts may aid the engineering of more robust agronomic strains, especially relevant in regions that are becoming warmer and saline due to climate change. Moreover, this work has geobiological relevance: hopanes, molecular fossils of hopanoids, are enriched in ancient sedimentary rocks at discrete intervals in Earth history. This is the first study to uncover roles for 2Me- and C35 hopanoids in the context of an ecological niche that captures many of the stressful environmental conditions thought to be important during (2Me)-hopane deposition. Though much remains to be done to determine whether the conditions present within the plant host are shared with niches of relevance to the rock record, our findings represent an important step toward identifying conserved mechanisms whereby hopanoids contribute to fitness.
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Affiliation(s)
- Gargi Kulkarni
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, California, USA
| | - Nicolas Busset
- IRD, Laboratoire des Symbioses Tropicales et Méditerranéennes (LSTM), UMR IRD/SupAgro/INRA/UM2/CIRAD, Montpellier, France
| | - Antonio Molinaro
- Dipartimento di Scienze Chimiche, Università di Napoli Federico II, Naples, Italy
| | | | - Clemence Chaintreuil
- IRD, Laboratoire des Symbioses Tropicales et Méditerranéennes (LSTM), UMR IRD/SupAgro/INRA/UM2/CIRAD, Montpellier, France
| | - Alba Silipo
- Dipartimento di Scienze Chimiche, Università di Napoli Federico II, Naples, Italy
| | - Eric Giraud
- IRD, Laboratoire des Symbioses Tropicales et Méditerranéennes (LSTM), UMR IRD/SupAgro/INRA/UM2/CIRAD, Montpellier, France
| | - Dianne K Newman
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, California, USA Howard Hughes Medical Institute, Pasadena, California, USA Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA
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Wörmer L, Lipp JS, Hinrichs KU. Comprehensive Analysis of Microbial Lipids in Environmental Samples Through HPLC-MS Protocols. SPRINGER PROTOCOLS HANDBOOKS 2015. [DOI: 10.1007/8623_2015_183] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
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