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1.
J Phys Chem B ; 126(45): 9271-9287, 2022 Nov 17.
Artigo em Inglês | MEDLINE | ID: mdl-36327977

RESUMO

The Fenna-Matthews-Olson (FMO) complex of green sulfur bacteria has been serving as a prototypical light-harvesting protein for studying excitation energy transfer (EET) dynamics in photosynthesis. The most widely used Frenkel exciton model for FMO complex assumes that each excited bacteriochlorophyll site couples to an identical and isolated harmonic bath, which does not account for the heterogeneous local protein environment. To better describe the realistic environment, we propose to use the recently developed multistate harmonic (MSH) model, which contains a globally shared bath that couples to the different pigment sites according to the atomistic quantum mechanics/molecular mechanics simulations with explicit protein scaffold and solvent. In this work, the effects of heterogeneous protein environment on EET in FMO complexes from Prosthecochloris aestuarii and Chlorobium tepidum, specifically including realistic spectral density, site-dependent reorganization energies, and system-bath couplings are investigated. Semiclassical and mixed quantum-classical mapping dynamics were applied to obtain the nonadiabatic EET dynamics in several models ranging from the Frenkel exciton model to the MSH model and their variants. The MSH model with realistic spectral density and site-dependent system-bath couplings displays slower EET dynamics than the Frenkel exciton model. Our comparative study shows that larger average reorganization energy, heterogeneity in spectral densities, and low-frequency modes could facilitate energy dissipation, which is insensitive to the static disorder in reorganization energies. The effects of the spectral densities and system-bath couplings along with the MSH model can be used to optimize EET dynamics for artificial light-harvesting systems.


Assuntos
Chlorobi , Complexos de Proteínas Captadores de Luz , Complexos de Proteínas Captadores de Luz/metabolismo , Proteínas de Bactérias/metabolismo , Chlorobi/metabolismo , Transferência de Energia , Bacterioclorofilas/metabolismo , Hormônios Estimuladores de Melanócitos/metabolismo
2.
PLoS One ; 17(10): e0275539, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-36227849

RESUMO

The geological record of microbial metabolisms and ecologies primarily consists of stable isotope fractionations and the diagenetic products of biogenic lipids. Carotenoid lipid biomarkers are particularly useful proxies for reconstructing this record, providing information on microbial phototroph primary productivity, redox couples, and oxygenation. The biomarkers okenane, chlorobactane, and isorenieratene are generally considered to be evidence of anoxygenic phototrophs, and provide a record that extends to 1.64 Ga. The utility of the carotenoid biomarker record may be enhanced by examining the carbon isotopic ratios in these products, which are diagnostic for specific pathways of biological carbon fixation found today within different microbial groups. However, this joint inference assumes that microbes have conserved these pathways across the duration of the preserved biomarker record. Testing this hypothesis, we performed phylogenetic analyses of the enzymes constituting the reductive tricarboxylic acid (rTCA) cycle in Chlorobiales, the group of anoxygenic phototrophic bacteria usually implicated in the deposition of chlorobactane and isorenieretane. We find phylogenetically incongruent patterns of inheritance across all enzymes, indicative of horizontal gene transfers to both stem and crown Chlorobiales from multiple potential donor lineages. This indicates that a complete rTCA cycle was independently acquired at least twice within Chlorobiales and was not present in the last common ancestor. When combined with recent molecular clock analyses, these results predict that the Mesoproterzoic lipid biomarker record diagnostic for Chlorobiales should not preserve isotopic fractionations indicative of a full rTCA cycle. Furthermore, we conclude that coupling isotopic and biomarker records is insufficient for reliably reconstructing microbial paleoecologies in the absence of a complementary and consistent phylogenomic narrative.


Assuntos
Chlorobi , Processos Autotróficos , Biomarcadores/metabolismo , Ciclo do Carbono , Isótopos de Carbono/análise , Carotenoides/metabolismo , Lipídeos/genética , Filogenia , Ácidos Tricarboxílicos/metabolismo
3.
Nat Commun ; 13(1): 5824, 2022 Oct 03.
Artigo em Inglês | MEDLINE | ID: mdl-36192412

RESUMO

The photochemical reaction center (RC) features a dimeric architecture for charge separation across the membrane. In green sulfur bacteria (GSB), the trimeric Fenna-Matthews-Olson (FMO) complex mediates the transfer of light energy from the chlorosome antenna complex to the RC. Here we determine the structure of the photosynthetic supercomplex from the GSB Chlorobaculum tepidum using single-particle cryogenic electron microscopy (cryo-EM) and identify the cytochrome c subunit (PscC), two accessory protein subunits (PscE and PscF), a second FMO trimeric complex, and a linker pigment between FMO and the RC core. The protein subunits that are assembled with the symmetric RC core generate an asymmetric photosynthetic supercomplex. One linker bacteriochlorophyll (BChl) is located in one of the two FMO-PscA interfaces, leading to differential efficiencies of the two energy transfer branches. The two FMO trimeric complexes establish two different binding interfaces with the RC cytoplasmic surface, driven by the associated accessory subunits. This structure of the GSB photosynthetic supercomplex provides mechanistic insight into the light excitation energy transfer routes and a possible evolutionary transition intermediate of the bacterial photosynthetic supercomplex from the primitive homodimeric RC.


Assuntos
Chlorobi , Proteínas de Bactérias/metabolismo , Bacterioclorofilas , Chlorobi/metabolismo , Citocromos c/metabolismo , Complexos de Proteínas Captadores de Luz/metabolismo , Subunidades Proteicas/metabolismo
4.
FEMS Microbiol Ecol ; 98(10)2022 Sep 24.
Artigo em Inglês | MEDLINE | ID: mdl-36073352

RESUMO

Anoxygenic photoautotrophic metabolism of green sulfur bacteria of the family Chlorobiaceae played a significant role in establishing the Earth's biosphere. Two known major ecological forms of these phototrophs differ in their pigment composition and, therefore, in color: the green and brown forms. The latter form often occurs in low-light environments and is specialized to harvest blue light, which can penetrate to the greatest depth in the water column. In the present work, metagenomic sequencing was used to investigate the natural population of brown Chl. phaeovibrioides ZM in a marine stratified Zeleny Mys lagoon in the Kandalaksha Bay (the White Sea) to supplement the previously obtained genomes of brown Chlorobiaceae. The genomes of brown and green Chlorobiaceae were investigated using comparative genome analysis and phylogenetic and reconciliation analysis to reconstruct the evolution of these ecological forms. Our results support the suggestion that the last common ancestor of Chlorobiaceae belonged to the brown form, i.e. it was adapted to the conditions of low illumination. However, despite the vertical inheritance of these characteristics, among modern Chlorobiaceae populations, the genes responsible for synthesizing the pigments of the brown form are subject to active horizontal transfer.


Assuntos
Chlorobi , Microbiota , Baías , Chlorobi/genética , Microbiota/genética , Fotossíntese , Filogenia , Água
5.
Chemosphere ; 307(Pt 3): 135944, 2022 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-35961446

RESUMO

A heterotrophic sulfur autotrophic integrated fluidized bed reactor was established for simultaneous and efficient removal of ClO4- and NO3- from water. The optimum operating conditions forecasted through the response surface method (RSM) were the hydraulic retention time (HRT) of 0.50 h, the influent acetate (CH3COO-) concentration of 55 mg/L and the reflux ratio of 14, contributing to ClO4- and NO3- removal of 98.99% and 99.96%, respectively, without secondary pollution caused by residual carbon (NPOC <3.89 mg/L). Meanwhile, the effluent pH fluctuated in a range of 6.70-8.02 and sulfur-containing by-products (i.e., SO42- and S2-) could be controlled by adjusting operation conditions throughout the experimental stage. The increase of the influent CH3COO- concentration reduced the load borne by autotrophic reduction process and further reduced SO42- production. Shortening HRT, increasing the influent CH3COO- concentration and decreasing the reflux ratio could all reduce alkalinity consumption. Shortening HRT and decreasing the reflux ratio could shorten contact time between sulfur and water and thus inhibit S0 disproportionation. High-throughput sequencing result showed that Proteobacteria and Chlorobi were the dominant bacteria. Sulfurovum, Sulfuricurvum and Ignavibacterium were the major heterotrophic denitrifying bacteria (DB)/perchlorate reducing bacteria (PRB), Ferritrophicum and Geothrix were DB, and Chlorobaculum was S0 disproportionation bacteria.


Assuntos
Chlorobi , Percloratos , Processos Autotróficos , Bactérias , Reatores Biológicos/microbiologia , Carbono , Desnitrificação , Nitratos , Óxidos de Nitrogênio , Enxofre/química , Água
6.
PLoS One ; 17(8): e0270187, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35913911

RESUMO

While most productivity on the surface of the Earth today is fueled by oxygenic photosynthesis, for much of Earth history it is thought that anoxygenic photosynthesis-using compounds like ferrous iron or sulfide as electron donors-drove most global carbon fixation. Anoxygenic photosynthesis is still performed by diverse bacteria in niche environments today. Of these, the Chlorobi (formerly green sulfur bacteria) are often interpreted as being particularly ancient and are frequently proposed to have fueled the biosphere during late Archean and early Paleoproterozoic time before the rise of oxygenic photosynthesis. Here, we perform comparative genomic, phylogenetic, and molecular clock analyses to determine the antiquity of the Chlorobi and their characteristic phenotypes. We show that contrary to common assumptions, the Chlorobi clade is relatively young, with anoxygenic phototrophy, carbon fixation via the rTCA pathway, and iron oxidation all significantly postdating the rise of oxygen ~2.3 billion years ago. The Chlorobi therefore could not have fueled the Archean biosphere, but instead represent a relatively young radiation of organisms which likely acquired the capacity for anoxygenic photosynthesis and other traits via horizontal gene transfer sometime after the evolution of oxygenic Cyanobacteria.


Assuntos
Chlorobi , Ciclo do Carbono , Chlorobi/genética , Ferro/metabolismo , Oxigênio/metabolismo , Fotossíntese , Processos Fototróficos , Filogenia
7.
Funct Plant Biol ; 49(6): 573-586, 2022 05.
Artigo em Inglês | MEDLINE | ID: mdl-35413232

RESUMO

In contrast to oxygenic photosynthesis, true anoxygenic photosynthesis is not associated with O2 evolution originated from water photolysis but still converts light energy to that of the phosphoanhydride bonds of ATP. In a narrow sense, anoxygenic photosynthesis is mainly known as to be related to the purple and green sulfur bacteria, but in a broad sense, it also occurs in the vascular plants. The portion of photosynthetic water photolysis that is compensated by the processes of O2 uptake (respiration, photorespiration, Mehler cycle, etc.) may be referred to as 'quasi' anoxygenic photosynthesis. Photoacoustic method allows for the separate detection of photolytic O2 at frequencies of measuring light about 20-40Hz, whereas at 250-400Hz, it detects the photochemical energy storage. We have developed a fast-Fourier transform photoacoustic method enabling measurements of both these signals simultaneously in one sample. This method allows to calculate oxygenic coefficients, which reflect the part of photochemically stored light energy that is used for the water photolysis. We show that the true anoxygenic photosynthesis in Ailanthus altissima Mill. leaves reached very high levels under low light, under moderate light at the beginning of the 1-h period, and at the end of the 40-min period under saturating light.


Assuntos
Ailanthus , Chlorobi , Oxigênio , Fotossíntese , Folhas de Planta , Água
8.
J Bacteriol ; 204(3): e0060521, 2022 03 15.
Artigo em Inglês | MEDLINE | ID: mdl-35225690

RESUMO

Light harvesting and charge separation are functions of chlorophyll and bacteriochlorophyll pigments. While most photosynthetic organisms use (bacterio)chlorophylls with a phytyl (2-phytenyl) group as the hydrophobic isoprenoid tail, Halorhodospira halochloris, an anoxygenic photosynthetic bacterium belonging to Gammaproteobacteria, produces bacteriochlorophylls with a unique 6,7,14,15-tetrahydrogeranylgeranyl (2,10-phytadienyl) tail. Geranylgeranyl reductase (GGR), encoded by the bchP gene, catalyzes hydrogenation at three unsaturated C=C bonds of a geranylgeranyl group, giving rise to the phytyl tail. In this study, we discovered that H. halochloris GGR exhibits only partial hydrogenation activities, resulting in the tetrahydrogeranylgeranyl tail formation. We hypothesized that the hydrogenation activity of H. halochloris GGR differed from that of Chlorobaculum tepidum GGR, which also produces a pigment with partially reduced hydrophobic tails (2,6-phytadienylated chlorophyll a). An engineered GGR was also constructed and demonstrated to perform only single hydrogenation, resulting in the dihydrogeranylgeranyl tail formation. H. halochloris original and variant GGRs shed light on GGR catalytic mechanisms and offer prospective bioengineering tools in the microbial production of isoprenoid compounds. IMPORTANCE Geranylgeranyl reductase (GGR) catalyzes the hydrogenation of carbon-carbon double bonds of unsaturated hydrocarbons of isoprenoid compounds, including α-tocopherols, phylloquinone, archaeal cell membranes, and (bacterio)chlorophyll pigments in various organisms. GGRs in photosynthetic organisms, including anoxygenic phototrophic bacteria, cyanobacteria, and plants perform successive triple hydrogenation to produce chlorophylls and bacteriochlorophylls with a phytyl chain. Here, we demonstrated that the GGR of a gammaproteobacterium Halorhodospira halochloris catalyzed unique double hydrogenation to produce bacteriochlorophylls with a tetrahydrogeranylgeranyl tail. We also constructed a variant enzyme derived from H. halochloris GGR that performs only single hydrogenation. The results of this study provide new insights into catalytic mechanisms of multiposition reductions by a single enzyme.


Assuntos
Bacterioclorofilas , Chlorobi , Bacterioclorofilas/química , Carbono , Chlorobi/metabolismo , Clorofila/química , Clorofila/metabolismo , Clorofila A , Ectothiorhodospiraceae , Hidrogenação , Oxirredutases , Estudos Prospectivos , Proteobactérias/metabolismo , Terpenos
9.
Phys Chem Chem Phys ; 24(4): 2601-2613, 2022 Jan 26.
Artigo em Inglês | MEDLINE | ID: mdl-35029248

RESUMO

Photosynthesis is a highly efficient process, nearly 100 percent of the red photons falling on the surface of leaves reach the reaction center and get transformed into energy. Most theoretical studies on photosynthetic complexes focus mainly on the Fenna-Matthews-Olson complex obtained from green-sulfur bacteria. Quantum coherence was speculated to play a significant role in this very efficient transport process. However, recent reports indicate quantum coherence via exciton transport may not be as relevant as coherence originating via vibronic processes to photosynthesis. Regardless of the origin, there has been a debate on whether quantum coherence results in any speedup of the exciton transport process. To address this we model exciton transport in FMO using a quantum stochastic walk (QSW) with only incoherence, pure dephasing and with both dephasing and incoherence. We find that the QSW model with pure dephasing leads to a substantial speedup in exciton transport as compared to a QSW model which includes both dephasing and incoherence and one which includes only incoherence, both of which experience slowdowns.


Assuntos
Proteínas de Bactérias/química , Elétrons , Complexos de Proteínas Captadores de Luz/química , Chlorobi/química , Transferência de Energia , Teoria Quântica , Processos Estocásticos
10.
Microbiologyopen ; 10(4): e1228, 2021 08.
Artigo em Inglês | MEDLINE | ID: mdl-34459548

RESUMO

The permanently stratified water columns in euxinic meromictic lakes produce niche environments for phototrophic sulfur oxidizers and diverse sulfur metabolisms. While Green Lake (Fayetteville, New York, NY) is known to host a diverse community of ecologically important sulfur bacteria, analyses of its microbial communities, to date, have been largely based on pigment analysis and smaller datasets from Sanger sequencing techniques. Here, we present the results of next-generation sequencing of the eubacterial community in the context of the water column geochemistry. We observed abundant purple and green sulfur bacteria, as well as anoxygenic photosynthesis-capable cyanobacteria within the upper monimolimnion. Amidst the phototrophs, we found other sulfur-cycling bacteria including sulfur disproportionators and chemotrophic sulfur oxidizers, further detailing our understanding of the sulfur cycle and microbial ecology of euxinic, meromictic lakes.


Assuntos
Chlorobi/isolamento & purificação , Chromatiaceae/isolamento & purificação , Cianobactérias/isolamento & purificação , Lagos/microbiologia , Enxofre/metabolismo , Chlorobi/classificação , Chlorobi/genética , Chromatiaceae/classificação , Chromatiaceae/genética , Cianobactérias/classificação , Cianobactérias/genética , Sequenciamento de Nucleotídeos em Larga Escala , Microbiota/genética , New York , RNA Ribossômico 16S/genética , Microbiologia da Água
11.
Int J Mol Sci ; 22(12)2021 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-34203823

RESUMO

There are two main types of bacterial photosynthesis: oxygenic (cyanobacteria) and anoxygenic (sulfur and non-sulfur phototrophs). Molecular mechanisms of photosynthesis in the phototrophic microorganisms can differ and depend on their location and pigments in the cells. This paper describes bacteria capable of molecular oxidizing hydrogen sulfide, specifically the families Chromatiaceae and Chlorobiaceae, also known as purple and green sulfur bacteria in the process of anoxygenic photosynthesis. Further, it analyzes certain important physiological processes, especially those which are characteristic for these bacterial families. Primarily, the molecular metabolism of sulfur, which oxidizes hydrogen sulfide to elementary molecular sulfur, as well as photosynthetic processes taking place inside of cells are presented. Particular attention is paid to the description of the molecular structure of the photosynthetic apparatus in these two families of phototrophs. Moreover, some of their molecular biotechnological perspectives are discussed.


Assuntos
Chlorobi/genética , Chlorobi/fisiologia , Chromatiaceae/genética , Chromatiaceae/fisiologia , Processos Fototróficos/genética , Anaerobiose , Chlorobi/classificação , Chromatiaceae/classificação , Filogenia , Enxofre/metabolismo
12.
Proc Natl Acad Sci U S A ; 118(29)2021 07 20.
Artigo em Inglês | MEDLINE | ID: mdl-34272281

RESUMO

Aromatic carotenoid-derived hydrocarbon biomarkers are ubiquitous in ancient sediments and oils and are typically attributed to anoxygenic phototrophic green sulfur bacteria (GSB) and purple sulfur bacteria (PSB). These biomarkers serve as proxies for the environmental growth requirements of PSB and GSB, namely euxinic waters extending into the photic zone. Until now, prevailing models for environments supporting anoxygenic phototrophs include microbial mats, restricted basins and fjords with deep chemoclines, and meromictic lakes with shallow chemoclines. However, carotenoids have been reported in ancient open marine settings for which there currently are no known modern analogs that host GSB and PSB. The Benguela Upwelling System offshore Namibia, known for exceptionally high primary productivity, is prone to recurrent toxic gas eruptions whereupon hydrogen sulfide emanates from sediments into the overlying water column. These events, visible in satellite imagery as water masses clouded with elemental sulfur, suggest that the Benguela Upwelling System may be capable of supporting GSB and PSB. Here, we compare distributions of biomarkers in the free and sulfur-bound organic matter of Namibian shelf sediments. Numerous compounds-including acyclic isoprenoids, steranes, triterpanes, and carotenoids-were released from the polar lipid fractions upon Raney nickel desulfurization. The prevalence of isorenieratane and ß-isorenieratane in sampling stations along the shelf verified anoxygenic photosynthesis by low-light-adapted, brown-colored GSB in this open marine setting. Renierapurpurane was also present in the sulfur-bound carotenoids and was typically accompanied by lower abundances of renieratane and ß-renierapurpurane, thereby identifying cyanobacteria as an additional aromatic carotenoid source.


Assuntos
Carotenoides/metabolismo , Chlorobi/metabolismo , Chromatiaceae/metabolismo , Sedimentos Geológicos/análise , Sulfetos/análise , Biomarcadores/análise , Biomarcadores/metabolismo , Carotenoides/análise , Ecossistema , Sedimentos Geológicos/microbiologia , Namíbia , Fotossíntese , Água do Mar/análise , Água do Mar/microbiologia , Sulfetos/metabolismo
13.
Biodegradation ; 32(6): 627-642, 2021 12.
Artigo em Inglês | MEDLINE | ID: mdl-34318374

RESUMO

The sulfur autotrophic reduction (SAR) process is promising in co-reduction of perchlorate and nitrate from aqueous solution. To further understand the reaction process, we developed a sulfur autotrophic fluidized bed reactor where the proceeding extent of sulfur (S) disproportionation was predicted by Response surface methodology (RSM) for the first time. Three fundamental reaction parameters including the hydraulic retention time (HRT), co-existing nitrate concentration ([Formula: see text]) and recirculation ratio (R) were considered for reactor optimization. The results demonstrated that S disproportionation was promoted by long HRT and high R, whereas was inhibited by high [Formula: see text]. Also, the optimal HRT, [Formula: see text] and R were 0.50 h, 10.00 mg/L and 14, respectively, the bioreactor can achieve high reduction efficiency of perchlorate and nitrate (> 98.45%), and generate less sulfate (236.07 mg/L). High-throughput sequencing showed that Chlorobaculum was related to S disproportionation, and Sulfurovum was associated with nitrate/perchlorate reducing. All results indicate that the sulfur autotrophic fluidized bed reactor is a promising candidate for the treatment of perchlorate and nitrate wastewater in future practical applications.


Assuntos
Chlorobi , Percloratos , Processos Autotróficos , Biodegradação Ambiental , Reatores Biológicos , Desnitrificação , Nitratos , Enxofre , Água
14.
J Phys Chem B ; 125(30): 8313-8324, 2021 08 05.
Artigo em Inglês | MEDLINE | ID: mdl-34314175

RESUMO

The structural basis for the spectral differences between the Fenna-Matthews-Olson (FMO) proteins from Chlorobaculum tepidum (C. tepidum) and Prosthecochloris aestuarii 2K (P. aestuarii) is yet to be fully understood. Mutation-induced perturbation to the exciton structure and the optical spectra of the complex provide a suitable means to investigate the critical role played by the protein scaffold. In this work, we have performed quantum-mechanics/molecular-mechanics calculations over the molecular dynamics simulation trajectories with the polarized protein-specific charge scheme for both wild-type FMOs and two mutants. Our result reveals that a single-point mutation in the vicinity of BChl 6, namely, W183F of C. tepidum, significantly affects the absorption spectrum, resulting in a switch of the absorption spectrum from type 2, for which the 806 nm band is more pronounced than the 815 nm band, to type 1, for which the 815 nm band is pronounced. Our observations agree with the single-point mutation experiments reported by Saer et al. (Biochim. Biophys. Acta, Bioenerg. 2017, 1858, 288-296) and Khmelnitskiy et al. (J. Phys. Chem. Lett. 2018, 9, 3378-3386). In contrast, the absorption spectrum of the P. aestuarii experiences the opposite transition (from type 1 to type 2) upon the same mutation. Furthermore, by comparing the contributions of individual pigments to the spectra in the wild type and its mutant, we find that a single-point mutation near BChl 6 not only induces changes in excitation energy of BChl 6 per se but also affects the excitonic structures of the neighboring BChls 5 and 7 through strong interpigment electronic couplings, resulting in a significant change in the absorption spectra.


Assuntos
Chlorobi , Proteínas de Bactérias/genética , Chlorobi/metabolismo , Complexos de Proteínas Captadores de Luz/genética , Complexos de Proteínas Captadores de Luz/metabolismo , Simulação de Dinâmica Molecular
15.
Microb Genom ; 7(5)2021 05.
Artigo em Inglês | MEDLINE | ID: mdl-33952388

RESUMO

Endolithic microbial symbionts in the coral skeleton may play a pivotal role in maintaining coral health. However, compared to aerobic micro-organisms, research on the roles of endolithic anaerobic micro-organisms and microbe-microbe interactions in the coral skeleton are still in their infancy. In our previous study, we showed that a group of coral-associated Prosthecochloris (CAP), a genus of anaerobic green sulphur bacteria, was dominant in the skeleton of the coral Isopora palifera. Though CAP is diverse, the 16S rRNA phylogeny presents it as a distinct clade separate from other free-living Prosthecochloris. In this study, we build on previous research and further characterize the genomic and metabolic traits of CAP by recovering two new high-quality CAP genomes - Candidatus Prosthecochloris isoporae and Candidatus Prosthecochloris sp. N1 - from the coral I. palifera endolithic cultures. Genomic analysis revealed that these two CAP genomes have high genomic similarities compared with other Prosthecochloris and harbour several CAP-unique genes. Interestingly, different CAP species harbour various pigment synthesis and sulphur metabolism genes, indicating that individual CAPs can adapt to a diversity of coral microenvironments. A novel high-quality genome of sulfate-reducing bacterium (SRB)- Candidatus Halodesulfovibrio lyudaonia - was also recovered from the same culture. The fact that CAP and various SRB co-exist in coral endolithic cultures and coral skeleton highlights the importance of SRB in the coral endolithic community. Based on functional genomic analysis of Ca. P. sp. N1, Ca. P. isoporae and Ca. H. lyudaonia, we also propose a syntrophic relationship between the SRB and CAP in the coral skeleton.


Assuntos
Antozoários/microbiologia , Chlorobi/classificação , Chlorobi/genética , Chlorobi/metabolismo , Genômica , Filogenia , Sulfatos/metabolismo , Animais , Bactérias/classificação , Bactérias/genética , Bactérias/metabolismo , DNA Bacteriano/genética , Desulfovibrionaceae , Genoma , Metagenoma , RNA Ribossômico 16S/genética
16.
Bioorg Med Chem Lett ; 40: 127931, 2021 05 15.
Artigo em Inglês | MEDLINE | ID: mdl-33705911

RESUMO

Green photosynthetic bacteria with an efficient light-harvesting system contain special chlorophyll molecules, called bacteriochlorophylls c, d, e, in their main antennae. In the biosynthetic pathway, a BciC enzyme is proposed to catalyze the hydrolysis of the C132-methoxycarbonyl group of chlorophyllide a, but the resulting C132-carboxy group has not been detected yet because it is spontaneously removed due to the instability of the ß-keto-carboxylic acid. In this study, the in vitro BciC enzymatic reactions of zinc methyl (131R/S)-hydroxy-mesochlorophyllides a were examined and a carboxylic acid possessing the C132S-OH was first observed as the hydrolyzed product of the C132-COOCH3.


Assuntos
Hidrolases de Éster Carboxílico/metabolismo , Clorofilídeos/metabolismo , Metaloporfirinas/metabolismo , Proteínas de Bactérias/metabolismo , Chlorobi/enzimologia , Clorofilídeos/química , Hidrólise , Metaloporfirinas/química , Estrutura Molecular , Zinco/química
17.
Molecules ; 26(4)2021 Feb 09.
Artigo em Inglês | MEDLINE | ID: mdl-33572047

RESUMO

Linear dichroism (LD) spectroscopy is a widely used technique for studying the mutual orientation of the transition-dipole moments of the electronically excited states of molecular aggregates. Often the method is applied to aggregates where detailed information about the geometrical arrangement of the monomers is lacking. However, for complex molecular assemblies where the monomers are assembled hierarchically in tiers of supramolecular structural elements, the method cannot extract well-founded information about the monomer arrangement. Here we discuss this difficulty on the example of chlorosomes, which are the light-harvesting aggregates of photosynthetic green-(non) sulfur bacteria. Chlorosomes consist of hundreds of thousands of bacteriochlorophyll molecules that self-assemble into secondary structural elements of curved lamellar or cylindrical morphology. We exploit data from polarization-resolved fluorescence-excitation spectroscopy performed on single chlorosomes for reconstructing the corresponding LD spectra. This reveals that LD spectroscopy is not suited for benchmarking structural models in particular for complex hierarchically organized molecular supramolecular assemblies.


Assuntos
Proteínas de Bactérias/química , Bacterioclorofilas/metabolismo , Chlorobi/metabolismo , Complexos de Proteínas Captadores de Luz/química , Organelas/metabolismo , Fotossíntese , Proteínas de Bactérias/metabolismo , Bacterioclorofilas/química , Complexos de Proteínas Captadores de Luz/efeitos da radiação , Fenômenos Ópticos , Espectrometria de Fluorescência
18.
Nat Commun ; 12(1): 830, 2021 02 05.
Artigo em Inglês | MEDLINE | ID: mdl-33547297

RESUMO

In marine and freshwater oxygen-deficient zones, the remineralization of sinking organic matter from the photic zone is central to driving nitrogen loss. Deep blooms of photosynthetic bacteria, which form the suboxic/anoxic chlorophyll maximum (ACM), widespread in aquatic ecosystems, may also contribute to the local input of organic matter. Yet, the influence of the ACM on nitrogen and carbon cycling remains poorly understood. Using a suite of stable isotope tracer experiments, we examined the transformation of nitrogen and carbon under an ACM (comprising of Chlorobiaceae and Synechococcales) and a non-ACM scenario in the anoxic zone of Lake Tanganyika. We find that the ACM hosts a tight coupling of photo/litho-autotrophic and heterotrophic processes. In particular, the ACM was a hotspot of organic matter remineralization that controlled an important supply of ammonium driving a nitrification-anammox coupling, and thereby played a key role in regulating nitrogen loss in the oxygen-deficient zone.


Assuntos
Ciclo do Carbono/fisiologia , Carbono/química , Chlorobi/metabolismo , Ciclo do Nitrogênio/fisiologia , Nitrogênio/química , Synechococcus/metabolismo , Compostos de Amônio/química , Compostos de Amônio/metabolismo , Anaerobiose/fisiologia , Processos Autotróficos , Carbono/metabolismo , Chlorobi/química , Clorofila/química , Clorofila/metabolismo , República Democrática do Congo , Ecossistema , Marcação por Isótopo , Lagos/química , Lagos/microbiologia , Nitrificação/fisiologia , Nitrogênio/metabolismo , Oxirredução , Synechococcus/química , Tanzânia
19.
ISME J ; 15(6): 1569-1584, 2021 06.
Artigo em Inglês | MEDLINE | ID: mdl-33452481

RESUMO

Temperate phages are viruses of bacteria that can establish two types of infection: a lysogenic infection in which the virus replicates with the host cell without producing virions, and a lytic infection where the host cell is eventually destroyed, and new virions are released. While both lytic and lysogenic infections are routinely observed in the environment, the ecological and evolutionary processes regulating these viral dynamics are still not well understood, especially for uncultivated virus-host pairs. Here, we characterized the long-term dynamics of uncultivated viruses infecting green sulfur bacteria (GSB) in a model freshwater lake (Trout Bog Lake, TBL). As no GSB virus has been formally described yet, we first used two complementary approaches to identify new GSB viruses from TBL; one in vitro based on flow cytometry cell sorting, the other in silico based on CRISPR spacer sequences. We then took advantage of existing TBL metagenomes covering the 2005-2018 period to examine the interactions between GSB and their viruses across years and seasons. From our data, GSB populations in TBL were constantly associated with at least 2-8 viruses each, including both lytic and temperate phages. The dominant GSB population in particular was consistently associated with two prophages with a nearly 100% infection rate for >10 years. We illustrate with a theoretical model that such an interaction can be stable given a low, but persistent, level of prophage induction in low-diversity host populations. Overall, our data suggest that lytic and lysogenic viruses can readily co-infect the same host population, and that host strain-level diversity might be an important factor controlling virus-host dynamics including lytic/lysogeny switch.


Assuntos
Bacteriófagos , Chlorobi , Viroses , Bacteriófagos/genética , Humanos , Lisogenia , Prófagos
20.
Can J Microbiol ; 67(4): 332-341, 2021 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-33136441

RESUMO

Hot Lake is a small heliothermal and hypersaline lake in far north-central Washington State (USA) and is limnologically unusual because MgSO4 rather than NaCl is the dominant salt. In late summer, the Hot Lake metalimnion becomes distinctly green from blooms of planktonic phototrophs. In a study undertaken over 60 years ago, these blooms were predicted to include green sulfur bacteria, but no cultures were obtained. We sampled Hot Lake and established enrichment cultures for phototrophic sulfur bacteria in MgSO4-rich sulfidic media. Most enrichments turned green or red within 2 weeks, and from green-colored enrichments, pure cultures of a lobed green sulfur bacterium (phylum Chlorobi) were isolated. Phylogenetic analyses showed the organism to be a species of the prosthecate green sulfur bacterium Prosthecochloris. Cultures of this Hot Lake phototroph were halophilic and tolerated high levels of sulfide and MgSO4. In addition, unlike all recognized species of Prosthecochloris, the Hot Lake isolates grew at temperatures up to 45 °C, indicating an adaptation to the warm summer temperatures of the lake. Photoautotrophy by Hot Lake green sulfur bacteria may contribute dissolved organic matter to anoxic zones of the lake, and their diazotrophic capacity may provide a key source of bioavailable nitrogen, as well.


Assuntos
Chlorobi/isolamento & purificação , Chlorobi/fisiologia , Lagos/microbiologia , Chlorobi/classificação , Temperatura Alta , Lagos/química , Sulfato de Magnésio/análise , Sulfato de Magnésio/metabolismo , Fixação de Nitrogênio , Processos Fototróficos , Filogenia , Estações do Ano , Sulfetos/análise , Sulfetos/metabolismo , Washington
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