scholarly journals A TonB-dependent receptor constitutes the outer membrane transport system for a lignin-derived aromatic compound

2019 ◽  
Vol 2 (1) ◽  
Author(s):  
Masaya Fujita ◽  
Kosuke Mori ◽  
Hirofumi Hara ◽  
Shojiro Hishiyama ◽  
Naofumi Kamimura ◽  
...  
Keyword(s):  
Vitamin B12 ◽  
Outer Membrane ◽  
Membrane Transport ◽  
Aromatic Compounds ◽  
Proton Motive Force ◽  
Negative Bacterium ◽  
Chemical Production ◽  
Gram Negative ◽  
Tonb System ◽  
Important Basis

AbstractTonB-dependent receptors (TBDRs) mediate substrate-specific transport across the outer membrane, utilizing energy derived from the proton motive force transmitted from the TonB−ExbB−ExbD complex located in the inner membrane (TonB system). Although a number of TonB systems involved in the uptake of siderophores, vitamin B12 and saccharides have been identified, their involvement in the uptake and catabolism of aromatic compounds was previously unknown. Here, we show that the outer membrane transport of a biphenyl compound derived from lignin is mediated by the TonB system in a Gram-negative bacterium capable of degrading lignin-derived aromatic compounds, Sphingobium sp. strain SYK-6. Furthermore, we found that overexpression of the corresponding TBDR gene enhanced the uptake of this biphenyl compound, contributing to the improved rate of platform chemical production. Our results will provide an important basis for establishing engineered strains optimized for use in lignin valorisation.

scholarly journals New Type of Outer Membrane Vesicle Produced by the Gram-Negative Bacterium Shewanella vesiculosa M7T: Implications for DNA Content

2013 ◽  
Vol 79 (6) ◽  
pp. 1874-1881 ◽  
Author(s):  
Carla Pérez-Cruz ◽  
Ornella Carrión ◽  
Lidia Delgado ◽  
Gemma Martinez ◽  
Carmen López-Iglesias ◽  
...  
Keyword(s):  
Outer Membrane ◽  
Dna Content ◽  
Membrane Vesicle ◽  
Membrane Vesicles ◽  
Freeze Substitution ◽  
Outer Membrane Vesicles ◽  
Negative Bacterium ◽  
Inner Membrane ◽  
Gram Negative ◽  
Content Type

ABSTRACTOuter membrane vesicles (OMVs) from Gram-negative bacteria are known to be involved in lateral DNA transfer, but the presence of DNA in these vesicles has remained difficult to explain. An ultrastructural study of the Antarctic psychrotolerant bacteriumShewanella vesiculosaM7Thas revealed that this Gram-negative bacterium naturally releases conventional one-bilayer OMVs through a process in which the outer membrane is exfoliated and only the periplasm is entrapped, together with a more complex type of OMV, previously undescribed, which on formation drag along inner membrane and cytoplasmic content and can therefore also entrap DNA. These vesicles, with a double-bilayer structure and containing electron-dense material, were visualized by transmission electron microscopy (TEM) after high-pressure freezing and freeze-substitution (HPF-FS), and their DNA content was fluorometrically quantified as 1.8 ± 0.24 ng DNA/μg OMV protein. The new double-bilayer OMVs were estimated by cryo-TEM to represent 0.1% of total vesicles. The presence of DNA inside the vesicles was confirmed by gold DNA immunolabeling with a specific monoclonal IgM against double-stranded DNA. In addition, a proteomic study of purified membrane vesicles confirmed the presence of plasma membrane and cytoplasmic proteins in OMVs from this strain. Our data demonstrate the existence of a previously unobserved type of double-bilayer OMV in the Gram-negative bacteriumShewanella vesiculosaM7Tthat can incorporate DNA, for which we propose the name outer-inner membrane vesicle (O-IMV).

scholarly journals Expression and Porin Activity of P28 and OMP-1F during Intracellular Ehrlichia chaffeensis Development

2008 ◽  
Vol 190 (10) ◽  
pp. 3597-3605 ◽  
Author(s):  
Yumi Kumagai ◽  
Haibin Huang ◽  
Yasuko Rikihisa
Keyword(s):  
Nutrient Uptake ◽  
Outer Membrane ◽  
Growth Phase ◽  
Exponential Growth ◽  
Outer Membrane Proteins ◽  
Exponential Growth Phase ◽  
Ehrlichia Chaffeensis ◽  
Negative Bacterium ◽  
Gram Negative ◽  
Pore Sizes

ABSTRACT Ehrlichia chaffeensis, an obligatory intracellular gram-negative bacterium, must take up various nutrients and metabolic compounds because it lacks many genes involved in metabolism. Nutrient uptake by a gram-negative bacterium occurs primarily through pores or channels in the bacterial outer membrane. Here we demonstrate that isolated E. chaffeensis outer membranes have porin activities, as determined by a proteoliposome swelling assay. The activity was partially blocked by an antibody that recognizes the two most abundant outer membrane proteins, P28/OMP-19 and OMP-1F/OMP-18. Both proteins were predicted to have structural features characteristic of porins, including 12 transmembrane segments comprised of amphipathic and antiparallel β-strands. The sodium dodecyl sulfate stability of the two proteins was consistent with a β-barrel structure. Isolated native P28 and OMP-1F exhibited porin activities, with pore sizes similar to and larger than, respectively, that of OprF, which is the porin with the largest pore size known to date. E. chaffeensis experiences temperature changes during transmission by ticks. During the intracellular development of E. chaffeensis, both P28 and OMP-1F were expressed mostly in the mid-exponential growth phase at 37°C and the late-exponential growth phase at 28°C. The porin activity of proteoliposomes reconstituted with proteins from the outer membrane fractions derived from bacteria in the mid- and late-exponential growth phases at 28°C and 37°C correlated with the expression levels of P28 and OMP-1F. These results imply that P28 and OMP-1F function as porins with large pore sizes, suggesting that the differential expression of these two proteins might regulate nutrient uptake during intracellular E. chaffeensis development at both temperatures.

scholarly journals Functional roles of multiple Ton complex genes in a Sphingobium degrader of lignin-derived aromatic compounds

2021 ◽  
Author(s):  
Masaya Fujita ◽  
Shodai Yano ◽  
Koki Shibata ◽  
Mizuki Kondo ◽  
Shojiro Hishiyama ◽  
...  
Keyword(s):  
Outer Membrane ◽  
Membrane Transport ◽  
Membrane Integrity ◽  
Uptake System ◽  
Chemical Production ◽  
Microbial Conversion ◽  
Uptake Capacity ◽  
Lignin Valorization ◽  
Functional Roles ◽  
Derivative Strain

TonB-dependent transporters (TBDTs) mediate outer membrane transport of nutrients using the energy derived from proton motive force transmitted from the TonB-ExbB-ExbD complex localized in the inner membrane. Recently, we discovered ddvT encoding a TBDT responsible for the uptake of a 5,5-type lignin-derived dimer in Sphingobium sp. strain SYK-6. Furthermore, overexpression of ddvT in an SYK-6-derivative strain enhanced its uptake capacity, improving the rate of platform chemical production. Thus, understanding the uptake system of lignin-derived aromatics is fundamental for microbial conversion-based lignin valorization. Here we examined whether multiple tonB-, exbB-, and exbD-like genes in SYK-6 contribute to the outer membrane transport of lignin-derived aromatics. The disruption of tonB2-6 and exbB3 did not reduce the capacity of SYK-6 to convert or grow on lignin-derived aromatics. In contrast, the introduction of the tonB1-exbB1-exbD1-exbD2 operon genes into SYK-6, which could not be disrupted, promoted the conversion of β-O-4-, β-5-, β-1-, β-β-, and 5,5-type dimers and monomers, such as ferulate, vanillate, syringate, and protocatechuate. These results suggest that TonB-dependent uptake involving the tonB1 operon genes is responsible for the outer membrane transport of the above aromatics. Additionally, exbB2/tolQ and exbD3/tolR were suggested to constitute the Tol-Pal system that maintains the outer membrane integrity.

scholarly journals The TonB Dimeric Crystal Structures Do Not Exist In Vivo

mBio ◽  
2010 ◽  
Vol 1 (5) ◽  
Author(s):  
Kathleen Postle ◽  
Kyle A. Kastead ◽  
Michael G. Gresock ◽  
Joydeep Ghosh ◽  
Cheryl D. Swayne
Keyword(s):  
Outer Membrane ◽  
Crystal Structures ◽  
Cytoplasmic Membrane ◽  
Proton Motive Force ◽  
Membrane Transporters ◽  
Motive Force ◽  
Carboxy Terminus ◽  
Tonb System ◽  
Outer Membrane Transporters

ABSTRACTThe TonB system energizes transport of nutrients across the outer membrane ofEscherichia coliusing cytoplasmic membrane proton motive force (PMF) for energy. Integral cytoplasmic membrane proteins ExbB and ExbD appear to harvest PMF and transduce it to TonB. The carboxy terminus of TonB then physically interacts with outer membrane transporters to allow translocation of ligands into the periplasmic space. The structure of the TonB carboxy terminus (residues ~150 to 239) has been solved several times with similar results. Our previous results hinted thatin vitrostructures might not mimic the dimeric conformations that characterize TonBin vivo. To test structural predictions and to identify irreplaceable residues, the entire carboxy terminus of TonB was scanned with Cys substitutions. TonB I232C and N233C, predicted to efficiently form disulfide-linked dimers in the crystal structures, did not do so. In contrast, Cys substitutions positioned at large distances from one another in the crystal structures efficiently formed dimers. Cys scanning identified seven functionally important residues. However, no single residue was irreplaceable. The phenotypes conferred by changes of the seven residues depended on both the specific assay used and the residue substituted. All seven residues were synergistic with one another. The buried nature of the residues in the structures was also inconsistent with these properties. Taken together, these results indicate that the solved dimeric crystal structures of TonB do not exist. The most likely explanation for the aberrant structures is that they were obtained in the absence of the TonB transmembrane domain, ExbB, ExbD, and/or the PMF.IMPORTANCEThe TonB system of Gram-negative bacteria is an attractive target for development of novel antibiotics because of its importance in iron acquisition and virulence. Logically, therefore, the structure of TonB must be accurately understood. TonB functions as a dimerin vivo, and two different but similar crystal structures of the dimeric carboxy-terminal ~90 amino acids gave rise to mechanistic models. Here we demonstrate that the crystal structures, and therefore the models based on them, are not biologically relevant. The idiosyncratic phenotypes conferred by substitutions at the only seven functionally important residues in the carboxy terminus suggest that similar to interaction of cytochromes P450 with numerous substrates, these residues allow TonB to differentially interact with different outer membrane transporters. Taken together, data suggest that TonB is maintained poised between order and disorder by ExbB, ExbD, and the proton motive force (PMF) before energy transduction to the outer membrane transporters.

scholarly journals Draft Genome Sequence of the Bacterium Paraburkholderia aromaticivorans AR20-38, a Gram-Negative, Cold-Adapted Degrader of Aromatic Compounds

2020 ◽  
Vol 9 (27) ◽  
Author(s):  
Caroline Poyntner ◽  
Dechao Zhang ◽  
Rosa Margesin
Keyword(s):  
Forest Soil ◽  
Genome Sequence ◽  
Aromatic Compounds ◽  
Draft Genome ◽  
Draft Genome Sequence ◽  
Negative Bacterium ◽  
Gram Negative ◽  
Content Type ◽  
Cold Adapted ◽  
Alpine Forest

ABSTRACT Here, we report the draft genome sequence of Paraburkholderia aromaticivorans strain AR20-38, a cold-adapted Gram-negative bacterium. It was isolated from Alpine forest soil and can degrade a range of aromatic compounds.

scholarly journals Phosphatidylethanolamine distribution and fluidity in outer and inner membranes of the gram-negative bacterium Erwinia carotovora

1980 ◽  
Vol 188 (1) ◽  
pp. 131-135 ◽  
Author(s):  
S D Shukla ◽  
C Green ◽  
J M Turner
Keyword(s):  
Outer Membrane ◽  
External Surface ◽  
Internal Surface ◽  
Erwinia Carotovora ◽  
Negative Bacterium ◽  
Membrane Structures ◽  
Membrane Bilayer ◽  
Inner Membrane ◽  
Gram Negative ◽  
Internal Surfaces

1. The distribution of phosphatidylethanolamine, the major lipid of Erwinia carotovora, was investigated in intact bacteria, spheroplasts and outer- and inner-membrane preparations, with the amino-group reagent 2,4,6-trinitrobenzenesulphonic acid. Only 4% was found on the external surface of the outer membrane with 30% on the internal surface, whereas the inner membrane had 27 and 38% on its external and internal surfaces respectively. Some comparative studies were made with three other bacteria. 2. The fluidity of the membranes of E. carotovora was studied by using the fluorescent probe 1,6-diphenylhexa-1,3,5-triene. Results were consistent with the hydrocarbon region of the outer membrane bilayer being less fluid than that of the inner one. 3. On the basis of these and other results a model for the outer- and inner-membrane structures of E. carotovora is proposed.

Sign in / Sign up

Export Citation Format

Share Document