Diverse high-torque bacterial flagellar motors assemble wider stator rings using a conserved protein scaffold

Although it is known that diverse bacterial flagellar motors produce different torques, the mechanism underlying torque variation is unknown. To understand this difference better, we combined genetic analyses with electron cryo-tomography subtomogram averaging to determine in situ structures of flagellar motors that produce different torques, fromCampylobacterandVibriospecies. For the first time, to our knowledge, our results unambiguously locate the torque-generating stator complexes and show that diverse high-torque motors use variants of an ancestrally related family of structures to scaffold incorporation of additional stator complexes at wider radii from the axial driveshaft than in the model enteric motor. We identify the protein components of these additional scaffold structures and elucidate their sequential assembly, demonstrating that they are required for stator-complex incorporation. These proteins are widespread, suggesting that different bacteria have tailored torques to specific environments by scaffolding alternative stator placement and number. Our results quantitatively account for different motor torques, complete the assignment of the locations of the major flagellar components, and provide crucial constraints for understanding mechanisms of torque generation and the evolution of multiprotein complexes.

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Correction for Beeby et al., Diverse high-torque bacterial flagellar motors assemble wider stator rings using a conserved protein scaffold

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1605597113 ◽

2016 ◽

Vol 113 (19) ◽

pp. E2759-E2759

Keyword(s):

Protein Scaffold ◽

Flagellar Motors ◽

High Torque

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Probing the Dynamic Self-Assembly Behaviour of Photoswitchable Wormlike Micelles in Real Time

10.26434/chemrxiv.7098695 ◽

2018 ◽

Author(s):

Elaine A. Kelly ◽

Judith E. Houston ◽

Rachel Evans

Keyword(s):

Real Time ◽

Absorption Spectroscopy ◽

Self Assembly ◽

Uv Light ◽

Wormlike Micelles ◽

Tetraethylene Glycol ◽

Light Illumination ◽

First Time ◽

Dependent Processes

Understanding the dynamic self-assembly behaviour of azobenzene photosurfactants (AzoPS) is crucial to advance their use in controlled release applications such asdrug delivery and micellar catalysis. Currently, their behaviour in the equilibrium cis-and trans-photostationary states is more widely understood than during the photoisomerisation process itself. Here, we investigate the time-dependent self-assembly of the different photoisomers of a model neutral AzoPS, <a>tetraethylene glycol mono(4′,4-octyloxy,octyl-azobenzene) </a>(C8AzoOC8E4) using small-angle neutron scattering (SANS). We show that the incorporation of in-situUV-Vis absorption spectroscopy with SANS allows the scattering profile, and hence micelle shape, to be correlated with the extent of photoisomerisation in real-time. It was observed that C8AzoOC8E4could switch between wormlike micelles (transnative state) and fractal aggregates (under UV light), with changes in the self-assembled structure arising concurrently with changes in the absorption spectrum. Wormlike micelles could be recovered within 60 seconds of blue light illumination. To the best of our knowledge, this is the first time the degree of AzoPS photoisomerisation has been tracked in-situthrough combined UV-Vis absorption spectroscopy-SANS measurements. This technique could be widely used to gain mechanistic and kinetic insights into light-dependent processes that are reliant on self-assembly.

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The Total Synthesis of Rhabdastrellic Acid A

10.26434/chemrxiv.7479944 ◽

2018 ◽

Author(s):

Yaroslav Boyko ◽

Christopher Huck ◽

David Sarlah

Keyword(s):

Total Synthesis ◽

Late Stage ◽

Cross Coupling ◽

Side Chains ◽

General Strategy ◽

Modular Approach ◽

Linear Sequence ◽

Generating Sequence ◽

First Time

<div>The first total synthesis of rhabdastrellic acid A, a highly cytotoxic isomalabaricane triterpenoid, has been accomplished in a linear sequence of 14 steps from commercial geranylacetone. The prominently strained trans-syn-trans-perhydrobenz[e]indene core characteristic of the isomalabaricanes is efficiently accessed in a selective manner for the first time through a rapid, complexity-generating sequence incorporating a reductive radical polyene cyclization, an unprecedented oxidative Rautenstrauch cycloisomerization, and umpolung 𝛼-substitution of a p-toluenesulfonylhydrazone with in situ reductive transposition. A late-stage cross-coupling in concert with a modular approach to polyunsaturated side chains renders this a general strategy for the synthesis of numerous family members of these synthetically challenging and hitherto inaccessible marine triterpenoids.</div>

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In situ structure and organization of the influenza C virus surface glycoprotein

Nature Communications ◽

10.1038/s41467-021-21818-9 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Steinar Halldorsson ◽

Kasim Sader ◽

Jack Turner ◽

Lesley J. Calder ◽

Peter B. Rosenthal

Keyword(s):

Membrane Fusion ◽

Hexagonal Lattice ◽

Surface Glycoprotein ◽

Structural Basis ◽

Virus Surface ◽

The Matrix ◽

Influenza C Virus ◽

Subtomogram Averaging ◽

Electron Cryotomography

AbstractThe lipid-enveloped influenza C virus contains a single surface glycoprotein, the haemagglutinin-esterase-fusion (HEF) protein, that mediates receptor binding, receptor destruction, and membrane fusion at the low pH of the endosome. Here we apply electron cryotomography and subtomogram averaging to describe the structural basis for hexagonal lattice formation by HEF on the viral surface. The conformation of the glycoprotein in situ is distinct from the structure of the isolated trimeric ectodomain, showing that a splaying of the membrane distal domains is required to mediate contacts that form the lattice. The splaying of these domains is also coupled to changes in the structure of the stem region which is involved in membrane fusion, thereby linking HEF’s membrane fusion conformation with its assembly on the virus surface. The glycoprotein lattice can form independent of other virion components but we show a major role for the matrix layer in particle formation.

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Engineered Phage Endolysin Eliminates Gardnerella Biofilm without Damaging Beneficial Bacteria in Bacterial Vaginosis Ex Vivo

Pathogens ◽

10.3390/pathogens10010054 ◽

2021 ◽

Vol 10 (1) ◽

pp. 54

Author(s):

Christine Landlinger ◽

Lenka Tisakova ◽

Vera Oberbauer ◽

Timo Schwebs ◽

Abbas Muhammad ◽

...

Keyword(s):

Bacterial Vaginosis ◽

Bactericidal Activity ◽

High Selectivity ◽

Ex Vivo ◽

Vaginal Microbiome ◽

Wild Type ◽

Wild Type Enzyme ◽

Promising Alternative ◽

First Time

Bacterial vaginosis is characterized by an imbalance of the vaginal microbiome and a characteristic biofilm formed on the vaginal epithelium, which is initiated and dominated by Gardnerella bacteria, and is frequently refractory to antibiotic treatment. We investigated endolysins of the type 1,4-beta-N-acetylmuramidase encoded on Gardnerella prophages as an alternative treatment. When recombinantly expressed, these proteins demonstrated strong bactericidal activity against four different Gardnerella species. By domain shuffling, we generated several engineered endolysins with 10-fold higher bactericidal activity than any wild-type enzyme. When tested against a panel of 20 Gardnerella strains, the most active endolysin, called PM-477, showed minimum inhibitory concentrations of 0.13–8 µg/mL. PM-477 had no effect on beneficial lactobacilli or other species of vaginal bacteria. Furthermore, the efficacy of PM-477 was tested by fluorescence in situ hybridization on vaginal samples of fifteen patients with either first time or recurring bacterial vaginosis. In thirteen cases, PM-477 killed the Gardnerella bacteria and physically dissolved the biofilms without affecting the remaining vaginal microbiome. The high selectivity and effectiveness in eliminating Gardnerella, both in cultures of isolated strains as well as in clinically derived samples of natural polymicrobial biofilms, makes PM-477 a promising alternative to antibiotics for the treatment of bacterial vaginosis, especially in patients with frequent recurrence.

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Chromosomal painting of the sandpiper (Actitis macularius) detects several fissions for the Scolopacidae family (Charadriiformes)

BMC Ecology and Evolution ◽

10.1186/s12862-020-01737-x ◽

2021 ◽

Vol 21 (1) ◽

Author(s):

Melquizedec Luiz Silva Pinheiro ◽

Cleusa Yoshiko Nagamachi ◽

Talita Fernanda Augusto Ribas ◽

Cristovam Guerreiro Diniz ◽

Patricia Caroline Mary O´Brien ◽

...

Keyword(s):

Chromosome Painting ◽

Diploid Number ◽

Chromosomal Evolution ◽

Long Distance ◽

Chromosomal Painting ◽

Cytogenetic Studies ◽

Burhinus Oedicnemus ◽

Clear Idea ◽

First Time

Abstract Background The Scolopacidae family (Suborder Scolopaci, Charadriiformes) is composed of sandpipers and snipes; these birds are long-distance migrants that show great diversity in their behavior and habitat use. Cytogenetic studies in the Scolopacidae family show the highest diploid numbers for order Charadriiformes. This work analyzes for the first time the karyotype of Actitis macularius by classic cytogenetics and chromosome painting. Results The species has a diploid number of 92, composed mostly of telocentric pairs. This high 2n is greater than the proposed 80 for the avian ancestral putative karyotype (a common feature among Scolopaci), suggesting that fission rearrangements have formed smaller macrochromosomes and microchromosomes. Fluorescence in situ hybridization using Burhinus oedicnemus whole chromosome probes confirmed the fissions in pairs 1, 2, 3, 4 and 6 of macrochromosomes. Conclusion Comparative analysis with other species of Charadriiformes studied by chromosome painting together with the molecular phylogenies for the order allowed us to raise hypotheses about the chromosomal evolution in suborder Scolopaci. From this, we can establish a clear idea of how chromosomal evolution occurred in this suborder.

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Stretchable supercapacitor at −30 °C

Energy & Environmental Science ◽

10.1039/d0ee04066e ◽

2021 ◽

Author(s):

Xuting Jin ◽

Li Song ◽

Hongsheng Yang ◽

Chunlong Dai ◽

Yukun Xiao ◽

...

Keyword(s):

First Time

A stretchable supercapacitor at −30 °C was developed for the first time by in situ growth of polyaniline onto the newly-designed anti-freezing organohydrogel polyelectrolyte.

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Direct TEM observation of the “acanthite α-Ag2S–argentite β-Ag2S” phase transition in a silver sulfide nanoparticle

Nanoscale Advances ◽

10.1039/c8na00347e ◽

2019 ◽

Vol 1 (4) ◽

pp. 1581-1588 ◽

Cited By ~ 6

Author(s):

S. I. Sadovnikov ◽

E. Yu. Gerasimov

Keyword(s):

Electron Microscopy ◽

Phase Transition ◽

Transmission Electron Microscopy ◽

Silver Sulfide ◽

Transmission Electron ◽

Silver Sulfide Nanoparticles ◽

Microscopy Method ◽

Electron Microscopy Method ◽

First Time

For the first time, the α-Ag2S (acanthite)–β-Ag2S (argentite) phase transition in a single silver sulfide nanoparticles has been observed in situ using a high-resolution transmission electron microscopy method in real time.

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Microbial N2O consumption in and above marine N2O production hotspots

The ISME Journal ◽

10.1038/s41396-020-00861-2 ◽

2020 ◽

Author(s):

Xin Sun ◽

Amal Jayakumar ◽

John C. Tracey ◽

Elizabeth Wallace ◽

Colette L. Kelly ◽

...

Keyword(s):

Kinetic Parameters ◽

Substrate Affinity ◽

N2o Production ◽

Anoxic Waters ◽

Production And Consumption ◽

Consumption Rates ◽

Anoxic Zones ◽

First Time ◽

Microbial N

AbstractThe ocean is a net source of N2O, a potent greenhouse gas and ozone-depleting agent. However, the removal of N2O via microbial N2O consumption is poorly constrained and rate measurements have been restricted to anoxic waters. Here we expand N2O consumption measurements from anoxic zones to the sharp oxygen gradient above them, and experimentally determine kinetic parameters in both oxic and anoxic seawater for the first time. We find that the substrate affinity, O2 tolerance, and community composition of N2O-consuming microbes in oxic waters differ from those in the underlying anoxic layers. Kinetic parameters determined here are used to model in situ N2O production and consumption rates. Estimated in situ rates differ from measured rates, confirming the necessity to consider kinetics when predicting N2O cycling. Microbes from the oxic layer consume N2O under anoxic conditions at a much faster rate than microbes from anoxic zones. These experimental results are in keeping with model results which indicate that N2O consumption likely takes place above the oxygen deficient zone (ODZ). Thus, the dynamic layer with steep O2 and N2O gradients right above the ODZ is a previously ignored potential gatekeeper of N2O and should be accounted for in the marine N2O budget.

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Some Palaeoliths from South Arabia

Proceedings of the Prehistoric Society ◽

10.1017/s0079497x00017953 ◽

1954 ◽

Vol 19 (2) ◽

pp. 189-218 ◽

Cited By ~ 16

Author(s):

G. Caton-Thompson

Keyword(s):

Geographical Society ◽

South Arabia ◽

First Time ◽

Do So

The material here described was found in the Hadhramaut by Elinor Gardner and myself between November 1937 and March 1938. My personal investigation of the Palaeolithic Age was limited by pre-Islamic excavations, and I am therefore indebted to her for the gathering of most of the specimens in situ in terrace gravels, and to her detailed study of their positions.The collection consists mainly of groups from four fairly widely separated localities; the physiography of these has already been outlined in a comprehensive paper published in the Geographical Journal. Whenever appropriate to the purpose of this account, which is to place for the first time on illustrated record all we observed about the palaeoliths, I have reused in this different context illustrations of Quaternary environment which appeared in that Journal. With thanks I acknowledge the permission of the Royal Geographical Society to do so.

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