Összes szerző

Longauer Beáta

az alábbi absztraktok szerzői között szerepel:

Barkó Szilvia
Phalloidin as a bacterial actin-labeling agent

Aug 28 - szerda

13:30 – 15:30

II. Poszterszekció

P45

Phalloidin as a bacterial actin-labeling agent 

Szilvia Barkó1,5, Beáta Longauer1, Emőke Bódis1, Dávid Szatmári1, Zoltán Ujfalusi1, Robert C. Robinson2,3 and Miklós Nyitrai1,4,5

1Department of Biophysics, Medical School, University of Pécs, Szigeti str. 12, Pécs, H-7624, Hungary

2Research Institute for Interdisciplinary Science, Okayama University, Okayama 700-8530, Japan.

3VISTEC, Thailand

4MTA-PTE Nuclear-Mitochondrial Interactions Research Group, Szigeti str. 12, Pécs, H-7624, Hungary

5Szentágothai Research Center, University of Pécs, Hungary

The visualization of subcellular objects by microscopy is one of the most important tools in biological studies. Some subcellular objects, due to their smallness in size, can challenge the physical barrier of resolution for microscopy. Although this area of biophysics is rapidly evolving limitations remain. The internal organization of eukaryotic cells is becoming better characterized due to the wealth of visualization probes that are available. Prokaryotes are smaller and their internal cellular organization has been resolved to a lesser extent. One recent study highlights one problem that there are only very few optical compounds that can be applied to visualize components of bacterial cells. The visualization of cytoskeletal components has a long history. For example, eukaryotic actin F-actin has been visualized in many studies by fluorescently conjugated phalloidin. This peptide is a toxin from the mushroom Amanita phalloides, which specifically binds to F-actin. However, in order to visualize F-actin in vivo, the cell membrane must be permeabilized because phalloidin is a membrane-impenetrable compound consequently it cannot enter the cell.

Two decades ago, phalloidin was reported to bind to bacterial actin-like proteins. At that time, microscopy technology had not developed sufficiently to solve the fine structure of the fluorescently-labelled cytoskeleton organization, and only low resolution images were obtained. Here, we used fluorescently-conjugated phalloidin to visualize MreB in vitro, and determine the in vivo localization of MreB in Gram positive and Gram negative cells. We tested the effects of phalloidin on the dynamics of MreB and on the viability of bacterial cells. By contrast to the harmful effects of phalloidin on actin dynamics and eukaryotic cell viability, phalloidin did not affect MreB dynamics of bacterial growth rates, however it did induce a morphology change to longer cell chain lengths.

Acknowledgement

OTKA-107776: An anchor biological systems characteristics: the structural and functional properties of bacterial filaments.

Longauer Beáta
A22 alter the polymerization properties of the bacterial actin-like MreB

Aug 27 - kedd

17:00 – 19:00

I. Poszterszekció

P11

A22 alter the polymerization properties of the bacterial actin-like MreB 

Beáta Longauer1, Szilvia Barkó1,2, Dávid Szatmári1, Zoltán Ujfalusi1,

and Miklós Nyitrai1,2,3

1Department of Biophysics, Medical School, University of Pécs

2Szentágothai Research Centre, University of Pécs, Hungary

3MTA-PTE Nuclear-Mitochondrial Interactions Research Group, Pécs, Hungary

The MreB protein is an actin orthologue in bacteria and similarly to actin it has essential role in the maintenance of cell shape. It is a crucial component of the cell growth, division and cell wall synthesis. Another common property of MreB and actin is the ability of binding and hydrolysing ATP[1]. A22 (S-(3,4-dichlorbenzyl)isothiourea) is the first chemical compound which was found to inhibits directly the MreB function in vivo. The mechanism of inhibition is not clear yet. Because this drug does not have any cytotoxic and genotoxic effects on eukaryotic cell lines, it could be a novel antibiotic agent against multidrug-resistant bacteria [2].

We studied the polymerization properties of Leptospira interrogans MreB (Li-MreB) protein in the presence of A22. Our spectroscopic data showed that A22 has significant effect on the ATP hydrolysis of MreB. By the help of fluorescent microscopy measurements we observed that the macroscopic conformation of the evolved filaments differs significantly in the presence and absence of A22. In case of GFP expressing E. coli cells, the A22 causes round cell shape (as it was described before) but MreB filaments did not dissociated to monomeric level.

We assume that in normal physiological circumstances the MreB molecules bind ATP or ADP-Pi, build long, stable filaments. In the presence of A22 the shortening of MreB filaments can be observed and although the relative amount of MreB filaments does not change, this conformation is not able to maintain the normal cell shape. Consequently, this MreB sensitive drug could be a good candidate in the war against antibiotic resistant bacteria.

Acknowledgment:

OTKA-107776: An anchor biological systems characteristics: the structural and functional properties of bacterial filaments.

References:

[1] Esue, O. et al. (2005). J. Biol. Chem. 280: 2628–35.

[2] Bonez, P. C. et al. (2016). Microbial Pathogenesis, 99, 14–18.