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NEWS

June 2024 ESRFnews

ESRF stages cryo-electron tomography

living environments.

Two teams led by Guy Schoehn

and Cecile Morlot at the Institut de

Biologie Structurale in France have

now trialled cryo-ET on bacterial

spores at the ESRF’s CM01 facility

and at the Central European Institute

of Technology in Brno, in the Czech

Republic. Bacterial spores are dormant

cells that can resist multiple stresses,

from antibiotics and disinfectants to

irradiation and high temperatures.

Their resistance is helpful when the

spores have a human benefit for

example in probiotics but it poses a

major problem if they are harmful as

there are limited ways to eradicate them

The researchers used cryoET to

study the structure of the spores

chromosome as well as its coat

the extracellular multiprotein

structure responsible for many of the

spores resistance properties They

found that during sporulation the

chromosome organises into a torus

shaped bundle of fibrils which is

likely a transition stage between

the initial compact structure of the

spore DNA and its final crystalline

structure. Meanwhile, the spore coat

assembles within distinct, stacked

layers formed by scaffolding proteins

(Nat. Commun. 15 1376). “Our work

lays the foundations for the dissection

of molecular mechanisms involved in

the development and the resistance of

the bacterial spore,” says Morlot.

Gregory Effantin, the CM01

scientist who collected the ESRF

data believes the technique has great

potential at the facility CryoET

provides both structural information

about individual protein complexes

and their spatial organisation within

the cell he explains It has the

potential to greatly advance structural

biology and cell biology in particular

by bridging the gap between light

microscopy and highresolution

approaches such as singleparticle

cryoEM Xray crystallography and

nuclear magnetic resonance

ESRF users and their colleagues have

conducted one of the first studies of

bacterial spores using cryo-electron

tomography (cryo-ET). The results

are helping researchers to understand

how bacterial spores become resistant

to hostile conditions, and show the

nascent technique’s potential for “in

cell” structural biology.

In the last decade, cryo-electron

microscopy (cryo-EM) has

transformed structural biology due

to its ability to obtain 3D structural

information without needing a

sample to be crystallised which is

often very difficult The next step

has been cryoET in which a larger

sample of biological tissue is plunge

frozen before being thinned and

imaged with an electron microscope

with nanometric resolution With

cryoET structural biologists have the

opportunity to move away from in vitro

studies and towards collecting data

from within the cell where proteins are

under the varied influences of their real

“Cryo-ET

provides both

structural

information

about

individual

protein

complexes and

their spatial

organisation

within the cell

E S R F/ S T E F C A N D É