A
new study from EPFL scientists has found that bacteria use mechanical forces to
divide, along with biological factors. The research, led by the groups of John
McKinney and Georg Fantner at EPFL, came after recent studies suggested that
bacterial division is not only governed by biology, but also by physics.
However, this interplay is poorly understood.
Most
bacteria are rod-shaped cells that multiply by doubling their length and
dividing in the middle to yield two "daughter cells." Mechanisms that
control these processes in space and time are critical for survival. The
importance of these mechanisms becomes even clearer, given how pervasive
bacteria are in everyday life, and how ubiquitous their use is in
biotechnology.
The
scientists studied bacteria that are very similar to the human pathogen that
causes tuberculosis, which kills more people than any other infectious disease.
To study the growth and division dynamics of these "mycobacteria" the
scientists built a special instrument that combines optical and atomic force
microscopy (AFM) to image and manipulate cells at the size scale of molecules.
The
data showed that mycobacterial cell division requires mechanical forces in
addition to previously identified division molecules (enzymes). Before a cell
divides, there is a progressive build-up of mechanical stress in the cell wall,
right at the point where the cell will divide.
The
build-up eventually culminates in a millisecond-fast splitting of the cell into
two new cells. Remarkably, when the researchers physically pressed on the
bacteria with an ultra-sharp AFM needle, they caused instantaneous and
premature cell division. "This experiment proves that physics is essential
for this important biological process," says Georg Fantner.
But
where is the biological part of the story? When a bacterial cell divides the
two daughters must separate, a process mediated by enzymes that dissolve the
molecular connections between them. The investigators found that this essential
process could be bypassed by pressing on the nascent division site using the
AFM needle.
"Our
work demonstrates that biological enzymes and mechanical forces 'collaborate'
to bring about the separation of daughter cells in bacterial cell
division," says John McKinney.
See:
Posted by Dr. Tim Sandle, Pharmaceutical Microbiology
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