Bacteria are survivors, and they can find ways to get around stuff we use to kill them, like disinfectants and antibiotics. Scientists and clinicians are constantly trying to stay a step ahead of pathogenic microbes that have the potential to cause serious harm if they can't be eradicated. To do so, we have to learn all we can about how bacteria avoid the harmful stuff in their environments.
Now researchers have shown that bacteria can change their shape to avoid antibiotics. While this is not a new finding, the researchers have found that by increasing the width of their cells, bacteria can keep growing even when they cannot make new proteins (because protein synthesis can be inhibited by some antibiotics). In this way, bacteria can survive antibiotic exposure over the long term, without necessarily needing to acquire new antibiotic-resistance genes or mechanisms. The findings have been reported in Nature Physics.
In the lab of Carnegie Mellon University Assistant Professor of Physics Shiladitya Banerjee researchers are studying the mechanical and physical phenomena underlying different cellular processes. Their research has shown, for example, that a cell's shape can have a significant impact on its survival and reproduction.
In this study, the lab worked with scientists at the University of Chicago to investigate how the growth and structure of the bacterium Caulobacter crescentus is affected by antibiotic exposure. They found that a C. crescentus cell could modify its shape as a survival strategy.
"Using single-cell experiments and theoretical modelling, we demonstrate that cell shape changes act as a feedback strategy to make bacteria more adaptive to surviving antibiotics," said Banerjee.
If the bacteria colony was exposed to sub-lethal doses of an antibiotic called chloramphenicol over several generations, the shape of the bacteria changed dramatically; the cells became wider and curvy.
The researchers created a theoretical model that showed that when the bacteria got more curvy, their surface-to-volume ratio got lower; this made it more difficult for particles of the antibiotic to penetrate the cell surface, and fewer got through. Thus, the shape change was aiding in the bacteria's survival.
"These shape changes enable bacteria to overcome the stress of antibiotics and resume fast growth," Banerjee said. "This insight is of great consequence to human health and will likely stimulate numerous further molecular studies into the role of cell shape on bacterial growth and antibiotic resistance."