A study published in the Nature Ecology & Evolution journal has upended a long-held belief that there should be a strong link between the evolution of the shape of bacteria and their ability to move, reports Science Daily.
“The shape of bacteria does not influence how well they can move — this is the surprising finding of new research which could have major implications for the future of the scientific and medical industries.”
Dr. Fouad El Baidouri and Professor Stuart Humphries from the School of Life Sciences at the University of Lincoln, UK, conducted the study, together with Dr. Chris Venditti from the University of Reading. The study was funded by a Leverhulme Trust Research Leadership Award.
The team was interested in understanding how the shape of single-cell organisms like bacteria affects their pathogenicity (ability to cause disease) as well as their mobility and lifestyle. The mobility-related findings ended up being the most surprising.
The team studied 325 different species of Firmicutes bacteria.
Professor Humphreys told reporters that they wanted to fill what they perceived as a surprising gap in global knowledge.
“[U]ntil now the scientific community has relied on mathematical models to predict the relationship between shape and movement in bacteria. We expected swimming bacteria to be rod-shaped in order to reduce their energy costs, but experimental tests are rare and, surprisingly, analyses of this relationship in an evolutionary context are lacking entirely.”
Mathematical models had led scientists to predict that the swimming bacteria would be rod-shaped, as this would reduce their energy expenditure. Obviously, such an optimization of shape to maximize energy efficiency would have had to have evolved ie. energy-efficient rod-shaped swimming bacteria would have been favored and their less energy-efficient swimming cousins with other shapes removed from the gene pool over time.
The scientists were surprised to find that previous researchers had relied on those mathematical models heavily and experimental tests had been done only rarely.
The question of how we can understand the shape/movement relationship in an evolutionary context had not been addressed at all.
Humphreys and colleagues found that the shape/movement relationship predicted by the models did not correspond to what they observed in the Firmicutes species.
“Our research has produced evidence that these theoretical predictions don’t match reality, at least in this group of bacteria, and it therefore makes a major contribution to our understanding of the evolution of bacteria.”
The researchers used a number of approaches to try to show that rod-shaped swimming bacteria moved more efficiently than spherical bacteria, and that shape and movement had co-evolved. They could find no evidence of such an association.
Science Daily reports that this means that the bacteria species Firmicutes “have an even greater evolutionary flexibility than previously thought.”
Scientists are moving rapidly towards developing a better understanding of bacterial mobility. A different team at Nagoya University did a detailed study that revealed the 3D structure of a particular bacterial propeller protein this year, reports Science Daily.
“Many bacterial species use spiral propellers (flagella) attached to motors to move through a liquid environment.”
The motor that lets a bacteria move has two components: a stator and a rotor. The study was the first to reveal in detail the structure of the stator for the MotA protein.
The stator propels the bacteria when it undergoes a structural change caused by a movement of charged particles (ions) through an internal channel. The electrochemical energy provided by the ions is converted into mechanical force.
“Previous studies investigated the stator and its interaction with the rotor by constructing mutant proteins and analyzing their functions. However, little was known about stator structure.”
To put it another way, “The flows of ions are converted into a rotational force by the interaction between the stator and the rotor.” The ions moving through the channel are Na+ or H+.
The Nagoya team used electron microscopy and biochemical techniques to make their discovery.
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