Our Ideas About Bacteria Evolution Are Wrong -- Scientists Make New Discovery

Sandra Hajda

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."

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."

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."

Science Daily reports that this means that the bacteria species Firmicutes "have an even greater evolutionary flexibility than previously thought."

"Many bacterial species use spiral propellers (flagella) attached to motors to move through a liquid environment."

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."

The Nagoya team used electron microscopy and biochemical techniques to make their discovery.