Bacteria With Same Genotype Show Different Phenotypes

Scientists have been puzzled by bacterial populations. In 'isogenic populations', it has been found that all bacteria show the same genes. Yet the behavior and growth are at different speeds.

Experts from the Institute of Science and Technology Austria (IST Austria) examined how Escherichia coli divides a protein complex. It leads to detoxification of cells when it pumps drugs and antibiotics out of the cell.

Hence, it was found that when bacteria divides, the pump proteins get distributed. One cell inherits more pump proteins than others and grows faster in low concentrations of antibiotics. When the pump protein is partitioned it can lead to different behaviors in a bacterial population, and also lead to the development of antibiotic resistance. The study was published in Science. The search was conducted by an interdisciplinary duo, including an experimentalist, Tobias Bergmiller, and a theorist, Anna Andersson.

There are thousands of individual bacteria in a bacterial population. They all have the same genetic make-up yet a range of phenotypes that look and behave in different ways due to random processes in cells influencing the manner in which the genetic instructions are used. The cytosol, the liquid inside the cell, contains proteins. They show random molecular processes including differences in the breakdown of proteins. There could also be random partitioning and cell division. The current study showed how a protein complex in the cell envelope around it could lead to heterogeneity or diversity of phenotypes, according to Phys.org.

AcrAB-TolC is one of the protein complexes in the bacteria that was explored. It pumps drugs out of Escherichia coli cells and is found in the cell envelope, where proteins clump together as "islands".

C Lin Guet explains how there might be "biased partitioning" that could lead to antibiotic resistance. He said that current research has revealed that mutations leading to antibiotic resistance can result fast when there are low concentrations of antibiotics. These are found in natural habitats or even patients when they are being treated. "Heterogeneity in a bacterial population that arises through a mechanism of biased partitioning of drug efflux pumps, as we identified in our study, could be a stepping-stone on the path of bacterial populations towards antibiotic resistance," he said.