Science Picture Of The Week | A different kind of flower

Escherichia coli and Acinetobacter baylyi bacteria form beautiful floral patterns when they grow together.

Escherichia coli and Acinetobacter baylyi bacteria form floral patterns.
Escherichia coli and Acinetobacter baylyi bacteria form floral patterns.

What seems like a colorful flower here is actually the work of bacteria. The microbes become artists under certain conditions - and form fascinating floral patterns as they grow.

E. coli and A. baylyi flower-like patterns.
E. coli and A. baylyi flower-like patterns

The cultures of E. coli and A. baylyi create floral patterns in a 24-hour period when they are grown together on an agar.

This work was done at the BioCircuits Institute, San Diego University of California and published in open-access paper" by L.Xiong, Y.Cao, R. Cooper, W.-J.Rappel, J. Hasty and L.Tsimring. Floral.

Bacteria mobility

Whether in the ground, in water, or on and in our bodies: microbes are found almost everywhere on Earth - above all bacteria. 

VIDEO - Flower-like pattern under microscope.

In the laboratory, microbiologists usually examine individual species in isolation from one another. But in nature, many different bacterial species inhabit the same space and interact with one another.

Researchers led by Liyang Xiong from the University of California in San Diego have now observed that true works of art can be created through such teamwork. 

They had mixed bacteria of the species Escherichia coli and Acinetobacter baylyi on an agar plate for a study. 

Normally, E. coli bacteria cannot move and spread well on this culture medium. However, with the help of the very mobile A. baylyi microbes, they succeeded in doing so. The team explains that they were practically hitchhiking with these bacteria.

What is special about it? 

As time passed, the growing colony of the two species of bacteria formed a flower-like pattern - "I immediately noticed the beauty of this pattern and wondered how these bacterial cells become artists," Xiong reports. 

In order to get to the bottom of the secret of flower formation, the researchers carried out further analyses. It became clear that the pattern formation originated at the outer borders of the spreading colony - and is related to the concentration of E. coli bacteria.

Where fewer of the immobile microbes accumulate, friction is lower and the colony progresses faster. In areas with many E. coli bacteria, however, this happens more slowly. This is how the typical petal shapes are formed. 

According to the researchers, such patterns are likely to form whenever mobile bacteria are mixed with immobile ones, which have a higher growth rate. 

"The pattern formation in bacteria has been studied for some time. But so far most studies have focused on the dynamics of colonies of a strain," says Xiong's colleague Lev Tsimring.