April 24 (UPI) -- When researchers placed bacteria in a maze, they found genetically identical sells exhibited individuality.
Scientists reported the unexpected discovery this week in the journal Nature Communications.
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In the maze, some bacterial cells quickly found their way to the highest concentration of the attractant, while others got lost swimming down the wrong channels. Photo by ETH Zurich
Even the simplest life forms, microorganisms, can sense and respond to their environment. Bacteria, for example, move toward food and away from harmful substances. The strength of their response reflects the concentration gradient of the substance they're reacting to.
This motility strategy is called chemotaxis, and until now, scientists assumed the ability was uniform among the cells of a single bacteria species or population.
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The latest research showed that is not the case.
To study the movement pattern of individual bacterial cells, scientists developed a microfluidic system featuring an arrow of narrow channels that branch out atop a thin glass plate.
Researchers allowed a chemical attractant to spread out across the family tree-like maze, with the tips of some branches featuring higher concentrations. All the bacteria cells were released at the base of the tree, where the attractant's concentration was weakest.
When the cells encountered a fork in the maze, they had to decide whether to keep swimming in the same direction, following the increasing concentration levels, or reverse course and follow a different branch.
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Scientists observed some cells easily making their way toward the branches with the highest concentration, while others struggled to navigate the maze.
While every cell has the same genetic coding, the results of the new study demonstrate the epigenetic diversity of each bacteria cell. Genes are expressed differently in each cell, producing biochemical diversity.
"There is biochemical noise in every cell. As a fundamental random component, this causes diversity of appearance and behavior," researchers reported.
Researchers suggest the biochemical variation present in different bacteria cells likely provides an evolutionary advantage. While cells adept at chemotaxis can travel to sources of food more efficiently, cells with less positional awareness are more likely to happen upon new sources of food.
"Non-genetic diversity has long been known in the biomedical life sciences; for example, it is thought to play a role in antibiotic resistance," said Roman Stocker, a professor of environmental engineering at ETZ Zurich. "Now, environmental scientists have shown that this diversity also affects fundamental behaviors of bacteria, such as locomotion and chemotaxis -- further expanding the concept of bacterial individuality."
