Bacteria Plan Ahead, Anticipating Future Events

June 26, 2009 -- Just as humans have learned to connect dark clouds with rain, so too have bacteria and yeast learned to use one event to predict the arrival of another.

"For multicellular organisms, there is a real benefit to understanding the temporal order of things," said Amir Mitchell, a scientist at The Weizmann Institute of Science in Israel and co-author of a paper that appeared recently in the journal Nature. "If you see clouds you might expect rain, and take an umbrella out with you."

The two organisms studied in the research, Escherichia coli and fermenting yeast, Saccharomyces cerevisiae, are widely used by humans for very different reasons. E. coli can travel through the human digestive tract. Winemakers have used yeast to turn sugar into alcohol for thousands of years.

In the human digestive tract, sugar lactose is present before sugar maltose. Introducing E. coli to lactose not only triggers genes that let the bacteria metabolize lactose, but also initiates the expression of genes that produce enzymes that can metabolize maltose. No maltose is yet present, but the bacteria are now equipped to metabolize maltose when they are exposed to it.

In wine bottles, yeast must withstand the heat produced during fermentation and then the chemical pressure of oxidation. As the bottles heat up, the yeast activate genes that allow them to survive the heat. This also triggers the activation of genes that enable the yeast to survive oxidation, the next stage of the fermentation process.

Related Content:

• Bacteria-Run Computer Solves Math Puzzle
• Bacteria Cells Programmed to Count
• HowStuffWorks.com: Winemaking
• More Discovery News

Over the course of hundreds of thousands of years, scientists speculate, bacteria and yeast adapted, or learned, to anticipate future events. The presence of maltose or lactose, or of heat and oxidation, are each discrete situations. Linking the two means that the bacteria and yeast have adapted to this sequence of events in time, and can use one event to predict a second.

The ability to predict and prepare for future events allows the bacteria or yeast to use their limited resources more effectively.

"It's neat because bacteria, yeast, or even people have adapted to changes in their environments," said John Hogenesch, Associate Director of the Penn Genome Frontiers Institute. "These changes occur in a temporally fixed pattern, so adaptation to one helps with the second. The reverse is not the case, however."

If scientists could uncover more of these patterns within other organisms, then they could eventually manipulate them -- short circuiting disease or jump starting other processes.

Scientists expect that this kind of genetic learning is hardwired across a multitude of organisms over time. However, they are still unsure about how much time is required for an organism to create this genetic regulation. They also cannot discern which specific genes and gene regulators are involved.

Whatever genetic elements are present, they are passed down to subsequent generations, preparing the offspring for possible future events.

"These traits are being passed on to future generations," said Mitchell. "This is evolution."

Related Links:

Ancient Yeast Reborn in Modern Beer

HowStuffWorks.com: Yeast

Earthly Cave Bacteria Hint at Mars Life

Get the Wide Angle on Synthetic Life