Bacteria are able to use their built-in 24-hour clocks to predict the arrival of new seasons, as revealed by research that was inspired by the ‘ice bucket challenge.’
Bacteria are able to use their built-in 24-hour clocks to predict the arrival of new seasons, as revealed by research that was inspired by the ‘ice bucket challenge.’
This finding could have significant effects on our understanding of how circadian rhythms—a molecular form of a clock—help various species adapt to climate changes, whether they are animals that migrate or plants that blossom.
The research team provided populations of blue-green algae (cyanobacteria) with different artificial day lengths, all at a constant warm temperature. For eight days, some samples were exposed to short days, others to equinox days (equal amounts of light and dark), and some to long days.
After this period, the cyanobacteria were subjected to ice for two hours, and their survival rates were observed.
Those samples that experienced several short days (eight hours of light and 16 hours of darkness) before facing the cold had a survival rate of 75%, which was up to three times greater than those that weren’t preconditioned in this way.
Just one short day wasn’t enough to enhance the bacteria’s cold resistance; only after several short days—ideally six to eight—did their chances of survival significantly improve.
For cyanobacteria that had their biological clock genes removed, survival rates remained consistent regardless of day length. This suggests that photoperiodism—the ability to assess day-night cycles and alter physiology in preparation for seasonal changes—is essential for helping bacteria adjust to prolonged environmental shifts, including new seasons.
“These results suggest that bacteria in the wild utilize their internal clocks to gauge day length, and when the number of short days reaches a specific threshold, similar to what occurs in autumn, they alter their physiology in preparation for the upcoming winter challenges,” explained Dr. Luísa Jabbur, the study’s first author. At the time of this research, she was a researcher at Vanderbilt University in Tennessee, working in Prof. Carl Johnson’s laboratory, and is currently a BBSRC Discovery Fellow at the John Innes Centre.
The Johnson lab has a strong track record of researching the circadian clocks of cyanobacteria from both mechanical and ecological perspectives.
Previous research has demonstrated that bacteria possess a form of biological clock, allowing them to differentiate day-night length, providing an evolutionary edge.
This study, published in Science, marks the first occasion where photoperiodism in bacteria has been shown to have evolved for anticipating seasonal indicators.
The implications of these findings open up new avenues for scientific inquiry. A central question arises: how does an organism with a lifespan of just six to 24 hours develop a mechanism that not only reacts to but also predicts future conditions?
“It’s as if they are communicating to their daughter and granddaughter cells, conveying the message that the days are getting shorter, and action is required,” said Dr. Jabbur.
As part of her BBSRC Discovery Fellowship, Dr. Jabbur and her colleagues at the John Innes Centre will use cyanobacteria, which reproduce quickly, to explore how photoperiodic responses may evolve in different species amidst climate change, potentially benefiting major crops.
A critical aspect of this research will focus on understanding the molecular memory systems that enable species to pass on information to subsequent generations. The study will examine whether the accumulation of certain compounds at night during short days acts as a molecular trigger for shifting to a different physiology or phenotype.
For Dr. Jabbur, this research represents a significant achievement in her early scientific career, despite initial doubts from her mentor and corresponding author, Professor Carl Johnson.
“Carl, who is not only an exceptional mentor but also sings in the Nashville Symphony Chorus and has an operatic laugh that resonates throughout the department, first reacted with surprise when I suggested the icy challenge to determine if photoperiod was a clue for cyanobacteria in their natural habitat,” shared Dr. Jabbur.
“To his credit, he encouraged me to pursue the idea, and when I left his office, he showed me a sign on his door with a quote from Frank Westheimer: ‘Progress is made by young scientists who carry out experiments that old scientists say would not work.’”
“It worked on the first attempt. Afterward, I replicated the experiments. There is something incredibly precious about peering at a set of plates with bacteria and realizing that at that moment, you possess knowledge that no one else does.”
Bacteria can anticipate seasonal changes: Photoperiodism in cyanobacteria is detailed in Science.
