April 13, 2024

Bacteria, constituting more than 10% of all living things, have recently been found to possess internal clocks, similar to humans, that synchronize their activities with the Earth’s 24-hour cycles. New research reveals the complexity and sophistication of these bacterial circadian clocks, opening up exciting avenues for study. This discovery may lead to precise timing for antibiotic use and smarter bioengineered gut and soil microbiomes. The study, involving international collaboration from several universities, explored gene expression as evidence of clock activity in the soil bacterium Bacillus subtilis.

Lead author Dr. Francesca Sartor from LMU Munich emphasizes the pervasive nature of the circadian clock in this microbe, regulating various genes and behaviors. Professor Antony Dodd from the John Innes Center is astonished by the clock’s properties in such a small genome. Previously, the team demonstrated the existence of a circadian clock in a lab-derived strain of B. subtilis, a first for this bacterium. Bioluminescence from an inserted enzyme guided their monitoring of the bacterial clock.

The study shows that circadian clocks are widespread in B. subtilis collected from natural environments. The bacterium exhibits circadian rhythms in both constant dark and light, with nuanced responses similar to those in more complex organisms, known as “aftereffects” and “Aschoff’s Rule.” This suggests the bacteria can synchronize their physiology and metabolism to different times of the day based on light and temperature conditions.

The implications of this discovery are significant for biotechnology, human health, and plant science. Understanding bacterial circadian clock properties could lead to improved health outcomes, sustainable food production, and advancements in biotechnology. It may also shed light on how microbiomes are formed and improve antibiotic efficacy against pathogenic bacteria at specific times of the day. Additionally, the knowledge can benefit crop protection, as Bacillus subtilis aids farmers in nutrient exchange, plant development, and defense against harmful microbes.

The team plans to develop Bacillus subtilis as a model organism for studying circadian clocks in bacteria. Their next steps involve identifying the genes comprising the clock mechanism and understanding how multicellular organization influences its functionality.

Circadian clocks, internal oscillators, confer selective advantages to organisms by adapting physiology and metabolism to environmental changes within a 24-hour cycle. They contribute to phenomena like jet lag when transitioning between time zones. Professor Ákos T. Kovács from Leiden University and the Technical University of Denmark remarks on the remarkable similarity between the circadian clock in Bacillus subtilis and those in complex organisms like flies, mammals, and plants.

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