Topic: Biology

Scientists discovered that certain bacteria have changed how they divide cells. Instead of separating DNA, they use a system to control cell shape.

Photosynthetic bacteria played a crucial role in shaping our Earth. Cyanobacteria, in particular, produced oxygen that allowed complex life to emerge. Now, scientists at the Institute of Science and Technology Austria (ISTA) have found something surprising about how these organisms work.

A biological system once thought to separate DNA has actually evolved to control the shape of cyanobacterial cells. This discovery offers new insights into how protein systems change over time and how multicellular life developed in these ecologically important bacteria.

Cyanobacteria are responsible for the Great Oxygenation Event about 2.5 billion years ago, when oxygen accumulated in the atmosphere and made aerobic life possible. Without them, it's safe to say that none of us would be here today.

These organisms remain essential to life on Earth. They contribute heavily to global biomass and play central roles in carbon and nitrogen cycles. One species, Anabaena sp. PCC 7120 (or simply Anabaena), has been studied for over three decades and serves as a model for understanding multicellular cyanobacteria.

Evolution Turns DNA System Into Cell-Shaping Structure

Benjamin Springstein worked with Professor Martin Loose's group alongside collaborators from ISTA, the Institut Pasteur de Montevideo (Uruguay), Kiel University (Germany), and the University of Zürich (Switzerland). Together, they found that Anabaena, and likely other multicellular cyanobacteria, have undergone a major evolutionary shift.

An ancient system once used to separate DNA during cell division has been repurposed into a cytoskeleton-like structure that helps determine cell shape. This discovery highlights the evolutionary plasticity of cytoskeletal systems in bacteria.

DNA in Bacteria Explained

All bacteria, including Anabaena, reproduce by dividing into new cells. This process depends on accurately copying and distributing DNA so that each new cell receives the genetic information it needs to survive.

A DNA Segregation System With a New Role

Springstein has studied Anabaena since 2014, exploring its biology and evolution. During the COVID-19 pandemic, when lab work paused, he spent time reviewing scientific literature and noticed something unexpected.

He found that Anabaena and some related cyanobacteria contain a system known as ParMR encoded within their chromosomes. Traditionally, this system is linked to plasmid segregation and had only been found on plasmids, which are mobile genetic elements.

This unusual placement led him to suspect that the system might have adapted to separate chromosomes instead. After joining ISTA as an IST-Bridge Fellow, Springstein set out to test this idea.

His experiments revealed something very different. One component, ParR, no longer binds to DNA. Instead, it attaches to lipid membranes, especially the inner membrane of the cell.

Meanwhile, ParM does not form structures in the cytoplasm to move DNA. Instead, it creates filament networks just beneath the inner membrane, forming a layer of protein polymers that resembles a cell cortex.

Why It Matters

This discovery shows how bacteria have evolved over time to adapt to their environment. Understanding this process can help us better appreciate the importance of these organisms in our ecosystem and potentially lead to new discoveries in fields like medicine and biotechnology.

Key Facts

• Cyanobacteria are responsible for producing oxygen that allowed complex life to emerge.
• Anabaena sp. PCC 7120 is a model species for understanding multicellular cyanobacteria.
• The ParMR system has evolved into a cytoskeletal system named CorMR with a function in cell shape control.
• Benjamin Springstein worked with Professor Martin Loose's group to study Anabaena and its evolution.

Key Terms

Cyanobacteria

A type of photosynthetic bacteria that produces oxygen.

Implications

This discovery shows how bacteria have evolved over time to adapt to their environment. Understanding this process can help us better appreciate the importance of these organisms in our ecosystem and potentially lead to new discoveries in fields like medicine and biotechnology.