Multicellular bacteria possess communication structures similar to higher, eukaryotic cells. The exchange of the element calcium also plays an important role in intercellular communication in bacteria.
Image Credit: Created using the help of AI: HHU/Khaled Selim
Scientific Frontline: Extended "At a Glance" Summary: Calcium-Regulated Intercellular Communication in Cyanobacteria
The Core Concept: Multicellular cyanobacteria possess specialized cell-to-cell communication structures regulated by calcium signals, fundamentally mirroring the intercellular communication systems found in higher eukaryotic organisms.
Key Distinction/Mechanism: Unlike the gap junctions exclusive to eukaryotes, these bacteria utilize analogous structures called "septum junctions." The formation and regulation of these junctions rely on a specific calcium-binding protein (CSE) that functions as a calcium buffer, enabling rapid intercellular signaling in simple organisms lacking a nucleus.
Origin/History: Published in 2026 by researchers from Heinrich Heine University Düsseldorf and the University of Tübingen, this discovery indicates that these tissue-like cellular connections date back over a billion years, well before the evolutionary lineages of eukaryotes and prokaryotes diverged.
Major Frameworks/Components:
- Septum Junctions: The primary physical structures coordinating direct communication between adjacent cyanobacterial cells.
- Calcium-Binding Protein (CSE): A unique protein, found exclusively in multicellular cyanobacteria, functioning as a calcium buffer essential for regulating the formation of septum junctions.
- Analytical Methodologies: Nuclear magnetic resonance (NMR) spectroscopy determined the structure of the calcium-bound CSE, while cryo-electron microscopy confirmed the severe physical reduction of connecting junctions in CSE-deficient mutant strains.
Branch of Science: Evolutionary Biology, Phototrophic Microbiology, Molecular Biology, Cellular Biology, and Structural Biology.
Future Application: Understanding these ancient calcium-signaling pathways could drive advancements in synthetic biology, the engineering of robust artificial microbial tissues, or the development of targeted strategies to disrupt cellular communication in pathogenic bacteria.
Why It Matters: The findings bridge a critical gap in evolutionary history, demonstrating that complex, calcium-driven intercellular communication is not exclusively a eukaryotic trait but an ancient, foundational mechanism of early multicellular life.
Communication between cells in plants, animals, and humans takes place via specialized connecting structures. An international team led by biologists from Heinrich Heine University Düsseldorf (HHU) and involving the University of Tübingen has now discovered how the regulation of very similar structures was already present in multicellular bacteria, implying that this must have originated much earlier in the course of evolution. In the scientific journal published by the European Molecular Biology Organization (EMBO), they describe that the exchange of calcium plays a central role in bacteria, just as it does in humans.
Higher, eukaryotic cells—that is, cells with a nucleus, such as those found in humans and all higher animals—possess structures that connect neighboring cells. It is known that, among other things, these structures facilitate fundamental communication processes between cells; without them, tissues such as the human heart could not function. Furthermore, nerve cells transmit the signals that control our bodies via these connecting structures. These structures and the communication between cells are regulated through the exchange of calcium ions (Ca²⁺).
The research group from the Institute of Phototrophic Microbiology led by Junior Professor Dr. Khaled Selim has now discovered that similar communication processes and connecting structures in bacteria are also regulated by calcium signals. However, bacteria are simpler cells that lack a nucleus—so-called prokaryotes. Professor Selim notes: “It came as a big surprise to us that one of the earliest life forms on Earth—evolutionarily older and simpler cells—had already developed communication structures regulated by calcium signals similar to those found in the cells of higher organisms, such as animals and humans.”
In The EMBO Journal, the research team reports the presence of such communication structures in multicellular cyanobacteria. “Analogous to the connecting structures in eukaryotes known as gap junctions—traditionally considered a eukaryotic trait—cyanobacteria coordinate their cell-to-cell communication via connecting structures called ‘septum junctions’. The signals regulating this cell-to-cell communication and the formation of septum junctions were previously largely unknown,” says Teresa Müller, a doctoral researcher in Selim’s research group within the Cluster of Excellence “Controlling Microbes to Fight Infections” (CMFI) at the University of Tübingen and first author of the study.
The biologists in Düsseldorf discovered a calcium-binding protein (designated as CSE) found exclusively in multicellular cyanobacteria. Using nuclear magnetic resonance (NMR) spectroscopy, they determined the structure of CSE in its calcium-bound state and demonstrated that it functions as a calcium-buffering protein. Furthermore, using cryo-electron microscopy, the researchers observed that the mutant of the bacterial cells lacking CSE exhibited significantly fewer connecting structures.
Selim emphasizes: “Our research offers new insights into evolution. It suggests that the functional principles of higher organisms were already present in simple, multicellular bacteria that form tissue-like structures, meaning that these cellular connections date back a billion years—before the time when the evolutionary lineages of eukaryotes and prokaryotes diverged.”
Published in journal: EMBO (European Molecular Biology Organization)
Title: The calcium-binding protein CSE links Ca²⁺ signaling with cell-cell communication in cyanobacteria
Authors: Teresa A Müller, Felicia Stahlecker, Karolina Roganowicz, Sherihan Samir, Gregor L Weiss, Murray Coles, and Khaled A Selim
Source/Credit: Heinrich Heine University Düsseldorf | Arne Claussen
Edited by: Scientific Frontline
Reference Number: ebio083126_01
