How bacteria communicate and compete
Bacteria may be microscopic, but they are constantly communicating with the microbes around them. New research reveals how cholera-causing bacteria can detect chemical signals from their neighbours, change their behaviour and outcompete other bacteria.
Bacteria don’t live in isolation. They are constantly interacting with other microorganisms, using molecular signals to sense their surroundings and change their behaviour.
Dr Brian Ho and his research team are interested in understanding the molecular systems bacteria use to interact with one another, and how these interactions shape entire microbial communities.
These communities are found almost everywhere in nature, from environmental ecosystems to the human body, where different species of bacteria live alongside one another and compete for space and resources.
Recent research has focused on Vibrio cholerae, the bacterium that causes cholera, and how it responds to signals produced by other bacteria.
Why is this research important?
Microbial communities play an important role in the stability and functioning of ecosystems and in human health. Understanding these communities requires looking not only at individual bacteria, but also at how they interact with the microorganisms around them.
A better understanding of these interactions could eventually help researchers find ways to influence microbial communities for human benefit.
For example, this research provides new insight into how a bacterial pathogen detects other bacteria and changes its behaviour in response. Understanding these interactions could eventually help researchers explore new ways of interfering with Vibrio cholerae during infection or identify risk factors in individuals more prone to the disease.
How is the research being conducted?
The research uses fluorescence microscopy to watch bacterial populations in real time.
This allows researchers to see how bacteria behave when they are growing alongside other species. Combining this live imaging with genetic manipulation allows the researchers to connect changes in observed bacterial behaviour with the molecular mechanisms behind them.
What findings are there so far?
The researchers made an unexpected discovery when examining mixtures of Vibrio cholerae and Escherichia coli (E. coli).
When Vibrio cholerae grew on its own, the bacteria formed large clusters, or aggregates. But in the presence of E. coli, these clusters dispersed.
The researchers found that the change was triggered by autoinducer-2 (AI-2), a small molecule produced by E. coli and detected by Vibrio cholerae. In response to the signal, Vibrio cholerae dispersed and mixed more closely with E. coli.
This gave Vibrio cholerae a competitive advantage. Its cells were able to come into closer contact with E. coli and attack neighbouring bacteria, allowing Vibrio cholerae to outcompete it.
The importance of AI-2 was confirmed by genetically modifying E. coli so that it could no longer produce the molecule. Without the signal, the Vibrio cholerae aggregates remained intact and E. coli was able to outgrow Vibrio cholerae.
The findings show how a signal produced by one bacterial species can trigger another to reorganise itself and change its behaviour in a way that helps it compete.
What do you hope the impact of the research will be?
It is now understood that Vibrio cholerae is not simply responding to conditions in its physical environment. It is also responding to signals produced by other bacteria already present in the gut and changing its behaviour accordingly.
This raises the possibility that in the future, it could be possible to interfere with this process. Understanding how Vibrio cholerae detects and responds to signals from other bacteria could help researchers explore ways of disrupting these interactions and preventing the bacterium from gaining a competitive advantage.
Another possibility is that the microbes present in a person's gut or stool could eventually be used as a diagnostic tool to identify people at greater risk of cholera infection.
More broadly, the research highlights the complexity of microbial communities and the importance of understanding bacteria as part of these communities, rather than as isolated organisms.
Project fact-file
- Full project title: Interspecies quorum sensing signals modulate multicellular organization and enhance contact-dependent antagonism in Vibrio cholerae
- Project funding: N/A
- Funder: N/A
- Dates of research: 2024-2026
- Lead researcher: Dr Brian Ho