New single‑cell technique reveals how tuberculosis‑like bacteria alter human cells
Researchers from King’s College London and the University of Surrey have developed a new technique to measure the content of individual human cells infected with bacteria that model tuberculosis – and it is already revealing biological changes that conventional analysis would miss.
Using the new method, the researchers have shown how bacteria used to model tuberculosis (TB) infection influences the metabolism of the human cell. The findings could help to understand why some human cells are vulnerable to infection while others remain uninfected.
Abigail Cook, PhD student at the University of Surrey and King’s College London, and lead author of the paper, said: “In this research, we have pushed the limits of detection to look at differences in the metabolism of individual infected and uninfected cells. These cells are, on average, 10 micrometres in diameter and have a volume of less than a picolitre – that's 100 million times smaller than the volume of a raindrop!”
Tuberculosis remains the world’s leading cause of death by a single infectious agent and is caused by the bacterium Mycobacterium tuberculosis. These bacteria primarily reside in immune cells called macrophages, the very cell designed to destroy pathogens. However, not all macrophages become infected. Understanding why some cells never get infected, and why some are more susceptible could lead to novel therapies to treat tuberculosis.
Seeing each cell’s metabolic ‘fingerprint’
Published in Analytical Chemistry, the study focused on developing methods sensitive enough to measure tiny concentrations of the by-products of metabolism in single human cells. This is done by selecting a single cell under a microscope and analysing it using a technique known as ‘liquid chromatography-mass spectrometry’ (LC-MS). This approach allows researchers to generate a metabolic ‘fingerprint’ – a unique pattern that can describe what processes are going on inside of the cell.
Until now, most methods have either looked at bulk mixtures of human cells all together or sorted cells into groups, which makes it impossible to see how cells affect their neighbours. With this new method, the researchers can use a microscope to selectively pick out and study individual infected and uninfected macrophages, while keeping them in their natural state and preserving knowledge of their location. This allows them to spot differences between these cells that were previously impossible to see.
The technique can also be used to map the location of cells in relation to their neighbours. This could pave the way for studies on how cells communicate with their surroundings and whether infected cells send warning signals to uninfected cells about the infection.
Such insights could help to uncover mechanisms behind infection and antimicrobial resistance and potentially guide the development of new treatments.
Professor Melanie Bailey, Professor in the Physical Sciences of Life at King’s College London and senior author of the paper, said: “We are so excited by this new approach because for the first time it allows us to relate visible features of a cell to its detailed chemistry. We are now using this approach to help researchers answer many other key biological questions extending from tuberculosis to other bacterial, viral and fungal infections, to cancer and furthering our understanding of how cells communicate with each other.”
Dr Dany Beste, Senior Lecturer in Microbial Metabolism at the University of Surrey and co-author of the paper, said: "This research is a great example of the importance of collaboration between biologists and chemists. While each of us specialises in our own field, working closely together has allowed us to tackle questions that neither could address alone.”
The team will now continue the research at the SEISMIC Facility based at King’s College London, which specialises in single cell studies.
This study was supported by the Doctoral College at the University of Surrey, Yokogawa Electric Corporation and grants from the Engineering and Physical Sciences Research Council (EPSRC) and the Biotechnology and Biological Sciences Research Council (BBSRC).
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Using the new method, the researchers have shown how bacteria used to model tuberculosis (TB) infection influences the metabolism of the human cell. The findings could help to understand why some human cells are vulnerable to infection while others remain uninfected.
Abigail Cook, PhD student at the University of Surrey and King’s College London, and lead author of the paper, said: “In this research, we have pushed the limits of detection to look at differences in the metabolism of individual infected and uninfected cells. These cells are, on average, 10 micrometres in diameter and have a volume of less than a picolitre – that's 100 million times smaller than the volume of a raindrop!”
Tuberculosis remains the world’s leading cause of death by a single infectious agent and is caused by the bacterium Mycobacterium tuberculosis. These bacteria primarily reside in immune cells called macrophages, the very cell designed to destroy pathogens. However, not all macrophages become infected. Understanding why some cells never get infected, and why some are more susceptible could lead to novel therapies to treat tuberculosis.
Seeing each cell’s metabolic ‘fingerprint’
Published in Analytical Chemistry, the study focused on developing methods sensitive enough to measure tiny concentrations of the by-products of metabolism in single human cells. This is done by selecting a single cell under a microscope and analysing it using a technique known as ‘liquid chromatography-mass spectrometry’ (LC-MS). This approach allows researchers to generate a metabolic ‘fingerprint’ – a unique pattern that can describe what processes are going on inside of the cell.
Until now, most methods have either looked at bulk mixtures of human cells all together or sorted cells into groups, which makes it impossible to see how cells affect their neighbours. With this new method, the researchers can use a microscope to selectively pick out and study individual infected and uninfected macrophages, while keeping them in their natural state and preserving knowledge of their location. This allows them to spot differences between these cells that were previously impossible to see.
The technique can also be used to map the location of cells in relation to their neighbours. This could pave the way for studies on how cells communicate with their surroundings and whether infected cells send warning signals to uninfected cells about the infection.
Such insights could help to uncover mechanisms behind infection and antimicrobial resistance and potentially guide the development of new treatments.
Professor Melanie Bailey, Professor in the Physical Sciences of Life at King’s College London and senior author of the paper, said: “We are so excited by this new approach because for the first time it allows us to relate visible features of a cell to its detailed chemistry. We are now using this approach to help researchers answer many other key biological questions extending from tuberculosis to other bacterial, viral and fungal infections, to cancer and furthering our understanding of how cells communicate with each other.”
Dr Dany Beste, Senior Lecturer in Microbial Metabolism at the University of Surrey and co-author of the paper, said: "This research is a great example of the importance of collaboration between biologists and chemists. While each of us specialises in our own field, working closely together has allowed us to tackle questions that neither could address alone.”
The team will now continue the research at the SEISMIC Facility based at King’s College London, which specialises in single cell studies.
This study was supported by the Doctoral College at the University of Surrey, Yokogawa Electric Corporation and grants from the Engineering and Physical Sciences Research Council (EPSRC) and the Biotechnology and Biological Sciences Research Council (BBSRC).
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