Researchers at the University of Basel have discovered how bacteria cooperate and share resources across generations, using a newly developed method that tracks gene expression and behavior in microbial communities over space and time.
Bacteria are microscopic organisms that usually live in communities, such as the gut microbiome or dental plaque. Living in communities provides many advantages to individual bacteria, such as increased resilience, colonization, and mutualism. However, the development of bacterial communities is a highly complex process, where bacteria form intricate three-dimensional structures and interact with each other in various ways.
A new method to study bacterial swarms
To investigate the dynamics of bacterial communities, the research team led by Professor Knut Drescher from the Biozentrum of the University of Basel used Bacillus subtilis as a model organism. This ubiquitous bacterium is also found in our intestinal flora and can form swarms on agar plates. The researchers developed a novel method that combines state-of-the-art adaptive microscopy, gene expression analysis, metabolite analysis, and robotic sampling. This method allows them to simultaneously measure gene expression and image the behavior of individual cells in microbial communities at precisely defined locations and specific times, as well as to identify the metabolites secreted by the bacteria.
Bacteria support each other across generations
The researchers found that the bacteria in the swarm cooperate and share nutrients across generations. They identified different subpopulations within the swarm, which produce and consume different metabolites. Some of the metabolites secreted by one subpopulation become the food for other subpopulations that emerge later during swarm development. For example, the bacteria at the swarm front produce acetoin, which is consumed by the bacteria in the intermediate region. The bacteria in the intermediate region produce glutamate, which is consumed by the bacteria in the swarm center. The bacteria in the swarm center produce surfactin, which helps the swarm to spread.
Bacteria differ in appearance, characteristics, and behavior
The researchers also observed that the bacteria in the swarm differ in appearance, characteristics, and behavior depending on the region. The swarm can be divided into three major regions: the swarm front, the intermediate region, and the swarm center. However, the three regions display gradual transitions. “Depending on the region, the bacteria differ in appearance, characteristics, and behavior. While they are mostly motile at the edges, the bacteria in the center form long non-motile threads, resulting in a 3D biofilm. One reason is the varying availability of space and resources,” explains first author Hannah Jeckel.
Bacteria show sophisticated swarming behavior
The study, published in Nature Microbiology, reveals the sophisticated swarming behavior of bacteria, which involves cooperation and resource sharing across generations. The researchers hope that their new method will enable further studies on the development and function of bacterial communities, as well as their interactions with other organisms and the environment.