A group of researchers discovered that harmless purple bacteria from the genus Rhodobacter could visualize aspects of tumor heterogeneity in cancerous tumors. The researchers used these microorganisms to visualize immune system cells known as macrophages, which also play a role in tumor development, using optoacoustic imaging.
The researchers developed the imaging technique that indicates where such macrophages are present and active with the help of photosynthetic bacteria.
They showed that bacteria of the genus Rhodobacter, which are not harmful to humans, can be used as indirect indicators of macrophage presence and activity. The photosynthetic pigment bacteriochlorophyll is abundant in Rhodobacter bacteria. Using multispectral optoacoustic imaging (tomography), the researchers detected bacteria in a tumor using this pigment (MSOT).
As part of their natural scavenging activity, macrophages engulf bacteria, a process known as phagocytosis. It changes the bacteria’s environment, their absorption of electromagnetic radiation, and, as a result, the optoacoustic signal. Rhodobacter bacteria thus serve as sensors for scientists, informing them of the presence and activity of macrophages. These bacteria will enable novel approaches to noninvasive technologies opening up new avenues for innovative diagnostic and therapeutic procedures. Bacteria may be able to detect increased macrophage activity and reveal the location of a tumor in the future.