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Harnessing microfluidics for microbiology: from bacteria-host interactions to emerging cancer therapies
The human body is characterized by the coexistence of mammalian and microbial cells, including bacteria, fungi, protozoa, and viruses. Bacteria are the most studied cohabitants and are present in the same order of magnitude as human cells, with an estimated ratio of 1.3:1 (human cells:bacteria), highlighting their fundamental role in maintaining homeostasis under healthy conditions1. Bacteria colonize within many human environmentally-exposed ecosystems, such as natural barriers, each defined by distinct physico-chemical features. For instance, skin, vagina, and stomach have a low pH2,3,4; the upper layer of skin, nasal passages, lungs are oxygen-rich niches3,5,6, while colon and vagina are anaerobic ones2,4,7. Occasionally, bacteria can also reach systemic organs, which are additionally submitted to mechanical constraints. The small intestine and blood vessels are submitted to mechanical stresses such as stretch or flow2,8,9,10, the brain is a soft tissue, while bones are stiff11; and all organs present diverse three-dimensional structures9,12. Within these niches, bacteria adapt to local conditions and perform specialized functions. The gut microbiota, which represents about 1% of human body mass13, is central to nutrient processing, epithelial maintenance, immune modulation, and vascular development14. On the skin, bacteria contribute to maintaining an acidic pH that deters pathogens, strengthen barrier integrity, and limit...
