Plural of bacillus; rod-shaped bacteria that can cause diseases like tuberculosis and food poisoning.
From Latin bacillus meaning 'small staff or rod,' derived from baculum 'staff.' The term was adopted in the 19th century when microscopes revealed these bacteria's characteristic elongated shape.
Bacilli were among the first microorganisms identified as disease-causers by scientists like Robert Koch in the 1880s, launching the germ theory of disease—basically, they're the bacteria that changed medicine forever and made us understand why washing hands actually matters!
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