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Joseph Lister publishes his study of lactic fermentation of milk, demonstrating the specific cause of milk souring. His research is conducted using the first method developed for isolating a pure culture of a bacterium, which he names Bacterium lactis.
Lister, J. 1878. On lactic fermentation and its bearing on pathology. Trans Path. Soc., Lond. xxix: 425-67. In Milestones in Microbiology: 1556 to 1940, translated and edited by Thomas D. Brock, ASM Press. 1998, p58 [pdf]