How could a harmless bacterium suddenly become capable of producing a dangerous toxin?

Answer 1

A harmless bacterium could suddenly become capable of producing a dangerous toxin through a process called horizontal gene transfer, which occurs when the bacterium acquires genes coding for the toxin from another bacterium or other source such as phages or plasmids. This process can occur through transformation, transduction, or conjugation. Additionally, changes in the bacterium's environment or genetic mutations could cause a change in gene expression, allowing the bacterium to produce the toxin.