Genetic engineering is regularly used to produce lethal bacteria

"It sounds like science fiction, but it is a deadly reality: lethal microbes, with no cure,

"Example 2: Transferring a lethal factor to harmless human gut bacteria
Genetic engineering could make previously harmless bacteria lethal biological weapons by introducing deadly genes from a highly pathogenic organism. This was done by US researchers as early as 1986. They isolated the gene for the lethal factor of Bacillus anthracis, the causative agent of anthrax, and introduced into Escherichia coli, a normally harmless gut bacteria. The US team reported that the lethal factor protein was active in E. coli and displayed the same deadly effects as it did when in its native B. anthracis.

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