Data and La Forge carefully extract a thorn from one of the large predatory vines using a phaser
Surata IV microbes were microorganisms contained in thorns on the large predatory vines of Surata IV. These microbes possessed elements of both a bacteria and a virus, and were designed to infect the nervous system of warm-blooded animals.
In 2365, Commander William T. Riker was stung in the calf by one of the vines. The microbes then attached themselves to the great sciatic nerve and began multiplying, fusing themselves to the nerves at a molecular level. Conventional surgery and the transporter's biofilter were unable to remove the microbes, which were causing no damage but were impeding neural functions. This led to eventual paralysis and brain infection. The growth rate of the microbes doubled when exposed to endorphins released by erotic dreams and decreased significantly when other chemicals were released by stimulated feelings of survival. (TNG: "Shades of Gray")