This app was probably one of the last ever made / released for Palm OS. It uses some of the technology from Olivier in Bhajis Loops, and is quite simple really, but you can get some noises out of it, so it’s worth a play, and of course it is free.
Download Bacterium here
Please note that I did not develop this app or its code, so download at your own risk. As far as I know there’s nothing suspicious about the app. I’ve used it on a Palm OS5 device, but I don’t think it’ll work on Palm OS4 or earlier.