[a235]

Sound can be recovered partially from visual observations of any vibrations (to some degree, this is your how CD works). So technically, you can 'listen' to bacteria with a compound phase contrast microscopes, which are used to observe living organisms.

With DNA its trickier. First of all, it's too small to be seen using compound (optic) microscopes. While an electron microscope scans a specimen, so either you have to do its with a frequency way higher than any vibrations, or 'focus' on a single place to 'listen' to it (pico stethoscope). There are few further complications, such as you may burn a hole though the specimen, not forgetting that it also requires special treatment to be observed in an electron microscope.

[jaydub]

This was interesting story from 2014 http://newsoffice.mit.edu/2014/algorithm-recovers-speech-fro...