To identify one poisoned bottle, you will need 10 bits of information. Let each subject be one of those bits. Number the bottles $0,\dots,999$ and get 10 subjects, and number them with powers of $2$: $1,2,4,\dots,512$. Prepare for each subject $b$ a mixture from each bottle $a$ where $a\; \&\; b=b$, where $\&$ is bitwise "and". The sum of the numbers of the subjects who keel over from the poison identifies the bottle.