You can try to get a bit more specific with them if you look for the hashtag version of these words: #microbiome and #metagenomics. This works OK for #microbiome but #metagenomics yields nothing right now.
Unfortunately, some potentially useful terms have been coopted by all sorts of non-interesting stuff. Consider evolution and bacteria, for example. In these cases, the words are too commonly used either for non sciency stuff (e.g., evolution of skateboards just came up) or for non interesting stuff (e.g., kitchen cleaners come up a lot with the bacteria search). In these cases, the hashtag versions are better though imperfect: #evolution and #bacteria.
The key seems to be to find terms that are used somewhat narrowly to be only about the topic you care about but are also used widely enough so that a lot of people in the field of interest use them.
Here are some of my current favorite/most useful search terms:
- genome evolution
- plos or #plos
- Craig Venter (this can be quite fun)
- genome sequencing
I continue to experiment with different approaches to this and would welcome any ideas for best ways to pull out useful material.
Also, I am curious. Do others out there who use twitter have some favorite terms they search for?