Bio organic weapons do exist in the FSpace universe, but aren't a major feature of warfare between the races in known space.
The Mechs are best known for their use of such weaponry, either species picked from worlds in their original state, or modified from their original state and used on alien worlds as part of an arsenal at their disposal to pacify technological worlds.
Humans while originally involved in a developing toxins (chemical warfare) and bacteria or virus based vectors for their own internal conflicts, will no doubt investigate such methods for use against aliens for future expected warfare.
However with advances in genetic engineering, human scale bio organic weapons are likely to be researched and developed into serviceable forms in secret labs alongside more traditional biologic weapons. As humans tamper with their own genome and that of other Earthly species, they are likely to unlock some terrible mutations during centuries of research and have a few interesting candidates for deployment, if they can be controlled sufficiently.
The Resident Evil series of games and movies is an example of this kind of evolution more in keeping with our own real world time frame, but stretches the bounds of imagination that such abominations are possible with our level of technology. Its just another classic zombie, come demonic creatures concept.
However in the later part of the 22nd century, it could be conceivable that we might develop such weapons, that infect and transform existing species into controllable weapon species.
The animated movie Resident Evil Damnation explores a revolution in an eastern european state and the lengths both the regime and the rebels will go to in using such weapons, their consequences for innocent humans stuck in the way, and how such activity can be exploited by interested parties.
The plot of the movie involves an American operative sent in to check out what is going on with the rebellion, and gets tangled up with the rebels and their eventually use of a parasite controller to harness the use of bio organic weapons to use against the regime, only to find that the regime had its own bio organic weapons programme.
The plot of that movie could work well on a distant and well populated human colony, where their is a revolt and both sides employ technology derived from a secret bio weapons plant on the planet.
Operatives from the USA, or one of the other major powers could be sent in covertly via drop pods and asked to investigate any human rights violations, and to see if the reports from the colonial governor match the reality. They then find themselves in the middle of a conflict involving bioweapons, and must try for survival and pick a side to back during the struggles. Damnation is a story that favour the rebels, but an inventive GM can decide paint a different story. Through in some corporate espionage with their operatives trying to steal materials from the secret lab (like in Damnation) then you've got a nice volatile mix.
Let the US Aerospace Marines, Royal Space Marines or even better Chinese Special Forces roll in to save the day and mop up the conflict, since a hand full of players is going to find it hard to clean up such a big mess (unless they manage to find weapons of mass destruction to use... like nukes).
This kind of scenario plot is bound to lead to follow on activities, like chasing the corporate operatives, investigating further claims of hidden labs, and misuse of the technology, maybe sale of it to alien powers, etc.