Answer:
Clostridium
Step-by-step explanation:
Clostridium is a genus of bacteria that includes many species capable of forming endospores. Endospores are a dormant and highly resistant form of the bacterium that allows it to survive harsh conditions such as lack of oxygen. The ability to grow only in the absence of oxygen is a characteristic of anaerobic bacteria, and Clostridium species are known for their anaerobic metabolism.
Some examples of Clostridium species include Clostridium tetani, which causes tetanus, and Clostridium botulinum, which produces the toxin responsible for botulism. These bacteria are commonly found in soil and the gastrointestinal tracts of animals.
Therefore, based on the given information, the genus likely associated with a gram positive endospore-forming rod that only grows in the absence of oxygen is Clostridium.