A deep-sea bacterium called ZRK33 can use sulfate and thiosulfate for energy production. This bacterium belongs to a group called Chloroflexota, which is important in sulfur cycling in deep-sea ecosystems. The bacterium was studied using various methods, and it was found that it can perform sulfate assimilation both in the lab and in deep-sea conditions. Genes related to sulfate reduction are common in Chloroflexota bacteria from deep-sea sediments, suggesting they play a role in sulfur cycling. This study expands our understanding of how deep-sea Chloroflexota bacteria contribute to sulfur metabolism in the ocean.