Most microbial biomass in the ocean is found in the deep sea. Deep-sea microbes are important agents for organic matter (OM) recycling and storage, but it’s unclear how these organisms cope with the fluctuating OM supply in the deep ocean, especially in the deepest areas: the hadal trenches. To learn more, a new study examined the metabolic potential of microbes in the phylum Chloroflexi using sediment samples from the Mariana Trench. Metagenomic sequencing revealed 6 novel species, 4 novel genera, 1 novel family, and 1 novel order of Chloroflexi in the sediment. Based on the sequences, the associated microbes were primarily OM consumers that could degrade various organic carbon (OC), sulfur, and halogenated compounds and could even metabolize degradation-resistant types of OM, such as polyaromatic hydrocarbons (PAHs). The deep-sea Chloroflexi could also make energy-storing compounds, like trehalose, and appeared to use a “feast-or-famine” strategy, adapting their metabolism depending on the nutrient conditions. Although more research is needed, the findings suggest that Chloroflexi in hadal trenches are important contributors to carbon, sulfur, and halogen cycles and highlight the adaptability of these organisms to the unpredictable food supply in the deep ocean.