The rising level of atmospheric nitrous oxide (N₂O) has garnered the attention of researchers to microorganism-mediated N₂O synthesis in recent years. According to the recent studies, one of the main sources of N₂O in the world is the nitrification process carried out by aerobic aerobic ammonia oxidizing microorganisms (AOMs). We summarized the taxa of AOMs, the ecological distribution of AOMs, the environmental factors influencing the distribution, and the hotspots, pathways, and influencing factors of AOM-mediated N₂O production. Finally, we prospected the future research directions in this field. This review improves our understanding of AOMs and their mechanisms of N₂O production.

China has considerable demands for crude oil and natural gas. After oil recovery by conventional methods (such as water flooding, gas flooding, chemical flooding, and microbial enhanced oil recovery), more than 50% of the crude oil remains inaccessible in subsurface oil reservoirs, unable to be recovered by conventional flooding techniques. The residual crude oil could be converted into natural gas by anaerobic microorganisms, which makes it exploitable as biogas. This innovative approach shows promise as a microbial enhanced energy recovery technology for exploiting residual crude oil in depleted oil reservoirs. This review summaries the historical development and recent advancements in the methanogenic degradation of crude oil and makes an outlook on the future research directions to facilitate the industrial application of this approach.

The wastewater containing petroleum hydrocarbons is mainly produced in the process of petroleum exploitation and petroleum products processing. It encompasses the water polluted by leakage in oil exploitation, the wastewater produced in machining, and the wastewater produced using auxiliaries in leather printing and dyeing. The wastewater containing petroleum hydrocarbons has high organic matter content, high toxicity, and poor biodegradability. Biodegradation has become one of the main research hotspots of the treatment of wastewater containing petroleum hydrocarbons because of no secondary pollution. Based on the latest literature and our research results, this paper details the composition of wastewater containing petroleum hydrocarbon, microbial species for biodegradation, biodegradation mechanism, biochar immobilization and remediation technology, and degradation genes and enzymes. This paper can provide reference for the further study of microbial flora degradation of wastewater containing petroleum hydrocarbon.