Methylotrophs and Hydrocarbon-Degrading Bacteria Are Key Players in the Microbial Community of an Abandoned Century-Old Oil Exploration Well

The search for microorganism that degrade hydrocarbons is highly relevant because it enables the bioremediation of these substances cheaply and without dangerous byproducts. In this work, we studied the microbial communities of an exploratory oil well, abandoned a century ago, located in the Cahuita National Park of Costa Rica. This well is characterized by a continuous efflux of methane and the presence of a mixture of hydrocarbons including C2-dibenzothiophene, phenanthrene or anthracene, fluoranthene pyrene, dibenzothiophene, tricyclic terpane, pyrene, sesquiterpenes, sterane and n -alkanes. Based on the analysis of 16S rRNA gene amplicons, we detected a significant abundance of methylotrophic bacteria ( Methylobacillus (6.3-26.0% of total reads) and Methylococcus (4.1-30.6%)) and the presence of common genera associated with hydrocarbon degradation, such as Comamonas (0.8-4.6%), Hydrogenophaga (1.5-3.3%) Rhodobacter ( 1.0-4.9% ) and Flavobacterium ( 1.1-6.5 % ). We show that the microbial community in the oil well is shaped mainly by C1 carbon sources, indicating a metabolism that includes carbon recycling and crossfeeding. This habitat provides insight into the evolution of hydrocarbon-degrading communities and corresponds to a niche of interest for the isolation of novel bacteria with potential in the degradation of oil components.