Could petroleum biodegradation be a joint achievement of aerobic and anaerobic microrganisms in deep sea reservoirs?

Abstract

Several studies suggest that petroleum biodegradation can be achieved by either aerobic or anaerobic microorganisms, depending on oxygen input or other electron acceptors and appropriate nutrients. Evidence from in vitro experiments with samples of petroleum formation water and oils from Pampo Field indicate that petroleum biodegradation is more likely to be a joint achievement of both aerobic and anaerobic bacterial consortium, refining our previous observations of aerobic degradation. The aerobic consortium depleted, in decreasing order, hydrocarbons > hopanes > steranes > tricyclic terpanes while the anaerobic consortium depleted hydrocarbons > steranes > hopanes > tricyclic terpanes. The oxygen content of the mixed consortia was measured from time to time revealing alternating periods of microaerobicity (O2 ~0.8 mg.L-1) and of aerobicity (O2~6.0 mg.L-1). In this experiment, the petroleum biodegradation changed from time to time, alternating periods of biodegradation similar to the aerobic process and periods of biodegradation similar to the anaerobic process. The consortia showed preferences for metabolizing hydrocarbons > hopanes > steranes > tricyclic terpanes during a 90-day period, after which this trend changed and steranes were more biodegraded than hopanes. The analysis of aerobic oil degrading microbiota by the 16S rRNA gene clone library detected the presence of Bacillus, Brevibacterium, Mesorhizobium and Achromobacter, and the analysis of the anaerobic oil degrading microbiota using the same technique detected the presence of Bacillus and Acinetobacter (facultative strains). In the mixed consortia Stenotrophomonas, Brevibacterium, Bacillus, Rhizobium, Achromobacter and 5% uncultured bacteria were detected. This is certainly a new contribution to the study of reservoir biodegradation processes, combining two of the more important accepted hypotheses.

Polycyclic Aromatic Hydrocarbon-Induced Changes in Bacterial Community Structure under Anoxic Nitrate Reducing Conditions

“…The same was true for the FdP samples where, despite a general decrease of the Firmicutes group, the Bacilli phylotypes increased especially in the naphthalene cultures. This increase of Bacilli relative abundance is noteworthy, since members of this class have been described as aerobic and anaerobic oil-degrading strains (Van Gestel et al, 2003; da Cruz et al, 2011; Maddela et al, 2016), which suggests a link between the increase of this group and the degradation process.…”

Subsurface Petroleum Microbiology

“…Recently da Cruz et al (2011) reported evidences from in vitro experiments that petroleum biodegradation could be jointly achieved by aerobic and anaerobic bacterial consortia in biofilms. In their study, an aerobic consortium depleted, in decreasing order, hydrocarbons > hopanes > steranes > tricyclic terpanes, while an anaerobic consortium depleted in the order of hydrocarbons > steranes > hopanes > tricyclic terpanes.…”

Processos naturais de biodegradação do petróleo em reservatórios

“…Os microrganismos aeróbios necessitam da presença de oxigênio molecular (condições óxicas) para seu crescimento e para converter os hidrocarbonetos em CO 2 , H 2 O e biomassa. Já os microrganismos facultativos podem crescer na presença (aerobiose) ou ausência (anaerobiose, fermentação) de oxigênio 22,24,25 (condições anóxicas). Os anaeróbios estritos utilizam diferentes aceptores, como nitratos (NO 3-), sulfatos (SO 4…”