Survival Strategies of Pseudomonas in Oil-Phase: Implications for Microbial Enhanced Oil Recovery

Microbially enhanced oil recovery (MEOR) stands out as an innovative tertiary oil recovery strategy, with the global petroleum industry increasingly recognizing its potential to enhanced oil recovery. Nevertheless, in practical field applications, MEOR often fails to reach the expected oil recovery efficiency, mainly because of the application of inappropriate microbial species. Thus, the screening of highly efficient strains is pivotal for effectively enhancing the oil recovery efficiency of MEOR. Recent findings have shown that crude oil harbors microorganisms (termed “oil-phase” microbes), and have also accentuated their substantial applicability in MEOR. However, the underlying mechanisms by which these microorganisms adapt within the crude oil environment remain largely uncharacterized. To address this, a large-scale cultivation strategy was employed to obtain the most core Pseudomonas species in the oil phase. Accordingly, a representative Pseudomonas strain was successfully separated from the oil phase of a reservoir in China’s Qinghai Oilfield. Genome analysis of this isolate revealed its remarkable versatility in metabolizing hydrocarbons. Experimental evidence further showed that the strain was capable of growing using crude oil and alkanes as its sole carbon source, thereby strongly corroborating the genomic analysis findings. Furthermore, we identified genes responsible for encoding: (a) diverse transporters facilitating nutrient uptake and detoxification; (b) a versatile respiration system for quick response to dissolved oxygen fluctuations; and (c) biosynthesis of multiple compatible solutes to endure osmotic and high-pressure stresses. These genes are fundamental for survival in the harsh oil reservoir environment. This study is the initial report on the genomic profile of oil-phase Pseudomonas populations. The findings are expected to be valuable for devising more effective strategies for MEOR and may also have implications for other biotechnological applications.