Abstract
In this study, we aimed at determining the impact of naphthalene and different oxygen levels on a biofilm bacterial community originated from a petroleum hydrocarbon–contaminated groundwater. By using cultivation-dependent and cultivation-independent approaches, the enrichment, identification, and isolation of aerobic and oxygen-limited naphthalene degraders was possible. Results indicated that, regardless of the oxygenation conditions, Pseudomonas spp. became the most dominant in the naphthalene-amended selective enrichment cultures. Under low-oxygen conditions, P. veronii/P. extremaustralis lineage affiliating bacteria, and under full aerobic conditions P. laurentiana–related isolates were most probably capable of naphthalene biodegradation. A molecular biological tool has been developed for the detection of naphthalene 1,2-dioxygenase-related 2Fe-2S reductase genes of Gram-negative bacteria. The newly developed COnsensus DEgenerate Hybrid Oligonucleotide Primers (CODEHOP-PCR) technique may be used in the monitoring of the natural attenuation capacity of PAH-contaminated sites. A bacterial strain collection with prolific biofilm-producing and effective naphthalene-degrading organisms was established. The obtained strain collection may be applicable in the future for the development of biofilm-based bioremediation systems for the elimination of PAHs from groundwater (e.g., biofilm-based biobarriers).
Highlights
Polycyclic aromatic hydrocarbons (PAHs), originating either from natural or from anthropogenic sources, are widespread persistent and toxic pollutants of great concern
We aimed at determining the impact of naphthalene (LMW-PAH) on a biofilm bacterial community, which developed initially in hydrocarbon-contaminated groundwater at the Bugyi site (Hungary), where the concentration of oxygen is generally low
We focused on the reductase component of the naphthalene 1,2dioxygenase gene found in Gram-negative bacteria (NDO; EC 1.14.12.12)
Summary
Polycyclic aromatic hydrocarbons (PAHs), originating either from natural or from anthropogenic sources, are widespread persistent and toxic pollutants of great concern. Based on global trends and taking into consideration sustainability, a better understanding of microbial communities responsible for efficient PAH biodegradation under different environmental circumstances—e.g., aquatic versus terrestrial ecosystem, marine versus freshwater environment, aerobic/oxygen-limited/anaerobic conditions—is a must. The targeted biofilms (Bugyi site, freshwater environment, Hungary) and microbial mats (Camargue site, marine environment, France) proved to be the habitat of complex networks of chemoorganotrophic and chemolithotrophic bacteria where microorganisms with opposite traits (e.g., aerobic/anaerobic, iron reducers/iron oxidizers) co-existed and interacted on complementary processes (Benedek et al 2016). We aimed at determining the impact of naphthalene (LMW-PAH) on a biofilm bacterial community, which developed initially in hydrocarbon-contaminated groundwater at the Bugyi site (Hungary), where the concentration of oxygen is generally low. Our results provide valuable information regarding PAH biodegradation in hypoxic subsurface freshwater ecosystems
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