Both Cycloclasticus spp. and Pseudomonas spp. as PAH-degrading bacteria in the Seine estuary (France)

Abstract

Like other highly urbanized and industrialized estuaries, the Seine estuary (France) has, for decades, received high inputs of polycyclic aromatic hydrocarbons (PAHs). In order to estimate the bioremediation potentials and to identify the bacterial species involved in hydrocarbon degradation, we used microcosms containing seawater from the Seine estuary supplemented with either naphthalene, phenanthrene, fluorene or pyrene. In the microcosms enriched with naphthalene or phenanthrene, hydrocarbon biodegradation was significant within 9 weeks (43% or 46%, respectively), as shown by analyses in GC-MS. In similar microcosms incubated also with naphthalene or phenanthrene, analysis of the 16S rRNA gene sequences (DNA and cDNA) with denaturing gradient gel electrophoresis and clone libraries indicated that the PAH-degrading communities were dominated by Cycloclasticus spp., confirming their universal key role in degradation of low-molecular-weight PAHs in marine environments. However, in contrast to previous studies, we found that Pseudomonas spp. also degraded naphthalene and phenanthrene in seawater; this occurred only after 21 days, as was confirmed by real-time PCR. Although this genus has been abundantly described in the literature as a good PAH-degrading bacterial group in soil or in sediment, to our knowledge, this is the first evidence of a significant fitness in PAH degradation in seawater.

Bacterial Community Response to Petroleum Hydrocarbon Amendments in Freshwater, Marine, and Hypersaline Water-Containing Microcosms

“…TPH results corroborated this observation. Although certain amounts of TPH were lost by evaporation, by abiotic degradation, or during hydrocarbon extraction steps before GC-MS analysis, as also observed by Niepceron et al (13), the occurrence of biodegradation in all contaminated microcosms can be assumed when the TPH results are compared to those obtained in the microcosms used as controls. Moreover, different bacterial strains were also isolated from each contaminated microcosm, and the hydrocarbon-degrading potential of these bacteria was detected.…”

“…However, microbial succession in petroleum-contaminated environments depends on the hydrocarbon fractions available to the microbial community, as suggested previously by McKew et al (10). Studies in marine environments have described the predominance of bacteria belonging to the Alcanivorax species (Oceanospirillales order) as the primary aliphatic hydrocarbon degraders (10,11) and those belonging to the Cycloclasticus species as the primary polycyclic aromatic hydrocarbon (PAH) degraders (12,13).…”

“…The contaminants used were heptadecane (a model of aliphatic hydrocarbons; Sigma-Aldrich, St. Louis, MO), naphthalene (a model of aromatic hydrocarbons; Sigma-Aldrich), and crude oil (Baiano oil, a light crude oil with low viscosity [American Petroleum Institute gravity, greater than 30] and a complex mixture of different aliphatic and aromatic hydrocarbons). On the basis of contaminant input, the C/N/K/P proportion was corrected to 100:10:1:1 to facilitate bacterial growth, as described by Niepceron et al (13). Two controls were used: (i) different water samples with the addition of C, N, K, and P but without any contaminants and (ii) water samples amended with C, N, K, and P, sterilized by autoclaving (121°C, 15 min), and subsequently supplemented with each contaminant.…”

Selection of Diazotrophic Bacterial Communities in Biological Sand Filter Mesocosms Used for the Treatment of Phenolic-Laden Wastewater

“…Three of these were closely related to bacterial taxa with a known capability to degrade/oxidize organic and/or aromatic compounds [11,32]. The selection of bacterial taxa possessing such catabolic capacities in BSF B was not unexpected, as it constitutes a direct community adaptation to the contamination [12,15]. Four were, however, closely related to well-known nitrogen-fixing microorganisms (Azotobacter species / Beijerinckia indica [DGGE-bands S1, S5, D1, D2]).…”

Meiofauna reduces bacterial mineralization of naphthalene in marine sediment

“…The isolated naphthalene-degrading bacteria were matched to a group containing known marine PAH degraders (Garcia-Valdes et al, 1988;Niepceron et al, 2009), which are susceptible to grazing (Brettar et al, 1994). The isolates were also analyzed with T-RFLP but the corresponding TRFs were not found in the community profiles, suggesting that their abundance are below the detection limit for T-RFLP or that more species than the ones isolated are responsible for the mineralization in our microcosms.…”