Bioremediation of PAH-Contaminated Soil by Fungi

Assessment of heavy metal contamination at Tallaboa Bay (Puerto Rico) by marine sponges' bioaccumulation and fungal community composition

The water filtering capacity, and the potential to accumulate contaminants such as heavy metals, make marine sponges suitable candidates for biomonitoring of marine ecosystems. Sponges also harbor a variety of endosymbionts, including fungi, which could be affected by the accumulation of contaminants. This work examined the bioaccumulation factors of heavy metals by sponges from coastal waters from Puerto Rico. Fungal communities associated with marine sponges were assessed to determine if their composition co-varied with heavy metals in sponge tissue. All sponges in our study where found to bioaccumulate arsenic, cadmium and copper. Fungi associated with the sponges showed variations in community composition among localities and sponge species. Our results suggest that sponges, specially Tedania ignis, could be used as a complementary component for biomonitoring of arsenic, cadmium and copper; and that members of the harbored fungal communities could be negatively affected by the accumulation of heavy metals in the sponges.

Continuing Impacts of Selective Inhibition on Bacterial and Fungal Communities in an Agricultural Soil

Selective inhibition (SI) has been routinely used to differentiate the contributions of bacteria and fungi to soil ecological processes. SI experiments typically measured rapid responses within hours since the addition of inhibitor, but the long-term effects of selective biocides on microbial community composition and function were largely unknown. In this study, a microcosm experiment was performed with an agricultural soil to explore the effectiveness of two bactericides (bronopol, streptomycin) and two fungicides (cycloheximide, captan), which were applied at two different concentrations (2 and 10 mg g^-1). The microcosms were incubated for 6 weeks. A radiolabeled substrate, [1,2,3,4,4a,9a-¹⁴C] anthracene, was spiked to all microcosms, and the derived CO₂ was monitored during the incubation. The abundance and composition of bacteria and fungi were assessed by qPCR and Miseq sequencing of ribosomal rRNA genes. It was demonstrated that only 2 mg g^-1 bronopol and cycloheximide significantly changed the bacteria to fungi ratio without apparent non-target inhibition on the abundances; however, community shifts were observed in all treatments after 6 weeks incubation. The enrichment of specific taxa implicated a selection of resistant or adapted microbes by these biocides. Mineralization of anthracene was continuingly suppressed in all SI microcosms, which may result in biased estimate of bacterial and fungal contributions to pollutant degradation. These findings highlight the risks of long-term application of selective inhibition, and a preliminary assessment of biocide selection and concentration is highly recommended.

Strategies for oxidation of PAHs in aged contaminated soil by batch reactors

Polycyclic aromatic hydrocarbons (PAH) are neutral, nonpolar and hydrophobic molecules that tend to sorb onto soil organic matter. Chemical oxidation is a good choice to avoid the limitations of bioremediation. To evaluate the efficiency of different types of oxidation (permanganate, hydrogen peroxide, and persulfate) and activation (heat, alkaline, and iron), batch reactors were prepared. The soil was contaminated with phenanthrene and pyrene (1200 ± 200 and 2800 ± 100mg per kg of dry soil, respectively) and aged for fifteen months. Treatments were prepared with 10g of contaminated dry soil and 20ml of water and incubated at room temperature for 7 days. Analyses of phenanthrene and pyrene concentrations, soil pH and electric conductivity were performed. Counts of heterotrophic cultivable bacteria on R2A medium and PAH-degraders were carried out after 7 days of treatment. The persulfate treatment at room temperature, without the addition of activators, achieved better results than treatments with the same doses of permanganate or hydrogen peroxide. All the strategies to improve persulfate treatments yielded higher degradation of pyrene than the biological control, as expected from the structural description of this compound by Clar's model. The thermal activation of persulfate (65°C for 6h) led to the degradation of more than 90% of both PAHs after 7 days of treatment.

Molecular Characterization of Fusarium Solani Degrades a Mixture of Low and High Molecular Weight Polycyclic Aromatic Hydrocarbons

Objectives:

This study evaluates the ability of a non-white rot fungus strain, HESHAM-1, to degrade a mixture of low (naphthalene and phenanthrene) and high (chrysene and benzo(a)pyrene) molecular weight polycyclic aromatic hydrocarbons (LMW and HMW PAHs).

Methods:

Strain HESHAM-1 was isolated from oil polluted soil by enrichment method using phenanthrene as the sole source of carbon and energy. The strain showed the ability to tolerate and degrade a mixture of both low and high molecular weight PAHs. In the presences of LMW-PAHs (naphthalene and phenanthrene) as co-substrate, chrysene and benzo(a)pyrene (HMW-PAHs) were, respectively degraded by the fungus strain HESHAM-1 which was confirmed by GC-MS analyses.

Results:

The degradation rate was found as 84.82% for naphthalene, 40.09% for phenanthrene, 57.84% for chrysene and 71.06% for benzo(a)pyrene at the end of 10 days. This is the first report describing the biodegradation of a mixture of four PAH compounds by non-white rot fungus strain HESHAM-1 isolated from Egyptian oil-polluted soil. The fungus strain HESHAM-1 was identified by morphological characteristics and molecular genetics technique based on PCR amplification and sequencing of the internal transcribed spacers (ITSs) of the rDNA region and intervening 5.8S rRNA gene. Blast result and phylogenetic analysis of gene sequencing suggested that strain HESHAM-1 was closely related toFusarium solaniwith 100% sequence identity.

Conclusion:

The present study clearly demonstrates that, strain HESHAM-1 could be used to remove the crude oil from the environment.