Manipulation of Unfrozen Water Retention for Enhancing Petroleum Hydrocarbon Biodegradation in Seasonally Freezing and Frozen Soil.

Manipulating the retention of unfrozen water in freezing contaminated soil to achieve prolonged bioremediation in cold climates remains unformulated. This freezing-induced biodegradation experiment shows how nutrient and zeolite amendments affect unfrozen water retention and hydrocarbon biodegradation in field-aged, petroleum-contaminated soils undergoing seasonal freezing. During soil freezing at a site-specific rate (4 to -10 °C and -0.2 °C/d), the effect of nutrients was predominant during early freezing (4 to -5 °C), alleviating the abrupt soil-freezing stress near the freezing-point depressions, elevating alkB1 gene-harboring populations, and enhancing hydrocarbon biodegradation. Subsequently, the effect of increased unfrozen water retention associated with added zeolite surface areas was critical in extending hydrocarbon biodegradation to the frozen phase (-5 to -10 °C). A series of soil-freezing characteristic curves with empirical α-values (soil-freezing index) were constructed for the tested soils and shown alongside representative curves for clays to sands, indicating correlations between α-values and nutrient concentrations (soil electrical conductivity), zeolite addition (surface area), and hydrocarbon biodegradation. Heavier hydrocarbons (F3: C16-C34) notably biodegraded in all treated soils (22-37% removal), as confirmed by biomarker-based analyses (17α(H),21ß(H)-hopane), whereas lighter hydrocarbons were not biodegraded. Below 0 °C, finer-grained soils (high α-values) can be biostimulated more readily than coarser-grained soils (low α-values).

Microbial community composition and PAHs removal potential of indigenous bacteria in oil contaminated sediment of Taean coast, Korea.

The tidal flats near Sinduri beach in Taean, Korea, have been severely contaminated by heavy crude oils due to the Korea's worst oil spill accident, say the Hebei Spirit Oil Spill, in 2007. Crude oil compounds, including polycyclic aromatic hydrocarbons (PAHs), pose significant environmental damages due to their wide distribution, persistence, high toxicity, mutagenicity, and carcinogenicity. Microbial community of Sinduri beach sediments samples was analyzed by metagenomic data with 16S rRNA gene amplicons. Three phyla (Proteobacteria, Firmicutes, and Bacteroidetes) accounted for approximately ≥93.0% of the total phyla based on metagenomic analysis. Proteobacteria was the dominant phylum in Sinduri beach sediments. Cultivable bacteria were isolated from PAH-enriched cultures, and bacterial diversity was investigated through performing culture characterization followed by molecular biology methods. Sixty-seven isolates were obtained, comprising representatives of Actinobacteria, Firmicutes, α- and γ-Proteobacteria, and Bacteroidetes. PAH catabolism genes, such as naphthalene dioxygenase (NDO) and aromatic ring hydroxylating dioxygenase (ARHDO), were used as genetic markers to assess biodegradation of PAHs in the cultivable bacteria. The ability to degrade PAHs was demonstrated by monitoring the removal of PAHs using a gas chromatography mass spectrometer. Overall, various PAH-degrading bacteria were widely present in Sinduri beach sediments and generally reflected the restored microbial community. Among them, Cobetia marina, Rhodococcus soli, and Pseudoalteromonas agarivorans were found to be significant in degradation of PAHs. This large collection of PAH-degrading strains represents a valuable resource for studies investigating mechanisms of PAH degradation and bioremediation in oil contaminated coastal environment, elsewhere.

Nocardioides litoris sp. nov., isolated from the Taean seashore.

A novel Gram-stain-positive, irregularly rod-shaped actinomycete, designated strain 002-2T, was isolated from sand beach sediment collected from the Taean seashore, Republic of Korea. Cells were aerobic, oxidase-negative and catalase-positive. Colonies of cells were bright yellow, circular, smooth and convex. The diagnostic diamino acid in the cell wall was ll-diaminopimelic acid. The predominant menaquinone was MK-8(H4). The polar lipids were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, an unknown phospholipid and two unknown amino phospholipids. The major fatty acids were iso-C16 : 0 and C17 : 1ω8c. The DNA G+C content was 68.8 mol%. 16S rRNA gene sequence analysis revealed that strain 002-2T belongs to the family Nocardioidaceae and formed a cluster with Nocardioides rubroscoriae Sco-A25T (98.1 % sequence similarity) and Nocardioides plantarum NCIMB 12834T (97.6 %). On the basis of the phenotypic and phylogenetic data, strain 002-2T (=KCTC 39838T=DSM 103718T) is considered to represent a novel species of the genus Nocardioides, for which the name Nocardioides litoris sp. nov. is proposed.