Bacterial Community Dynamics and Polycyclic Aromatic Hydrocarbon Degradation during Bioremediation of Heavily Creosote-Contaminated Soil

Abstract

Bacterial community dynamics and biodegradation processes were examined in a highly creosote-contaminated soil undergoing a range of laboratory-based bioremediation treatments. The dynamics of the eubacterial community, the number of heterotrophs and polycyclic aromatic hydrocarbon (PAH) degraders, and the total petroleum hydrocarbon (TPH) and PAH concentrations were monitored during the bioremediation process. TPH and PAHs were significantly degraded in all treatments (72 to 79% and 83 to 87%, respectively), and the biodegradation values were higher when nutrients were not added, especially for benzo(a)anthracene and chrysene. The moisture content and aeration were determined to be the key factors associated with PAH bioremediation. Neither biosurfactant addition, bioaugmentation, nor ferric octate addition led to differences in PAH or TPH biodegradation compared to biodegradation with nutrient treatment. All treatments resulted in a high first-order degradation rate during the first 45 days, which was markedly reduced after 90 days. A sharp increase in the size of the heterotrophic and PAH-degrading microbial populations was observed, which coincided with the highest rates of TPH and PAH biodegradation. At the end of the incubation period, PAH degraders were more prevalent in samples to which nutrients had not been added. Denaturing gradient gel electrophoresis analysis and principal-component analysis confirmed that there was a remarkable shift in the composition of the bacterial community due to both the biodegradation process and the addition of nutrients. At early stages of biodegradation, the ␣-Proteobacteria group (genera Sphingomonas and Azospirillum) was the dominant group in all treatments. At later stages, the ␥-Proteobacteria group (genus Xanthomonas), the ␣-Proteobacteria group (genus Sphingomonas), and the Cytophaga-Flexibacter-Bacteroides group (Bacteroidetes) were the dominant groups in the nonnutrient treatment, while the ␥-Proteobacteria group (genus Xathomonas), the ␤-Proteobacteria group (genera Alcaligenes and Achromobacter), and the ␣-Proteobacteria group (genus Sphingomonas) were the dominant groups in the nutrient treatment. This study shows that specific bacterial phylotypes are associated both with different phases of PAH degradation and with nutrient addition in a preadapted PAH-contaminated soil. Our findings also suggest that there are complex interactions between bacterial species and medium conditions that influence the biodegradation capacity of the microbial communities involved in bioremediation processes.

A novel degradation pathway in the assimilation of phenanthrene by Staphylococcus sp. strain PN/Y via meta-cleavage of 2-hydroxy-1-naphthoic acid: formation of trans-2,3-dioxo-5-(2′-hydroxyphenyl)-pent-4-enoic acid

“…In recent years, the biodegradation of PAHs has received considerable attention and a variety of micro-organisms have been reported to play important roles in the process (Pothuluri & Cerniglia, 1994;Shuttleworth & Cerniglia, 1995;Kanaly & Harayama, 2000;Habe & Omori, 2003;Tortella et al, 2005). Bioremediation technologies have increasingly been proposed to decontaminate PAH-contaminated sites (Harayama, 1997;Samanta et al, 2002;Parrish et al, 2004;Vinas et al, 2005).…”

“…In recent years, the biodegradation of PAHs has received considerable attention and a variety of micro-organisms have been reported to play important roles in the process (Pothuluri & Cerniglia, 1994;Shuttleworth & Cerniglia, 1995;Kanaly & Harayama, 2000;Habe & Omori, 2003;Tortella et al, 2005). Bioremediation technologies have increasingly been proposed to decontaminate PAH-contaminated sites (Harayama, 1997;Samanta et al, 2002;Parrish et al, 2004;Vinas et al, 2005).Phenanthrene, a PAH with three condensed rings fused in angular fashion, has a 'bay-region' and a 'K-region' and is often used as a model substrate for studies on the metabolism of carcinogenic PAHs. Over the last 60 years, a number of studies on phenanthrene degradation by several Gram-negative and Gram-positive bacterial species have been reported (Evans et al, 1965;Kiyohara et al, 1976Kiyohara et al, , 1982Kiyohara & Nagao, 1978;Barnsley, 1983;Gibson & Subramanian, 1984;Houghton & Shanley, 1994;Adachi et al, 1999;Samanta et al, 1999), where various pathways and metabolic diversity involved in phenanthrene degradation were documented.…”

Characterization and Control Strategies of an Integrated Chemical−Biological System for the Remediation of Toxic Pollutants in Wastewater: A Case of Study

“…20 Another important group of clones belonged to Xanthomonas phylotype (4% of clones) which have been found as dominant group in bacterial community degrading aromatic hydrocarbons. 21 This study shows that identification of microbial diversity is a promising tool for the control of process performance.…”

Autochthonous bioaugmentation to enhance phenanthrene degradation in soil microcosms under arid conditions

“…As a result, substrate and nutrient diffusion are restricted and microbes become substrate limited. Holman and Tsang (1995) determined that a water content of 50-70 % of field capacity was optimum for biodegradation of aromatic hydrocarbons to proceed at maximum rate; also Viñas et al (2005) found that in a heavily creosote-contaminated soil, the higher percentage of hydrocarbon degradation was obtained with a 40-60 % of soil water-holding capacity (WHC), while with 20 % WHC, only slight degradation was observed. In our case, values near 20 % WHC (10 % of water content) drastically inhibited the phenanthrene biodegradation; when the moisture was increased, reached a 25 % WHC (15 % of water content), the soil biodegradation activity was recovered.…”