The effects of perennial ryegrass and alfalfa on microbial abundance and diversity in petroleum contaminated soil

Enhanced rhizosphere degradation uses plants to stimulate the rhizosphere microbial community to degrade organic contaminants. We measured changes in microbial communities caused by the addition of two species of plants in a soil contaminated with 31,000 ppm of total petroleum hydrocarbons. Perennial ryegrass and/or alfalfa increased the number of rhizosphere bacteria in the hydrocarbon-contaminated soil. These plants also increased the number of bacteria capable of petroleum degradation as estimated by the most probable number (MPN) method. Eco-Biolog plates did not detect changes in metabolic diversity between bulk and rhizosphere samples but denaturing gradient gel electrophoresis (DGGE) analysis of PCR-amplified partial 16S rDNA sequences indicated a shift in the bacterial community in the rhizosphere samples. Dice coefficient matrices derived from DGGE profiles showed similarities between the rhizospheres of alfalfa and perennial ryegrass/alfalfa mixture in the contaminated soil at week seven. Perennial ryegrass and perennial ryegrass/alfalfa mixture caused the greatest change in the rhizosphere bacterial community as determined by DGGE analysis. We concluded that plants altered the microbial population; these changes were plant-specific and could contribute to degradation of petroleum hydrocarbons in contaminated soil.     

Remediation of oil spills in temperate and tropical coastal marine environments

Oil is the world’s primary source of non-renewable energy, and it has also contaminated ocean coastlines due to spills. It is therefore important to have remediation treatments that are both effective, and ecologically not harmful. Current in situ bioremediation methods consist primarily of biostimulation, through addition of nutrients, and bioaugmentation, the addition of hydrocarbon degrading microorganisms. The purpose of this article is to discuss successful and unsuccessful remediation through the use of biostimulation, bioaugmentation, or a combination of both. As microbial treatments are capable of enhancing coastal oil remediation in temperate and tropical settings, the success of a particular remediation approach will be determined based on the type and amount of oil, type of soil and/or sediment, microbial inoculants and the often changing physical, chemical and biological environmental conditions. Environmental factors and limitations will be discussed as to why certain bioremediation events were successful while others were not.     

Note From the Publisher and the Editor-in-Chief

Water, Air, &; Soil Pollution: Focus -     

Editorial. Mistakes/Errors during Experimentation

Water, Air, &; Soil Pollution: Focus -