Assessment of soil potential to natural attenuation and autochthonous bioaugmentation using microarray and functional predictions from metagenome profiling

Dose–Response Effect of Nitrogen on Microbial Community during Hydrocarbon Biodegradation in Simplified Model System

Knowledge about the influence of C:N ratio on the biodegradation process of hydrocarbon compounds is of significant importance in the development of biostimulation techniques. The purpose of this study was to assess the impact of nitrogen compounds on the environmental consortium during the process of biological decomposition of hydrocarbons. The experimental variants represented low, moderate, and excessive biostimulation with nitrogen compounds. The metabolic activity of the consortium was tested using the flow cytometry technique. The efficiency of the biodegradation of hydrocarbons of the consortium, based on the gas chromatography method, and metapopulation changes, based on the analysis of V4 16srRNA sequencing data, were assessed. The results of the research confirm the positive effect of properly optimized biostimulation with nitrogen compounds on the biological decomposition of polycyclic aromatic hydrocarbons. The negative impact of excessive biostimulation on the biodegradation efficiency and metabolic activity of microorganisms is also proven. Low resistance to changes in the supply of nitrogen compounds is demonstrated among the orders Xanthomonadales, Burkholderiales, Sphingomonadales, Flavobacteriales, and Sphingobacteriales. It is proven that quantitative analysis of the order of Rhizobiales, characterized by a high-predicted potential for the decomposition of polycyclic aromatic hydrocarbons, may be helpful during biostimulation optimization processes in areas with a high nitrogen deficiency.

Factors Influencing the Bacterial Bioremediation of Hydrocarbon Contaminants in the Soil: Mechanisms and Impacts

The discharge of hydrocarbons and their derivatives to environments due to human and/or natural activities cause environmental pollution (soil, water, and air) and affect the natural functioning of an ecosystem. To minimize or eradicate environmental pollution by hydrocarbon contaminants, studies showed strategies including physical, chemical, and biological approaches. Among those strategies, the use of biological techniques (especially bacterial biodegradation) is critically important to remove hydrocarbon contaminants. The current review discusses the insights of major factors that enhance or hinder the bacterial bioremediation of hydrocarbon contaminants (aliphatic, aromatic, and polyaromatic hydrocarbons) in the soil. The key factors limiting the overall hydrocarbon biodegradation are generally categorized as biotic factors and abiotic factors. Among various environmental factors, temperature range from 30 to 40°C, pH range from 5 to 8, moisture availability range from 30 to 90%, carbon/nitrogen/phosphorous (C/N/P; 100:20:1) ratio, and 10–40% of oxygen for aerobic degradation are the key factors that show positive correlation for greatest hydrocarbon biodegradation rate by altering the activities of the microbial and degradative enzymes in soil. In addition, the formation of biofilm and production of biosurfactants in hydrocarbon-polluted soil environments increase microbial adaptation to low bioavailability of hydrophobic compounds, and genes that encode for hydrocarbon degradative enzymes are critical for the potential of microbes to bioremediate soils contaminated with hydrocarbon pollutants. Therefore, this review works on the identification of factors for effective hydrocarbon biodegradation, understanding, and optimization of those factors that are essential and critical.

Microbial Degradation of Hydrocarbons-Basic Principles for Bioremediation: A Review

Crude oil-derived hydrocarbons constitute the largest group of environmental pollutants worldwide. The number of reports concerning their toxicity and emphasizing the ultimate need to remove them from marine and soil environments confirms the unceasing interest of scientists in this field. Among the various techniques used for clean-up actions, bioremediation seems to be the most acceptable and economically justified. Analysis of recent reports regarding unsuccessful bioremediation attempts indicates that there is a need to highlight the fundamental aspects of hydrocarbon microbiology in a clear and concise manner. Therefore, in this review, we would like to elucidate some crucial, but often overlooked, factors. First, the formation of crude oil and abundance of naturally occurring hydrocarbons is presented and compared with bacterial ability to not only survive but also to utilize such compounds as an attractive energy source. Then, the significance of nutrient limitation on biomass growth is underlined on the example of a specially designed experiment and discussed in context of bioremediation efficiency. Next, the formation of aerobic and anaerobic conditions, as well as the role of surfactants for maintaining appropriate C:N:P ratio during initial stages of biodegradation is explained. Finally, a summary of recent scientific reports focused on the removal of hydrocarbon contaminants using bioaugmentation, biostimulation and introduction of surfactants, as well as biosurfactants, is presented. This review was designed to be a comprehensive source of knowledge regarding the unique aspects of hydrocarbon microbiology that may be useful for planning future biodegradation experiments. In addition, it is a starting point for wider debate regarding the limitations and possible improvements of currently employed bioremediation strategies.