CHARACTERIZATION OF BACTERIA FROM HYDROCARBON POLLUTED SITE

CHAPTER ONE

INTRODUCTION

1.1       Background of the Study

Hydrocarbons are any of a class of organic chemical compounds composed only of the elements carbon (C) and hydrogen (H). The carbon atoms join together to form the framework of the compound, and the hydrogen atoms attach to them in many different configurations. Hydrocarbons are the principal constituents of petroleum and natural gas. They serve as fuels and lubricants as well as raw materials for the production of plastics, fibres, rubbers, solvents, explosives, and industrial chemicals. Hydrocarbons are considered to be the primary source of energy throughout the world. Large amount of fuel is required, especially for the transportation, industrial production, and lubrication. Hydrocarbon contaminations are dangerous to animal and plant lives due to their carcinogenic and mutagenic traits (Islam Sajib and Rahman, 2017). Hydrocarbon contamination is one of the most significant source of pollution around the world. Petroleum is a hydrocarbon and is used as a conventional energy source even though it has prominence as a global environmental pollutant. The increase in automobiles, number of gasoline stations and auto mobile service is ever increasing. During transfer and service, oil is spilled by which soil is contaminated (Das and Chandran, 2010). Contamination causes soil to lose its useful properties such as binding capacity and fertility. Oil released into the environment affects many plants, animals, micro-organisms and humans within the oil impacted environment. Studies have shown that hydrocarbon pollution usually decreases microbial diversity with consequent disruption of the ecosystem dynamics as a result the alteration of soil organic matter, mineralization and demineralization ratio (John et al., 2011).

Pollution with petroleum and its products is considered a major problem worldwide due to its impact on human health and the environment. Petroleum hydrocarbons are considered to be the most common group of persistent organic contaminants and are known to be toxic to many organisms. Moreover it has been shown that petroleum hydrocarbons cause significant losses in soil quality due to their toxicity towards biological processes catalyzed by soil microorganisms (Althalb and Singleton, 2017). Prolonged exposure to oil as well as high concentration of oil could cause the development of liver or kidney disease, possible damage to the bone marrow and an increased risk of cancer. The clean-up of soil pollution caused by hydrocarbon compounds is the utmost challenge in environmental remediation. Petroleum hydrocarbon compounds in the environment cause serious health risks due to their carcinogenic and mutagenic effects. Studies have shown that hydrocarbon pollution usually decreases microbial diversity with consequent disruption of the ecosystem dynamics as a result the alteration of soil organic matter, mineralization and demineralization ratio. Major interrelated factors affects soil microbial activities including soil physicochemical properties, vegetation and land use type. The relative effects of these factors differ in different soil zones, horizons and climatic zones (Teknikio et al., 2018).

While these hydrocarbons contain plenty of carbon and hydrogen atoms, they are very nutritionally poor and insufficient to sustain many microorganism species. The toxicity of these hydrocarbons to microorganisms means that contaminated soil may experience drastic changes to the population and abundances of various microbial species. The extent of these changes to the microbial populations is dependent on several factors including: the composition of the microbial community prior to the contamination, the chemical composition of the contaminant (crude oil), and the physiochemical factors of the contamination site (Abbasian et al., 2016). Fortunately, the degradation of these oils in the environment is possible through several techniques: physical, chemical or biological. The technology commonly used for the soil remediation includes mechanical, burying, evaporation, dissolution, dispersion and washing. However, these technologies are expensive and can lead to incomplete decomposition of contaminants. To overcome these problems, microbial bioremediation is the only way to preserve our nature. The presence of different substrates and metabolites in hydrocarbon contaminated soils has provided an environment for the development of a quite complicated microbial community. Some microorganisms can utilize the hydrocarbons as sole carbon sources for getting their energy and metabolic activities. Among them Bacillus spp., Rhizobium spp., Microbacterium oxydans and Arthrobacter spp., Micrococcus spp., Corynebacterium spp., Flavobacterium spp., Pseudomonas spp. have been reported (Teknikio et al., 2018).

Certain microbial species face a challenge when grown in the presence of hydrocarbons due to their hydrophobicity and insolubility – leading to restriction of absorption by these cells, ultimately leading toxicity (Abbasian et al., 2015). Moreover, these hydrocarbons affect the microorganisms’ membrane fluidity; thus, microorganism exposed to petroleum products must adapt their membrane structure to survive (Jin et al., 2014). The extent of these changes are depending on the type of hydrocarbon contaminant and their carbon chain length. Some hydrocarbon-degrading microorganisms learn to adapt by producing and secreting a surfactant compounds to emulsify the hydrocarbon and form micelles – to be taken up later in various ways. Microorganisms are a key player in maintaining sustainable environment and ecosystem (Varjani, 2017).

However, microorganisms are known to be the most effective tools to naturally degrade crude oil after a spillage episode. Bioremediation is a process in which microorganism are utilized to convert dangerous organic pollutants from crude oil into environmentally friendly compounds such as CO₂ and H₂O. In the process of biodegradation, oleophilic microbes are utilized and administrated to degrade the hydrocarbons and remediate the site of spillage (Varjani and Upasani, 2013). Microorganisms are highly efficient and versatile in their ability to degrade hydrocarbons (Adebusoye et al., 2007). Bacteria that biodegrade polynuclear aromatic hydrocarbons (PAHs), monoaromatic hydrocarbons and aliphatic hydrocarbons are readily isolated from the environment that have been contaminated with petroleum hydrocarbon (Manchola and Dussan, 2014). A reviewed list of bacterial genera has listed 79 genera that can utilize hydrocarbon as the sole source of carbon and energy (Head et al., 2006). Many microbial ecologists have identified various microbial species that are effective degrader of hydrocarbons in natural environments. Many of these microbial consortia have been isolated from heavily contaminated areas. However, bacteria play the central role in hydrocarbon degradation. The driving force for petroleum biodegradation is the ability of microorganisms to utilize hydrocarbons to satisfy their cells growth and energy needs (Ameh and Kawo, 2017). The effect of hydrocarbon contaminants on human health and the environment cannot be over emphasized. It is therefore important to reduce or eliminate the total petroleum hydrocarbon (TPH) content in petroleum polluted sites by applying desirable property of hydrocarbon-utilizing bacteria isolated or found in the contaminated environments (Wokem et al., 2017).

1.2       Aim and Objectives of the Study

1.2.1    Aim    

This research was aimed at isolating, characterizing and identifying bacteria from hydrocarbon polluted sites.

1.2.2    Objectives of the Study

The objectives included;

1.     To isolate bacteria from hydrocarbon polluted sites.

2.     To characterize and identify bacteria isolated from hydrocarbon polluted sites.

1.3       Significance of the Study

The result of this research will be of help to environmentalists as it will provide knowledge on the microorganisms which can be used for bioremediation of oil polluted areas in the country. The findings of this study if further studied will equally help the government and environmental bodies to eradicate the harmful oil polluted areas with a natural and much safer method of treating oil spills in order to better the lives of people living in affected areas. The results of the study could further provide information to researchers interested in working on topics related to the study or who wish to embark on improving the study.

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