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The effect of hydrocarbon contamination on the activities diazotrophs and phosphate solubilizing bacteria in a garden soil located in Uyo metropolis, Akwa Ibom State was monitored using standard microbiological and analytical techniques. The result revealed a significant (p≤ 0.05) reduction in the loads of phosphate solubilizing bacteria (PSB)  (7.6 xImage to 1.9 x Image CFU/g) and Diazotrophs (2.49 x 102 to 1.6 x 101 CFU/g) after hydrocarbon contamination. Bacteria isolated from the uncontaminated sample include; Bacillus megaterium, B. laterosporous, B. polymyxa, B. subtilis, Bacillus sp. and Aeromonas salmonicida while Enterococcus Sp. and Bacillus subtilis, represents the only isolate obtained from the contaminated sample. The study revealed that increasing level of hydrocarbon contamination led to a corresponding reduction in the number and diversity of phosphate solubilizers and diazotrophs in the garden soil samples. Since the activities of these microbial groups are crucial in soil nutrient cycling, it is therefore recommended that bioremediation should be taken to remediate hydrocarbon contaminated arable soils in order to preserve soil fertility and enhance crop productivity.   

TABLE OF CONTENTSCHAPTER                TITLE                    PAGETitle page    -    -    -    -    -    iDeclaration        -    -    -    -    iiCertification    -    -    -    -    -    iiiDedication    -    -    -    -    -    ivAcknowledgement -    -    -    -    -    vAbstract    -    -    -    -    -    viTable of content -    -    -    -    -    viiList of Table    -    -    -    -    -    ix

CHAPTER ONE             INTRODUCTION1.1                     Background of the study    -    -    -    11.2                     Statement of problem    -    -    -    -    3    1.3                     Aim and Objectives    -    -    -    -    3CHAPTER TWO            LITERATURE REVIEW  2.1                         Hydrocarbon Composition    -    -    -    4    2.1.2                       Uses of Hydrocarbon    -    -    -    42.1.3                        Effect of Hydrocarbon contamination -    -    52.1.4                      Effect of Hydrocarbon Contamination on                             Microbial Diversity in the Soil      -    -    62.2                       Remediation     -    -    -    -    -    72.2.1                     Methods of Bioremediation     -    -    -    8    2.3                      Phosphate Solubilizing Bacteria (PSB)-     -    9    2.4                       Diazotrophs     -    -    -        -    -    11

CHAPTER THREE        MATERIALS AND METHODS3.1                    Materials used      -    -    -    -    133.2                     Experimental design    -    -    -    -    133.3                     Sample collection    -    -    -    -    133.4                     Culture media used    -    -    -    -    133.5                     Microbiological analysis    -    -    -    143.6                     Determination of the Number of                                          Diazotrophs Loads      -    -    -    -    143.7                     Determination of the Number of                                     Phosphate Solubilizing Bacteria Loads-    -    14    3.6                    Maintenance of Pure Microbial Isolate-    -    153.7                    Morphological and Biochemical                                     characterization of Isolates     -    -    -    15

CHAPTER FOUR            RESULT4.1                    Microbial Load of Garden soil Sample  -    -    194.2                    Morphological and Biochemical                                     Characteristics of Microbial Isolates                                     Obtained from the Garden Soil Sample-    -    20        4.3                    Distribution and Occurrence of the                                     Microbial Isolate in the Garden Soil                                     Sample      -    -    -    -    -    23   

CHAPTER FIVE            DISCUSSION, CONCLUSION AND                     RECOMMENDATION5.1                    Discussion     -    -    -    -    -    245.2                        Conclusion     -    -    -    -    -    255.3                    Recommendation    -    -    -    -    25                       References     -    -    -    -    -    26Appendices    -    -    -    -    -    30


TABLE             TITLE                                PAGE4.1                Microbial load of the garden soil samples     -    -    194.2a                Biochemical Characteristics of microbial isolates                             obtained from the uncontaminated soil sample -    -    21       4.2b                Biochemical Characteristics of microbial isolates                             obtained from the contaminated soil sample     -    -    224.3                Distribution and occurrence of the microbial                 Isolates of soil sample      -    -    -    -    23

CHAPTER ONEINTRODUCTION1.1    Background of the Study

Hydrocarbons are used in large quantities as fuels (Bierkens and Geerts, 2014). Hydrocarbons are becoming a global problem for the environment. They are highly persistent in the environment, toxic and present significant health risks to humans (Hentati et al., 2013).Hydrocarbons and other organic compounds can bring up serious environmental problems when spill occur (Zhang et al., 2010). Despite the economic benefits of hydrocarbon industry, hydrocarbons influences and alters soil microbial community composition and biogeochemical cycles, and triggers strongly negative impacts in sustainable soil fertility and environmental quality. The hydrocarbon pollutants enters into the soil, influences plant growth and causes human health concerns.Soil is a habitat for microorganisms and is the most bio diverse environment on earth (Tamames et al., 2010). Soil microorganisms are very important part of the environment ecosystems, which could adjust energy flow and cycle of matter by digesting animal, plant and oil residues, and plays a vital role in growth and development of agriculture crops, balancing of the soil ecosystem, organic matter transfer and bioremediation. Furthermore, the diversity of the microbial community in the soil is closely related to the function and structure of its surrounding ecosystem and is one of the components to maintain soil productivity. The present research in this field is mainly focused on functional diversity (Trivedi et al., 2012), species diversity (David et al., 2014), genetic diversity (Julia et al., 2014) and structural diversity (Thorsten et al., 2015). Hydrocarbon is very important to our economy. Its discovery as a source of energy has brought about high rate of civilization in our economy. It is one of the most important energetic resources in the world which is used as a raw material in numerous industries. It generates heat, making modern living possible especially in colder climates. It could also be used to make modern furniture like sofa, doors etc, it could also be used to fuel machines which makes life more comfortable.Hydrocarbon contamination on the coastal areas of different states in Nigeria has caused a lot destruction of flora, fauna and resort centers, pollution by drinking water as well as displacement of individuals, loss of lives and properties. When oil spilled onshore or near shore the soil and other components of the terrestrial ecosystem are inevitably affected in terrestrial environment, it can penetrate and spread on soil through topography nature of the soil environment. The soil as known is the main tool for agricultural productivity and socio-economic activities and so any threat to the soil usually affects the people’s livelihood and results into public outcry (Adewole and Moyinoluwa, 2012).It is important for hydrocarbon contamination to be remediated. This effect can be remedied by bioremediation using compost; microorganisms present in compost are utilized under some specified conditions to remedy the negative effects in cost-effective and environmentally friendly approach of all methods (chemical, physical, biological) of remediating crude oil contaminated land, biological methods is the most effective and consequence free. The hydrocarbonclastic microorganisms are the main tool used in biological methods to remove hydrocarbon from contaminated surfaces. Soil enzymatic have a central role in soil environment and are used as attractive bio-indicators for monitoring various impact on the soil e.g. Dehydrogenases are enzymes that catalyze the removal of hydrogen atom from substrates (Nelson and COX lehninger, 2000). Catalase are iron porphyryin and oxidant enzymes that catalyses very rapid decomposition of hydrogen peroxide to water and oxygen. Both catalase and hydrogenase are used as biomarkers for microbial activities in the soil as they are very sensitive to pollution by hydrocarbon.

1.2    Statement of Problem The contamination of soil hydrocarbon is a wide spread environmental problem that often requires clearing up of the contaminated sites. These hydrocarbons adversely affect the germination and growth of plant in soil (Saming et al., 2002).Hydrocarbon contamination affects plants by creating conditions which makes essential nutrient like nitrogen and oxygen needed for plant growth unavailable to them (Adam et al., 2002). Widespread use of hydrocarbon products without adequate infrastructure and measures to control their leakage into environment has resulted in many contaminated sites across the globe (Singh et al., 2009).This study therefore seeks to explore and provide updated information on the effect of hydrocarbon contamination on the activities of diazotrophs and phosphate solubilizing bacteria in an impacted garden soil.   

           1.3    Aim and Objectives The overall aim of this research work is to evaluate the effects of hydrocarbon contamination on phosphate solubilizing bacteria and diazotrophs in an impacted garden soil. To achieve this, the following will be done.1.    Enumeration of phosphate solubilizing bacteria and diazotrophs before and after contamination of the garden soil.2.    Isolation, characterization and identification of the isolated obtained from contaminated sample.


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