ABSTRACT

Petroleum – polluted sites are disturbed ecosystem with scanty plants. Study was carried out in such sites to assess the area of its rhizobacterial status, particularly comparing that of the rhizospheres and non-rhizospheres in the site. The samples were suspended and serially diluted in physiological saline and inoculated on nutrient media by spread plates method. After incubation and isolation, the isolates were characterized by morphological examination, gram staining, biochemical tests, biodegradation test, and motility test. The isolated bacteria were Acinetobacter species, Pseudomonas species, Micrococcus species, and Bacillus species. The total heterotrophic bacterial counts of rhizosphere samples were sample Ar 1.3 x 106 cfu/g, sample Br 2. 54 x 106 cfu/g, sample Cr. 2.96 x 106 cfu/g, and sample Dr. 2.37 x 106 cfu/g, while the total heterotrophic counts of non – rhyzosphere samples were sample An 1.01 x 106 cfu/g, Bn 1.12 x 106 cfu/g, sample Cn 1.11 x 106 cfu/g, sample Dn 1.02 x 106 cfu/g. All the isolates were able to grow in medium containing crude oil. But while Pseudomonas species showed heavy growth, Bacillus species and Acinetobacter species showed moderate growths, and Micrococcus species showed scanty growth. Petroleum – polluted soils contain rhizobacteria. But while rhizosphere of such soils contains more, non rhizosphere contains less. Therefore, rhizosphere will be very helpful in bioremediation of petroleum – polluted soils. 

TABLE OF CONTENTS

Title Page i

Certification ii

Dedication iii

Acknowledgment iv

Table of Contents v

List of tables vi

Abstract viii

CHAPTER ONE - INTRODUCTION

1.1 INTRODUCTION 1

1.2 Objectives: 2

CHAPTER TWO - LITERATURE REVIEW

2.1 Rhizobacteria 3

2.1.1 Nitrogen fixation 3

2.1.2 Symbiotic relationship 4

2.1.3 Promotion of plant growth 5

2.1.3.1 Mechanisms of action of plant growth promoting rhizobacteria (PGPRs) 6

2.1.4 Biocontrol function of rhzibacteria 7

2.2 Petroleum polluted soil 8

2.2.1 Ecological impacts of hydrocarbon contamination 9

2.2.1.1 Soil Quality 10

2.2.1.2 Plants 10

2.2.1.3 Microorganisms 11

2.3 Remediation of hydrocarbon-contaminated soil 14

2.3.1 The aim of remediation 15

2.3.2 Bioremediation 15

2.3.3 Phytoremediation 17

CHAPTER 3 - MATERIALS AND METHOD

3.1 Sample Collection 21

3.2 Materials Used 21

3.3 Preparation of culture media 22

3.3.1 Nutrient agar (NA) 22

3.3.2 Nutrient broth (NB) 22

3.3.3 Mineral salt broth (MSB) 22

3.4 Sterilization of Culture Media 22

3.5 Bacterial Isolation 23

3.6 Characterization of Bacterial Isolates 23

3.6.1 Morphological examination 23

3.6.2 Gram staining test 24

3.6.3 Biochemical test 24

3.6.4 Biodegradation test 26

3.6.5 Motility test 26

CHAPTER FOUR

4.0 Result 27

4.1 Morphological characteristics of the isolated bacteria 27

4.2 Bilochemical and characterization of the isolated bacteria 29

4.3 Screening test for utilization of petroleum hydrocarbon by isolates 31

4.4 Isolated rhizobacteria and the total heterotrophic bacterial counts 

(THBC) of rhizosphere soil. 33

4.5 Isolated rhizobacteria and the total heterotrophic bacterial counts 

(THBC) of non rhizosphere soil. 35

CHAPTER FIVE

5.1 Discussion 37

5.2 Conclusion and Recommendation 38

References 39