Assessment And Characterization Of Rhizobacteria In Petroleum-Polluted Soil In Umuahia

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