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 Pagei

Certificationii

Dedicationiii

Acknowledgmentiv

Table of Contentsv

List of tablesvi

Abstractviii

CHAPTER ONE - INTRODUCTION

1.1INTRODUCTION 1

1.2Objectives: 2

CHAPTER TWO - LITERATURE REVIEW

2.1Rhizobacteria 3

2.1.1Nitrogen fixation3

2.1.2Symbiotic relationship 4

2.1.3Promotion of plant growth 5

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

2.1.4Biocontrol function of rhzibacteria 7

2.2Petroleum polluted soil 8

2.2.1Ecological impacts of hydrocarbon contamination9

2.2.1.1Soil Quality 10

2.2.1.2 Plants10

2.2.1.3Microorganisms11

2.3Remediation of hydrocarbon-contaminated soil14

2.3.1The aim of remediation15

2.3.2 Bioremediation15

2.3.3Phytoremediation17

CHAPTER 3 - MATERIALS AND METHOD

3.1Sample Collection 21

3.2Materials Used21

3.3Preparation of culture media22

3.3.1Nutrient agar (NA)22

3.3.2Nutrient broth (NB)22

3.3.3Mineral salt broth (MSB)22

3.4Sterilization of Culture Media22

3.5Bacterial Isolation 23

3.6Characterization of Bacterial Isolates 23

3.6.1Morphological examination 23

3.6.2Gram staining test24

3.6.3Biochemical test24

3.6.4 Biodegradation test26

3.6.5Motility test 26

CHAPTER FOUR

4.0Result27

4.1Morphological characteristics of the isolated bacteria27

4.2Bilochemical and characterization of the isolated bacteria29

4.3Screening test for utilization of petroleum hydrocarbon by isolates31

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

5.1Discussion37

5.2 Conclusion and Recommendation 38

References39

LIST OF TABLE 

Table 1: Morphological characteristics of the isolated bacteria28

Table 2: Biochemical and characterization of the isolated bacteria30

Table 3: Screening test for utilization of petroleum hydrocarbon by isolates32

Table 4: Isolated rhizobacteria and the total heterotrophic bacterial

   counts (THBC) of rhizosphere soil. 34

Table 5: Isolated rhizobacteria and the total heterotrophic bacterial counts 

  (THBC) of non rhizosphere soil. 36