ABSTRACT

Soil is the major repository of microorganism that produce antibiotics. Clinically useful antibiotics have been isolated from several groups of soil microorganisms including bacteria (Streptomyces sp, Bacillus sp.).  Bacillus and actinomycetes are the most abundant microorganisms present in soil and inhibit the growth of other microorganisms present in soil and inhibit the growth of other microorganism.  In this research, Ten samples of soil collected from a cultivated Farmland within the premises of College of Crop and Soil Sciences were screened for antibiotic, producing microorganisms.  Ten fold serial dilutions of the soil samples were prepared and inoculated on Nutrient Agar and Saboraud Dextrose Agar.  A total number of Twenty three isolates were recovered.  Ten of the total isolates were subcultured on Nutrient agar and incubated at 37℃ for 24hrs.  Out of these ten isolates four are Micrococcus, four Bacillus species and two Actinomycetes were obtained.  Five different isolates was tested against four test organisms namely; Pseudomonas aeruginosa (ATCC®27853™), Staphylococcus aureus (ATCC®25923™) Escherichia coli (ATCC®28735™) and Mycobacterium smegmatis (ATCC®28735™) to observe their antimicrobial activity against the test organisms.  One of the isolates (CCSSH1) that is actinomycete was able to inhibit growth of Staphylococcus aureus with a clear inhibition range with a clear inhibititon range of 0 – 14 mm, which indicates an antibacterial activity against S.aureus while others showed no antimicrobial activity against the test organisms.  This shows that the screening and isolation of CCSSH1 from this study area may contribute to the discovery of new antibiotics with further extraction and purification of the isolate.  

TABLE OF CONTENTS

Title page i

Certification

Dedication

Acknowledgements

Table of contents v

List of tables

Abstract

CHAPTER ONE

1.0 INTRODUCTION 1

1.1 Aims and Objectives

CHAPTER TWO

2.0 LITERATURE REVIEW 5

2.1 Microbial Sources of Antibiotics-General Overview 5

2.2 Antibiotic Formation by Actinomycetes 7

2.2.1 Antibiotic Formation by Rare Actinomycetes 8

2.3 Industralization, Biostimulation and Bioaugmentation 9

2.4 The Soil Rhizosphere 10

2.4.1 Soil Antimicrobial Agent Producing Microbes 11

CHAPTER THREE

3.0 MATERIALS AND METHODS 14

3.1 Collection and Preparation of Soil samples 14

3.2 Sterilization of Materials

3.3 Media Used

3.4 Serial Dilution

3.4.1 Culturing

3.4.2 Colonial Examination

3.4.3 Sub Culturing

3.5 Gram Staining

3.6 Biochemical Tests

3.6.1    Hydrogen Sulfide Production Test 17

3.6.2  Nitrate Reductase Test    18

3.6.3  Starch Hydrolysis

3.7 Confirmation of Antimicrobial Activity 19

3.8 Test Bacteria

CHAPTER FOUR

4.0 RESULTS 20

CHAPTER FIVE 

5.0 DISCUSSION, CONCLUSION AND RECOMMENDATION FOR 

FURTHER STUDIES 24

5.1 Discussion 24

5.2 Conclusion 25

5.3 Recommendation for further studies 25

REFERENCES 26

LIST OF TABLES

Table Title       Page

1 Microorganisms producing antibiotics 8

2 Description of soil samples collected from locations of cultivated

farmland and numbers of isolates. 21

3 Colonial Characteristics and Biochemical Characterization of the Bacterial 

Isolates 22

4: Zone of inhibition in millimeter (mm) of bacteria isolates against test organisms. 23