ABSTRACT

Antibiotics are one of the most important commercially exploited secondary metabolites produced by microorganisms. Most of the antibiotics used today are from microbes. In this present project work, soil microorganisms were isolated and screened for antibiotic production. The media used in this research study were Nutrient agar, Tryptone Soya agar and Sabouraud Dextrose agar. One gram (1g) of each of the soil samples was serially diluted in sterile normal saline to make soil suspensions. An aliquot of 0.1ml of the suspensions was innoculated on the medium by spread plate method. The inoculated plates were incubated at 35oC for 24 hours. After which the morphological and biochemical properties of the colonies were observed. A total of 57 isolates were obtained from the samples. The inhibitory activities of the isolates were investigated against some important pathogenic bacteria like; Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853, Staphylococcus aureus ATCC 25923 and Enterococcus  faecalis ATCC 7080. Out of the 57 isolates obtained, 2 isolates were found to exhibit antibacterial activity against the test organisms. Although the identification of these isolates were not done up to species level, their morphological and biochemical characteristics indicate that they belong to the genus Bacillus.

TABLE OF CONTENTS

CERTIFICATION                                                                                              i

DEDICATION                                                                                                    ii

ACKNOWLEDGEMENTS                                                                                iii

TABLE OF CONTENTS iv

LIST OF TABLES                                                                                              vi

ABSTRACT                                                                                                        vii

CHAPTER ONE

1.0 INTRODUCTION 1

1.1Aims and objectives 2

CHAPTER TWO

2.0 LITERATURE-REVIEW 3

2.1Soil microbial interactions 5

2.2 Types of microorganisms found in the soil 6

2.2.1 Actinomycetes 6

2.2.2 Fungi 7

2.2.3 Algae 7

2.2.4 Protozoa 8

2.2.5 Some bacteria that produce antibiotics 8

2.3. Factors affecting antibiotic production, activity and detection 9        

2.3.1 Extraction from soil or plant material: physical and chemical considerations 10

2.3.2 Sample collection and preparation 11

CHAPTER THREE

MATERIALS AND METHODS

3.0 Collection of samples 12

3.1 Media preparation 12

3.2 Isolation of microorganism from soil samples 12

3.3Subculturing 13

3.4 Characterization and identification of isolates 13

3.4.1Colonial examination 13

3.4.2Gram staining 13

3.4.3Biochemical tests 14

3.4.3.1Starch hydrolysis test 14

3.4.3.2 Hydrogen sulfide 14

3.5 Determination of antimicrobial activity 14

CHAPTER FOUR

RESULTS 17

CHAPTER FIVE

DISCUSSION, CONCLUSION AND RECOMMENDATION

5.0 Discussion 21

5.1 Conclusion 22

5.2 Recommendation 22

REFERENCES

LIST OF TABLES

Table                               Title                                                             Page

1:     Description of soil sample location 18

2:     Morphology and biochemical properties of isolates 19

3:     Antibiotic activity of bacterial isolates 20