ABSTRACT

The lack of new therapeutic options to replace many antimicrobial agents that are losing their efficacy against resistant bacteria is a growing concern. The search for new antimicrobials from rare and/or existing sources have thus become a worthwhile effort in recent years. Soil samples collected from Umudike were studied in an effort to screen for novel antibiotics produced by soil microbes. A total of 45 bacterial and 19 fungal isolates were successfully obtained from the soil samples. Antibiotic activity screening using the paper disc diffusion technique was used to evaluate the antagonistic potentials of the isolates against ATCC Strains of bacteria including Staphylococcus aureus (ATCC 25923), Salmonella typhi, Escherichia coli (ATCC 25922). Of the 64 isolates, 6.25% (4/64) were active against at least one of the test organisms with diameter zones of clearing that ranged from 10.0mm to 17.0mm. Isolate VC7 exhibited the strongest antibacterial activity against S. typhi and E. coli with diameter zones of clearing of 17mm and 11.0mm respectively followed by VC29 which recorded a zone of inhibition of 14mm and 10mm against E. coli and S. aureus respectively. VC7 was tentatively identified as an Enterobacter species based on their colonial morphology and biochemical tests results. Among the isolates which demonstrated antagonism against the test bacteria, VC18, VC26, and VC7 were identified as Bacillus spp., Penicillium spp and Enterobacter spp respectively. 

TABLE OF CONTENTS

Title Page   i

Certification iii

Dedication iv

Acknowledgement v

Table of Contents vi

List of Tables vii

Abstract ix

CHAPTER ONE: INTRODUCTION 1

1.1 Aims and Objectives 6

CHAPTER TWO: LITERATURE REVIEW 7

2.1 Antimicrobials 8

2.2 Antibiotics from Microorganisms 9

2.2.1 Actinomycetales 10

2.2.2 Actinomycetes as a novel source of antimicrobials 10

2.2.2.1 Isolation of Actinomycetes 13

2.2.3 True Bacteria 14

2.2.4 Fungi 14

2.2.4 Biochemistry of Antibiotic Production 14

2.3 Natural Habitat of Antibiotic Producing Microorganisms 18

2.4 Antibiotic Producing Soil Microbes 20

2.5 Secondary Metabolites from Bacillus sp. in Soil 21

2.6 Importance and Diversity of Secondary Metabolites Produced by Actinomycetes 23

CHAPTER THREE: MATERIALS AND METHODS 24

3.1 Sample Collection 24

3.2 Isolation of Soil Microorganisms 24

3.3 Characterization and Identification of the Isolates 25

3.3.1 Gram Staining 25

3.4 Biochemical Tests 25

3.4.1 Catalase Test 25

3.4.2 Indole Test 25

3.4.3 Citrate Utilization Test 26

3.4.5 Oxidase Test 26

3.4.6 Starch Hydrolysis 26

3.5 Identification of Fungal Isolates 27

3.6 Preparation of Inoculums of Test Organisms 27

3.7 Preparation of Inoculum of each Isolate and Antimicrobial Testing 28

CHAPTER FOUR: RESULTS 29

CHAPTER FIVE: DISCUSSION AND CONCLUSION 34

5.1 Discussion 34

5.2 Conclusion 37

References