Isolation And Screening Of Soil Micro Organisms For Antibiotic Production

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