ABSTRACT

The soil environment is rich in microorganisms capable of antibiotics production but the rate of occurrence and distribution of these microorganisms at ecologically significant levels has not been much clear. In the past few decades, microorganisms have been demonstrated as synthsizers of varieties of antibiotics even under field conditions in the rhizosphere. In the present work, soil smples were collected randomly from the forest environment in Michael Okpara University of Agriculture, Umudike, in Abia-state, Nigeria and were screened for antibiotics-producing microorganisms by the agar sensitivity assay using paper discs impregnated with the isolates from the forest soil. Forty-eight (48) isolates were gotten on the total, out of which thirteen 13 (27.1%) isolates active against different test organisms (Salmonella typhi , Staphylococcus aureus ATCC 25923TM, Escherichia coli ATCC 25922TM, Pseudomonas aeruginosa ATCC 27893TM). Nine (9) (18.8%) bacterial isolates were active against the test pathogenic bacteria and they were identified by their cellular characteristics, colonial morphology and biochemical tests. These active isolates sort into the Genus Bacillus and Micrococcus and the ones that were not fully characterized yet are probably members of the Streptomyces genera. Four (4) (8.3%) fungal isolates were also active against the test bacteria and were identified based on their fungal morphology as probably Penicillium spp. and Aspergillus spp. Of all the isolates, isolate 36 which is probably a Streptomyces spp., has the highest range of antibacterial activity with 12mm zone of inhibition on Pseudomonas aeruginosa, 12mm on Staphylococcus aureus 5mm on Salmonella typhi and 4mm on Escherichia coli. Isolates 35 and 40 had the highest zones of inhibition, both on Salmonella typhi. The present work has once more contributed to the existing truth in cases of isolation of antibiotics-producing microorganisms from the forest soil and promises to contribute hugely in all enquiries into the antibiotics producing micro-flora in the forest environment.

TABLE OF CONTENTS

Cover Page i

Title Page ii

Certification Page iii

Dedication iv

Acknowledgement v

Table of Contents vi-viii

List of Tables                            ix

Abstract x

CHAPTER ONE

1.0 INTRODUCTION 1

1.1 Factors Affecting Soil Microbial Composition 1

1.2 Definition of Antibiotics 1

1.3 Bacillus spp. and antibiotics 3

1.4 Aims and Objectives 4

CHAPTER TWO

2.0 LITERATURE REVIEW 5

2.1` Soil and Antibiotics 5

2.2 Review on Different Soil Environment and Their Antibiotics-Producing Microbes Composition

2.3 Fungi and Antibiotics 7

2.4 Sources of Nutrients for Soil Microbes 9

2.5 Formation of Antibiotics in the Soil 9

2.6 Factors Influencing Natural Stimulation of Secondary Metabolite Production 9

2.7 Class: Actinomycetales 10

2.7.1 Actinomycetes 10

2.8 Estimation of Soil Microbial Flora 11

2.9 Distribution of the Actinomycetes in the Soil 13

2.10 Classification of Antibiotics 13

2.11 Streptomyces: Wide-range Antibiotics Producers 14

2.12 Ecological and Geographical Distribution of Microorganisms in Soils 14

2.13 Problems Encountered In Determining Soil Microbial Distribution 14

2.14 Factors Encouraging Antibiotics Production by the Streptomycetes 14

2.15 Effects of Isolation Media in Antibiotics Production 16

2.16 Techniques in Identifying Antibiotic Producers in Media Plates. 16

2.17 Failure of In-use Antibiotics and the need for Novel Antibiotics 16

2.18 Concentration, Inactivation, pH and Adsorption as Factors Affecting Effectiveness of Antibiotics in the Soil

2.19. The Need for Specific Isolation Media in Screening for Antibiotics Production 18

CHAPTER THREE

3.0   MATERIALS AND METHODS 20

3.1 Study Area and Period 20

3.2 Collection of Samples 20

3.3 Sterilization of Equipment and Preparation of Media 20

3.4 Preparation of Sample 21

3.5. Sample Inoculation, Incubation and Isolation of Microbes 21

3.6 Colonial Examination 22

3.7 Subculturing and Storage of Isolates 22

3.8 Testing for Antibiotic Production 22

3.9 Gram Staining 22

3.10 Biochemical Tests 23

3.10.1 Starch Hydrolysis Test 23

3.10.2 Hydrogen Sulphide Test 23

3.10.3 Sugar Utilization Test 24

CHAPTER FOUR

4.0 RESULTS 25

CHAPTER FIVE

5.1 Discussion 32

5.2 Recommendations 34

5.3 Conclusion 35

References 36