ABSTRACT

The soil environment constitutes largely an untapped source of microorganisms with the potentiality of producing antibiotics. The soil microorganisms are responsible for a great percentage of discovered bioactive secondary metabolites notably antibiotics. In this study, 10 soil samples from different ecological sites were obtained and cultured in microbiological media to isolate antibiotic producing microorganisms. Ten fold serial dilution of each soil sample was carried out. 0.1ml of the serially diluted samples were plated on Nutrient agar and Sabouraud Dextrose agar (SDA) using the spread plate inoculation technique. A total of 25 isolates mostly Gram- Positive organisms (Bacillus sp, Micrococcus sp and Actinomycetes were recovered from the 10 samples analyzed. Of this number, 5 isolates was tested against four organisms (Escherichia coli ATCC 25922, Staphylococcus aureus ATCC 25923,  Pseudomonas aeruginosa  ATCC 27153 , Mycobacterium smegmatis ATCC 14468) for antibacterial activity. Out of the five isolates, only two (BL61 and BL42) exhibited inhibitory effect against one of the test organisms (Pseudomonas aeruginosa) with zones of inhibition of 9mm and 13mm respectively. The remaining isolates showed no antimicrobial activity against the test organisms. Considering the fact that soil harbours a wide range of microflora, there is the tendency of finding out new species and strains that have antimicrobial property. Hence this area of study needs an extensive and wide research on the soil micro environment to discover potential antibiotics that can be effective against microorganisms in the face of the current antibiotic resistance.

TABLE OF CONTENT

Cover page i

Certification ii

Dedication iii

Acknowledgements iv

Table of Contents v

List of Tables vii

Abstract viii

CHAPTER ONE

1.0 Introduction    1

1.1 Aims and Objectives 3

CHAPTER TWO

2.0 Literature Review 4

2.1 Antibiotics 5

2.1.1    GENUS Streptomyces 6

2.1.2 Secondary metabolites and their functions 7

2.1.3 Genes for secondary metabolites 9

2.2 Microbial diversity in Soil 10

2.3 Microorganisms as Sources of Natural Products 12

2.3.1 Enzyme production 12

2.3.2 Antibiotic production 12

CHAPTER THREE

3.0   Material and methods 14

3.1 Collection and preparation of soil sample             14

3.2 Media used            14

3.2.1 Sterilization of materials 14

3.3 Sample preparation 14

3.3.1 Sub- Culturing 15

3.4 Gram Staining 15

3.4.1 Biochemical tests 16

3.4.1.1  Hydrogen sulfide test 16   

3.4.1.2 Nitrate reduction test     16

3.4.1.3 Starch hydrolysis test 16

3.5 Primary Screening of Isolates            16

3.6 Test bacteria 17

CHAPTER FOUR

4.0        Results 18

CHAPTER FIVE

5.0       Discussion 22

5.1 Conclusion 23

5.2 Recommendation 23     

References

LIST OF TABLES

TABLE 1: Gram reaction from all the soil samples and their percentage 

Occurrence 18

TABLE 2:    Description of samples collected from different sites in Michael 

Okpara University of Agriculture, Umudike (MOUAU). 19

TABLE 3: Macroscopic and Microscopic examination of isolates and their

percentage (%)   occurrence 20

TABLE 4: Zone of inhibition in millimeter (mm) produced by isolates against 

test organisms.