ABSTRACT
The quest to
harness the microbial world's potential for antibiotic discovery has led to
extensive research endeavors, particularly in regions abundant with microbial
diversity such as the soils of farmlands. This study aimed to isolate and
screen soil microorganisms from farmlands in Amakama, Umuahia South Local
Government Area of Abia State, Nigeria, for their antibiotic-producing
capabilities.
Soil samples
were meticulously collected from various farmlands in the designated area,
focusing on the rhizosphere, where microbial activity is enriched. Isolates
were purified through sub-culturing on nutrient agar plates, and the resulting
colonies were stored for further analysis. Test organisms including
Staphylococcus aureus, Escherichia coli, Enterococcus faecalis, and Salmonella
typhi were prepared for sensitivity testing.
The
antibacterial potential of the isolates was assessed using the paper disc
diffusion method. Clear zones of inhibition around the impregnated discs
indicated the presence of antimicrobial compounds. Furthermore, the isolated
bacteria were characterized and identified through gram staining and a series
of biochemical tests including the indole test, citrate utilization test,
starch hydrolysis test, catalase test, and hydrogen sulfide test.
Results revealed
the isolation of thirty-five bacterial isolates from twenty soil samples,
highlighting the rich microbial diversity within the sampled farmlands. The
colonial morphology and biochemical characteristics of the isolates with
antimicrobial activity were meticulously documented. Sensitivity testing
provided insights into the efficacy of the isolated compounds against a panel
of pathogenic bacteria.
The findings of
this study underscore the immense potential of soil microorganisms from farmlands
in Amakama for antibiotic production. While the discovery of antibiotics
remains one of the most significant achievements in microbiology, the journey
from discovery to application in chemotherapy demands rigorous exploration and
refinement. The study's results emphasize the necessity of further exploration
into the antimicrobial capabilities of these bacteria, highlighting avenues for
future research and drug development.
In conclusion,
the search for novel antibiotics in microbial ecosystems such as farmland soils
holds promise for addressing the global challenge of antimicrobial resistance.
The findings of this study provide a foundation for continued investigation
into the diverse microbial communities residing in agricultural soils, with the
potential to unlock new avenues for combating infectious diseases and improving
public health outcomes.
TABLE OF CONTENTS
CHAPTER
ONE
1.0 INTRODUCTION
1.1 AIMS AND OBJECTIVES
CHAPTER
TWO
2.0 LITERATURE REVIEW
2.1 ANTIBIOTIC RESISTANCE
2.2 MICROBIAL DIVERSITY IN SOIL
2.3 FACTORS AFFECTING THE ISOLATION OF SOIL
MICROORGANISMS
CHAPTER
THREE
3.0 MATERIALS AND METHODS
3.1 SAMPLE COLLECTION
3.2 ISOLATION OF SOIL MICROORGANISMS
3.3 PURIFICATION OF ISOLATES
3.4 PREPARATION OF INOCULUM OF TEST ORGANISMS
3.5 PREPARATION OF INOCULUM OF EACH ISOLATE
3.6 CHARACTERIZATION AND IDENTIFICATION OF
ISOLATES
3.6.1 GRAM STAINING
3.6.2 BIOCHEMICAL TESTS
3.6.2.1 INDOLE TEST
3.6.2.2 CITRATE UTILIZATION TEST
3.6.2.3 STARCH HYDROLYSIS TEST
3.6.2.4 CATALASE TEST
3.6.2.5 HYDROGEN SULPHIDE TEST
CHAPTER
4
4.0 RESULTS
CHAPTER
5
5.0 DISCUSSION
5.1 CONCLUSION
REFERENCES
LIST
OF TABLES
Table 1: Some clinically important antibiotics produced by
microorganisms
Table 2: Antibiotics produced by Bacillus species
Table 3: Description of soil samples and number
of organisms isolated from each.
Table 4: Cultural morphology and biochemical
characterization of isolated organisms
with antimicrobial activity.
Table 5: Zones of inhibition (mm) produced by
isolates against test organisms.
LIST OF FIGURES
Fig.1 Antagonistic effect
of bacterial suspension on different pathogenic bacteria:
CHAPTER
ONE
1.0 INTRODUCTION
The soil being the outermost layer of the
earth crust is a natural reservoir for microorganisms and their antimicrobial
products. The numbers and species of microbes in the soil is dependent on
environmental conditions like nutrient availability, soil texture, presence of moisture
in soil and type of vegetation cover, and their number varies according to the
type of environmental condition. The soil is a favourable habitat for the
growth of microorganisms including bacteria, algae, fungi, viruses and
protozoa. Microorganisms are found in large numbers in soil, usually several
millions are present per gram of soil with bacteria and fungi being the most
prevalent.
An antibiotic was in previous times
defined as chemical substances produced by various species of microorganisms
that is capable, in low concentrations, of inhibiting the growth of or killing
other microorganisms. Today, this definition has been replaced by any substance
produced by a microorganism or a similar product produced wholly (synthetic) or
partially (semi-synthetic) by chemical synthesis and in low concentrations
inhibits the growth of or kills microorganisms. Antibiotics are one of the most
important commercially exploited secondary metabolites produced by bacteria and
employed in a wide range use in Medicine and Agriculture (Musliu and
Salawudeen, 2012).
However, soil microorganisms with known
antibiotic properties are mainly bacteria and fungi. A group of Gram-posititve
bacteria distinguished from other bacteria by their morphology called
actinomycetes have been identified as the major producers of antibiotics (Abebe
et al., 2013). More than 70% of
naturally occurring antibiotics have been isolated from different genera of
actinomycetes especially Streptomyces spp
(Khanna et al., 2011). Other
bacterial species that have the ability to produce antibiotics are Bacillus species and Lactobacillus species (Musliu and
Salawudeen, 2012) while Penicillium and
Cephalosporium, terrestrial and
marine molds respectively are antibiotic-producing fungi.
The worldwide use of antibiotics has
rapidly increased since the accidental discovery of Penicillin by Alexander
Fleming in 1928. Since then, thousands of useful secondary metabolites of
microbial origin have been discovered (Nordenfjäll, 2014). While many
antibiotics are known to exist, efforts to discover new antibiotics still
continue. Therefore many species such a Streptomyces,
Bacillus and Penicillium have
been studied continuously for their ability to produce antibiotics (Sandeepta et al., 2015). Some antibiotics like
Penicillin, Erythromycin and Methicillin which used to be one-time effective
treatment against infectious diseases are now less effective because bacteria
have become more resistant to such antibiotics (Raja et al., 2010).
Pathogenic bacteria are acquiring
resistance to existing antibiotics, most of which are expensive and have been
associated with side effects like nephrotoxicity. Bacteria have evolved numerous
strategies for resisting the action of antibiotics and antibacterial agents
(Sandeepta et al., 2015). Antibiotic
resistant pathogens such as Methicillin and Vancomycin resistant strains of Staphylococcus aureus and others are
enormous threat to the treatment of serious infections and to avoid this happening,
immediate replacement of the existing antibiotic is necessary.
The problem of resistance against the present
antibiotics in bacteria increases day by day. So there is an urgent need to
search new antibiotics or the sources of new antibiotics. A lot of work has
been done during last few decades that has witnessed the production of novel
antibiotics from different microorganisms (Mashoria et al., 2014). Considerable research is being done in order to find
new antimicrobial producing bacteria isolated from soil. One of the possible
ways to increase the chance of finding novel antibiotics is to find new
approaches for isolating interesting bacteria and fungi or at least make the
existing methods more efficient (Nordenfjäll, 2014).
1.1 AIMS AND OBJECTIVES
1.
To
isolate soil microorganisms from soil samples collected from farmlands in
Amakama.
2.
To
screen isolates for production of antibiotics against several bacterial
pathogens.
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