ABSTRACT
This study was conducted to isolate sulphur oxidising bacteria from Oguta lake of Oguta local government area, Imo state and their sulphur oxidation ability was evaluated. Results showed that in total five sulphuroxidising bacteria were isolated from four different points of the lake. From the qualitative screening it was found that out of the Nine bacterial isolates, five isolates could efficiently reduce the pH of the medium up to 3.8 from the initial pH 8.1. Their sulphate ion production abilities were in the range of 1.67 mg/ml-2.58 mg/ml. From morphological and biochemical characterisation, most of the isolates were identified as Micrococcus sp., Bacillus sp., Pseudomonas sp., Klebsiella sp. and xanthobacter sp.
TABLE OF CONTENTS
Cover Page i
Title Page ii
Certification iii
Dedication iv
Acknowledgement v
Table of content vi
List of Tables
vii
Abstract viii
Chapter One
1.1 Introduction 1
1.2 Statement
of Problem 3
1.3 Aim and Objective 3
1.3.1 Specific
Objective 3
Chapter Two
Literature
Review 4
2.1 Sulphur Oxidizing Microorganisms 4
2.2 The
Sulphur-Oxidizing Bacteria 5
2.3 Other
Sulphur Bacteria 6
2.4 Isolation, Characterization And
Identification Of Sulphur Oxidizing Bacteria 6
2.4.1 Isolation 6
2.4.2 Characterization and Identification 7
2.5 Review
of Sulphur Oxidizing Bacteria 9
2.5.1 Isolation of Sulphur-Oxidizing Bacteria At
37°C & 50°C 10
2.5.2 Moderately Thermophilic Sulphur-Oxidizing
Bacteria 11
2.6 Forms of Sulphur Oxidizing Bacteria 11
2.6.1 Green Sulfur Bacteria 11
2.6.2 Purple Sulfur Bacteria 12
2.6.3 Thiobacillus 12
2.6.4 Thermococcus 13
2.7 Effect of Sulfur Bacteria or Hydrogen
Sulfide 13
2.7.1 Problems Associated With Sulfur Bacteria Or
Hydrogen Sulfide 14
2.8 Sulfates and Hydrogen
Sulfide 14
2.8.1 Sulfate\ 15
2.8.2 Hydrogen Sulfide 15
2.9 Health
Issues Associated With Sulfate 16
2.10 Testing Options for Sulphur 17
2.11 Drinking
Water Standards 17
2.12 Oxidation 22
2.12.1 Photoautotrophic Oxidation of Sulphide 23
2.12.2 Chemolithothrophic Sulphide Oxidation 24
2.13 Enzyme Responsible For Sulphur Oxidation 26
2.14 Sox Gene In Sulphur Oxidising Bacteria 27
2.15 Some Important Biological Application
Of Sulphur Oxidizing Bacteria 28
2.15.1 Bioleaching 28
2.15.2 Biofertiliser 28
2.15.3 Plant Growth Promotion 29
2.15.4 Biocontroling Agent 29
2.15.5
Deodorization 30
2.15.6 Rubber Recycling 30
Chapter Three: Materials and Methods 32
3.1 Source
of Materials 32
3.2 Sampling
and Sample Preparation 32
3.2.2 Preparation Of Medium For Qualitative
Sulphur Oxidizing Test
(Thiosulphate Agar Broth). 32
3.3
Preparation of Media For Bacteria Isolate. 33
3.4. Isolation
of Bacteria 33
3.5. Qualitative
Screening for Sulphur Oxidizing Bacteria Isolates 34
3.6. Determination
of Sulphur Production Activity Of Sob Isolates 34
3.7.
Identification of Sulphur Oxidizing Isolates 35
3.7.1
Morphological Characteristics 35
3.7.2
Gram Staining 36
3.7.2. Biochemical Characteristics 36
3.7.4. Identification 37
Chapter Four: Result 38
Chapter Five
Discussion and Conclusions
5.1
Discussion 44
5.2
Conclusion 45
References
Appendix
LIST
OF TABLES
Table Title page
1 Identification
of the bacterial isolates is described 39
2 The
occurrence of the bacterial isolates on the various sample 40
3 The
change in pH of the suspected SOB 41
4 The
reaction of the SOB on the thiosulphate medium 42
5 Sulphur
production activity of sulphur oxidizing bacteria 43
CHAPTER ONE
1.1 Introduction.
Sulfur oxidizing bacteria play an important
role in mineral cycling in environments. The species of the genus Thiobacillus
include a wide diversity of Gram negative, rod sulfur oxidizing bacteria
which obtain energy from oxidation of reduced sulfur. They fall into α, β and γ
subclasses of the Proteobacteria and could be classified as Acidithiobacillus,
Halothiobacillus and Thermithiobacillus (Kelly and Wood, 2000).
Biological reduced sulfur species such as aqueous (hydro) sulfide as well as
insoluble metal sulfides, polysulfides, elemental sulfur, sulfite, thiosulfate
and polythionates are finally oxidized to sulfate, or more precisely to
sulfuric acid. During these processes, protons are produced. The oxidation of
reduced sulfur to sulfuric acid is of great importance for
biohydrometallurgical technologies. Contrary to its significant role in the
global sulfur cycle and its biotechnological importance, the microbial
fundamentals of sulfur oxidation are incompletely understood. (Bruser et al., 2000).
Sulfur oxidizing bacterium (SOB) exhibits a
wide range of metabolic flexibility, particularly with respect to processes
involving respiration and energy transduction.
Previous studies concluded that there were at
least two metabolic pathways of SOB during the thiosulfate oxidation (Friedrich
et al., 2001). Some SOB was involved
in the toxicity of heavy metal ion and possesses unique metabolic and
ecophysiological features with extraordinary properties. Novel SOB with
extraordinary properties was reported (Sorokin et al., 2009).
Bacteria are the major participants
in the carbon, sulfur, nitrogen and phosphorous cycles in lake (Rojas et al., 2001). Heterotrophic metabolism
of sulfate-reducing bacteria is responsible for most of the production of
hydrogen sulfide (H2S). Sulphate reducing bacteria use sulphate as a
terminal electron acceptor for the degradation of organic compounds, resulting
in the production of sulphide. Subsequently, the sulphide can be oxidized by
sulphur oxidising bacteria to produce sulphate (Holmer and Storkholm, 2001). As
the original source of reduced sulfur compounds, H2S hence, supports
abundant populations of sulfur-oxidizing bacteria (Holguin et al., 2006).
Sulphur is now considered the fourth major plant nutrient
after N, P and K, and is one of the sixteen nutrient elements which are
essential for the growth and development of plants, especially in the
agricultural crop production (Vidyalakshmi and Sridar, 2007). The majority of
sulphur taken up by plant roots is in the form of sulphate (SO4),
which undergoes a series of transformations prior to its incorporation into the
original compounds. Most of the known sulphur oxidising bacteria (SOB) belongs
to the genera Thiobacillus, Thiothrix, Thiomicrospira, Achromatium and Desulfuromonas (Das et al., 2012).
However, oxidation of sulfur compounds is not restricted to the true sulfur
bacteria; this process also occurs in heterotrophic bacteria isolated from soil
and marine environment (Das et al., 2012).
Thiobacilli are reported not to be present in significant numbers in
most lake. In this context, ( Graff and Stubner, 2003)
presumed that aerobic heterotrophic S-oxidizing bacteria were more important S0
oxidizers than Thiobacilli in Scottish lake. It was reported that both Thiobacillus
specie and aerobic heterotrophic S-oxidizing bacteria oxidized reduced S0
intermediate compounds, for instance thiosulfate and the intermediate compounds
consequently were oxidized to sulfate (Suzuki
et al., 1999). Most of the
heterotrophic bacteria belong to the genera Pseudomonas, Xanthobacter,
Escherichia coli strains are mostly involve in sulphur oxidation (Sorokin et al., 2009).
1.2 Statement
of Problem
Sulphur oxidising bacteria in the lake has not been
addressed to the same extent as that of other environments. To date, only a few
obligately heterotrophic bacteria have been studied in detail and adequately
described that are able to generate metabolically useful energy from the
oxidation of reduced sulfur compounds. A more thorough description of the sulphur
oxidising bacterial diversity and distribution in a lake would improve our
understanding of sulphur bacteria as well as microbial metabolism of suphur in
that ecosystem.
1.3 Aim
and Objective
The aim of this study is to isolate, and identify the sulphur
oxidizing bacteria from Oguta lake
1.3.1 Specific objective
- Isolation of sulphur oxidizing
bacteria from Oguta lake
- Identification of sulphur
oxidizing bacteria from Oguta lake.
- Quatitative screening for
sulphur ions produced by oxidizing bacteria isolates.
- Determination of sulphur
production activity of SOB isolates
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