ABSTRACT
Biofilms are aggregates of microbial cells embedded in self –produced matrix of extracellular polymeric substance (EPS) and adhering to non-living or living surfaces. The purpose of this research on microbial communities developing biofilms in drinking water sources in MOUAU was to determine the presence of pathogenic organisms that are present in the water which causes the contamination of the water system and to know their tendency in biofilm formation. The morphological characteristics, Gram reaction and Biochemical tests were carried out to characterize them. The study reveals the percentage of occurrence E. coli as 10 (38.5%), P. aeruginosa - 8 (30.8%), P. vulgaris - 6 (23.0%) and S. aureus – 2(7.7%) and biofilm detection test was carried out using qualitative biofilm detection method (tube method). The screening for the biofilm forming organisms using the tube method revealed E. coli, P. aeruginosa and P. vulgaris to have strong biofilm formation while S. aureus gave moderate positive result.
TABLE OF CONTENTS
Title i
Certification ii
Dedication iii
Acknowledgement iv
Table
of Contents v
List
of Tables viii
List
of Figure ix
Abstract
x
CHAPTER ONE
INTRODUCTION
1.1 Background
of the Study 1
1.2 Objectives of the Study 3
1.3 Problem
Statement 3
CHAPTER TWO
LITERATURE REVIEW
2.1 Definition of Biofilm 4
2.2. Biofilms
Formation and Development 5
2.2.1 Factors Affecting Biofilm Formation 6
2.2.1.1 Substratum Effect 7
2.2.1.2 Conditioning
Film 7
2.2.1.3 Hydrodynamics
7
2.2.1.4 Characteristics
of Aqueous Medium 7
2.2.1.5 Horizontal
Gene Transfer 8
2.2.1.6 Quorum
Sensing 8
2.3. Biofilm
Structure and Function 9
2.3.1 Extracellular
Polymeric Substances 9
2.3.2 Protein 10
2.3.2 Interaction
of Particles 11
2.4.3 Community:
biofilms and communal behavior 11
2.4.3.1 Biofilms as
multicellular organisms 11
2.4.3.2 Division of the metabolic burden 13
2.4.3.3 Selfless behavior 13
2.5 Environmental
factors influencing biofilm development 14
2.5.1 Effect of pH 14
2.5.2 Rheological and
adhesive properties of biofilms 15
2.5.3 Effect of
temperature 16
2.6 Water 17
2.6.1 Sources of
Water 17
2.6.1.1 Surface Water 17
2.6.1.2 Ground Water 17
2.6.2 Sources of
Contamination Water 18
2.7
Biofilms of Drinking Water
Distribution Systems 18
2.8 Effect of long storage of water on
Biofilm Formation 19
CHAPTER THREE
MATERIALS AND METHODS
3.1 Sample
Collection 20
3.2 Preparation of
Media and Sterilization 20
3.3 Sample
Inoculation 20
3.3.1 Isolation of
Bacteria 20
3.4 Identification
of the Isolates 21
3.4.1 Macroscopic
Examination 21
3.4.2 Microscopic
Examination (Gram Staining) 21
3.5 Biochemical
Tests 21
3.5.1 Catalase test 21
3.5.2 Citrate
Utilization Test 22
3.5.3 Coagulase
Test 22
3.5.4 Oxidase Test 22
3.5.5 Motility,
Urease and Indole (MUI) Tests 22
3.5.6 Methyl Red-
Vogus Proskauer Test 23
3.5.7 Sugar Fermentation Test 23
3.6 Detection of
Biofilm using Tube Method 24
CHAPTER FOUR
RESULTS 25
CHAPTER FIVE
DISCUSSION, CONCLUSION AND RECOMMENDATION
5.1 Discussion 30
5.2 Conclusion 33
5.3 Recommendations 33
References 34
LIST OF
TABLES
Table Title
Page
4.1: Morphological Identification and Biochemical
characteristics 27
of the
Bacterial Isolates
4.2: Percentage of
Occurrence of Bacterial Isolates 28
4.3: Qualitative Detection of Biofilm formation 29
LIST OF
FIGURE
Figure Title Page
4.1: The screening
of biofilm forming bacteria using the Tube Method 26
CHAPTER ONE
INTRODUCTION
1.1 BACKGROUND OF THE STUDY
Water is essential to sustain life and a satisfactory
(adequate, safe and accessible) supply must be available to all (WHO, 2004).
The quality of life depends on the key elements such as the quantity and the
quality of water available for consumption. A rational use of resources
considering the support capacity of the ecosystems in which we live indicates a
sustainable society. Strategies such as the management and protection of water
sources, effective treatment methods, the proper distribution and handling of
water are intended to be implemented worldwide. Trends to increase productivity
are evident in water sectors, as well as in food industry, in order to provide
indispensable consumer products for a continuously growing population. Drinking water is not only a liquid for
hydration. It interacts with all industrial, agricultural, economic, social and
cultural components characterizing the human society (Ancuţa, 2012).
Drinking water distribution systems have an intake of
suspended bacteria from different sources as such the bacteria present in
groundwater and raw surface waters which is not removed even after the
treatment, the bacteria yielding from the treatment processes such as
biofilters and/or bacteria which is introduced by water is obstructed from
other aquatic environments. Many problems in drinking water distribution
systems (DWDS) are microbial in nature, including biofilm growth,
nitrification, microbially mediated corrosion and the occurrence and
persistence of pathogens (Regan et al., 2003;
Beech and Sunner, 2004; Camper, 2004 and Emtiazi et al., 2004).
Microbial adhesion to surfaces and biofilm formation
occur in environment, on board ships (potable water systems, water-treatment
facilities; air-conditioning equipment). Biofilms represents a protected mode
of growth, allowing microorganisms to survive in hostile environments.
Depending on the environment in which the biofilm has developed, noncellular
materials such as minerals, crystals, corrosion particles, clay or silt
particles, or blood components may also be found in the biofilm matrix (Donlan,
2002). Biofilms grow on nearly every surface that is in contact with water,
even at extremely low nutrient concentrations. One possible survival strategy
for microorganisms is the colonization and growth on solid surfaces. The
advantages of bacterial adherence are the greater availability of nutrients
attached to these surfaces (Marshall, 1989) and the possibility of optimal
long-term settlement supported by the secretion of extracellular polymer
substance (EPS). EPS are organic polymers of microbial origin which in biofilm
systems is frequently responsible for binding cells and other particulate
materials together (cohesion) and to the substratum (adhesion) (Characklis and
Wilderer, 1989). Researchers have described this organic polymer matrix as a
trap for nutrients from the water (Mittelmann and Geesey, 1985). Biofilm
formation protects embedded bacteria against such environmental influences as
antimicrobials and other bioactive compounds (Fletcher, 1991; LeChevallier,
1991).
The presence of biofilm has a number of negative
effects, such as biofouling of filters and biocorrosion and biocontamination of
drinking water distribution network, but it also has positive effects. For
example, biofilm reactors employ an important role in the degradation or
production of chemical substances in the wastewater treatment process
(Sutherland, 1998; Geesey and Bryers, 2000; Geesey et al., 2000; Lazarova and Manem, 2002). According to Krampitz and
Hollander (1991); Evans et al.,
(2009); Kim and Han (2011), biofilms may have a self-cleaning function in tanks
and many regulate microbial quality in stored rainwater. The nature of a
biofilm is determined by the specific microbes that are produced and live
within. In addition, the properties of the bulk fluid (nutrient concentration,
flow velocity, pH and oxygen) and the substratum (texture or roughness,
hydrophobicity and conditioning film) also influence biofilm development
(Donlan, 2002).
1.2 PROBLEM STATEMENT
The problems associated with the presence
of biofilms in drinking water sources are as follows:
·
They may be responsible for a wide range of water quality and
operational problems
·
They can be responsible for loss of distribution system
disinfectant residuals, increased bacterial levels, reduction of dissolved
oxygen, taste and odour changes
·
Microbial-influenced corrosion, hydraulic roughness and
reduced materials life
1.3 OBJECTIVES OF THE STUDY
·
To determine a bacterial
contaminant that is present in drinking water
·
To identify and
characterize bacteria isolated from drinking water sources in MOUAU.
·
To investigate the
bacteria that has the tendency of forming biofilms in drinking water sources
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