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Bacteriology Dr. Iman Thabet & Dr. Sultan Alsharif

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Presentation on theme: "Bacteriology Dr. Iman Thabet & Dr. Sultan Alsharif"— Presentation transcript:

1 Bacteriology Dr. Iman Thabet & Dr. Sultan Alsharif

2 Overview Brief description of the main outcomes for the student course e.g., teaching and postgraduate studies. Use of sources e.g., internet and libraries Publish work e.g., recent related research Dr. Iman Thabet & Dr. Sultan Alsharif

3 Bacteriology: It is the branch of microbiology which study the bacteria
Prokaryotic organisms that lack a true nucleus (a nucleus defined by a membrane) Bacteria maintain their genetic material, deoxyribonucleic acid (DNA), in a single, circular chain. Bacteria also contain DNA in small circular molecules termed plasmids Dr. Iman Thabet & Dr. Sultan Alsharif

4 Eukaryotes Prokaryotes
Characteristic Typically mm in diameter Typically mm in diameter Size of cell True nucleus, consisting of nuclear membrane & nucleoli No nuclear membrane or nucleoli (nucleoid) Nucleus Present; examples include lysosomes, Golgi complex, endoplasmic reticulum, mitochondria Absent Membrane-enclosed organelles Complex; consist of multiple microtubules Consist of two protein building blocks Flagella When present, chemically simple Usually present; chemically complex (typical bacterial cell wall includes peptidoglycan) Cell wall Sterols and carbohydrates that serve as receptors present No carbohydrates and generally lacks sterols Plasma membrane Cytoskeleton; cytoplasmic streaming No cytosketeton or cytoplasmic streaming Cytoplasm Larger size (80S) Smaller size (70S) Ribosomes Multiple linear chromosomes Single circular chromosome Chromosome (DNA) arrangement Mitosis Binary fission Cell division Dr. Iman Thabet & Dr. Sultan Alsharif

5 Distribution of Bacteria
1- Bacteria are widely distributed on earth 2- Every thing expose to atmosphere or water contaminated by bacteria 3- In the upper respiratory tract and digestive tract 4-The solid tissue of healthy individuals, contain few numbers as liver, spleen, blood and lymph nodes 5- There are useful bacteria 1- Digestive tract : - Intestinal bacteria synthesize vitamins - Bacterial flora digest cellulose 2- Industrial bacteria: - Vinegar making, cheese manufacture, acetone, antibiotic industry 3- Agricultural bacteria: - Nitrogen fixing bacteria and the leguminous plants - Utilization of sewage Dr. Iman Thabet & Dr. Sultan Alsharif

6 Identifying and Classifying Bacteria
The identification schemes of Bergey's Manual are based on: morphology (coccus, bacillus) staining (gram-positive or gram-negative) cell wall composition (presence or absence of peptidoglycan) oxygen requirements (aerobic, anaerobic, facultatively anaerobic) biochemical tests (in which sugars are aerobically metabolized or fermented) Dr. Iman Thabet & Dr. Sultan Alsharif

7 Bacterial Morphology Dr. Iman Thabet & Dr. Sultan Alsharif

8 Spherical shape of bacteria - diplococci - streptococci - tetrads
and arrangements 1- Shape Cocci Spherical shape of bacteria - diplococci - streptococci - tetrads - staphylococci Dr. Iman Thabet & Dr. Sultan Alsharif

9 Bacilli - single - diplobacilli - streptobacilli
Dr. Iman Thabet & Dr. Sultan Alsharif

10 Spiral vibrio spirilla spirochete
Dr. Iman Thabet & Dr. Sultan Alsharif

11 Factors affecting variation in bacterial shape
1- Environmental factors E. coli on media contain reducing agents (crystal violet, penicillin) (, while on media contain raising agents ( ca.chlorid filamentous becomes Becomes spherical 2- Bacterial metabolic products Such as pigments and toxins 3- Age of culture autolysis Old culture, bacteria smaller due to Bacteria larger in size Young culture, Dr. Iman Thabet & Dr. Sultan Alsharif

12 Size of bacteria Average diameter of bacteria: 1- cocci: 1-2 µm
Width: µm, Length: 1-3 µm 1- cocci: 1-2 µm 2- Spirochaetes: width 0.2 µm, length µm 3- Bacilli: Small size: width µm, length µm Medium size: width µm, length 2-4 µm Large size: width 1-2 µm, length 5-15 µm Dr. Iman Thabet & Dr. Sultan Alsharif

13 Bacteria are small compared to cells with nuclei
Euglena 100 µm Plant cell µm Animal cell 5-30 µm Spirocheta 10 µm Virus nm Dr. Iman Thabet & Dr. Sultan Alsharif

14 Bacterial cell structure
Dr. Iman Thabet & Dr. Sultan Alsharif

15 Structure of bacterial cells
Dr. Iman Thabet & Dr. Sultan Alsharif

16 Dr. Iman Thabet & Dr. Sultan Alsharif

17 The nucleoid - It is an irregularly-shaped region within the cell of a prokaryote that contains all or most of the genetic material. - The genome of prokaryotic organisms generally is a circular, double-stranded piece of DNA. - In contrast to the nucleus of a eukaryotic cell, it is not surrounded by a nuclear membrane. Also there is no nucleolus. Dr. Iman Thabet & Dr. Sultan Alsharif

18 Bacterial Cell Walls Functions: Layer outside the plasma membrane.
1- Determination of shape of the bacterial cell 2- Protection of the bacterial cell due to its rigidity and osmotic insensitivity 3- Play a role in the cell division, as forming a transverse septum 4- Porous so allow free exchange between the cell and the surrounding media 5- Its integrity essential for the viability of the bacterial cell 6- Responsible for staining affinity of cell wall due to its composition Dr. Iman Thabet & Dr. Sultan Alsharif

19 The main components of the cell wall is peptidoglycan.
Bacterial Cell Walls The main components of the cell wall is peptidoglycan. Dr. Iman Thabet & Dr. Sultan Alsharif

20 A comparison between Gram positive and Gram negative cell wall
Item Thin (single-layered) Thick (multilayered) Peptidoglycan layer Absent Present Teichoic acids present Periplasmic space High Virtually none Lipopolysaccharide (LPS) content Low Lipid and lipoprotein content Resistance to physical disruption Inhibition by basic dyes Susceptibility to anionic detergents Resistance to drying Can be decolorized to accept counter stain Retain crystal violet dye and stain dark violet Gram reaction Dr. Iman Thabet & Dr. Sultan Alsharif

21 Cytoplasmic membrane Function:
It is an elastic membrane surrounding the cytoplasm. It consists of lipoprotein so it is semipermeable and allow the passage of important substances such as water and soluble substances and allow passage of endproducts Function: 1- Responsible for selective permeability. 2- Active transport of substances which cant enter the cell passively because it contain permease enzyme. 3- Energy production, as it the site for oxidation, phosphorylation and active transport. 4- Excretion of toxins and hydrolytic enzymes 5- Biosynthesis of cell wall and other proteins 6- Play important role in cell division as being site for DNA attachment and help in formation of the transverse septum Dr. Iman Thabet & Dr. Sultan Alsharif

22 Cytoplasm A gel like substance contain a variety of organic and inorganic salts
Dr. Iman Thabet & Dr. Sultan Alsharif

23 Important inclusions floating in the cytoplasm
1- Ribosomes In most bacteria the most numerous intracellular structure is the ribosome. It is the site of protein synthesis. Polyribosome: A group of ribosomes linked together like beads with messenger RNA Dr. Iman Thabet & Dr. Sultan Alsharif

24 Inclusions - Inclusions are considered to be nonliving components of the cell that do not possess metabolic activity and are not bounded by membranes. The most common inclusions are glycogen, lipid droplets, crystals, and pigments. (food stores or reserves) - Volutin granules are cytoplasmic inclusions of complexed inorganic polyphosphate. These granules are called metachromatic granules due to their displaying the metachromatic effect; they appear red or blue when stained with the blue dyes as methylene blue. Gas vacuoles Gas vacuoles are membrane-bound, spindle-shaped vesicles. Dr. Iman Thabet & Dr. Sultan Alsharif

25 Capsule It is a thick gelatinous circumscribed layer lie outside the cell wall. Type: 1- Well-developed capsule ( when bacteria grow on rich media) 2- Microcapsule (thin layer detected by electron microscope) Detection: 1- Special stain ( wet or dry Indian ink) 2- By Gram stain appears a hollow zone 3- By electron microscope Composition: Consists mainly of water and little solids as hyaluronic acid, polysaccharides or polypeptide. Dr. Iman Thabet & Dr. Sultan Alsharif

26 Function: Slime layer:
1. Contribute to virulence of bacteria by preventing phagocytosis A. Clostridium welchii B. Bacillus anthracis 2.Prevents drying out or desiccation 3. Allows bacteria to adhere to various surfaces - Streptococcus mutans - enamel on teeth to cause dental carries - Klebseilla pneumoniae - attaches to respiratory tract. 4. Used in classification and diagnosis of some bacteria. Slime layer: Is an easily removed, unorganized layer of extracellular material that surrounds bacterial cells. capsule. It has the same structure of the It is loose so permit passage of metabolism and allow entrance of antibiotics Dr. Iman Thabet & Dr. Sultan Alsharif

27 Flagella - Thread like structures that extend from the surface of the envelope - Function  Locomotion, allow bacteria to seek favorable conditions. Dr. Iman Thabet & Dr. Sultan Alsharif

28 Flagella Structure Three distinct parts 1- Filament: longest portion, flagellin protein arranged in chains & forms a helix around a hollow core. 2- Hook, short thickened bent It is a region act as a joint. Driven motor 3- Dr. Iman Thabet & Dr. Sultan Alsharif

29 Flagella Arrangement 1- Monotrichous: Single flagellum at one pole.
3- Lopotrichous: Two or more at one or both poles. 2- Amphitrichous: Single flagellum at each pole. 4- Peritrichous: Flagella all over the surface. Dr. Iman Thabet & Dr. Sultan Alsharif

30 Pili - Straight hair like projections made of protein pilins
- May be short or several cell lengths long. - Main function is attachment  each type of bacteria attach to specific surfaces - Present in virtually all Gm(-), absent in many Gm(+). Dr. Iman Thabet & Dr. Sultan Alsharif

31 Sex Pili 1-10 in number, Larger than fimbriae, Determined by conjugative plamids Required for conjugation Attaches one bacterial cell to another during mating Dr. Iman Thabet & Dr. Sultan Alsharif

32 Fimbriae - Filamentous appendages that are shorter, finer, hairlike, thinner, straighter and more numerous than flagella - Found mostly in Gram (-) bacteria - Used for attachment and also required for twitching motility of some species. Dr. Iman Thabet & Dr. Sultan Alsharif

33 Bacterial spores Definition:
is a dormant, tough, and temporarily non-reproductive structure produced by certain bacteria, in response to adverse changes in the environment, formed in the bacilli such as Bacillus and Clostridium. Characteristics: 1- Endospores enable bacteria to survive periods of environmental stress lasting at least several thousand years. 2- When the environment becomes more favorable, the endospore can reactivate itself to the vegetative state. Dr. Iman Thabet & Dr. Sultan Alsharif

34 Factors conditioning the spore formation: 1- Exhaustion of the nutrients. 2- Accumulation of harmful end products. 3- Gradual desiccation. 4- Increasing or decreasing of oxygenation. 5- Exposure to extreme heat or cold. Dr. Iman Thabet & Dr. Sultan Alsharif

35 Cross section of a bacterial spore
Structure Exosporium: A thin covering which overlies the spore coat Spore coat: which acts like a sieve that excludes large toxic molecules like lysozyme . Spore cortex: beneath the spore coat and consists of peptidoglycan. Core wall: lies beneath the cortex and surrounds the protoplast or core of the endospore The core: contains the spore chromosomal DNA and is encased in chromatin-like proteins known as SASPs, The core also contains normal cell structures, such as ribosomes and other enzymes, but is not metabolically active. Cross section of a bacterial spore Dr. Iman Thabet & Dr. Sultan Alsharif

36 Location Classification of the spores:
- According to the position Central, subterminal, terminal - According to the size smaller, the same, larger than the bacilli - According to the shape oval, rounded, lancet (lemon- shape) The figure shows how the shape, location and the relative size of the formed-spore A = oval, terminal; B = rectangular, terminal; C = rectangular, subterminal, D = rectangular, central; E = circular, terminal; F = circular, central; G = terminal, club-shaped. Dr. Iman Thabet & Dr. Sultan Alsharif

37 Plasmids - Extrachromosomal DNA express < 30 genes. - Double-stranded DNA molecules, usually circular, or linear that can exist and replicate independently of the chromosome or may be integrated with it (episomes). - Plasmids are inherited during cell division Dr. Iman Thabet & Dr. Sultan Alsharif

38 Type of plasmids 1- Fertility (F- plasmid): which contain tra genes. They are capable of conjugation and result in the expression of sex pilli. 2- Resistance factor (R plasmid): have genes that code for enzymes capable of destroying or modifying antibiotics. Often resistance genes are within mobile genetic materials known as transposons. 3. Virulence plasmids: Encode factors that make their hosts more pathogenic. 4. Col plasmids, which contain genes that code for bacteriocins known as colicins and other proteins that can kill other bacteria 5. Metabolic plasmids (Degradative plasmids), carry genes for the enzyme that degrade substances such as atomatic compounds (tolune,), pesticides (2,4-dichlorophenoxyacetic acid) & sugars (Lactose). Dr. Iman Thabet & Dr. Sultan Alsharif

39 Bacterial cell reproduction and growth
Dr. Iman Thabet & Dr. Sultan Alsharif

40 Bacterial reproduction
Asexual Reproduction in Bacteria Bacteria reproduce by a way of asexual reproduction called binary fission. BINARY FISSION In one bacterium, the single circular chromosome duplicates. Then, the two resulting chromosomes attach to the inside of the plasma membrane. The cell elongates and separates into two strands. Finally, the cell membrane grows inward, the cell wall forms separating two daughter cells each with a chromosome. 1- in Bacilli it occurs transverse never longitudinal 2- in cocci it occurs at any line of the diameter. Another a sexual forms of reproduction in higher bacteria: 1- Fragmentation 2- Budding 3- Formation of conidia (trichobacteria) which later generate to give mycelia. Dr. Iman Thabet & Dr. Sultan Alsharif

41 Process of Sexual Reproduction in Bacteria :Conjugation
Is the process in which male cell passes DNA to female cell by means of a conjugation tube . In this process one bacterium attaches itself to another bacterium through a tube like structure known as sex pili. Genetic material is then transferred from one bacterium to the other. Transformation: The bacteria picks up DNA from the surrounding environment. In this, a fragment of DNA from the dead donor attaches itself to the cell wall of the living bacteria, which incorporate it. The new DNA then binds to the recipient bacteria and genetic recombination takes place. When a foreign plasmid is introduced into bacteria it amplifies it and makes many copies of it. Transduction: Is a process in which the bacteriophages carry DNA from one cell to another. Bacteriophage inserts its genome into the bacterium. Then, the viral genome, enzymes, and viral components are replicated and assembled within the host bacterium. Newly formed bacteriophage then lyses or splits open the bacterium, and releases the replicated viruses. Dr. Iman Thabet & Dr. Sultan Alsharif

42 Dr. Iman Thabet & Dr. Sultan Alsharif

43 Bacterial growth Physical Requirements: -Temperature - pH
Bacterial Growth: refers to the increase in the number of cells, not the size of the cells Requirements for Growth 1- Physical 2- Chemical Physical Requirements: -Temperature - pH - Osmotic Pressure Chemical Requirements: - Macro & Micro Elements - Oxygen - water Dr. Iman Thabet & Dr. Sultan Alsharif

44 PH Physical Requirements Temperature
1- psychrophiles (cold loving microbes ) °C - 20°C 2- mesophiles (moderate temp. loving microbes) 20°C - 40°C 3- thermophiles (heat loving microbes) °C -100°C PH - Most bacteria grow between pH pH 7.5 - Very few can grow at below pH 4.0 Osmotic Pressure Microbes obtain almost all their nutrients in solution from the surrounding water Tonicity isotonic hypertonic hypotonic Dr. Iman Thabet & Dr. Sultan Alsharif

45 Chemical Requirements
: Water Water constitute 80-90% from bacterial cell that it is an essential factor for growth Macro & Micro Elements : Inorganic compounds such as vitamins & minerals Organic compounds such as carbohydrates & proteins Oxygen : Aerobic and anaerobic bacteria can be identified by growing them in liquid culture: 1: Obligate aerobic: gather at top of test tube to absorb maximal amount of oxygen. 2: Obligate anaerobic: gather at bottom to avoid oxygen. 3: Facultative anaerobes: gather mostly at the top, since aerobic respiration is most beneficial; but as lack of oxygen does not hurt them, they can be found all along the test tube. 4: Microaerophiles gather at upper part of test tube, not at top. Require O2, but at low concentration. 5: Aerotolerant bacteria are not affected by oxygen, and they are evenly spread along the test tube. Dr. Iman Thabet & Dr. Sultan Alsharif

46 Microbes & Oxygen Dr. Iman Thabet & Dr. Sultan Alsharif
1: Obligate aerobic 2: Obligate anaerobic. 3: Facultative anaerobes 4: Microaerophiles 5: Aerotolerant Dr. Iman Thabet & Dr. Sultan Alsharif

47 Growth curve Dr. Iman Thabet & Dr. Sultan Alsharif

48 2- Log (Exponential) Phase 3- Stationary Phase 4- Death Phase
Growth phases 1- Lag Phase 2- Log (Exponential) Phase 3- Stationary Phase 4- Death Phase 1. Lag Phase - Bacteria are first introduced into an environment or media - Bacteria are “checking out” their surroundings - Cells are very active metabolically - The number of cells changes very little - Lasts from1hour to several days Dr. Iman Thabet & Dr. Sultan Alsharif

49 2. Log Phase 3. Stationary Phase
- Rapid cell growth (exponential growth) - Population doubles every generation - Microbes are sensitive to adverse conditions and antibiotics 3. Stationary Phase - Death rate = rate of reproduction - Cells begin to encounter environmental stress - Lack of nutrients - Lack of water - Absence of enough space - Accumulation of metabolic wastes - pH changes - Endospores would form now Dr. Iman Thabet & Dr. Sultan Alsharif

50 4. Death Phase - Death rate > rate of reproduction
- Due to limiting factors in the environment Dr. Iman Thabet & Dr. Sultan Alsharif

51 Dr. Iman Thabet & Dr. Sultan Alsharif
Bacterial products Bacterial Enzymes Bacterial pigments bacterial toxins Dr. Iman Thabet & Dr. Sultan Alsharif


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