Microbiology Past Paper (MansNurCMSc 105) - 2024/2025 - PDF

National Mansoura University Faculty of Nursing Microbiology (MansNurCMSc 105) Level 1 General Bacteriology 2024/2025 3 National Mansoura University Faculty of Nursing Microbiology (MansNurCMSc 105) Level 1...

National Mansoura University Faculty of Nursing Microbiology (MansNurCMSc 105) Level 1 General Bacteriology 2024/2025 3 National Mansoura University Faculty of Nursing Microbiology (MansNurCMSc 105) Level 1 Microbiology Microbiology: It is defined as the study of organisms that are too small to be seen clearly by the naked eye, that is the study of microorganisms. e.g. Bacteria, fungi, algae, and viruses Microorganisms are organized into fields of study: Bacteriology Virology Mycology Protozoology Parasitology. A microorganism: is simply a very, very small organism that you cannot see with your naked eye, but you sure feel its effect 2024/2025 4 National Mansoura University Faculty of Nursing Microbiology (MansNurCMSc 105) Level 1 Bacteria are prokaryotic organisms A prokaryotic organism is a one-celled organism that does not have a true nucleus. Nomenclature: The first word =genus (first letter always capitalized) the second word= species (not capitalized). Both words are always italicized or underlined ex: Staphylococcus aureus or S. aureus or Staphylococcus aureus Bacillus anthracis or B. anthracis or Bacillus anthracis Escherichia coli or E. coli or Escherichia coli Typical structure of Bacterial cell: Cytoplasm ‫ ٭‬All components are present in all types of bacterial cells except capsule, pilus, and flagellum 2024/2025 5 National Mansoura University Faculty of Nursing Microbiology (MansNurCMSc 105) Level 1 Capsule: - Composed of polysaccharides. - Protects bacterial cells from immune system or from attack by antibiotics. Flagellum: - For the movement of bacteria. Pilus: - Attachment of bacteria to surface of human cells. - Transfer of genetic material from one cell to another. Cell wall: - It is a rigid, porous layer. - Composed of polymeric material called murein (peptidoglycan). - Function: - It provides the definite shape of the bacteria. - Protects the cell from mechanical damage and lysis. The basic structure of peptidoglycan is an alternating series of two major subunits, N-acetylmuramic acid (NAM) N-acetylglucosamine (NAG). cross-linked to one another by tetrapeptide chains 2024/2025 6 National Mansoura University Faculty of Nursing Microbiology (MansNurCMSc 105) Level 1 Cell membrane: - Composed of lipid bilayer that completely surrounds the cell and separates the inside from the outside. - Function: Control movement of substances (Ions, proteins, nutrients) between the cell and the surrounding environment. Cytoplasm: - It is the fluid that fills the cells and composed mainly of water and salts. - It contains different components of the cell (Components are called organelles). Ribosome: - Synthesis of proteins of the cell. - DNA or (Chromosome): - Carries all the genetic information of the bacterial cell. Plasmids are circular, supercoiled, double-stranded DNA molecules. - They carry EXTRA GENES that can be used for special situations such as antibiotic resistance, production of toxins synthesis of enzymes. 2024/2025 7 National Mansoura University Faculty of Nursing Microbiology (MansNurCMSc 105) Level 1 Nucleoid region: - It is an irregularly shaped part of a bacterial cell where DNA is present. - It lacks the membrane that is found around the nucleus of eukaryotic cells. Other components (organelles) that are present in other living cells but not bacteria (eukaryotes): Mitochondria: - Synthesis and storage of energy (ATP) for the cell. Golgi apparatus: - Responsible for transporting, modifying, and packaging proteins and lipids for delivery to targeted destinations. Endoplasmic reticulum: - Folding of proteins (Allow proteins to take the functional structure and transport to Golgi apparatus. Nucleus: - Typical nucleus with a membrane. Scale of size of living organisms: 2024/2025 8 National Mansoura University Faculty of Nursing Microbiology (MansNurCMSc 105) Level 1 Comparison between Prokaryotic and Eukaryotic cells: Eukaryotic cells Prokaryotic cells ‫حقيقيات النواة‬ Property ‫بدائية النواة‬ 1- Cell size Small cells (0.5 -5) µm Large cells (5 -50) µm 2- Nucleus Absent Present Cell division by binary 3- Cell division by mitosis and meiosis. fission. 4- Sexual systems absent present DNA composed of only DNA composed of: 5- DNA one chromosome 2-46 chromosomes 7- Mitochondria absent Present 8- Golgi apparatus absent Present 9- Endoplasmic reticulum absent Present 10- Examples: Bacteria Human cells, animal cells, fungi Additional resources Structure and Replication of Bacterial Cells Mechanisms of antibiotic action 2024/2025 9 National Mansoura University Faculty of Nursing Microbiology (MansNurCMSc 105) Level 1 1- In this bacterium “Bacillus anthracis” the genus is: a. Anthracis b. Bacillus c. Both a and b 2- Flagella in bacteria enable bacteria to a. Reproduce b. Move c. Nutrition d. No answer is true 3- The following components of the cell determine its shape: a. Cell wall b. Flagellum c. Capsule d. pili 2024/2025 10 National Mansoura University Faculty of Nursing Microbiology (MansNurCMSc 105) Level 1 Bacterial shape and classification Shape of bacteria: Cocci: spherical in shape Bacilli: rod shape Cocco-bacilli: elongated bacilli Vibrio: comma-shaped Spirillum: spiral Arrangement of bacteria: Cocci: a) Diplococci: Pairs of cocci b) Streptococci: Chain of cocci c) Staphylococci: Grape-like structure d) Tetrads e) Sarcina Bacilli: a) Scattered: No special arrangement. b) Diplobacilli: pairs of bacilli c) Streptobacilli: Chains of bacilli 2024/2025 11 National Mansoura University Faculty of Nursing Microbiology (MansNurCMSc 105) Level 1 Classifications of bacteria: According to the cell wall composition into: A- Gram positive Bacteria. B- Gram negative Bacteria. The ability of bacteria to cause disease (pathogenicity). A- Pathogenic bacteria: Able to cause a disease B- Non-pathogenic bacteria: Don’t cause a disease. According spore formation into: A- Endospore forming bacteria. B- Non-endospore forming bacteria. Bacterial classification according to the cell wall composition: Parameter Gram- Positive Gram-Negative Peptidoglycan layer Thick layer Thin layer Lipid content Low high Outer membrane Absent present (lipopolysaccharide) Teichoic acid, present Absent Lipoteichoic acid Gram stain Violet Red- purple Examples Staphylococcus aureus, Escherichia coli. Bacillus anthracis 2024/2025 12 National Mansoura University Faculty of Nursing Microbiology (MansNurCMSc 105) Level 1 Outer membrane consists of lipid bilayer and lipopolysaccharides (LPS) LPS consists of: 1- Lipid A: It causes fever. 2- The polysaccharide moiety (O Antigen): Antigen: Means substance that stimulates the host immune system to produce antibodies. Types of bacteria that are not Gram-positive or negative bacteria: Cell wall free bacteria: e.g. Mycoplasma Acid fast bacteria: (Bacteria resistant to acids) - It has small amount of peptidoglycan and large amounts of glycolipids. - e.g. Mycobacterium tuberculosis 2024/2025 13 National Mansoura University Faculty of Nursing Microbiology (MansNurCMSc 105) Level 1 Classifications of bacteria according to pathogenicity: Pathogenic bacteria Non-pathogenic bacteria Able to cause a disease. don’t cause a disease The degree of pathogenicity differs from one Normal flora or Commensal bacteria bacterium to another Present naturally in the human body (e.g. on skin, in mouth, in stomach, intestine) Present in the environment e.g.: Soil, Seawater, Rivers. Useful and used in the biotechnology field: - Streptomyces griseus from soil is used for production of Streptomycin. - Lactobacillus is used for production of yoghurt. Classifications of bacteria according to spore formation: Endospore: A specialized form of bacterial cells that allows bacteria to resist unfavorable conditions of growth. The structures may remain dormant for perhaps 100 years, or even longer, It is highly resistant to antimicrobial agents and sterilization process. 2024/2025 14 National Mansoura University Faculty of Nursing Microbiology (MansNurCMSc 105) Level 1 can germinate, to become a multiplying cell, called a vegetative cell. Bacteria are classified according to spore formation into: Endospore forming bacteria usually Non-endospore forming bacteria bacillus bacteria e.g. Bacillus anthrax. Microbial growth requirements I. Nutritional requirements. II) Environmental requirements. 1- Macronutrients 1- Temperature 2- Trace elements 2- pH. 3- Growth factors 3- Oxygen. 4- Osmotic pressure (Salt concentration). 2024/2025 15 National Mansoura University Faculty of Nursing Microbiology (MansNurCMSc 105) Level 1 I.Nutritional requirements. 1- Macronutrients: Microorganisms require about ten elements in large quantities, because they are used to construct carbohydrates, lipids, proteins, and nucleic acids. They constitute 95% or more of cell dry weight: Carbon, oxygen, nitrogen, sulfur, phosphorus, hydrogen, potassium, calcium, magnesium and iron. 2- Trace elements: Needed in very small amounts and act as parts of enzymes and cofactors. Usually mineral elements: such as copper, molybdenum, and zinc. 3- Growth factors: A- Amino acids: are needed for protein synthesis. B- Purines and pyrimidines are needed for nucleic acid synthesis. C- Vitamins: make up all or part of enzyme cofactors 2024/2025 16 National Mansoura University Faculty of Nursing Microbiology (MansNurCMSc 105) Level 1 1- Examples of the useful use of microorganisms in biotechnology is Production of: A. Bread B. Insulin C. Both A & B D. No answer is correct 2- S. aureus differs from E. coli in that: A. It contains no cell wall B. It contains no cell membrane C. It contains no periplasmic space D. All the above 3- The organelle that is responsible for protein synthesis is: A. Ribosome B. Mitochondria C. Endoplasmic reticulum D. Golgi apparatus 4- The following shape of bacteria is called: A. Cocci B. Vibrio C. Bacilli D. Spiral 5- Bacteria A is less pathogenic than B, this means that bacteria A: a. More able to cause a disease b. Difficult to be detected in labs. c. Both a and b. d. No answer is correct 2024/2025 17 National Mansoura University Faculty of Nursing Microbiology (MansNurCMSc 105) Level 1 Microbial growth Microbial growth requirements II. Environmental requirements. 1- Temperature: According to the optimum temperature for growth the organism can be classified into: a) Psychrophiles: - Grow best between 0-15 oC. - None can live in the human body. - Cause spoilage of refrigerated foods. b) Mesophiles: - Include most microorganisms and grow best between 25 and 40 oC. - Human pathogens are included in this category and most grow best near human body temperature (37 oC). c) Moderate thermophiles: - Grow best between 55 and 65 oC. (Bacteria live in hot springs) d) Extreme thermophiles: - Grow best between 80 and 113 oC. (Bacteria live in volcanic vents) - 2024/2025 18 National Mansoura University Faculty of Nursing Microbiology (MansNurCMSc 105) Level 1 2- PH: - Most bacteria prefer neutral pH (6.5-7.5). - Fungi and yeast grow in acidic pH between 5 and 6. - Acidity inhibits most microbial growth and is used frequently for food preservation (Ex. pickling). - Alkalinity inhibits microbial growth but is not commonly used for food preservation. 3- Oxygen requirement: a) Aerobic: Growth occurs only in the presence of oxygen. b) Obligate anaerobes: Growth occurs only in the absence of oxygen. c) Facultative anaerobes: Growth is best in the presence of oxygen but can grow in its absence. d) Aerotolerant anaerobes: Anaerobic bacteria that can grow in the presence of oxygen. e) Microaerophilic: Aerobic organisms that do not tolerate atmospheric concentrations of oxygen. Growth occurs only at a lower level of oxygen concentration. 2024/2025 19 National Mansoura University Faculty of Nursing Microbiology (MansNurCMSc 105) Level 1 Microbial growth & reproduction: Microbial growth: an increase in the number of cells. Reproduction of bacteria occurs by binary fission. Growth curve: Microbial growth is measured by the growth curve. Growth cycle of microbes composed of four characteristic phases: 2024/2025 20 National Mansoura University Faculty of Nursing Microbiology (MansNurCMSc 105) Level 1 (a) Lag phase: cells begin to synthesize inducible enzymes and use stored food reserves to start reproduction (0-2 h from cultivation) (b) Logarithmic (log = exponential) phase: The number of cells increases exponentially. (2-8 h from cultivation) (c) Stationary phase: The number of cells is constant. (8-20 h from cultivation) - reproduction rate is equal to death rate (d) Death (decline) phase: The number of cells decrease. (After 20 h cultivation) - death rate is more than reproduction rate Cultivation of bacteria Culture media: Nutrient material prepared for the growth of microorganisms Can be used to: - Enrich the numbers of bacteria - Select for certain bacteria and suppress others. - Differentiate among different kinds of bacteria The media may be: Liquid medium Components are dissolved in water and sterilized. Solid medium A medium to which has been added a gelling agent [Agar (most commonly used), Gelatin, Silica gel] 2024/2025 21 National Mansoura University Faculty of Nursing Microbiology (MansNurCMSc 105) Level 1 Types of culture media There are two basic types of media: A- Complex media B- Synthetic media A- Complex media - Often consist of plant or animal extracts, such as soybean meal, milk protein, etc. Include most routine laboratory media. e.g., tryptic soya broth 1- Basal media: E.g. nutrient broth/agar 2- Enriched media - Complex medium to which additional nutrients are added (blood or serum) - Eg. Blood agar medium 3- Selective media - media contain a selective agent, allowing some bacteria to grow, while inhibiting other bacteria. Eg. Lowenstien-Jensen (L-J) media 4- Differential media - Medium contains substances that allow certain groups of bacteria to appear differently when growing on it (differential agent). - Eg. blood agar 5- Selective and Differential - Media has both selective and differential agent - Eg. Mannitol Salt Agar 2024/2025 22 National Mansoura University Faculty of Nursing Microbiology (MansNurCMSc 105) Level 1 B- Synthetic media - Chemically defined media. - Contain pure chemical compounds. - Ingredient must be of analytical quality. - Water must be distilled. Identification of microorganism 1. Microscopy 3. Biochemical - Staining: Gram, Zeel-Nielsen - Oxygen requirement - Shape and arrangement - Enzymes 2. Culture 4. Serology: antigen antibody interaction - Media: liquid, solid, differentiate, 5. Genetic selective - Morphology Bacterial Growth in the Lab Additional resources Identify the oxygen requirement of organisms in tubes 1-6 2024/2025 23