Lecture 1 Microbiology & Microbial Growth PDF

Faculty of Medicine Department of Microbiology Lecture (1) Microbiology & Microbial Growth Prepared by: Dr. Farkad Bantun  Learning Objectives By the end of the...

Faculty of Medicine Department of Microbiology Lecture (1) Microbiology & Microbial Growth Prepared by: Dr. Farkad Bantun  Learning Objectives By the end of the lecture, students should be: Knows the difference between taxonomy and classification Understand the current organisms nomenclature system Understand the main classification of living cells (Prokaryotes and Eukaryotes) Know the definition of Microbiology and Understand the different sizes and types of Microorganisms Know the different effects and aspects of Microorganisms Know the difference between the major groups of microorganisms  Taxonomy VS Classification Taxonomy The science dealing with the description, identification, naming, and classification of organisms. Classification The ‘grouping’ of organisms based on particular characters.  History of Taxonomy ▪1758- Carlous Linaaeus: Animalia & Plantae ▪1866- Ernst Haeckel: Added Protista (Unicellular) ▪1925- Édouard Chatton: Prokaryotes & Eukaryotes ▪1969- Robert Whittaker added Kingdom of Fungi ▪1977- Carl Woese: Divide archaea, bacteria, and eukaryote domains based on 16S rRNA  Naming of organisms Binomial Linnaeus system for scientific nomenclature. Each organism has two names: 1. Genus. 2. Specific epithet (Species). - Italicized or underlined. - The genus is capitalized, and the specific epithet is with lowercase. - Could be as an honour for the scientist, with a Latin origin. e.g: Escherichia coli (E. coli) …>  discoverer: Theodor Escherich  describes the habitat (colon/intestine)  Prokaryotes vs Eukaryotes Each Organ has specific tissue and each tissue is composed of cells. “Cell is the structural and functional unit of life” , containing all the necessary infrastructure to perform all functions. Based on cellular structure, cells classified as prokaryotic and eukaryotic cells. In most cases, prokaryotes are single cells, whereas eukaryotes are either single cells or part of a multicellular tissue system.  Prokaryotes vs Eukaryotes Prokaryotes Eukaryotes Small cell (< 5µm) Larger cells (> 10 µm) Always unicellular Unicellular / multicellular No nucleus or any membrane Always have nucleus and bound organelles membranes bound organelles DNA circular DNA is linear Ribosomes are small 70S Ribosomes are large 80S Cell division is by meiosis and Cell division is by binary fission.mitosis Reproduction is sexual and Reproduction is always asexual.asexual Prokaryotes vs Eukaryotes  Microbiology Study of different living organisms that is too small to be seen with the naked eye, known as “microorganisms”. organisms or life forms that can only be seen by the aid of Microscopes. Such as: Virology, Mycology, Bacteriology, Immunology, Microbial Ecology, Biotechnological Microbiology, Environmental Microbiology, Food Microbiology, Molecular Biology.  History of Microbiology In the golden age of Islamic civilization, Ibn cenna one of the first to hypothesize the existence of microorganisms, Ibn Zuhr discovered scabies mites, Al-Razi who gave the Ibn cenna (980-1037) earliest known description of smallpox. First primitive compound microscope, made by Zacharias Janssen, was used late 1600s by Robert Hooke who observed many microorganisms (Micrographia). Zacharias Janssen )1580-1638( Robert Hooke (1635-1703)  Koch’s postulate The involvement of a microorganism in a disease: 1.The agent must be present in every case of the disease. 2.The agent must be isolated and cultured in vitro. 3.The disease must be reproduced when a pure Robert Koch )1843-1910( culture of the agent is inoculated into a susceptible host. 4.The agent must be recoverable from the  Microbiology & Microorganism Microbiology: Microorganisms: - Study of microorganisms. - Living organisms that is too small to Such as: be seen with the naked eye. Virology, Mycology, Bacteriology, - All of the following may be Immunology, Microbial Ecology, considered microorganisms: Biotechnological Microbiology, 1- Bacteria Environmental Microbiology, Food 2- Fungi (yeast & molds) Microbiology, Molecular Biology. 3- Viruses 4- Microscopic algae 5- Protozoa & Helminths Microorganism Sizes  Microorganisms Can be unicellular (single cell), or multicellular (more than one cell). They are ubiquitous. Communities are either swimming freely or attached to a surface (biofilm). Most microorganisms do not cause disease and many are helpful. Microorganisms  Microorganisms Effects and aspects of Microorganisms Beneficial Harmful - Food (Bread, Cheese, Yoghurt, - Food spoilage Wine) - Diseases (Bacterial, Viral, - Industrial application (Enzymes, Fungal) Microorganism known as Amino acid, Vitamins, Antibiotic, Vaccines, Sewage treatment) “Pathogen” - Agriculture (Recycling of elements, Nitrifying bacteria) Microorganisms Characteristics of major groups of Microorganisms  Bacteria Prokaryotic Unicellular with Simple Internal structure. Grow on artificial laboratory media. Reproduction asexual (mostly simple cell division – Binary fission) Some cause diseases. Some perform role in natural cycling of elements and increase soil fertility. Manufacture of valuable compounds in Industry.  Archaea Prokaryotic (initially classified as bacteria) Similar to bacteria in size and simplicity of structure but radically different in molecular organization. An ancient group which is intermediate between the bacteria and eukaryotes. Obligate anaerobes living in environments low in oxygen. living in extreme environments  Fungi Eukaryotic Yeast: Unicellular Molds: Multicellular Grow on artificial laboratory media Reproduction asexual (cell division / budding) or sexual Some cause diseases some are used as food preparartion Manufacture of alcoholic beverages  Protozoa Eukaryotic Unicellular Some cultivated on laboratory media while some are intracellular parasites Reproduction asexual or sexual Some cause diseases Food for aquatic animals  Algae Eukaryotic Unicellular or Multicellular. Photosynthetic Most occur in aquatic environments Reproduction asexual or Sexual Production of food in aquatic environments Source of food and in Pharmaceuticals Some produce toxic substances  viruses Too small to be observed with light microscope. Consists of DNA/RNA core. Core is surrounded by protein coat. Coat may be enclosed in a lipid envelope. Viruses are replicated only when they are in living host cell. Bacteriophage: viruses that infect bacteria.  Prions Protein that can cause infection Prions cause neurodegenerative disease by aggregating extracellularly within the central nervous system to form plaques known as amyloid, which disrupt the normal tissue structure. Causes Bovine Spongiform Encephalopathy (BSE) Also causes Creutzfeldt-Jacob Disease (CJD) Control of Microbial Growth  Learning Objectives By the end of the lecture, students are expected to: Understand the importance of controlling the microorganisms growth and spreading Understand different mechanisms to control microorganisms, uses, significance and definitions Know the different antimicrobial agents and the resistance mechanisms of the microbes  Control of Microbial Growth Control of microbial growth is necessary in many practical situations, including medical, agricultural or food preparation. Control of microbial growth means to inhibit or prevent growth of harmful microorganisms  Why? Can easily cause contamination, infection or decay Therefore, it becomes necessary to remove or destroy them from consumed materials or from areas Microbial control is crucial because it allow us to: Controls infectious diseases which decreases morbidity and mortality. Minimizes cross and nosocomial infections and prevents surgical complications. Prevents food from spoilage. Ensures the provision of safe drinking water to public.  How? How are Microorganisms controlled? They are controlled using different anti-microbial agents. An agent that kills microorganisms or inhibits their growth is called as Antimicrobial agent Types of antimicrobial agents 1. Physical agents 2. Chemical agents  Resistance…!! Microorganisms differ greatly in their ability to withstand chemical and physical treatment due to their biochemical composition of the cell wall and the protective mechanisms. Bacterial spores are the most resistant type, followed by Mycobacteria, non-lipid viruses, fungi, bacteria, and lipid viruses. Bacterial spores have coats rich in proteins, lipids and carbohydrates as well as cores rich in dipicolinic acid and calcium. Viruses containing lipid-rich envelopes are more susceptible to the effects of detergents and wetting agents.  Sterilization Killing or destroying all forms of microbial life (including endospores) in an object or media. Sterile object is totally free of viable organisms, spores, or other infectious agents. Sterilant any chemical agent used for sterilization To preserve sterility or prevent contamination we use Aseptic techniques.  Sterilization The process of sterilization is mainly used in: 1.Microbiology: to prevent contamination by extraneous organisms. 2.Surgery & wound to maintain asepsis. 3.Food and drug industry to ensure safety from contaminating organisms  Disinfection Reducing the number of pathogenic microorganisms to the point where they no longer can cause diseases. Disinfectant: A chemical agent Applied to inanimate objects. Antiseptic: A chemical agent for disinfection applied to skin or living tissue. Sepsis: (Greek word: decay) The presence of bacterial contamination. Asepsis: The absence of bacterial contamination.  Disinfection Bacteriostatic Agent: An agent that inhibits/stops the growth of bacteria, but does not necessarily kill them. Germicide: An agent that kills certain microorganisms. Bactericide: An agent that kills bacteria. Virucide: An agent that inactivates viruses. Fungicide: An agent that kills fungi. Antimicrobial agents Physical agents Chemical agents.1 Sunlight.1 Phenol.2 Desiccation.2 Halogens.3 Moist heat.3 Alcohol.4 dry heat.4 Aldehydes.5 Filtration.5 Metallic Salts.6 Radiation.6 Oxidizing Agents.7 Ultrasonic  Physical Agents In this lecture, the following will be discussed in details: 1. Heat (Moist & Dry) 2. Filtration 3. Radiation  Moist Heat This process kills microorganisms by coagulating their proteins. In general, moist heat is much more effective than dry heat. A.Boiling: Heat to 100°C or more Start killing most of the pathogenic microorganisms within 10 minutes. Hepatitis virus: Can survive up to 30 minutes of boiling Endospores: Can survive up to 20 hours or more of boiling  Moist Heat B. Autoclave Chamber filled with hot steam under pressure (121°C at 15 lbs pressure for 15 min). Reliable sterilization with moist heat requires temperatures above that of boiling water. Preferred method of sterilization for non-heat sensitive materials  Moist Heat C. Pasteurization: Developed by Louis Pasteur to prevent the spoilage of beverages. Classic Method: Milk exposed to 65°C for 30 minutes. High Temperature Short Time (HTST): Used nowadays where Milk is exposed to 72°C for 15 seconds.  Moist Heat (Pasteurization..) Ultra High Temperature (UHT): Milk is treated at 140°C for 3 seconds and then cooled very quickly in a vacuum chamber. Advantage: Milk can be stored at RT for several months. Disadvantage: May damages proteins and vitamins and change in smell and taste of dairy product.  Dry Heat This process kills microorganisms through oxidation effects. 1.Direct Flaming: Used to sterilize inoculating loops and needles. 2.Incineration: Effective way to sterilize disposable items (paper cups, dressings) and biological waste.  Dry Heat 3.Hot-air sterilization Oven operated by electric power and used mainly for sterilizing glassware. e.g. Flasks, tubes, pipettes in microbiological laboratories.  Filtration Removal of microbes by passage of a liquid or air through a screen like material with small pores. Used to sterilize heat sensitive materials like vaccines, enzymes, antibiotics, and some culture media. Membrane Filters: Uniform pore size. Different sizes: 0.22 and 0.45um Pores: Used to filter most bacteria. Don’t retain spirochetes, mycoplasma and viruses. 0.01 um Pores: Retain all viruses and some large proteins. Filtration  Radiation Electromagnetic radiations are employed for sterilization. U.V. (250- 260 nm, cause damage to cornea & skin, used in hospitals at OR) X-rays, γ- rays used to sterilize heat-sensitive items such as surgical gloves and syringes, or for X-rays images.  Chemical Agents In this lecture, the following will be discussed in details: 1. Phenol 2. Alcohols 3. Halogens 4. Aldehydes 5. Heavy Metals 6. Oxidizing agents  Phenol Used as disinfectant in the past Rarely used today because it is a skin irritant and has strong odour. Destroys plasma membrane and denatures proteins Advantages: Stable, persist for long times after applied  Alcohol Kill most bacteria and fungi, but not endospores. Act by denaturing proteins and disrupting cell membranes. Evaporate, leaving no residue. Used to mechanically wipe microbes off skin before injections or blood drawing.  Halogens A.Iodine Tincture of iodine was one of first antiseptics used. Stains skin and clothes, somewhat irritating. Used as skin antiseptic in surgery. B. Chlorine Used to disinfect drinking water, pools, and sewge  Aldehydes A.Formaldehyde gas: Excellent disinfectant Disadvantage: Irritates mucous membranes, strong odour. B.Gluteraldehyde: Less irritating and more effective than formaldehyde. One of the few chemical disinfectants that is a sterilizing agent. Commonly used to disinfect hospital instruments.  Heavy Metals Heavy metals and their compounds are microbicidal Include silver, copper, selenium, zinc, and mercury Silver Nitrate 1% (v/v) used to protect (prophylactic) against ophthalmia neonatorum Selenium: Used for fungal infections (anti-dandruff shampoos) Zinc chloride is used in mouthwashes  Oxidizing Agents A.Ozone: Used to disinfect water. Helps neutralize unpleasant tastes and odors. More effective killing agent than chlorine, but less stable and more expensive. B.Hydrogen peroxide: Used as an antiseptic in the past. Not good for open wounds - quickly react with catalase enzyme in human erythrocytes. Effective in disinfection of inanimate objects. Sporicidal at higher temperatures.  Reference David Greenwood, Richard Slack, John Peutherer, Mike Barer: Medical Microbiology. A Guide to microbial infections: Pathogenesis, immunity, laboratory diagnosis and control. Seventeenth edition. Lippincott’s illustrated reviews: Microbiology. Third edition.