Characteristics of Microorganisms PDF

Characteristics of Microorganisms Chapter 2 Week: 2 Course: Microbiology and Infection Control Updated: April 2024  Characteristics of Microorganisms & Cell Theory Objectives: Define microbiology and understand t...

Characteristics of Microorganisms Chapter 2 Week: 2 Course: Microbiology and Infection Control Updated: April 2024  Characteristics of Microorganisms & Cell Theory Objectives: Define microbiology and understand the importance of infection control. List the various types of microorganisms. Describe the shape, size, and cellular arrangements of bacteria. Describe the structure and function of prokaryotic cells: chromosome, flagella, capsule, endospore, fimbriae, plasmids, ribosomes, and cell wall. Describe the structure and functions of a eukaryotic cell. Describe the classification of viruses and differentiate between viruses and bacteria. List some common viruses. List the characteristics of fungi. Compare a prokaryotic cell and a eukaryotic cell. 2  Major Groups Of Microorganisms (MOs) 1. Bacteria - makes up a large group of one celled mo’s; vary in size, shape, & arrangement of cells; grows best at 98.6 F in moist, dark environment 2. Viruses - small in size and cause fatal diseases; this mo can live and multiply only inside an appropriate host cell 3. Algae – range from single-celled to larger multiple cell organisms that are known as seaweed and kelp; most of these mo’s do not produce human disease 4. Protozoa - large group of one-cell organisms; do not have a rigid cell wall; found in freshwater, marine habitat & moist soil; small number are responsible for intestinal infections of humans and others invade the blood, lungs, liver, or brain 5. Fungi - mushrooms, yeast, & mold; oral candidiasis is a common form of this group of mo’s found in the dental office. 6. Archaea- single- cell microbes morphologically similar to bacteria, but with genes & metabolic pathways closely related to eurokaryotes. 3  Bacteriophage(“bacteria eaters”) Viruses that infect bacteria were discovered in 1915 and in 1922 Prion: infection agent composed entirely of protein, causing a rare degenerative brain disease in humans called Creutzfeldt- Jacob Prions are not microorganisms; prion diseases are usually rapidly progressive and ALWAYS fatal. In animals , cause bovine spongiform encephalopathy, called”mad cow disease”.  Prokaryotes vs. Eukaryotes 1.Prokaryotes cells: Primitive cells NO internal membrane NO NUCLEUS e.g. Bacteria 2.Eukaryote cells: Complex cells WITH internal membranes. HAVE A NUCLEUS e.g. protozoa, algae, fungi, plants and animals. Viruses will not be placed into these two categories 5 https://www.youtube.com/w atch?v=URUJD5NEXC8 6  Prokaryotic (Bacteria) vs Eukaryotic (Animal, Plants, Fungi) Eukaryotic Cell structure 7 Structure of Prokaryotic vs. Eukaryotic Cell Prokaryotic Cell Eukaryotic Cell Cell Wall Cell wall Fimbriae, Pili Cilia Cytoplasm/Cytoplasmic membrane Plasma (cytoplasmic) Membrane Nucleoid region Nucleus Flagella Flagella Ribosomes Ribosomes Plasmids Chloroplasts Granules Granules Cell Envelope Mitochondria Golgi Complex Lysosomes Endoplasmic reticulum Vacuoles Vesicles 8 9  Prokaryotic Cell Flagella - long, thin extension that provides mobility (propeller) Fimbriae, Pili - hair-like projections with fine short appendages that allow bacteria to adhere Cytoplasmic Membrane - regulates amount of molecules entering or leaving the cell. surrounds the cytoplasm; transport of nutrients; energy metabolism - composed of lipids & proteins - antimicrobial agents, hand washing agents, and mouth-rinses kill or inhibit the growth of bacteria by acting on the cytoplasmic membrane Mesosomes: Present mostly in gram-positive bacteria - are inward foldings of the cytoplasmic membrane 10  Cytoplasm -contained within cytoplasmic membrane - aqueous solution which contains water, proteins, carbohydrates and inorganic salts. Cell wall: - gives cell its shape; rigid; protection from mechanical damage Outer membrane of gram- negative bacteria: Contains endotoxin; transport of nutrients. When endotoxin is released from bacteria present in the body, it can cause damage to nearby body cells). Capsule: Gelatinous covering produced by the cytoplasmic membrane Protection from drying, antiphagocytic; attachment to surfaces. The presence of capsules reduces the ability of WBC to surround, engulf, and destroy the bacterium through phagocytosis 11  Prokaryotic Cell, continued Granules - function as an energy reserve Ribosomes - contain RNA and proteins (protein synthesis) Nucleoid - contains the DNA - is embedded in the cytoplasm Endospores: Thick wall-walled structure; One of the most resistant forms of life against heat, drying, and chemicals. Defence mechanism/ protection against adverse conditions. Plasmids- extra-chromosomal DNA - give ability of bacteria to grow by being resistant to physical & chemical agents, and antibiotics 12 Eukaryotic Cell 13  Eukaryotic Cell Cell Wall-maintains rigidity of the cell Flagella-provides mobility; each flagella contains hollow filaments called microtubules Cilia-provides movement and permits faster mobility than flagella Plasma (Cytoplasmic) Membrane-permits movement of molecules across membrane by active and passive transport; endocytosis and exocytosis occurs at this site Endocytosis – taking in of matter Exocytosis – content released to exterior 14  Eukaryotic Cell, continued Endoplasmic Reticulum-fluid-filled channels that synthesize lipids (smooth)and proteins (rough). Smooth ER-lacks ribosomal attachment and appears smooth Rough ER contains ribosomes and appears rough Granules-contain polysaccharides (starch) and lipids Vacuoles- function to gather food. 15  Eukaryotic Cell, continued Vesicles - surrounds proteins; that occur in endocytosis and exocytosis Ribosomes - produce protein - larger in eukaryotic cells than prokaryotic cell Mitochondria - function as the powerhouse Chloroplasts - function in photosynthesis Golgi Complex - function to package protein; especially important for proteins destined for secretion Lysosomes - membranous sacs that contain digestive enzymes Nucleus - contains genetic DNA material 16 Characteristics Of Bacteria Cell Size: ~ Smallest of the unicellular organisms (single celled) ~ Approx. 1-1.5 micrometers wide and 2-6 micrometers long. ~ Bacteria have a very rapid metabolic rate due to large surface area to volume. A staining procedure developed by Dr. Christian Gram differentiates bacteria into: 1. Gram –positive (blue /purple) have cell walls composed of a thick layer 2. Gram –negative( pink / red) bacteria have cell walls with a thin layer 17 Cell Morphology (size and shape) Three basic shapes: 1. Spheres or cocci(singular coccus) - spherical shape. 2. Rods or bacilli (singular bacillus) - rod shaped. 3. Spirilla or spirochetes (singular spirillum) - spiral shape. 18 19 Bacterial Growth (multiplication) Is defined as an increase in cell numbers The cells divide by a process called binary fission(each cell divides into two daughter cells) Colonies of different bacteria vary in size, shape, color, and texture. Left, shows approximately 30 colonies on the plate. Right, shows a few hundred colonies. Each colony contains thousands of bacterial cells. Each colony was originally derived from one or a few cells. 20 The common morphologies of prokaryotic cells as revealed by phase-contrast photomicrographs of unstained :(A) Staphylococcus aureus (cocci), (B) Bacillus subtilis (rods), and (C) Treponema denticola (spirals) compared to (D) human red blood cells. B. subtilis has been mixed with the red blood cells in D for size comparison. Bar is 10 µm 21  Growth requirements of bacteria Five major chemical or physical conditions influence growth of bacteria: 1.Temperature 2. Acidity: *pH of 5.5 -8.5, optimal growth @ pH 7.0 3. Nutrients 4. Oxygen metabolism 5. Water 22 Temperature Three groups, based on temperature: Thermophiles: grow best at 56 degree Celsius, with a range from 45 – 70 degrees Celsius Mesophiles: grow best at body temperature (37 degree Celsius), with range from 22-45 degrees Celsius Psychrophiles: optimal growth at refrigerator temperature (7 degrees Celsius), with range from 1- 22 degrees Celsius 23 Acidity pH is a measure of acidity 24 Acidity Most bacteria that survive in the human body grow over a pH range from 5.5 to 8.5, with optimal growth at pH 7.0. Acidogenic: bacteria that produce acids during growth Aciduric: bacteria that survive and grow in an acidic environment( usually below pH 5.5) 25 Nutrients Bacteria must synthesize all of the macromolecules of protein, polysacharides, lipids, and nucleic acids( DNA and RNA) needed to grow. These macromolecules are synthesized from the building blocks of amino acids, monosaccharides, fatty acids, etc. Bacteria also must use a variety of smaller molecules, such as vitamins and inorganic substances. Many bacteria make extracellular proteases, which are enzymes released into the environment that break down proteins into amino acids that can enter the cell. 26 General bacterial metabolism. Nutrients are taken into the cell and processed through catabolic reactions that generate the building blocks and energy needed to synthesize macromolecules through anabolic reactions. Waste products generated exit the cell. 27  Oxygen metabolism Obligate Aerobes- require oxygen at 20% concentration Microaerophiles: tolerate low (4%) oxygen concentration Obligate anaerobes- cannot tolerate oxygen Facultative anaerobes- can grow with or without oxygen 28 Water All life forms require water to dissolve nutrients and to permit nutrient entrance or transport into cells. The water molecule is required in several enzymatic reactions to breakdown( e.g., hydrolyze) certain substances. 29 Culturing Bacteria “The ability to grow microbes is an essential step in being able to utilize their power, identify harmful culprits and advance our understanding and capabilities”(Karen Steward, PhD) Colony- forming units(CFUs): the original cells that begin multiplication to form a colony Metabolic activities Metabolism is the sum of chemical reactions that occur in the cell Catabolism: the chemical breakdown of molecules in which energy is released Anabolism: the synthesis of large molecules from simpler components Enzymes: biological catalysts required for catabolic & anabolic reactions Energy production: through fermentation(anaerobic process) & respiration Bacterial Genetics DNA replication and protein synthesis: the genetic information in the DNA is used to form messenger RNA (mRNA), process referred as transcription. The mRNA associates with ribosomes – process referred as translation. Gene transfer between cells-can occur through: 1.Conjugation: DNA from a donor(male) bacterium passes to a recipient cell( female) 2. Transformation: the bacterial cell takes up extracellular DNA released from other bacteria 3. Transduction: where viruses(bacteriophages)multiply within the bacterial cell; DNA is transferred when the virus is released and infects a new bacterial cell 32  Controlling Growth of Bacteria Preventing their multiplication can be achieved by:  change/eliminate nutritional requirement for growth,  using a chemical agent that interferes with cell division 1. Bactericidal agents: kill bacteria (chemical or physical means) 2. Bacteriostatic agents: prevent growth without killing them 3. Adding/removing oxygen 4. Change pH 5. Antibiotics: To treat bacterial diseases  can result in inhibiting growth or in killing the cells, depending on the bacterium and the antibiotic used. e.g. Penicillin's-> interfere with metabolic activity of bacteria 33  Killing Bacteria Killing of bacteria is accomplished by physical or chemical means. It is an important aspect of disease prevention and infection control. 1.High temperatures 2.Strong chemicals on inanimate objects- not used in or on the body Bactericidal, Virucidal, or Fungicidal: agents or conditions that kill microorganisms rather than just prevent their growth (suffix –cide/-cidal means to kill) 34 Common Bacterial Diseases Tuberculosis Syphilis Anthrax Leprosy Pneumonia Dental Caries/Periodontal Disease Strep Throat E-Coli Colitis Meningitis 35 Periodontal Disease Gingivitis/ Periodontitis 36 VIRUSES 37  Characteristics of Viruses Size: ~ extremely small; about one-tenth the size of bacteria ~ composed of a nucleic acid core (DNA or RNA), surrounded by a protein coat, called a capsid. Some viruses also have an outer structure of lipids, proteins, and polysaccharides, called the envelope. * Viruses depend on a host cell for growth and replication “obligate intracellular parasites” 38 A representative virus. The shape of the nucleocapsid (capsid plus nucleic acid core) varies. Some viruses do not have an envelope, and the host cell attachment sites are located on the capsid. 39 Life Cycle of a Virus 40 Viral Replication Viruses replicate in host cells in several steps or stages: 1. Attachment or adsorption: virus binds to host cell surface (in order to replicate & infect a host) 2. Penetration: virus enters host cell 3. Uncoating: Capsid is degraded to release nucleic acid 4. Replication or syntheses of virus: virus uses host mechanisms to replicate, synthesize new viral nucleic acid & capsid 5. Assembly: capsid surrounds nucleic acid 6. Release from Host Cell: after invading host cell it must be able to release from host cell and replicate elsewhere 41  Classification of Viruses Viruses may be grouped into families but are not classified and are defined by: 1. Their type of nucleic acid: DNA or RNA 2. The symmetry of the virus: helical, polyhedral, spherical, complex 3. Whether or not there is an envelope surrounding itself (enveloped or non-enveloped) 42 Viruses cannot generate energy or synthesize nucleic acid and proteins by themselves, so they must rely on a host’s metabolic machinery. 43 Transmission of Viruses Human viruses may be transmitted by: 1. Droplets (e.g. sneezing) 2. Direct Transfer (e.g. Touching) 3. Contaminated food or water 4. Insects **** Most common route of transmission is through droplets. Many viruses will invade the respiratory tract by entering the nasal cavity.*** 44  Viral Infections Viral infections have different characteristics from those caused by bacteria. For example: 1. There is often an incubation period  virus is multiplying within a host but there are no evident symptoms  At this time, host can transmit virus to new and unsuspecting hosts 2. Viruses cannot be treated the same as bacterial infections  They do not respond to antibiotics 45  Viruses and the Mysterious Common Cold Bacteriophages https://www.youtube.com/watch?v=PHp6iYDi9ko https://www.youtube.com/watch?v=YI3tsmFsrOg 46 Controlling Viral Replication Inside the body- antimicrobial chemicals- inhibit the metabolic machinery of the microorganism damage the host cell Viral diseases are difficult to treat: must try and prevent them from occurring through immunization or infection control procedures. Viruses can be killed outside the body by heat or chemicals 47  Common Viral Diseases HIV/AIDS Hepatitis A, B, C Herpes Simplex I & II S.A.R.S., COVID-19 Measles Varicella-Zoster (Chickenpox) Papillomavirus (Warts) Shingles Influenza/Common Cold West Nile 48 Viruses in Dentistry Specific Oral diseases: e.g. Herpes infections Diseases in body that may result in lesions occurring in the mouth: e.g. measles Blood-borne diseases: e.g. Hepatitis B or acquired immunodeficiency syndrome Other diseases that can be transmitted without proper infection control: e.g. influenza 49  Characteristics of Protozoa In the developed part of the world, protozoa are not as common as bacteria and viruses. In developing countries they are more prevalent. Size: They are the largest microorganism encountered in microbiology Characteristics: Composed of a single cell, free living and thrive in water Contain no chlorophyll in their cytoplasm so cannot produce carbohydrates by photosynthesis Important as decomposers and recycle organic material and important in our food chain Protozoa can be found in the stomach and break down cellulose and produce nutrients for their host 50 Transmission of Protozoa Protozoa that are parasites and produce infections can be transmitted by: 1. Direct Contact 2. Insects 51 Common Protozoa Diseases Malaria 52  Fungi  Fungi include: 1. Mushrooms 2. Molds 3. Yeasts  Certain members of molds and yeasts are capable of causing diseases in human beings. 53 Characteristics of Fungi Are eukaryotic cells Contain a nucleus and nuclear membrane but lack chlorophyll Most are Aerobic (requires O2 for growth) exception to some yeasts that can grow anaerobically and ferment to alcohol (Brewers yeast) Exist in one of two forms: 1. A yeast form: unicellular form 2. A mold: elongated cells and produce spores that can be airborne and transmitted 54 55  Common Diseases of Fungi Oral Candidiasis Athlete’s Foot ‘tinea pedis’ Diseases caused by fungi can be treated with topical antifungals such as “Nystatin” 56  In Dentistry…. Fungal infection: oral candidiasis 1. Thrush 2. Denture stomatitis Candida Albicans (yeast/fungus) Results from: depressed body defenses, trauma to tissues, debilitating systemic diseases, long-term antibacterial therapy Yeast cells outside the body: killed by heat and certain chemicals 57  Characteristics of Algae Consist of unicellular or multi-cellular organisms. Contain chlorophyll. Have one or more flagella. Are found in abundance in both freshwater or marine habitants. Has a typical membrane-bound nuclei and cytoplasmic organelles. Most do not produce human disease. 58  References Chris H Miller. Infection Control & Management of Hazardous Materials for the Dental Team. 7th Edition, 2023 Elsevier/ Mosby, ISBN-13:978-0-323-08257-0 Darby, Michelle, Walsh, Margaret. Dental Hygiene Theory & Practice. 5th edition. ISBN #: 978-1-4557-4548-7 CDHO Standards of Practice. Retrieved from http://www.cdho.org/for-the- public/dental-hygienists/standards-of-practice Toronto College of Dental Hygiene Pre Clinic Manual 2023 Royal College of Dental Surgeons of Ontario. Guidelines: Infection Prevention and Control in the Dental Office, November 2023. 59