Unformatted text preview: Lesson 2: Lesson 2: Classification and Structures of Microorganisms To safeguard against microorganism exposure in a dental office, a basic understanding of how pathogens pass from an infected person to a susceptible person is important. What are they? What do they look like? And what does it mean to me? Microorganisms can be classified into 2 different cell categories: Prokaryotes and Eukaryotes Prokaryotes Prokaryotes A name that reflects the absence of a nucleus in a cell
Examples include: Bacteria, rickettsiae, chlamydinae and cyanobacteria Eukaryotes Eukaryotes Have larger cells with nuclei and complex internal structures. Examples include protozoa, fungi, plants and animals (including humans). Eukaryotic Cell
Eukaryotic Cell This drawing of a eukaryotic cell illustrates its nucleus and organelles. Prokaryotic Vs. Eukaryotic Cells
Prokaryotic Vs. Eukaryotic Cells
Property Prokayotic Eukaryotic Size Small Larger Nucleus No Yes DNA
Organelles One - small,
Few or none Several large, linear
Many Cell wall Yes Yes – plants
No – animals
Organization Unicellular Topics of Discussion
Topics of Discussion What makes a cell? Who are these Microbes? What Makes a Cell?
What Makes a Cell? Smallest entity capable of independent life.
Separated from the environment by a cell envelope. Always has a cell membrane. Sometimes a cell wall.
Contain internal structures. Requirements for Life
Requirements for Life Highly complex and organized.
Possesses and uses genetic program.
Produces more of themselves.
Acquires and utilizes energy.
Eliminates waste products.
Carries out chemical reactions.
Engages in mechanical activities.
Responds to stimuli.
Regulates themselves. Who are these Who are these Microbes?
6. Prions and Viroids
7. Bacteria Microbe Complexity
Prions Viruses Bacteria
Viroids Most Complex Algae Insects
Protozoa Plants Fungi Animals 1. Algae 1. Algae May be unicellular, colonial or filamentous. e images are from the Molecular Evolution and Organelle Genomics program at the University of Montreal. Copyright 19941997 by Charles J. O’Kelly and Tim Littlejohn. Distribution for noncommercial purposes permitted so long as this copyright notice is included and acknowledgement is made. The photo on the left shows the unicellular life stage of Halosphera minor. The one on the right shows the colonial stage of the same organism. Algae:
Algae: Aquatic or terrestrial. (In an aquatic environment, algae are a very important carbon dioxide fixer, oxygen supplier and food source). Mostly plantlike characteristics.
Great variety of types, but all contain chlorophyll.
Some animallike characteristics like phagocitosis of other organisms. Algae continued: Algae continued: Diatoms and Dinoflagellates This photo is a diatom. They are a type of marine algae that are a very important marine food source Examples of diseases caused from algae:
Examples of diseases caused from algae: Red tide redpigmented dinoflagellates reproduce in excess and fill the water with a rusty/red color. Red tides produce a toxin that is poisonous to humans and animals. The toxin concentrates in mussels, clam and scallops. When ingested by humans it causes tingling numbness in lips, mouth, tongue and fingertips followed by lack of coordination and slurred speech and difficulty swallowing. No none antidote to the toxin
Red tide is dangerous to swimmers who ingest it directly. 2. Protozoa
2. Protozoa Single celled eukaryotes, but may form colonies. Some are sporulating (enclosed in several protein coats that resist drying, heat and most chemicals) . Often called an ameoba
Live in fluids in the bloodstream, mouth and intestinal tract This image is from the Molecular Evolution and Organelle Genomics program at the University of Montreal. Copyright 19941997 by Charles J. O’Kelly and Tim Littlejohn. Distribution for noncommercial purposes permitted so long as this copyright notice is included and acknowledgement is made. Protozoa continued:
Protozoa continued: Ingest organic matter for nutrients.
Vary greatly in size from 0.003mm to 5mm.
Many are human parasites. Examples of human diseases caused by Examples of human diseases caused by protozoa are: Malaria / sleeping sickness – first 2 weeks fever and soreness at the point of entry. Spread by mosquitoes and sleeping sickness is spread by the tsetse fly. Both require drug therapy to kill the parasites in the blood. Dysentery / amebic dysentery – symptoms are sever diarrhea and in extreme cases, abscesses in the liver. Prevalent in countries where the drinking water is contaminated. Drug treatment is necessary to kill the parasite. Periodontal disease – is caused by protozoa and bacteria. Both microbes are found in the inflamed tissue around the tooth. Treatment includes thorough debridement, good oral hygiene and sometimes antibiotic therapy. 3. Rickettsiae:
3. Rickettsiae: are parasites. cannot live outside of host
often lice, fleas, ticks and mites are hosts to rickettsiae.
multiply by invading the cells of another life form. the host transmits the disease. Examples of diseases caused by rickettsiae:
Examples of diseases caused by rickettsiae: Rocky mountain fever – is rare. Symptoms occur about a week to 10 days after transmission from the host and are much like that of the flue. Small pink spots appear on the ankles and wrists. Eventually the body is covered with the spots. Treatment is antibiotic therapy.
Typhus – is rare. Microorganism is spread by host . Symptoms include severe headache, back and limb pain, constipation and high fever. Rash similar to measles, confusion and weak heart beat. Treated with antibiotics.
Head lice / pediculosis – is the state of being infected with head lice. Tiny, bloodsucking, wingless parasites the are transmitted from individual to individual through direct contact. Found on the hair shaft. Treatment is special medicinal shampoos and combing to loosen the nits. Bedding, towels, brushes, combs and cloths must be washed with very hot soap and water. 4. Fungi (yeasts and molds)
4. Fungi (yeasts and molds) Very diverse group of eukaryotes. Not all are microbes.
Yeasts are unicellular and spherical.
Molds are filamentous with branching. The preceding Pyromyces sp. image is from the Department of Microbiology and Evolutionary Biology at the University of Nijmegen, the Netherlands. http://wwwmicrbiol.sci.kun.nl/micrbiol/micrgala.html Fungi (continued):
Fungi (continued): Nonphotosynthetic.
Require the uptake of organic matter for nutrients.
Saprophytic (live off organisms that are alreadydead) or parasitic (uses the complex molecules of another organism as nutrients).
Propagate by spores.
Common fungi include: yeasts, central to bread and spirits industries. Examples of human diseases caused by fungi are:
Examples of human diseases caused by fungi are: Candidiasis /Thrush – is an infection by the fungus Canidida albicans. Symptoms include thick white/creamey raised patches on the mucosa (vaginal or oral) Tinea Tinea (includes any group of common fungal infections) acquired from another infected person, animal or inanimate object. (such as a shower stall or sharing work gloves). Tinea pedis/Athletes foot causes cracking and itching between the toes and on the foot. Tinea unguium – characterized by white patches on the toe and fingernail. Nail thickens, overgrow, becomes brittle or becomes totally destroyed. Treatment – antifungal medications, lotions, ointments or oral antibiotics. 5. Viruses:
5. Viruses: are a single strand of nucleic acid (DNA or RNA) and are surrounded by a protein coat. Some viruses have additional structures like a lipopolysacchride envelope that helps them to penetrate the host cell (as seen in this slide) or tail fibers that help them attach to the host cell and inject their DNA. Viruses Viruses Are they really alive? Viruses do not grow; they produce no waste products; they display none of the chemical reactions we associate with living things and they are unable to reproduce independently of a host cell. Viruses reproduce actively within their host cells. Some minutes or hours later, hundreds of new viruses exit from each cell, often leaving disintegrated host cells. Outside a host cell, a virus is an inert particle, When it encounters a host cell it becomes a highly efficient replicating machine
This slide illustrates the basic steps in a viruses life cycle.
Beginning at the top right and going clockwise:
1. The virus will attach to the host cell.
2. Inject its DNA (or enter the host cell and release its DNA).
3. The DNA will circularize or if the virus contained RNA the viral protein reverse transcriptase will make a complementary double stranded DNA copy.
4. If the virus is one that has a lysogenic life cycle, the viral DNA will be incorporated into the host chromosome until environmental signals cause it to be excised.
5. The viral DNA is replicated and its genes are transcribed and translated to make the viral structural proteins.
6 & 7. The new viral particles are assembles into new offspring.
8. The new viruses are released by the lysing of the host cell or by budding. Example of Diseases caused by viruses:
Example of Diseases caused by viruses: Measles, Mumps and Rubella – childhood illnesses caused by viruses.
Measles – cause a rash, and a fever is spread by airborne droplets of nasal secretions.
Mumps – symptom include swelling of the parotid (salivary glands) on one side or both. Spreads by airborne droplets.
Rubella/German measles – appears as a rash on the face and may spread to the trunk and limbs. Only serious in pregnant womencauses birth defects. Example of Diseases caused by Example of Diseases caused by viruses: Chicken Pox – caused by the varicellazoster virus. Characterized by a rash and slight fever. Virus remains dormant in the nerve tissue and later in life cause an outbreak of Herpes Zoster/Shingles. Spread through airborne droplets. Poliomyelitis / Polio – attacks the central nervous system and in many cases lead to extensive paralysis. Spread by airborne droplets. Few cases since 1950's. Example of Diseases caused by Viruses (continued):
Example of Diseases caused by Viruses (continued): Herpes simplex: Type I / cold sore associated with the mouth, lips and face. Spreads by direct contact with fluidfilled lesions. Extremely contagious. Symptoms appear during fever, sun, stress or some type of immune suppression. Type II – is normally associated with lesions in the genital area but can be seen in the oral cavity. Viral hepatitis A and E – symptoms rage from generally flulike symptoms to acute liver injury. Transmitted by persontoperson contact or ingestion of contaminated water or food Hepatitis B transmitted through contaminatd needles and syringes. Symptoms include loss of appetite, digestive upset, upper abdominal pain and tenderness, fever, weakness muscle pain and jaundice. HIV – Human immunodeficiency virus – is the cause of AIDS transmitted via sexual intercourse, blood transfusions and sticks with infected needles. Viruses (continued): Viruses (continued): Adenovirus Rhinovirus (both are human cold viruses). Copyright notice: This notice must accompany any copy of the images. The images must not be used for commercial purposes without the consent of the copyright owners. The images are not in the public domain. The images can be freely used for educational purposes. Copyright 1994 Veterinary Sciences Division. 6. Prions and Viroids 6. Prions and Viroids (are not viruses but are viruslike particles that cause disease) Prions are proteins that are believed to cause diseases like mad cow disease.
Viroids are small single stranded molecules of RNA’s without a protein coat. Cause diseases in plants.
Neither fit the criteria for living organisms, but they are microbes and are therefore studied by microbiologists. 7. Bacteria:
7. Bacteria: are ubiquitous. (They are everywhere). They are in every breath we take, on everything we touch and in and on every part of our bodies. Bacteria range from beneficial to harmful. Bacteria Bacteria Reproduce: 1. Asexually by fission (a mature bacterium increases in size and its enzymes replicates its DNA to yield 2 chromosomes. New cell walls and membranes grow inward from the margin of the cell and the 2 chromosome separate and 2 bacterial cells result). 2. or sexually by conjugation. Vary greatly in shapes, sizes, metabolisms, and growth conditions. Some main characteristics used in identification are: 1. Colony appearance 2. Cell size and shape 3. Physiology 4. Metabolism Characteristics of bacterial colonies:
Characteristics of bacterial colonies: Colony Appearance Colony Appearance This figure shows an agar plate with three different types of bacteria growing on it. It is obvious there are three different types of bacteria because of the size, shapes and colors of the colonies. Bacteria can also be studied and characterized Bacteria can also be studied and characterized by using a microscope.
Bacterial shapes include: Bacterial Stains
Bacterial Stains Bacteria are not always easy to see under a microscope. In order to see them better, stains are used. A negative stain is one that will stain the bacteria and make them stand out from the background.
A Gram stain stains bacteria based on their cell wall characteristics. The purple stain will bind to certain bacteria which are designated Gram positive and the others are Gram negative. Gram negative cells appear colorless or transparent. The Gram negative cells are generally stained with a pink negative stain so that they can be seen. Disease caused by bacteria Disease caused by bacteria include: Tuberculosis – symptoms include fatigue, lowgrade fever, night sweats loss of weight and eventually a persistent cough. Treatment includes antibiotic therapy.
Diptheria – appears as a severe throat infection and fever
Pertussis/whooping cough – primarily affects children. Tetanus / lock jaw – symptom include a stiffness of the jaw. (All three of these disease can be prevented with combined vaccinations Diseases caused by bacteria include:
Diseases caused by bacteria include:
Strept throat – most common bacterial disease infecting humans. Symptoms are sore throat, fever and general malaise. Treatment antibiotic therapy Staphylococcal infections – staph infections include gangrene, toxic shock syndrome, venereal diseases and some form of pneumonia. Treatment – antibiotic therapy Bacillus anthracis – causes anthrax in grazing animals. Humans can contract the disease by eating infected meat and cuts in the skin. Chlamydinae – causes various genital, eye and lymph node infections. (most common STD) Treatment is with antibiotics. The End
Reading Assignment: Chapter 3 Cell Structure and Taxonomy
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