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Microorganisms
What are they?
What do they do?
What do they look like?
Microbiology• Study of microorganisms
– Organisms not visible with naked eye
– Require magnifying glass or microscope
– Includes wide variety of different organisms
Microorganisms are:
• Bacteria• Viruses• Fungi• Protozoa• Animals
Microorganisms are Ubiquitous
• Found virtually everywhere• Most are harmless• Some are beneficial
– Used in research– Used to make foods (yeast, mold)– Used to make antibiotics
Light Microscope
• Allows one to view most types of microorganisms (not most viruses)
• Magnifies 40x – 1000x• Works by passing light through a series of
glass lenses that bend or refract light rays• Microorganisms viewed may be living or
fixed and stained to enhance visibility
Microscopy: The Instruments
• A simple microscope has only one lens
• This is A. Van Leeuwenhoek’s microscope from the 1600’s
Figure 1.2b
Parts of a typical light microscope
Electron Microscopes
• Use beam of electrons, instead of light to magnify
• Magnify up to 100,000X or more• Allow us to look inside cells and even see
molecules
Units of Length
• Light microscope can view objects measured in millimeters and micrometers
• Electron microscope can view objects measured in micrometers and nanometers
Bacteria
• Prokaryotic cells– The genetic material in
their cells is not contained in a nucleus
• Appear as different shapes– Bacilli (rod-shaped)– Cocci (round)– Spirilla (spiral)
• Most ubiquitous microorganism
Stained Bacteria
• Average size: 0.2 -1.0 µm 2 - 8 µm• Basic shapes:
Bacterial Morphology
coccibacilli
spirals
Usefulness of Bacteria
• Decomposers: (“nature’s recyclers”) break down dead matter
• Clean up the Earth’s land & water• Help with digestion• Make vitamins your body needs• Used to make medicines (insulin)• Food production: cheese, yogurt, sour
cream, sauerkraut, pickles, etc.
Viruses
• Tiny, nonliving particle that enters and then reproduces inside a living cell
• Most are harmful
Characteristics of Viruses
• Does not have all the characteristics essential for life
• Viruses can only multiply when they are inside a living cell
• Acts like a parasite– Parasite: an organism that lives on or in a
host and causes it harm– Host: an organisms that provides a source of
energy for a virus
Usefulness of Viruses
• Gene Therapy– Take advantage of a virus’s ability to enter a
host cell– Gene therapy allows scientists to deliver
needed genetic material to cells
Viruses, Bacteria, & Your Health
Pathogenic Microorganisms
• Are harmful to humans• Able to cause pathology (damage) in host
- Invade host and damage tissue• Cause infectious disease
– Disease that is transmitted from one source to another
– Bacteria and viruses responsible for most infectious diseases
Infectious Diseases
• Can spread through contact with:– An infected person (touching, hugging, or
kissing)– A contaminated object (sharing drinks or
eating utensils)– An infected animal (an animal bite)– An environmental source (eating
uncooked eggs or meat)
Common Infectious Diseases
• Bacterial–Lyme Disease–Tuberculosis–Tetanus–Strep Throat
• Viral–The cold–The flu–Cold sores–Chicken pox–AIDS
Streptococcal Skin Infection
Anthrax Lesion
Rash From Lyme Disease
• Common Cold & The Flu Virus– Many different strains
• Round virus –Chicken pox:
causes an itchy rash on human skin
• Bullet-shaped–Rabies virus
infects nerve cells in certain animals
Viral Infection – Cold Sores
Treating Infectious Diseases
• Bacterial Diseases– Antibiotics– Antibiotic resistance
• Results when some bacteria are able to survive in the presence of an antibiotic
• Viral Diseases– No medications that can cure viral
infections
Vaccines
• Important tools that help prevent the spread of infectious diseases
• Vaccine: a substance introduced into the body to stimulate the production of chemicals that destroy specific viruses or bacteria– Made from dead or weak or altered viruses
and bacteria
Fungi
• Eukaryotic cells• Can be multicellular
molds or unicellular yeasts
Protozoa
• Unicellular eukaryotic organisms
• Show various forms of motility– Flagella– Cilia– Pseudopodia
Animals
• Multicelluar– Worms– Small arthropods
• Serve as vectors for disease transmission
• Ectoparasites– Feed on blood by
biting
Microscopy
• Microorganisms not visible with naked eye– Only visible with some method of
magnification– Most microorganisms require a microscope to
view them• Light microscope – provides 40X to 1000X• Electron microscope – provides 5000X to
500,000X
Measuring Microorganisms
• Microorganisms, because of their small size, require small units of measurement– Micrometer (um) – is 1x10-6 meter or 0.001
mm• Sufficient to measure bacteria, fungi, protozoa
– Nanometer (nm) – is 1X10-9 meter or 0.001um• Sufficient to measure viruses and sub cellular
particles
Units of Length
• Light microscope can view objects measured in millimeters and micrometers
• Electron microscope can view objects measured in micrometers and nanometers
TEM and SEM