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Chapter 20. Viruses and Bacteria. Measurement Microorganisms: very small Use metric system Meter (m): standard unit Micrometer (mm) = 0.000001 meter or 1 X 10-6 meter Nanometer (nm) = 0.000000001 meter or 1 X 10-9 meter. Viewing Bacteria. Preparation of Smears for Staining

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chapter 20
Chapter 20
  • Viruses



MeasurementMicroorganisms: very small Use metric system Meter (m): standard unit Micrometer (mm) = 0.000001 meter or 1 X 10-6 meter Nanometer (nm) = 0.000000001 meter or 1 X 10-9 meter

viewing bacteria
Viewing Bacteria
  • Preparation of Smears for Staining
  • Bacteria are colorless when viewed under light microscope
  • Fix or attach bacteria to slide.
  • Stain: salts composed of a positive and negative ion. One of which is colored chromophore.
    • Basic dyes: the color is a positive ion.
    • Acidic dyes: the color is a negative ion.
gram stain
Gram Stain
  • Gram stain
    • crystal violet: primary stain
    • iodine: mordant
    • alcohol or acetone-alcohol: decolorizer
    • safranin: counterstain
  • Gram positive: purple
  • Gram negative: lose purple. Stain pink-red.
  • Why are prokaryotic cells classified in a different Kingdom from the eukaryotic cells?
no nucleus
No Nucleus
  • DNA is not in a membrane; is a circular chromosome.
no organelles
NO Organelles
  • Lack other membrane-enclosed organelles.
no chromosomes
No chromosomes
  • DNA is not associated with histone proteins.
  • Prokaryotes Divide by binary fission
  • Shapes of Procaryotes
  • Cocci: round
    • diplococci
    • streptococci
    • tetrads-groups of 4
  • Rods: coccobacilli
  • Spiral: vibrios, spirilla, spirochetes
  • Star-shaped, square flat cells, triangular
A. The Bacteria that we generally refer to as "GERMS" are classified in the KINGDOM EUBACTERIA, or EUBACTERIA, or simpler yet BACTERIA.
  •     B. The Other Type of bacteria are called ARCHAEBACTERIA, and belong to the KINGDOM ARCHAEBACTERIA.  These are the more ancient bacteria.
kingdom archaebacteria
  • The PREFIX "ARCHEA" means ANCIENT.  They are considered ancient because they probably resemble the FIRST FORMS of LIFE on Earth.




kingdom eubacteria
  • PREFIX "EU" means TRUE
  • classified by:
  • Shape:
  • Cocci - round bacterial cells.
  • Bacilli - rod-shaped bacterial cells.
  • Spirilli - spiral-shaped bacterial cells.
  • staphylo - a prefix used with the shape name to indicate clusters. strepto - a prefix used with the shape name to indicate filaments
herpes virus
Herpes Virus
  • Herpes viruses are extremely common and around 100 have been identified in a variety of animal species.  
  • All of the herpes viruses are members of one family, the Herpesviridae, and have certain characteristics in common, such as their ability to establish latency during primary
why does it come back
Why does it come back?
  • Following initial infection the virus remains dormant, to be reactivated by certain triggers such as an individual’s immune status, stress or sunlight.
herpes viruses
Herpes Viruses
  • To date, eight human herpes viruses have been identified.
  • These include:
herpes groups
Herpes groups
  • Epstein-Barr virus, which causes infectious mononucleosis (also known as ‘mono’ and ‘glandular fever’);
  • Varicella zoster, which causes chickenpox and shingles
  • Herpes simplex virus type 1, the cause of cold sores;
  • infectious mononucleosis.
  • Herpes simplex virus type 2, the most common cause of genital herpes.
cold sores
“Cold Sores”
  • Herpes simplex virus type 1, the cause of cold sores;
  • Typical blisters associated with cold sores due to HSV
chicken pox
Chicken Pox
  • Varicella zoster, which causes chickenpox and shingles;
  • Typical rash of chickenpox in an adolescent.
  • Anthrax is a bacterial infection caused by spores from the bacterium that is shaped like a rod: bacillus anthracis
are viruses alive
Are viruses alive?
  • What do you think?
  • They contain a protein coat and some genetic material either DNA or RNA
  • They use living cells to reproduce themselves.