BASIC MICROBIOLOGY

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BASIC MICROBIOLOGY
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Definition

• Microbiology is the science that studies living
  organisms that cannot be seen with the naked eye
  (microorganisms or microbes)
• microorganisms are commonly known as germs

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Nature of Microorganisms

• Pathogens microorganisms that cause disease
• most microorganisms are harmless
• some microorganisms found in the body are
  beneficial to us
• when a microorganism enters a part of the body
  other than where it is intended to be, it can be
  harmful
• eg. E. coli from the colon (breaks down
  waste/makes vitamin K) can enter the urinary
  tract and cause an infection

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Factors that Influence Microbial Growth

• 5 factors affect the growth of microorganisms
• temperature
• pH (only a few live in acidic environments)
• moisture
• food
• oxygen
• these factors must be favorable if microorganisms
  are to live
• different microorganisms require different
  conditions for survival
• eg. aerobic microorganisms grow best with high
  levels of oxygen, while anaerobic microorganisms
  grow best in the absence of oxygen

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Methods that Destroy Microorganisms

• 3 common methods destroy microorganisms
• Antiseptics (eg. alcohol and betadine)
• used on the skin
• slow or prevent the growth of pathogens
• Disinfection (eg. bleach solution zephirin)
• not used on skin because irritation may result
• Sterilization
• autoclaves use steam under pressure to kill ALL
  microorganisms (first two methods are not
  effective against spores)
• other methods include the use of chemicals,
  radiation, and gas

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Types of Microorganisms

• 5 major types are
• Bacteria
• Fungi
• Protozoa (protists)
• Parasites (rickettsiae)
• Viruses

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Bacteria

• most familiar of the microbes that infect humans
• classified by their shape and arrangement

Type Shape Arrangement
Diplococci Round in pairs
Staphylococci Round in groups or clusters
Streptococci Round in chains
Bacilli Rod-shaped in pairs, single, or in chains
Spirilla Cork-screw or spiral single