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BASIC MICROBIOLOGY
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
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
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
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
Types of Microorganisms
• 5 major types are:
• Bacteria
• Fungi
• Protozoa (protists)
• Parasites (rickettsiae)
• Viruses
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