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