Introduction to Microbiology
The Microbial World and You
What Are Microorganisms?
• Minute living things
• Too small to be seen with the unaided eye
• Members of several different groups
Different groups of microorganisms
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bacteria
fungi
protozoa
microscopic algae
Ways that microbes affect us
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cycling chemicals through our environment
serve as the basis of food chains
aid normal functioning of animal systems
commercial applications
cause disease
Chemical elements are cycled by
microbes
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by photosynthesis: C, H, O
by chemosynthesis: C, H, N, S, P
by aerobic respiration: C, H, O
by anaerobic respiration: C, H, N, S, P
by fermentation: C, H, O
Basis of food chains
• phytoplankton (producers)
• zooplankton (first level of consumers)
Aiding functioning of animal
systems
• aiding in the digestion of ruminants and
termites
• synthesizing B vitamins and vitamin K
Commercial applications of
microbes
• normal synthesis of chemical products
• food production
• synthesis of abnormal products
Chemical products normally
synthesized by microbes
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acetone
organic acids
enzymes
alcohols
drugs
Foods produced by microbes
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vinegar
sauerkraut
pickles
alcoholic beverages
green olives
soy sauce
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buttermilk
cottage cheese
cheese
yogurt
bread
sourdough bread
Products of genetically modified
microorganisms
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human insulin and human growth hormone
digestive aids
cellulose
drain cleaner
Some microbes cause disease
• pathogens (disease-producing microbes)
• opportunists (microbes that do not
normally cause disease, but my do so
under certain conditions)
Naming Microorganisms
• genus name is first and is always
capitalized
• species name (specific epithet) follows the
genus name and is never capitalized
• genus and species names are italicized
• example: Staphylococcus aureus
• the cursive indicator of italics is underlining
Family Micrococcaceae
• Micro- means very tiny
• Family members are found on human skin
• Genus Staphylococcus can ferment
sugars, and, therefore, can grow with or
without oxygen
• Genus Micrococcus cannot ferment
sugars, and, therefore, cannot grow
without oxygen
Genus Staphylococcus
• Staphylo- means clusters of cells
• coccus- means spherical cells
• Staphylococcus means clusters of very
tiny, spherical cells
• aureus means golden-colored colonies
• Staphylococcus aureus means goldencolored colonies of clusters of very tiny,
spherical cells
Genus Staphylococcus, continued
• Staphylococcus aureus: golden-colored
colonies
• S. epidermidis: normal microbe of the skin
• S. saprophyticus: a microbe that causes
decay of organic matter
• After using the full genus name once in a
paragraph, it is then permissible to
abbreviate that genus name.
Genus Micrococcus
• Micrococcus luteus: bright mustard-yellow
colonies of clusters of very tiny, spherical
cells
• M. roseus: rose-colored colonies
Classifications of Microorganisms
• Prokaryotes: cells lack nuclei, membranebound organelles, sterols and
carbohydrates in membranes
• Eukaryotes: cells possess nuclei,
membrane-bound organelles, sterols and
carbohydrates in the membranes
Prokaryotes
• Bacteria: most of the procaryotes, cell
walls contain peptidoglycan and D amino
acids, a few bacteria are pathogenic.
• Archea: may lack cell walls or have
unusual cell walls composed of
polysaccharides, proteins, and
pseudomurein, but never peptidoglycan.
Archea are often found in extreme
environments.
Bacteria
• Cell morphology: cocci, bacilli, spirilli, starshaped, squares
• Cell arrangement: individual, pairs, chains,
tetrads, sarcina (8), (grape-like) clusters
• Cell walls contain different amounts of
peptidoglycan and other substances which result
in characteristic staining properties such as
Gram-positive, Gram-negative, and Acid-fast
cells.
• Many bacteria are motile by means of flagella
• Nutritional requirements are extremely diverse
Eukaryotes
• Algae: photosynthetic unicellular or simple
multicellular, mostly aquatic, organisms with cell
walls of cellulose
• Fungi: saprophytic or opportunistic unicellular
(yeasts) or simple multicellular organisms with
cell walls of chitin
• Protozoa: unicellular, mostly motile organisms
without cell walls, that absorb or ingest nutrients
• Helminths: parasitic worms: flatworms and
roundworms
VIRUSES
• Living? or Nonliving?
• Contain a core of one nucleic acid only
(either DNA or RNA)
• Nucleic acid core is surrounded by a
protein coat called a capsid
• Viruses are host-specific: animal, plant,
bacterial
• Some animal viruses possess envelopes