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
• bacteria
• fungi
• protozoa
• microscopic algae
Ways that microbes affect us
• 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
• 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
• acetone
• organic acids
• enzymes
• alcohols
• drugs
Foods produced by microbes
• vinegar• sauerkraut• pickles• alcoholic beverages• green olives• soy sauce
• buttermilk• cottage cheese• cheese• yogurt• bread• sourdough bread
Products of genetically modified microorganisms
• 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 golden-colored 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, membrane-bound 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, star-shaped, 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
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