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