Lab 2: Bacteria

Bacteria (bacterium)

microscopic prokaryotic unicellular organisms widely distributed in nature

cocci (coccus)

spherical bacteria cell shape

bacilli (bacillus)

rod-like bacteria cell shape

spirilla (spirillum)

corkscrew bacteria cell shape

culture

laboratory growth of bacteria

culturing

growing of bacteria

pure culture

contains one kind of bacteria

mixed culture

contains two or more kinds of bacteria

medium (media)

substrate bacteria grows on

liquid/broth media

aqueous solutions of nutrients the bacteria use

solid/jelly-like media

nutrient solutions solidified with agar

agar

white powder from algae that has no nutritional value, but acts as a support medium when mixed with the nutrient solution

autoclaving

the process of boiling the medium under steam pressure to sterilize it and dissolve the agar

colony

bacterium progeny when it falls/its placed on the surface of a solid nutrient medium

staining

using dye to color bacteria

simple staining

bacteria is stained with one dye

differential staining

combining different stains

Gram stain

classifies eubacteria in to Gram-positive or Gram-negative

crystal violet stain

used for gram-positive bacteria became their cell walls (single-membrane; thick peptidoglycan) bind to it

safranin/fuchsine stain

used for gram-negative bacteria because their cell walls (double-membrane; thin peptidoglycan) prefer it over the crystal violet stain

the Gram stain process involves

primary stain (crystal violet), mordant (Gram’s iodine), decolonizer (ethanol) and counterstain (fuchsin)

inoculation

addition of microorganisms from a culture into fresh, sterile medium while avoiding contamination from microorganisms in the air

antibiotic

selctively-toxic compound produced by microorganisms

contamination

introduction of undesirable microorganisms into a sterile environment or pure culture

during aseptic work, everything needs to be clean. this is done using a ___

bunsen burner to sterilize with heat/fire