microbiology general definitions

• what is meant by prokaryotae


  this is the kingdom that bacteria are found in
• what is the general shape of coccus bacteria


  spherical
• what is the general shape of spirillum bacteria


  corkscrew shaped(spiral shaped)
• what is the general shape of bacillus bacteria


  rod shaped
• what colour will gram positive bacteria stain in the gram stain test and why


  it will be purple due to the crystal violet dye
• what colour will gram negative bacteria stain in the gram stain test and why


  it will be red/pink due to the safranin
• what type of wall does the positive gram bacteria consist of


  peptidoglycan
• what types of wall does teh negative gram bacteria consist of


  lipopolysaccharide and peptidoglycan
• what is meant by binary fission


  this is the process by which bacteria divide
• by what process does bacteria divide


  binary fission
• what is meant by an obligate aerobe


  can only survive in the presence of oxygen
• what is meant by an obligate anaerobe


  can only survive in the absence of oxygen
• what is meant by the facultative anaerobe


  these are organisms that can survive in the absence of oxygen but prefer to survive in the presence of oxygen
• what is meant by aseptic technique


  this is the process by which equipment and apparatus are kept free of microorganisms
• what is an autoclave


  a sealed vessel in which equipment is sterilised
• what type of equipment is sterilised in an autoclave


  metal and glass
• what are the conditions inside an autoclave


  121 degrees at higher pressure
• what is used to make the autoclave 121 degrees


  steam
• what is a total cell count


  a count of all cells both dead and alive in a sample
• what is a total viable count


  this is the total number of living cells in a known volume of liquid
• what type of microscope slide is used to count cells


  a haemocytometer
• what is serial dilution

  this is method of calculating viable cell counts using a repeated dilution of a bacterial culture
• what is meant by under dilution


  this causes colonies to merge
• what will under dilution (or clumping) lead to


  inaccurate counting
• what is over dilution


  this is when there are too few colonies on each plate
• what is meant by turbidimetry


  this is a method of indirectly counting cells using a colorimeter