Chapter 10 Tortora

1
Chapter 10 Tortora

• Classification of Microorganisms

2
Miscellaneous information

• 2001 launched the All Species Inventory which
  will attempt to identify ALL life on earth in 25
  years
• Many similarities among organisms
• All are composed of cells
• All have a plasma membrane
• All use ATP for energy
• All have DNA
• All descended from a common ancestor
• Darwin proposed all similarities/differences are
  due to survival (natural selection)

3
3 domains

• Based on differences in ribosomes, membrane lipid
  structure, transfer RNA, and sensitivity to
  antibiotics
• Domain Eucarkya comprised of animals, plants,
  fungi and protists
• Domain Bacteria includes all pathogenic and many
  nonpathogenic prokaryotic organisms
• Domain Archaea-includes prokaryotic organisms
  with no peptidoglycan and live in extremes

4
Bergeys Manual

• Contains the taxonomic classification for
  prokaryotics.
• Divides prokaryotes into Domain Bacteria and
  Domain Archaea
• A prokaryotic species is defined as a population
  of cells with similar characteristics
• Sometimes pure cultures are not identical in
  every way and are referred to as a strain.

5
Methods of classifying/identifying microbes

• Morphological characteristics like endospores or
  flagella
• Differential staining
• Biochemical tests-involves enzymatic activity
• Now have rapid identification methods for faster
  identification of pathogens (see flow chart page
  295)

6
Continued

• Serology-science that studies serum and immune
  responses evident in serum
• Serological testing can be used to tell the
  difference between species and strains
• Slide agglutination test-unknown placed in saline
  then antiserum added, look for agglutination
  (clumping)

http//www.cdc.gov/groupBstrep/lab/slides/thumb4.h
tm
7
Phage typing

• This is a test for determining which phages a
  bacterium is susceptible to
• Phages (bacteriophages) are viruses that infect
  bacteria and usually cause lysis
• They are highly specialized and only infect
  members of certain species or strains
• One strain may be susceptible to 2 phages, or
  another might be susceptiblet o those 2 and a 3rd.

8
Other methods

• Fatty acid profiles-FAME (fatty acid methyl
  ester)
• Flow cytometry-used to ID bacteria in a sample
  without culturing the bacteria
• DNA base composition-percentage of G-C complexes
• DNA fingerprinting-can determine entire base
  sequence, but it is impractical.
• Instead use restriction enzyme to cut fragments

9
Other methods

• Polymerase chain reaction (PCR)-used when a
  bacterium cant be cultured by conventional
  methods
• This increases the amount of DNA
• Nucleic acid hybridization-measures the ability
  of DNA strands from one organism to hybridize
  with DNA strands from another
• Heat, separate, and reunite
• Can use in southern blot technique

10
One more time!

• DNA chips-new technology which will make it
  possible to identify a gene unique to a pathogen
• use flouroescent dye and add it to chip
  containing probes, and allow hybridization
  between probe and unknown sample
• Ribotyping and ribosomal RNA sequencing-can
  determine phylogenetic relationships between
  organisms
• Fluorescent in situ (in place) hybridization
  (FISH)-determines identity, abundance, and
  relative activity of microbes in environment