Bacterial%20Shapes

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3 DOMAIN SYSTEM
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Initially Archaea seem more similar to Eubacteria
than to Eukaryotes.   Archae and Eubacteria are
BOTH PROKARYOTIC organisms they both have
closed, circular DNA They both are
transcription and translation linked and they
both usually reproduce by fission.
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However, there are several differences between
Archae and Eubacteria.

1.  They utilize different metabolic pathways. 
2. They also differ in number of ribosomal proteins
   and in the  size and shape of their ribosomal S
   unit. 
3. The Eubacteria genome is almost two times larger
   and they contain more plasmids than Archae. 
4. Archaea are similar to Eukaryotes in that they
   have several kinds of RNA polymerase, have a
   great number of histone-like proteins, have DNA
   in the form of nucleosomes, and contain introns.

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Bacterial Shapes
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Common Disease Causing Bacteria
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Biochemical determination

• Archaebacteria are distinguished by cell walls
  with pseudopeptidoglycan or protein components,
  and cell membranes composed of branched
  hydrocarbons linked to glycerol molecules.

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ALL ABOUT ARCHAEBACTERIA

• Archaea are highly diverse organisms, both
  morphologically (form and structure) and
  physiologically (function). 
• The organisms' possible shapes include spherical,
  rod-shaped, spiral, lobed, plate-shaped,
  irregularly shaped, and pleomorphic. There are
  many different types of Archaea that live in
  extremely diverse environments. 
• Modern-day Archaebacteria are found in extreme
  environments, such as areas of intense heat or
  high salt concentration.

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EUBACTERIA
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BACK TO EUBACTERIA!
Within their domains, identification of microbes
begins with their physical appearance, followed
by biochemical and genetic tests.
SHAPE is/was the most commonly used physical
appearance for determination of species.
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Sex or conjugation Pili for the transfer of extrachromosomal DNA between donor and recipient.                              
 Attachment Pili or Fimbriae. There are many and are used for attachment to surfaces. Pili are virulence factors.                                

Pili Made of the protein pilin and project from
the cell surface. There are 2 types

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Gram positive bacteria
Gram negative bacteria
Have a thin layer of peptidoglycan in their cell
wall. AND have lipopolysaccharides with protein
channels in the cell membrane. This keeps dyes
(along with antibiotics) out!
Have an extra layer of peptidoglycan in their
cell wall, and retain dye.
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Under environmental stress (lack of water, nutrients etc.) some vegetative cells produce endospores e.g. Clostridium and Bacillus. Spores can be dormant for many years. They can survive extreme heat, desiccation, radiation and toxic chemicals. However, when conditions become favorable they revert to a vegetative state. Spore germination is activated by heat in the presence of moistures but the endospore must degrade the layers around the spore.
ENDOSPORES
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PROKARYOTIC CELL DIVISION

• Binary Fission
• cell elongates, duplicates its chromosome

Allocation of chromosomes to daughter cells
depends on MESOSOME an extension of the cell
membrane
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A diagram of the attachment of bacterial
chromosomes, indicating the possible role of the
mesosome.

• It ensures the distribution of the "chromosomes"
  in a dividing cell.
• Upon attachment to the plasma membrane, the DNA
  replicates and reattaches at separate points.
• Continued growth, to about twice the size of the
  cell, gradually separates the chromosomes.

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BACTERIA
VIRUS
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What is an antibiotic?

• Chemical substances that INHIBIT the growth of
  bacteria or KILL it.
• HOW
• Prevent cell wall from forming properly
• Prevent protein synthesis
• Interfere with chromosome replication
• Disrupt plasma / outer membrane
• Interference with metabolism

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Alexander Fleming discovers the first antibiotic
(1928)

• Sir Alexander Fleming discovers the drug
  penicillin, which counteracts harmful bacteria.
  Fleming makes the discovery by accidentally
  contaminating a bacteria culture with a
  "Penicillium notatum" mold.

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• He notices that the non-toxic mold halts the
  bacteria's growth, and later conducts experiments
  to show penicillin's effectiveness in combating a
  wide spectrum of harmful bacteria

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ZONE OF INHIBITION
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What is antibiotic resistance?

• The ability of a bacterial cell to resist the
  harmful effect of an antibiotic. This could be
  incorporated into the chromosome or plasmid.
• System to prevent entry?
• To destroy the antibiotic if into cell
• To block action of antibiotic
• A pump system to move antibiotic out

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How is antibiotic resistance acquired?

• Consistent exposure to antibiotics
• Long-term therapy
• Farm animals
• Indiscriminate usage of antibiotics
• For example for a cold/flu
• Non-therapeutic use
• For animals to gain weight