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					Microbes


Bacteria, Fungi and Viruses
Bacteria prokaryotes

                    They have the usual
                     differences between
                     a prokaryote and a
                     eukaryote, Draw a
                     table highlighting the
                     differences.
Classification

 Gram  reactions
 Cell shape

 Metabolic patterns

 Mode of nutrition

 DNA Fingerprinting
Colony types

 Diplo – pairs of cells
 Staphylo – clusters of cells

 Strepto – chains of cells
Streptococcus
 bacteria 



     Staphylococcus
         bacteria
     Gram Staining
   The gram stain reaction further divides bacteria into
   +ve or –ve types, this is due to the cell wall structure
    of that particular bacteria.
   Those that are stained purple are Gram +ve and
    those that are pink are Gram –ve.
   The cell wall of a bacteria is made from a chemical
    sometimes called murein or peptidoglycan. This is a
    carbohydrate based substance.
Cell Wall Structure
Gram stain Procedure
   •   Make a smear of bacteria on slide and heat fix it.
   •   Stain with crystal violet stain for 30 seconds.
   •   Rinse with lugols iodine for 30 s.
   •   Rinse with distilled water.
   •   Flood with alcohol/acetone for 10 s, wash with water.
   •   Flood slide with (Counterstain) safrannin for 1 minute.
   •   Dry and add cover slip, observe under the microscope.
Gram Staining
   The peptidoglycans that make up the majority of the
    gram+ve cell wall forms purple complexes with iodine
    that remain lodged in this layer even after washing
    with iodine.

   Gram-ve bacteria have a relatively impermeable
    outer membrane. So it is difficult for the purple dye to
    complex (bond) with the peptidoglycan and iodine
    and so is washed off by the alcohol. The counterstain
    (pink) just makes them more visible.
   Salmonella typhi
   Herpes zoster
   Escherichia coli
   Clostridium botulinum
   Saccharomyces cerevisiae
   Clostridium dificile
   Neiserria gonohorea
   Neiserria meningitidis
   Aspergillus niger
   Influenza
   Staphylococcus aureas
   Bacillus anthracis
   Yersinia pestis
Bacteria

    Most widely distributed organism on the earth, ice caps
     to hot springs
    Some are photosynthetic
    Majority are 0.5-1.0 mm wide and 1-5mm long
    Many are harmless, some useful, some killers
    Can double in numbers every 20 minutes
    Many can live in the presence or absence of oxygen
    Some can live on very strange food sources, e.g. waste
     paper processing material to using the sulphur in coal to
     survive
Metabolic diversity

               Autotrophs
 Photosynthetic

 Chemosynthetic Autotrophs

 Heterotrophs
Essential Requirements
   Carbon source                  Most bacteria will
   Energy source
                                    have specific growth
   Hydrogen
   Oxygen
                                    requirements that
   Nitrogen source (amino          can be added to the
    acids or nitrate/ammonium       culture medium (an
    ions)
                                    agar plate) to make
   Mineral ions
   Growth factors (vitamins)
                                    it grow.
Bacterial Survival Needs – source of food, a way to break it
down (respiration) to release energy, etc.

Autotrophs (some use photosynthesis, others in deep oceans
use chemical ways)
Heterotrophs (some make yogurt, cheese, apple cider)
Decomposers = (“recyclers”) that live in soil and break down
chemicals in dead animals and plants.
Endospore = a thick, rounded, thick-walled, resting cell
formed inside a bacterial cell.
      * Some bacteria form this when the environment is to
      harsh for growth. (Anthrax is an example.)
      * Endospores can resist freezing, heating, and drying.
These are plates with different bacteria
Bacterial Respiration
   Obligate aerobes- need free molecular oxygen for metabolism
    and growth, e.g. oxygen gas.
   Obligate anaerobes- need oxygen free environments and are
    killed by oxygen gas. (The reason for this sensitivity is that in the
    presence of oxygen bacteria produce hydrogen peroxide, which
    is harmful. This group lacks the enzyme to break it down, so are
    killed by oxygen’s presence. The other two types of bacteria do
    have the enzyme.)
   Facultative anaerobes- can grow and survive in aerobic
    conditions, but can switch to anaerobic if oxygen supply is in
    short supply.
Asexual Reproduction
   Asexual reproduction is called Binary Fission, the cell
    basically splits in two
   This results in genetically identical cells
   This is often preferred when a bacterium needs to
    colonise an area quickly.
   Or because it has an adaptation to that particular
    environment and so sexual reproduction may involve
    the production of offspring that does not contain
    similar genes to the parent, which would mean death.
Growth Curves
   If the growth of a
    micro-organism
    is measured at
    regular intervals
    of time and the
    data plotted, a
    Sigmoid or S-
    shaped curve is
    obtained.
Lag phase

       This is where the bacteria are becoming accustomed to the new
       conditions.
       There is little increase in cell numbers
       This time may be used to synthesise cell organelles such as
       ribosome’s.
       This can last different periods of time depending upon viability of
       starting cells
Log phase
This is the stage of maximal growth, during which the population doubles.
At this point all variables are at their optimal conditions and so grows
optimally.
Eventually food starts to run out and overcrowding and toxic waste
products build up so growth curve gradient starts to slow, but more cells
still produced than were dying
Stationery Phase
The population does not increase, the number dying is exactly balanced by
those being produced.
Substrates will be used up and toxic by products may accumulate and so
to conserve energy they stop multiplying, some may even start to form
endospores
Death phase
The accumulation of toxic waste increases and the lack of oxygen or other
nutrients makes life unfavourable, cells start to lyse or break down.

				
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posted:9/24/2012
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