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Lecture 1

BIOLOGY 2EE3 Lecture Notes - Lecture 1: Eosin, Bile Acid, Yeast Extract


Department
Biology
Course Code
BIOLOGY 2EE3
Professor
Turlough Finan
Lecture
1

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Ebola virus disease (October 1)
Ebola virus disease (EVD), or Ebola haemorrhagic fever
a case fatality rate of up to 90%.
natural hosts -fuitbats? transmitted to people from wild animals and through
human-to-human transmission.
No licensed specific treatment or vaccine is available for use in people or animals.
Signs and symptoms: illness often characterized by the sudden onset of fever, intense
weakness, muscle pain, headache and sore throat. This is followed by vomiting,
diarrhoea, rash, impaired kidney and liver function, and in some cases, both internal and
external bleeding.
The incubation period, that is, the time interval from infection with the virus to onset of
symptoms, is 2 to 21 days.
(Oct 1-3) Cultivating Microorganisms: (Chapter 6) Outline:
Nutritional requirements of microorganisms:
What do microorganisms generally need in order to grow?
To build macromolecules.
oThey need carbon, nitrogen, phosphorus, sulfur, and oxygen
(macronutrients)
oMicroorganisms must obtain these elements from their environment in
order to make these macromolecules
Required for protein structure/activity
oVarious micronutrients -including several metal ions (Na+, Mg2+, Mn2+,
etc.)
Protroph vs Auxotroph
Prototroph-synthesizes all cellular components from basic nutrients glucose, ammonia,
phosphate and sulphate
A prototroph will grow in a mineral salts medium with a carbon source.
Auxotroph requires supplements in order to grow e.g. a vitamine, amino acid(s), purine,
pyrimidine.
Many microorganisms are protrophs, what about humans? Humans are
auxotrophs
Major factors affecting growth of Microorganisms –Water, temperature and
oxygen (for aerobes ), pH,
Amino acids regarded as essential for humans are phenylalanine, valine,
threonine, tryptophan, isoleucine, methionine, leucine, lysine, and histidine

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Acquisition of energy
Chemotrophs-energy from oxidation of reduced organic or inorganic
compounds.
Phototrophs–energy from light.
Electron sources
Organotrophs: electrons from organic molecules (e.g., glucose)
Lithotrophs(‘rock-eaters’): electrons from inorganic sources (e.g., H2gas , NH4,
H2S, and elemental sulfur)
Acquisition of Carbon
Autotrophs assimilate carbon from inorganic sources.
Heterotrophs assimilate carbon in preexisting organic form
Acquisition of nitrogen
Critical to making numerous macromolecules
oAmino acids
oNucleic acids
Microbes must be able to incorporate nitrogen into a usable form
The Enzyme, Glutamate Dehydrogenase converts alpha-ketoglurate using NH3
into Glutamate making NADP+ into NADPH
Ammonia assimilation
Two different systems:
1. GS-GOGAT works best at low ammonium concentrations.
2. GDH works best at high ammonium concentrations.
Note: Both systems readily incorporate ammonia to form amino acids for cells.
Amino acid synthesis

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Main metabolic pathways give the initial carbon skeleton of amino acids.
Ammonia assimilation is then used to bring in the amino groups of the amino
acids.
Nutritional requirements of microorganisms
The molar C:N:P ratio for microbial samples is ~ 50C:10N:1P
What C, N or P sources can a microorganism utilize (metabolize)?
Examples of carbon sources are: glucose, fructose, cellobiose, sucrose, mannitol
Growth: distinguish between cell density and growth rate.
Nutrient concentration
oGrowth rate will depend on the amounts of nutrients in the
environment.
oOne key nutrient, available in the lowest amount, will dictate how
much growth can occur over time (i.e., it will be a limiting factor –the
limiting nutrient)
Effects of oxygen on microbial growth
Aerobes grow in the presence of oxygen.
oObligate aerobes REQUIRE oxygen.
oMicroaerophiles grow best when there is less oxygen than normal.
Anaerobic growth occurs without oxygen.
oAerotolerant anaerobes aren’t harmed by oxygen but don’t use it,
either.
oObligate anaerobes cannot grow when oxygen is present.
oFacultative anaerobes CAN use oxygen but can also grow in the
absence of oxygen.
Often determined by what defenses are available against oxygen’s negative effects
in the cell
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