Requirements for microbial growth – Part 2 Flashcards
what do microbes need to make new cell material
carbon
what do microbes need for growth
an energy source
where do phototrophs get their energy from
from the light
where do chemotrophs get their energy from
obtain energy from oxidation & reduction of chemicals
Chemoorganotrophs?
organic chemicals
Chemolithotrophs?
inorganic chemicals
what do autotrophs require
only c02 as a carbon source
what do hetrotrophs require
require organic forms of carbon
what are the 4 nutritional categories of organisms
Photoautotrophs
Photoautotrophs
Chemolithoautotrophs
Chemolithoautotrophs
For chemotrophs, two mechanisms for energy generation & conservation are known:
Respiration & fermentation
what is fermentation?
anaerobic catabolism of organic compounds (generally carbohydrates
summarise fermentation?
Simple method of generating energy
Oxidation & reduction of organic chemicals
Absence of usable terminal electron acceptor
what is respiration?
anaerobic or aerobic catabolism
summarise respiration?
Generation of energy with terminal electron acceptor
Oxygen if aerobic respiration
Electron acceptor other than oxygen if anaerobic
what does glycolsis produce?
atp and reduces NAD to NADH
what does the krebs cycle produce
produces some ATP by substrate-level phosphorylation,
what happens in the ETC
the energy of the
electrons is used to
produce a great deal of
ATP by oxidative
phosphorylation
WHAT HAPPENS IN FERMENTATION?
In fermentation, the pyruvic acid and the electrons carried by NADH from glycolysis are incorporated into fermentation end-products.
why is respiration more efficient that fermentation
Fermentative microbes grow slowly
A far higher yield of ATP is possible with respiration
what is microbial nutrion about?
all about supplying cells with the chemical tools, or nutrients, that they need to make monomers
in nature what does microbes use for nutrients for growth
host tissues/food
Organic tissues & food have complex heterogeneous structures therefore their chemical properties vary widely
what does this result in?
the characteristics of tissue/food components dictates the microbial flora that may grow
what enzymes act on what/
Amylases act on starches
Proteases act on proteins
Lipases act on lipids/fats
what are macronutrients
Macronutrients – nutrients required in large amounts
what are micronutrients
Micronutrients – nutrients required in trace amounts
why is nitrogen important in cells
Integral component of proteins, nucleic acids, phospholipids & cell wall
where is nitrogen most abundant
forms but the bulk of available nitrogen is in inorganic form
what is phosphrus used for>
required by the cell primarily for the synthesis of nucleic acids & phospholipids
inorganic phosphates (PO43-)
what is sulphur used for?
structural role in the amino acids cysteine & methionine & present in vitamins (e.g. thiamine & biotin) & coenzyme A
(sulphate (SO42−), sulphide (HS−)
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what is potassium used for?
required by all organisms as many enzymes require potassium for activity
various K salts or K+ in solution
what is magnesium used for?
functions to stabilise ribosomes, membranes & nucleic acids
what is calcium used for?
helps stabilise cell walls & plays a key role in the heat stability of endospores
what is sodium used for?
– required by some but not all microbes. Typically a reflection of the habitat
what is the role of iron?
Plays major role in cellular respiration
what does iron form under anoxix conditions?
generally ferrous (Fe2+) form & soluble
what does iron form under oxic conditions
generally ferric (Fe3+) form in insoluble minerals
what does iron also produce?
produce siderophores (iron-binding agents) to obtain iron from insoluble mineral form & from animal iron-binding proteins
what does a poor iron environment mean to some bacteria
requires certain bacteria to express siderophores for survival (e.g. aquachelin)
what do trace elements play a role in?
components of enzymes or as vitamin cofactors
what micronutrietns called/
called trace elements because they are only required in tiny or trace amounts
what are growth factors
Growth factors – organic compounds needed in relatively small amounts by certain organism (requirements vary)
what are some examples of growth factors?
Vitamins – function as coenyzmes. Most commonly required growth factors
Amino acids – for synthesis of proteins
Purines & pyrimidines – for synthesis of nucleic acids (DNA & RNA)
what are some psychical requirements for microbial growth
Temperature
pH
Osmotic effects
Oxygen
Pressure
what are some chemical requirements for microbial growth
Macronutrients
Micronutrients (trace elements)
Growth factors
