growth of bacteria Flashcards
Describe the different forms of
reproduction in bacteria.
- asexual reproduction and in which the most common type is binary fusion .
- Other forms include asexual reproduction such as budding ,fragmentation and condiospores/sporangiospores.
Draw and explain activities
occurring in the different
phases of a bacterial growth.
There are four distinct phases of the growth curve: lag, exponential (log), stationary, and death.
The initial phase is the lag phase where bacteria are metabolically active but not dividing.
The exponential or log phase is a time of exponential growth.
In the stationary phase, growth reaches a plateau as the number of dying cells equals the number of dividing cells.
The death phase is characterized by an exponential decrease in the number of living cells.
Determine the generation
time of a bacterial species.
refer to notes
Discuss the advantages and disadvantages of the different techniques available to determine the number of bacteria
refer to notes
Understand the importance
and function of different
elements in the metabolism of
bacteria
Elements such as C, O, H, N, S & P are required in large quantities (in grams). These are referred to as the
major macroelements and are used to synthesise the basic building blocks of life i.e carbohydrates, proteins,
lipids and nucleic acids.
Minor macroelements include cations such as K+
, Ca2+, Mg2+, Fe2+, Fe3+ which are used in the synthesis of
enzymes and their co-factors. These elements are required in mg quantities.
The synthesis of enzymes and co-factors also require trace elements such as Zn2+
, Mn2+, Mo, Se, Co, Cu,
Ni & W in μg quantities
Identify the compounds used
to store energy
ask for assistance
Define the terms: autotroph, heterotroph, phototroph, auxotroph, chemotroph, organotroph, fermentation, respiration, catabolism, anabolism, metabolic pathway, oxidative phosphorylation
-Heterotrophs are microorganisms that obtain their carbon from organic compounds (including other living material) such as
carbohydrates and proteins.
-Autotrophs can only obtain their carbon directly
by fixing CO2.
-Chemical work is metabolic reactions in which cell constituents are
synthesised (anabolism) and substrates are broken down (catabolism).
-Phototrophs contain photosynthetic pigments which can trap energy in the form of light by the process
of photosynthesis. Most autotrophs are phototrophs. However the majority of heterotrophs bacteria are
chemotrophs and they obtain energy from the breakdown of organic molecules during oxidation and
fermentation
Identify terminal electron
acceptors in the absence of
oxygen
other organic compounds such as nitrate, sulphate
or sulphur are the terminal electron acceptors
Explain the principles of the different biochemical tests and understand how these biochemical characteristics can be be used in the identification of bacteria
Biochemical tests can differentiate between mixed acid
fermenters and butanediol fermenters. The Voges Proskauer test (aka acetoin test) detects the presence of
butanediol. Mixed acid fermenters are normally negative for this test. The methyl red test is dependent on
the acidity of the medium in which the bacteria are cultured. When pH of the medium drops below pH 4.4,
the methyl red indicator will change colour due to the different acids produced by the bacteria. Both tests
are conducted in MRVP medium.
Compare passive and
facilitated diffusion.
Passive diffusion
This is the movement of molecules from a region with a high concentration of solutes to a region with a
lower concentration of solutes. This system does not require energy.
Facilitated diffusion
This is the movement of molecules from a region with a high concentration of solutes to a region with a
lower concentration of solutes with the aid of carrier proteins but without energy
Compare diffusion and active
transport.
Diffusion: molecules from a region with a high concentration of solutes to one with a low concentration of solutes. no energy may / may not need transport proteins Active transport: Molecules move against the concentration gradient Energy required Transport proteins used
Explain how a proton gradient
is formed.
The proton motive force (pmf) gradient is generated during electron transport chain activity. H+ are
pumped out of the cell during the transfer of electrons so that there is a difference in electric potential and
pH on either side of the membrane, thereby forming a gradient
Describe nutrient uptake by
means of the proton motive
force, the sodium ion gradient
and group translocation.
refer to notes
Describe how bacteria acquire
iron.
Iron is essential for the functioning of cytochromes and enzymes. Very little iron is available and that
which is available is mainly ferric iron which is highly insoluble and cannot be taken up by aerobic or
aerotolerant bacteria in this form. Bacteria and fungi secrete siderophores when iron levels are low.
Siderophores are low molecular weight molecules that can bind Fe3+ and solubilise it. There are various
siderophores. Fungi possess hydroxymates such as ferrichrome while bacteria like E.coli secrete phenolcatecholates such as enterobactin. Once the ferric iron has complexed with the siderophore, the siderophore
binds to its receptor on the surface of the bacterial or fungal cell. Then either the iron is released and enters
the cell on its own or the entire complex of siderophore and iron is transported into the cell. The ferric iron
then dissociates from the siderophore and it is reduced to ferrous iron
Define the groups of bacteria
according to the temperature
range in which they grow
refer to the effects of temperature notes :pscychrophiles,psychotrophs,mesophiles,thermophiles,and hyperthermophiles
