BIOL243 L3

  • Created by: Katherine
  • Created on: 03-04-17 17:26
What are the 4 phases of bacterial growth in culture?
Lag, exponential, stationary and death
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What is a batch fed culture?
Culture vessel is inoculated at low bacterial density and then incubated at an appropriate temperature for growth.
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What happens in the death phase of culture growth?
The viable count goes down.
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What is the ratio microbial cells to human cells?
1:1 to 10:1
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Where are the most skin microbes associated?
With sweat glands (under arms, genital regions, *******) and hair follicles.
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Why does microbial growth occur best in moist areas?
Because there is inreased availability of urea, amino acids, salts, lacticacid and lipids.
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What are the typical microbial colonisers of skin?
Corynebacterium, Staphylococcus and Micrococcus.
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What are the features of skin dwelling microbes?
They are usually gram +ive. They survive well in dry environments. Generally ferment or respire sugars. Some have the opportunity to be opportunistic pathogens.
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What is the composition of microbial flora influenced by?
It is influenced by diet. E.g. high meat consumption sees accumulation of proteolytic Bacreroides, relative to coliforms and lactic acid and bacteria.
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In the large intersine microbial flora provide a source of...
Vitamins K and B12. Digestion of compex carbohydrates into absorbable sugars.
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In the large intestine, microbial flora modify and activate...
Steroid compounds synthesised in the liver and released as bile from the gall bladder.
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How does resident flora protect the body?
It provides a microbial barrier that prevent the rise in population of potentially harmful micro-organisms - this can be pertubed following antibiotic treatment.
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What are the two extreme environements provided by the digestive tract?
The acidic stomach and the anaerobic large intestine
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How does bacteria survive in very acidic envrionemnts?
It burrows into the epithelial wall - it's highly specialised.
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What is the environment of the large intestine, and why?
Facultative aerobes consume the available oxygen creating a strictly anoxic (anaerobic) environment.
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What type of bacteria grow in the large intestine due to the conditions?
Facultative aerobes (
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Are resident anaerobes of the colon found elsewhere?
No, O2 is toxic to obligate anaerobes.
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Why is O2 toxic to obligate anaerobes?
Oxygen derivatives (Reactive oxygen species (ROS)) damage (oxidise) organic compounds including macromolecules.
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How are ROS produced?
They are produced as a ubiquitous side product of aerobic respiration. O2 + 4e- + 4H+ = 2H2O. Upon exposure to 2, obligate anaerobes generate ROS because many enzymes will react with O2 to produce superoxide.
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What enzymatic defences are used by aerobes to detoxify oxygen species?
Catalse, Peroxidase, Superoxide dismutase, Superoxide dismutase/ catalase in combination.
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How does Catalase act as a defence mechanism?
H2O2 + H2O2 -> 2H2O + O2
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How does Peroxidase act as a defence mechanism?
H2O2 + NADH + H+ -> H2O2 + NAD+
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How does Superoxide dismutase act as defence mechanism?
O2- + O2- +2H+ -> H2O2 + O2
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How does Superoxide dismutase/ catalase in combination act as protection?
4O2- + 4H+ -> 2H2O + 3O2
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What does superoxide dismutase use as a co-factor?
Metal (Fe, Mn, Cu, Zn)
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What does superoxide reductase do and where is it found?
It is present in some obligate anaerobic prokaryotes. This enzyme catalyses reduction of superoxide without production of oxygen - i.e. the microbe limits further oxygen exposure during de-toxification.
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In microbes containing superoxide reductase, how is hydrogen peroxide removal done?
It is done via peroxidases
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If obligate anaerobes possess the enzymes to detoxify ROS, why is O2 nonetheless so toxic to this class of microbes?
Possibly, there is a limited capacity to detoxify ROS relative to aerobes. Or O2 directly poisons some of the essential enzymes required for anaerobic energy generation. This, in obligate anaerobes, O2 itself, not necessarily ROS, is the toxin.
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What are the main areas of a human colonised by microbial flora?
Skin, mouth, urogenital tract, eyes, digestive tract.
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The catabolism of carbon sources in heterotrophs generates... which is used in ....
ATP which is used in biosynthetic (anabolic) pathways and other processes.
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What is anabolism used for?
ATP dependent synthesis of cell membranes, cell walls and proteins.
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ATP hydrolysis is also coupled to:
Nutrient uptake and motility.
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What else do catabolic reactions create?
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How do enzymes promote the interconversion of individual metabolites over milli and micro second timescales?
By lowering the energy of activation that is required to convert substances into products.
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During catabolism, what are enzyme calatsed reactions used to do?
To destabilise and then breakdown fuel molecules. The energy liberate from breaking chemical bonds can be coupled to energy (ATP) production.
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What provides a common organic energy source?
Glucose, fructose, mannose, sucrose, lactose, maltose.
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Which carbohydrates are available in the gut?
Polmers, cellulose; laminarin; paramylon, agar, chitin, pectin and dectran.
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What is the Embden Meyerhof pathway of Glycolysis?
Glucose phosphorylated by ATP to form glucose 6-phophate. The atoms of glucose 6 phosphate are rearranged to form fructose 6 phosphate. This is phosphorylated by ATP to form fructose 1,6 bisphosphate. This is cleaved to fomr G3P and DHAP.
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What then happens in the process? ( 2)
DHAP is rearranged to form another G3P. Inorganic phosphates are added to the 2 G3P, and 2 NAD+ are reduced. 2 ADP are phosphorylated by substrate level phosphorylation to form 2 ATP. Remaining phosphates are moved to the middle carbons.
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What then happens in the process? ( 3)
A water molecule is removed from each substrate. 2 ADP are phosphoryalted by substrate level phosphorylation to form 2 ATP. 2 pyruvic acid are formed.
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What are the outcomes of glycolysis?
2 ATP per glucose molecule metabolised. Addition of Pi to G3- results in electron transfer from G3P to NAD+ resulting in the production of NADH.
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The Entne Doudoroff pathway is another alternative to glycolysis. What are the key points?
The pathway deviates from glycolysis after production of glucose 6 phosphate. It requires 2 key enzymes of restricted evolutionary distribution.
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What are the outcomes of Entner Doudoroff?
Production of 1 NADPH per glucose catabolised. Production of 1NADH per glucose catabolised. Reduced ATP yield as compared with glycolysis (only 1 ATP per glucose molecule catabolised).
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What are 2 opportunistic pathogens that use the Entner Doudoroff pathway?
Pseudomonas aeruginosa, Enterobacter faecalis.
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What is Pseudomonas aeruginosa?
Gram -ve; heterotrophic; rod. It is an ecologically important soil dwellers. Capable of metabolising many carbon sources. It is an opportunistic pathogen - causes infections (UTI ect).
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What is Enterobacter faecalis?
Gram -ve; spherical. It is ubiquitous in the large intestine. It uses fermentation as metabolic strategy. Poor personal hygiene can result in inection.
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Carboyhdrate metabolism results in the synthesis of...
ATP through substrate level phosphorylation
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During the metabolism of a sugar, what happens to electrons?
They are transferred from the fuel source to NAD+/NADP, resulting in the production of NADH and/or NADPH
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In order to sustain an active metabolism, what must happen to the NADH produced duing catabolism?
It must be oxidised to regenerate NAD+
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What happens during fermentation?
The electrons are transferred from NADH to an endogenous, organic metabolite, resulting in the production and secretion of a fermentation waste product.
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What are common or useful products derived from fermentation products?
Cheese, Wine, Beer, Alcohol, Vinegar
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What is fermentation?
It is the production of ATP via substrate level phosphorylation using organic compounds as electrons acceptors and donors.
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What are the end products of fermentation?
CO2, Formate, Butyrate, Acetate, Propionate, 2 Alkyl acetate
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Give an example of a obligate fermenter
Clostridium. Capable of fermenting a vast array of different carbon sources using some of the pathways.I
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Is fermentation an efficient metabolic strategy?
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What are Clostridium?
Gram +ve, rod; endospore forming bacteria. Obligate fermenters. Soil dwellers, can be pathogenic.
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Other cards in this set

Card 2


What is a batch fed culture?


Culture vessel is inoculated at low bacterial density and then incubated at an appropriate temperature for growth.

Card 3


What happens in the death phase of culture growth?


Preview of the front of card 3

Card 4


What is the ratio microbial cells to human cells?


Preview of the front of card 4

Card 5


Where are the most skin microbes associated?


Preview of the front of card 5
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