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29 Cards in this Set
- Front
- Back
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What are the four main factors used when describing bacterial colonies? |
Form - circular, filamentous, spindle
Elevation - flat, raised, convex Margin - entire, undulate, lobate Size |
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What are the four phases of growth in batch culture? |
Lag - adapting to media, inducing enzymes
Log - all cells viable, constant growth rate Stationary - no net increase in cell no., compos. changes, secondary metabolites Death - irreversible loss of ability to divide |
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What is the VBNC hypothesis? |
Viable but non-culturable
Cells are starved - temporarily non-culturable but can regain capacity to reproduce. |
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What is the specific growth rate of a unicellular organism |
Mean growth rate (u) - the number of generations per unit time Reciprocal of doubling time (g) g = 1/u |
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What equipment is used for continuous culture? |
Chemostat
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Example of microbial responses to water activity |
Osmophiles - wide range
Mild/moderate/extreme Halophile - 5/10/20% salt Halotolerant - some salt OK, best without Xerophiles - dry |
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Example of microbial responses to pH |
Most have optimum around 2 (1-3)
Acidophile - <5.4, Acontium Neutrophile - Esherichia, 5.4-8.5, pathogens Alkolophile - Bacillus alcalophilus |
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Example of microbial responses to temp |
Psychrophile - optimum below 15 degrees, 0 OK Psychrotroph - opt. 20-30, can grow at 0-7 Mesophile - 20-45, E.Coli, pathogens, thermoduric - can survive bursts of high temps (hyper)Thermophile - 50 |
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Example of microbial responses to oxygen conc. |
Obligate aerobe - completely dependent, fungi
Obligate anaerobe - Clostridium |
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Example of microbial responses top pressure |
Barophile - high hydrostatic pressure
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Graph for growth rate/water availability? |
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What about oxygen makes Obligate anaerobe unable to survive?
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ROS - removed from SOD and catalase |
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Examples of ROS formation |
O2 + e− → O2·− (superoxide radical) O2·− + e− + 2H+ → H2O2 (hydrogen peroxide) H2O2 + e− + H+ → H2O + ·OH (hydroxyl radical) |
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Removal of ROS with SOD |
2O2·− + 2H+ → H2O2 + O2 |
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Removal of ROS with Catalase |
2H2O2 → 2H2O + O2 |
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What is an aerobe?
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Uses molecular oxygen as terminal electron acceptor |
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What is an obligate aerobe? |
Cannot live in the absence of molecular oxygen |
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What is a facultative anaerobe? |
Can use molecular oxygen when it is present Can utilise fermentation as a means of generating energy when oxygen is absent E.Coli, Salmonella ssp. |
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What are Microaerophiles and anaerobes? |
Microaerophiles are unable to grow in air (20 % oxygen), but require 2-10 % oxygen Anaerobes generate energy from fermentation only and cannot utilise oxygen in energy generation. Some can grow in the presence of oxygen and others are killed by it! |
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What is a biofilm? |
Any group of microorganisms in which cells stick to each other on a surface Dynamic communities |
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Formula for generation time |
Time/number of generations |
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Where does your normal flora come from? |
Foetus, no microbes Microbiome collected during birth |
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What are endosymbionts? |
smaller symbiotic partners living inside a host organism, |
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What is the importance of natural flora? |
Prevents growth of other organisms - by competition, release inhibitory substances (amensalism) |
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Microbes in skin |
Oily/moist - water, aa, urea, electrolytes Flora restricted by desiccation, lack of nutrients, lysozymes |
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What are lysozymes? |
Catalyse hydrolysis of 1,4-beta-linkages between: - N-acetylmuramic acid - N-acetyl-D-glucosamine residues in a peptidoglycan |
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Microbes in nose |
Lysozyme secreted by nasal passages restricts flora to the nose |
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How are microbes removed from respiratory tract? |
- Mucus (produced by goblet cells) traps them - Ciliated cells moves the mucus upwards to be swallowed and digested - Phagocytic macrophages - Lysozyme |
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Microbes in genitourinary tract |
Upper GU tract (kidneys, ureters and urinary bladder) - free from microbes
Few in distal - urethra |
