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Description
Flashcards by J yadonknow, updated more than 1 year ago
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Created by J yadonknow
almost 7 years ago
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| Question | Answer |
| Describe the process of binary fission | Septum cleavage as cross-walls form between diving cells Time for 1 division = generation time Vibrio natriengens divide every 10 minutes |
| Why are bacterial growth curves referred to as semilogarithimic graphs | As the X axis is still linear |
| How would one work out the generation time? | n= # generations in time (t) G= generation time G=t/n |
| How would you calculate growth? | N=No2^n N=Final cell count No=Initial cell count n= #generations during period of exponential growth |
| How do you calculate n? | n=(logN-logNo)/log2 |
| What is the lag phase? | Time between inoculation into fresh media and arrival of significant growth |
| What is exponential phase dictated by? | Nutrient/space availability, genetic characteristic of the organism Healthiest cell state |
| Growth rate at stationary phase? | 0 No net increase/decrease in cell numbers |
| What are the issues with microscope counting? | Hard to distinguish between dead/alive cells Debris could be mistaken for a cell |
| What is the viable count | Number of cells that are able to divide and produce offspring |
| What is the major assumption of plate counting? | 1 colony = 1 cell |
| What is the 2 methods to do this? | Spread plate method / pour plate method |
| What other problem arises with mixed cultures? | Not all cells are optimised to grow in the same conditions. |
| What are batch cultures? | Microbes cultured in an enclosed vessel A closed system Typically a flask or tube |
| What are continuous cultures? | An open system Fresh media constantly flowing over growth vesel Rate of flow in = rate of flow out Steady state, growth vessels reach equilibrium with cell number, nutrients and waste |
| What are chemostats? | Continuous cultures Stirrers prevent sedimentation Chemostat controls growth by controlling dilution rate |
| How is cell density regulated? | Regulating concentration of a limiting nutrient i.e. C or N. |
| Why must an equlibrium be reached? | Too little dilution = cells die from starvation Too high dilution = Cells can't grow fast enough and are washed out |
| Draw a diagram comparing batch cultures to continuous cultures | bahjooobie |
| How can you measure growth? | Count cell number Samples dried out into slides/liquid samples |
| What is a counting chamber used for? | Counting liquid samples, akin to taking a punnet square and up-scaling from there |
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