Microbiology VI

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Flashcards on Microbiology VI, created by J yadonknow on 22/01/2018.
J yadonknow
Flashcards by J yadonknow, updated more than 1 year ago
J yadonknow
Created by J yadonknow about 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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