Question

1. A bacterium is grown at its optimal growth temperature of 37°C in a chemostat. Describe and explain what would happen to the shape growth curve (what phase, the slope, etc) of the culture if:  

   1. The chemostat was placed at 27°C.

   2. The chemostat at 37°C broke and no longer supplied new nutrients or removed wastes.

   3. You took a sample out of the chemostat containing a complex media and placed it into media that was chemically defined, minimal media
   4. 
      
      

   5. 2. You took a sample out of the chemostat containing a complex media and placed it into media that was chemically defined, minimal media.

Answer 1

A chemostat (from chemical environment is static) is a bioreactor to which fresh medium is continuously added, while culture liquid containing left over nutrients, metabolic end products and microorganisms are continuously removed at the same rate to keep the culture volume constant. So, there will be no nutrient limitation and optimal temperature 37C. So, the bacterial growth will be exponential like J shaped (a)

(a)Exponential (un- restricted) growth (b)Logistic (restricted) growth Carrying capacity of environment The Population size The growth rate of the population accelerates Population size rate slows down The rate acceler- ates Point of maximum growth 0 U .. . Lima : Time

(Image was sourced from https://www2.estrellamountain.edu/faculty/farabee/biobk/BioBookpopecol.html)

When it will be kept at unfavourable temperature of 27C which is 10C less than optimal. Growth crurve will no longer remain like a but become like b and decline of population will start after initial stationary phase.

Breaking the Chemostat and keeping in minimal media from complex media will also lead to slowing down of growth as nutrient limitation will happen now. So again after initial fast growth the population will soon enter in stationary or decline phase ( logistic Curve)