A lake sample was collected during July and was inoculated and incubated using t

Question

A lake sample was collected during July and was inoculated and incubated using the criteria listed in the table, the results of the inoculated and incubated sample were graphed and are depicted in the growth curve below. Temperature 37 degree C pH: 7 Medium: Lactose broth Incubation time: 48 hours Oxygen: facultative anaerobe (in thioglyocollate broth) Each line (I) represents 1 hour on the graph above Label the 4 phases of growth on the graph: stationary, death, log, lag. Draw the appearance of the inoculated lactose broth after 4 hours. Draw appearance of thioglyocollate broth based on the oxygen results. Name the phase of growth that could be used to calculate generation time. _____ List several reasons why phase c occurs.

Explanation / Answer

16. The four phases of growth seen in bacterial growth are lag phase- in this phase very little or no bacterial growth is observed.

Log phase- In this phase the number of bacterial cells starts to double at a constant exponential rate.

The stationary phase- The phase where the growth levels is almost equal to the rate of cell death. To at this stage the graph does not show an upward movement, it is parallel to the time axis.

Death phase- In this phase a steady decline is observed. Here the population numbers decline due to starvation.

So in the above diagram,

a- Lag phase

b- Log phase

c- Stationary phase

d- Death phase

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