An overnight culture of E. coli is about 10^10/ml. The organism is at the statio

Question

An overnight culture of E. coli is about 10^10/ml. The organism is at the stationary phase of the standard growth curve by then. In General terms how does your sample compare to such a culture of E. coli? Swimming beaches are not considered safe if coli form counts (E. coli and related lactose fermenting Gram-negative rods are called coliforms) are greater than 200/100ml. What do you think about the safety of swimming in your water sample? Even one E. coli/100ml would make drinking water questionable. Would you feel safe drinking your water sample?

Explanation / Answer

5.

The E. coli culture has followed the typical bacterial growth curve. There has been an exponential increase in the number of bacteria in the medium. As the organism has exhausted the nutrients in the medium, the bacteria are not able to divide further and they are in the stationary phase. Further growth is only possible in new culture is added or the bacteria are transferred to a new medium. Otherwise, the culture will soon enter the death phase and there will be a reduction in the number of cells in the medium.

6.

If by referring to water sample, the reference is to the culture mentioned in Question No. 5 then the conclusion would be that the water sample in the swimming pool is highly contaminated with E. coli. As against the standard value of 200/ 100 ml we have a count of 1010/ ml. swimming in such waters should not be recommended.

7.

No, this water sample should not be consumed. This water sample is unfit for human consumption.

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