Introduction
E,coli bacteria is a commonly found within the human colon and it is a rod shaped enteric bacterium that grows in ideal conditions of 370 C. The bacterium can be cultured or grown in liquid or solid culture media within the lab. When grown in the ideal conditions, say LB broth, they tend to take a specific pattern while when grown in large amount of media they tend to take a lag phase where growth is minimal or none at all (Ding, Rahman, Purev & Oh, 2010). In the ideal environment, the bacteria tend to grow exponentially with their numbers doubling every 20 to 30 minutes. Beyond this ideal medium, the growth rate tends to slow or even halt (Ishii et al., 2010).
Methods
The first step is to set the spectrophotometer to a viable wavelength say 650nm. The spectrophotometer is then allowed to warm for a short period of up to 15 minutes. This will be used to estimate the concentration of E. coli in the culture. After the 15 minutes set the transmittance to zero and place a test tube containing the LB broth (ideal medium) into the sample chamber of the instrument and allow the absorbance to read zero. Take one for the flasks containing the 30 ml LB broth from the 370 C water bath and label it with some unique initials. Add 0.6 ml of E.coli stock into the mix using the sterile method.
Using a pipette, take 3ml of the mixture and place it into a glass culture tube and observe the spectrophotometer. Record the value in a table corresponding to time zero. Place the labeled flask into the water bath (370C) and note the time. After every 30 minutes record the value on the spectrophotometer corresponding to the accumulative time. Repeat the process severally each time recording the value against the accumulative time. Repeat the process with a flask now in water baths of 250C and 300C and record the values in the table. Plot the graph for the values.
Results
The graph indicates that the growth of E.coli was optimal when the flask was in the water bath 370C and lower in the water bath 300C and lowest in the water bath 250C. There was a significant increase in the growth of E.coli in each of the three sets. However, exponential growth was experienced in the water bath of 370C. For the water bath 250C, the growth of E.coli was slow and the change was minimal in concentration of E.coli.
Conclusion
E.coli bacteria tend to grow exponentially in their idea environment of 370C. When all other factors are constant, the bacteria will replicate and their population will increase by double within durations of 30 minutes. The slow growth in the 300C water bath is attributed to the inhibiting of some bacteria due to the low temperatures (Garzio-Hadzick et al., 2010). Little changes are experienced when the water bath of 250C is used for the flasks. This is because the temperatures are too low for the survival of E.coli and thus the rate if replication is equally slow and in some instances even lower than the concentration recorded at time zero. E.coli can only survive in the ideal environment with a temperature of 370C (Ishii et al., 2010).
References
Ding, T., Rahman, S. M. E., Purev, U., & Oh, D. H. (2010). Modelling of Escherichia coli O157: H7 growth at various storage temperatures on beef treated with electrolyzed oxidizing water. Journal of Food Engineering, 97(4), 497-503.
Garzio-Hadzick, A., Shelton, D. R., Hill, R. L., Pachepsky, Y. A., Guber, A. K., & Rowland, R. (2010). Survival of manure-borne E. coli in streambed sediment: effects of temperature and sediment properties. water research,44(9), 2753-2762.
Ishii, S., Yan, T., Vu, H., Hansen, D. L., Hicks, R. E., & Sadowsky, M. J. (2010). Factors controlling long-term survival and growth of naturalized Escherichia coli populations in temperate field soils. Microbes and Environments, 25(1), 8-14.
