Bacteria growth

Growth Curve Report of
Bacterial E.Coli

By: Lidny Pizarro
T.A: Ken Lou“On my honor, I have neither given nor received unauthorized aid in doing this assignment.”
Abstract
Escherichia coli is one of the most abundant bacteria found among microorganisms. In thisexperiment, E. Coli bacteria was selected to compare generation times at two different temperature conditions. A spectrophotometer apparatus was utilized to obtain optical density measurements for each of the conditions. From the data obtained, a growth curve was created by drawing best-fit lines and extrapolating the generation times for each of the conditions based on these lines. Resultsdemonstrated that the bacterium grows rapidly and effectively at a moderate mammalian body temperature of 37°C with a generation time of 41 minutes. The milder room temperature of 20°C, yielded a longer generation time of 58 minutes. These generation times coincide with known optimal moderate temperature ranges for E. coli. The accuracy of the method utilized for obtaining generation times is however indoubt, since it accounts for the number of both dead and alive cells in the broth of bacterial cells. Despite this disadvantage, the method provides the overwhelming advantages of being rapid, low cost and non-destructive.
Introduction
Microorganisms are incredibly diverse, and even though most of them are beneficial to humans, some are pathogenic. Bacteria are one of the most abundant types ofmicroorganisms, and they can be found virtually everywhere in the environment. Bacteria adapt to particular environmental conditions, in which they experience optimal microbial growth. Therefore, the classification of bacteria may be based upon the optimal temperature range that they occupy. Bacteria thrive in differential temperature ranges, and can be divided into those that require coldtemperatures such as psychrophiles or “cold-loving”, “heat-loving” thermophiles, and mesophiles that prosper in moderate ranges, such as room or mammalian body temperatures.
Growth in bacteria refers to an increase in the number of cells in a population. Bacterial growth may be divided into four separate phases. The first phase is referred to as the lag phase, in which cells adjust to their newenvironment, and necessary enzymes are made. Individual bacteria are maturing, and not yet able to divide, therefore no increase in cell number is observed during this phase. Following adjustment to their new environment, bacterial cells begin to grow in what is known as the exponential or logarithmic phase. This period is characterized by cell doubling, and is essential for calculating generation time. Asa result of nutrient depletion and accumulation of waste products, the stationary phase is reached. In this phase, the rate of multiplication equals the rate of death. Finally, as nutrients are exhausted, and waste products build-up the bacterial cells enter the death phase in which no growth occurs.
In laboratory settings, bacterial growth characteristics may be assessed utilizing a culturemedium. This medium supports the growth of microorganisms by providing the appropriate physical and chemical environmental conditions in a solution of nutrients. Broths were the first type of liquid media used to culture microorganisms. This type of growth media allowed scientists to produce a vast amount of cells, yet did not isolate the cells effectively. Another highly nutritious growth medium...