The Effects of Environmental Factors on the Absorbance of Escherichia Coli
Introduction
In this experiment, the gram negative bacterium Escherichia coli is being subjected to various environmental factors that affect the rate of growth. These factors scrutinized were the different types of nutrients, the intensity of aeration, or the temperature at which it was stored. The purpose of this lab is to determine which factor affects the Escherichia coli the greatest. It is known that these abiotic factors affect the rate of growth the greatest if they remain at the correct conditions for living.
Escherichia coli and other bacteria will go through four phases; a lag phase, log phase, stationary phase, and a death phase. In the lag phase, the bacteria reproduce fairly slowly, as they are preparing for the rapid division (Doyle). In this lag phase the bacteria is making fats and proteins which will jump-start the log phase (Doyle).
The next phase in the bacteria 's life cycle is the log (logarithmic or exponential) phase. At this point, the bacteria begin replicating swiftly. Once the culture reaches high densities, their living space and nutrients begin to deplete, and the toxicity levels begin to increase (Doyle).
Due to this rapid growth, the next step is the stationary phase. In this phase, about fifty percent of the new bacteria population will undergo autolysis and become inactive or die, and the other fifty percent will remain and continue replication (binary fission) (Doyle).
The last stage of a bacteria 's life cycle is the death stage. In the death stage, there are not enough nutrients for the entire culture to survive. This causes the death rate of Escherichia coli to increase, and the division of the living cells will slow down. In other words, the birth rate will be lower than the death rate, and this will be displayed in the graph at the leveling off, or downward slope. From this growth curve that a bacterium produces, the Mean Generation Time (MGT) can be calculated. Because Escherichia coli is a known
In this experiment, the gram negative bacterium Escherichia coli is being subjected to various environmental factors that affect the rate of growth. These factors scrutinized were the different types of nutrients, the intensity of aeration, or the temperature at which it was stored. The purpose of this lab is to determine which factor affects the Escherichia coli the greatest. It is known that these abiotic factors affect the rate of growth the greatest if they remain at the correct conditions for living.
Escherichia coli and other bacteria will go through four phases; a lag phase, log phase, stationary phase, and a death phase. In the lag phase, the bacteria reproduce fairly slowly, as they are preparing for the rapid division (Doyle). In this lag phase the bacteria is making fats and proteins which will jump-start the log phase (Doyle).
The next phase in the bacteria 's life cycle is the log (logarithmic or exponential) phase. At this point, the bacteria begin replicating swiftly. Once the culture reaches high densities, their living space and nutrients begin to deplete, and the toxicity levels begin to increase (Doyle).
Due to this rapid growth, the next step is the stationary phase. In this phase, about fifty percent of the new bacteria population will undergo autolysis and become inactive or die, and the other fifty percent will remain and continue replication (binary fission) (Doyle).
The last stage of a bacteria 's life cycle is the death stage. In the death stage, there are not enough nutrients for the entire culture to survive. This causes the death rate of Escherichia coli to increase, and the division of the living cells will slow down. In other words, the birth rate will be lower than the death rate, and this will be displayed in the graph at the leveling off, or downward slope. From this growth curve that a bacterium produces, the Mean Generation Time (MGT) can be calculated. Because Escherichia coli is a known
Cited: Michael P. Doyle, "Food-borne disease", in AccessScience@McGraw-Hill, http://www.accessscience.com, DOI 10.1036/1097-8542.YB000610, last modified: December 13, 2000. M. R. J. Salton, et al., "Bacterial physiology and metabolism", in AccessScience@McGraw-Hill, http://www.accessscience.com, DOI 10.1036/1097-8542.069000, last modified: June 10, 2004. Robert E. Hungate, et al., "Bacteria", in AccessScience@McGraw-Hill, http://www.accessscience.com, DOI 10.1036/1097-8542.068100, last modified: January 18, 2001.