Growth of Microorganisms
Lab 5: Growth of Microorganisms (100 points)
Student Name: Student Name: Jonathan R. Maynor
Student ID: 7075949
Course ID: BIOL202 B002 Spring 2024
-Each question on the lab worksheet must be answered completely, thoroughly, in complete
sentences and correctly in order to be considered for full credit
-If the question asks you to do research or find a source, a reputable, credible and/or scholarly
source citation must be included in order to be considered for full credit
-If a math formula is required to arrive to an answer, work must be shown otherwise, no credit
will be awarded
Pre-Lab Questions
1. Why don’t microorganisms in cultures exhibit constant exponential growth? What
are some steps you could take to extend the lifespan of a microbial culture? (5
points)
One can easily assume that if a microorganism in placed in a culture, then for the rest of
time it will continue to grow at an exponential rate without ever defaulting, however this
is not a factual statement for various reasons. The first reasons come with the aspect of
nutrition, which can be referenced back to all experimented conducted in this course.
The first step of all of the experiments that we have conducted have begun with placing
nutrient agar into a petri dish. Microorganisms are a living thing; therefore, they need
nutrients to sustain grow and exist. There comes a point where in a culture were a
microbe will consume all the nutrients within the experiment (i.e., petri dish). Because
they consume all the nutrients, they can no longer receive them to continue growth. For
example, if you were to leave your petri dished in an incubator for multiple months,
eventually the bacteria would die due to the unavailability of nutrients to survive. A way
you could extend this potential of growth would be to add more nutrients to the
specimen, which could be nutrient agar. Another option could be transferring the
microbes to a new petri dish.
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Growth of Microorganisms
2. Using a textbook or a reputable online source, describe how lab cultures are
maintained in a continual pattern of growth. Focus particularly on those used in
biotechnology, such as E. coli, which is used to make human insulin. (5 points)
As mentioned above, in order to keep a culture maintained, a constant state of nutrients
must be introduced to the sample. Additionally, you must also account for the removal of
waste as microbes are a living thing and produce by products from growth. The constant
relationship of providing new nutrients and the removal of waste are two key elements of
keeping an microbe maintained, which is no different when it comes to that of E. coli.
Another aspect of maintaining a culture such as E. Coli comes with the process of
freezing the sample. This process allows for the sample to be preserved for a extended
time. Typically, E. Coli is diluted into an average 30% of glycerol and then stored in a
freezer to be preserved (Tuttle, 2021).
3. What are the four phases of bacterial growth in a closed system? (5 points)
When it comes to bacterial growth in a closed system, there are four stages to this
process. The first is called the lag phase, which is the initial time frame were the cells of
that bacteria are adapting to the new environment in which they are placed. The second
phase is the exponential stage, which is also names as the log phase. This is where the
cells will begin the process of binary fission in order to reproductive rapidly. The third
phase is the stationary stage, in which the cells stop reproducing, however is continuing
to remain in a metabolically active state. The final stage is known as death or the decline
phase, in which the cells begins to lose its ability to reproductive, therefore the dead
cells begin to out number the live cells leading to decline and eventually death of the
cell.
4. What are the physical and chemical methods of microbial control and what are the
two methods used? (5 points)
When it comes to the control of microbes, there are three main methods which consists
of physical, chemical, and mechanical. These are all methods you can use against the
microbes to control them in terms of negative or positive impacts. When it comes to
physical controls, one could impose aspects such as temperature, pressure, and
filtration. An example of a control I use, is placing my petri dishes into an incubator, I can
physically control the temperature in the incubator which is a way I can control the
microbe. When it comes to chemical controls, they consist of disinfectants, antibiotics, as
well as antiseptics. As discussed in previous assignments, we have talked about the use
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