Question

Labster - Bacterial Growth Curves Extension

Learner Outcomes
BI280-04 Compare and contrast the growth and reproduction of microorganisms.
BI280-04.02 Compare the phases of microbial growth and describe the relation to generation time.
Lab Extension
At 82% progress is this lab simulation you are asked to create your own experiment.

What observation or questions are you investigating with this experiment?

Write down your hypothesis.

Describe the experimental design .

Define the term control group. Which tube is the control?

Define the term experimental/treatment group. Which tube is the experimental/treatment group?

Define independent variable. In this experiment what is the independent variable?

Define dependent variable. In this experiment what is the dependent variable?

. Describe the data collected from the experiment. Include the temperatures you tested and how the growth curves differed. Describe differences (if any) in the lag phase, exponential phase, stationary phase, and death phase. At this point do NOTinterpret the results.

Was your hypothesis supported or rejected?

Interpret the results to draw a conclusion. Think about WHY you had the results you did and HOWthis relates to temperature as a limiting factor in bacterial growth.

Answer 1

Compare and contrast the growth and reproduction of microorganisms?

Microbial Growth:

Microbial Growth is defined as increment in the bacterial cell number rather than size. This is dependent on accessibility of nutrients and their passage into cells, environmental factors like aeration, oxygen supply, temperature and pH and chemical requirements like nitrogen, sulfur, trace elements. The growth is also dependent on media that is required for the development like complex media, or simple media, or special media required for growth of specific bacteria (Selective media). The growth of bacteria is dependent on doubling time of the cells to divide

Reproduction of microorganisms:

During the bacterial growth phases, microorganisms go through reproduction several times by asexual process called as binary fission producing the increased numbers in bacterial population. In this process, the chromosomal DNA doubles thereafter the bacterial membrane and cell wall propagate inside to meet one another and divide the cells in two. There are few class of bacteria that use uncommon forms of cell division to reproduce. These organisms grow to more than double their cell size and practice multiple divisions to produce multiple offspring cells. Some other bacterial cells reproduce by budding for example Cyanobacteria.

Phases of microbial growth

Microbes divide by binary fission and undergo 4 different phases. They include Lag, Log, Stationary and Death Phases. In LAG phase, the bacterial cell population remains the same as the bacteria become adapted to new atmosphere. Metabolic activity takes place and new cells are being produced. Later cell enters Log phase also called as Exponential phase. In this phase cells divide through binary fission and doubles in number at each generation time. In Stationary phase, cell growth begins to deteriorate as the existing and available nutrients become exhausted and waste products start to gather. Bacterial cell growth reaches a plateau where the same number of dividing cells are equal the same number of cells dying. This leads to no overall population increment. Finally cell enters death phase where nutrients are least available and waste accumulation increase and cell death rises. During this phase the cell completely fails its ability to reproduce. In the graph the curve bends downwards.

The control groups are also called as comparison group is used in an experimental design where we look into the parameters and guarantee that experiment mechanizes correctly. It is a way to ensure that the treatment given is producing the results. Control groups are also two types: positive or negative control groups. In Positive control groups the conditions of the experiment are set to agreement that it produces a positive result. A positive control group can lead to the experiment is operative appropriately as calculated whereas Negative control groups are group of experiments where conditions of experiment are fixed to cause a negative consequences.

An experimental group also termed as treatment group is a group which accepts treatment of a drug or chemicals in an ongoing experiment.

An independent variable is a variable that viewpoints alone and is not changed by other existing variables that are being tried to measure.

A dependent variable is what we want to measure in experiment and what is affected during the experiment. The dependent variable replies to independent variable and is so called dependent since it is dependent on the independent variable. For example, to see how stress affects heartbeat, the independent variable will be stress and dependent variable will be heartbeat.