Optimum Growth Temperature for Streptococcus epidermidis Katy Essay

Optimum Growth Temperature for Streptococcus epidermidis

Katy Dangal, Candis Barrientez, Angie Wright

Instructor: Dr. Dakota Jackson



Often when we heard the word bacteria, we think of it as something bad but in reality, the bacteria can be both positive and negative which can have big impact on our body and environment. Different bacteria have an optimum growth temperature. We wanted to look at staphylococcus epidermidis and find out what it’s optimum growth temperatures, so we grew S. epidermidis in three temperature (20 °C, 40 °C, 60°C) which was cold, moderate and extreme.

After the data was collected, we plotted those data on graph and compare the absorbance level at each temperature. The graph result shows that the S. epidermidis grew the best around 40 °C which was closed to human body temperature.


Cell is the smallest unit of life and all of known life on earth fall into three different domain which are Archaea, Bacteria and Eukarya. Any organism in Archaea and bacteria are known as prokaryotes and any organism in Eukarya are known as eukaryotic.

Prokaryotic and eukaryotic share lot of similarities and differences between them. Both the prokaryotic and eukaryotic are composed of cell in which each cell encircle by cell membrane and they both also have ribosomes. The prokaryotic cell reproduce through the process of cell division which is called the binary fission while eukaryotic cell used a different process of cell division which I known as mitosis which included cell cycle of growth and development. Staphylococcus epidermidis is a Gram-positive bacterium, and epidermidis is one of over 40 species which belong to the genus Staphylococcus. This bacterium is commonly found on human skin, and while generally harmless, S. epidermidis has the potential to cause a host of undesirable symptoms in us. S. epidermidis can also be positive to human body because they can help us protect from other harmful bacteria like staphylococcus aureus which can cause skin infection. Did you know that Staphylococcus is also used to make biofilms which is used on surgery and many other procedures? This is why it is important for us to understand what environment effect their growth and what don’t. (Pavlovsky 2015). The purpose of conducing this experiment was to find out the optimal growth temperature of staphylococcus epidermidis. There was a similar experiment which was conducted by Ketter 2018 in which they were able to find out how blood platelets can be stored while preventing S. epidermidis from growing on it. While working on it they also find out that the temperature play crucial role on S. epidermidis growth. We perfume this experiment while using an article as a reference in which they look at different pH levels and temperatures. (Stavropoulous 2018) For this experiment, three different temperatures were chosen which was high, low, and moderate temperatures. The reason these temperatures were chosen was because bacteria can grow on extreme temperatures which could be extremely cold or hot, so we wanted to know which temperature will be ideal for growing staphylococcus epidermidis.


This experiment was conducted in the TCC Science lab under lab instructor supervision. The experiment started with 250 mL of preheated fresh sterile TSB media and then we transfer 4mL of media into a new cuvette. This new cuvette with 4Ml of media was used as a blank for this experiment. Once the blank was made, we then transfer 10 mL of overnight culture S. Epidermidis to the rest of preheated fresh preheated sterile media. We then transfer the 4 mL of inoculated broth to clean cuvette and measure it’s absorbance by inserting it into spectrometer which was blanked and set at 650 nm. We measure the absorbance at time 0 to 20-minute gap to recheck the bacteria growth. Next, we placed the remaining culture in water bath and setting at 20? for 20 minutes. The absorbance was measure from time 0 to every 20 minus which took total of 80 minutes for each temperature. We had three trials at each temperature in which we repeated this process on all three of our temperature which was 20°C, 40°C, and 60°C. Once we collected all the data, we then calculated the average absorbance reading from three trials of each temperature. We then plotted that data and created a line graph which shows absorbance reading of all three temperature.


As we were conducting the experiment, we got to see the highest absorbance around 40°C.

Table 1: Average absorbance at 20°C, 40°C, and 60°C.

Time (min) Absorbance 20°C Absorbance 40°C Absorbance 60°C.

0 0.000 0.000 0.000

20 0.106 0.297 0.204

40 0.105 0.310 0.137

60 0.101 0.334 0.075

80 0.112 0.400 0.123



While looking at result we as a group came to conclusion that the optimal growth temperature for staphylococcus epidermidis is 40°C. We saw the highest absorbance reading at 40°C as we were expecting to see. Our data show similarity with other experiment which was conducted by Stavropoulous 2018 in which they came to conclusion that bacteria need have optimal growth on specific temperature. Which mean the temperature 20°C was too cold for them but we were surprised to know that they did have a decent growth on 60°C. Matter of fact they grew well on first 20 minutes of 60°C which you can see on graph above. The absorbance did went down after the first 20 minutes. Which mean the 60°C was too warm for S. epidermis to grow. But this unexpected data made me remember something which was that there are some bacteria which tend to survive on extreme temperature as well.

Still stressed from student homework?
Get quality assistance from academic writers!