Identifying Two Unknown Species of Bacteria Essay

An unknown bacterium was handed out by Dr. Honer. The appropriate tests were prepared and applied. The first procedure that was done was the gram stain. Under a microscope, if the gram stain is purple, the bacterium is gram positive, if the stain is red, it is gram negative. The next test was the fermentation tests for glucose, sucrose and

The Methyl Red test is a differential test for bacterial respiration used to differentiate strains of coliform bacteria capable of performing mixed acid fermentation that will lower the pH despite the phosphate buffer (http://faculty.deanza.fhda.edu). Mixed acid fermentation is confirmed by using methyl red as an indicator. It is red ant pH 4.4 and below, yellow at pH 6.2 and above, and orange in between. Red is a positive result reported as (+), yellow is a negative result reported as (-), and orange is negative or inconclusive.

The colonies were smooth, translucent, and had a white brownish color. The Gram stain resulted in Gram positive cocci. After the Gram stain was completed, the bacteria were streaked on a Mannitol-Salt Agar plate and a Catalase test was performed. After these test were completed a Phenol Red Dextrose Fermentation tube was inoculated, and a SIM Tube inoculated.

The first result of importance was the result of the Gram stain. The observations of the unknown bacteria from the slant culture after Gram staining showed that the unknown bacteria were Gram negative bacilli (Image 1). After determining the unknown bacteria was Gram negative, an oxidase test was conducted on a sample from the slant culture. The cotton swap with the sample of bacteria did not change color when the oxidase reagent was applied, thus providing a negative result. With a negative oxidase test, further tests were conducted to determine various characteristics of the unknown bacteria. A MR-VP broth was inoculated with a sample from a slant culture of unknown bacteria. After incubation, the methyl red reagent was added to the broth, and the broth turned red, providing a positive result (Image 2). An EMB agar streak plate was inoculated with a sample from a slant culture of the unknown bacteria, and after incubation, growth was found on the plate, providing a positive result (Image 3). A Citrate agar slant was inoculated, and after incubation, growth was found on the media, providing a positive result (Image 4). A Urea agar slant was inoculated, and after incubation, the agar had changed from a peach color to a bright pink color, providing a positive result (Image 5). Using the flowchart (Figure 1) developed from the Table of Expected Results, the lab partners started at the oxidase test. Given the negative result of the oxidase test, the flowchart is

The next step of the project included preparing a Gram stain to discover the cell shape, arrangement, and if the bacteria is gram positive or

This test is used to detect the hemolytic activity in the bacteria. A darkish green color on the media around the bacteria would represent incomplete hemolysis. A transparent media around the bacteria colony represents complete lysis of the red blood cells. If no change is observed around the bacteria colony then the bacteria is non-hemolytic. For my

There are many reasons for knowing the identity of microorganisms. The reasons range from knowing the causative agent of a disease in a patient, so as to know how it can be treated, to knowing the correct microorganism to be used for making certain foods or antibiotics. This study was done by applying all of the methods that I have been learned so far in the microbiology laboratory class for the identification of an unknown bacterium.

Read in your lab manual about the following agar mediums: Blood Agar (pg 168), EMB Agar (pg 170), Mannitol Salt Agar (MSA)(pg 172) ), MacConkey Agar (pg 174), and PEA Agar (pg 176) to answer the following:

This experiment was conducted to find the genus and species of an unknown bacteria prescribed by the lab teacher, which was unknown bacteria GA3 in my case. Identification of unknown bacteria techniques are used on an every day basis to figure out what type of bacteria it is and to find the best method of how to treat a patient with this bacteria (1). All five “I’s” of Microbiology were used in the testing for the unknown culture. Inoculation was used several times to put the unknown culture into agar plates or into biochemical test tubes. After Inoculation of these tubes or plates, they always were placed into the incubator for further growth and development. Isolation was used to make sure we got the correct bacteria we were testing for. After each further isolation, we gram stained the culture and inspected the culture under a microscope to further help in the identification process of the unknown bacteria. Multiple tests were done on the unknown culture to make sure we were confident in what kind of bacteria the unknown was.

There are many reasons for knowing the identity of microorganisms. The reasons range from knowing the causative agent of a disease in a patient, so as to know how it can be treated, to knowing the correct microorganism to be used for making certain foods or antibiotics. This study was done by applying all of the methods that have been learned so far in the microbiology laboratory class for the identification of unknown bacteria. The identification process can be completed with a series of deferential stains and biochemical tests. Creating a dichotomous key helps to limit the amount of biochemical tests done on an unknown organism and by observation

For the Urease test, I incoluated my Urea test tube with my unkown bacteria from a TSA plate using and inoculating loop. The Urea tube was then incubated at 37 degrees Celsius for 8 days to observe for a color change. The Urea tests for the ability of a bacteria grown in urea broth produces urease. This medium contains the pH indicator phenol red. If urease is produced the pH of the media will raise thus causing the phenol red to change from yellow to a pink color.

Methods and materials The first process of identifying the bacteria was obtaining a TSA plate and using the streak method called the three sector technique. The streak plate is used for the purpose of separating the two bacteria’s and establishing colonies as explained in the lab manual. The two plates were incubated at 37 degrees Celsius for a period of forty eight hours.

In the world of microbiology it is vitally important to be able to discern the identities of microorganisms. Not only is it important in a lab setting but as well as in healthcare in general. Properly identify what strain of bacteria a person has will aid in the proper medicine and dose given. Throughout the semester we have learned about different types of bacteria and certain test that can clearly identify them. The purpose of this lab report is to identify a Gram-positive or Gram-negative bacterium. Using all the knowledge of procedures and lab techniques identify the unknown and discuss all the tests you performed.

The bases of this experiment was to discover the identify of the unknown from three possible specimens: Klebsiella pneumonia, Escherichia coli, and Enterobacter aerogenes. Utilizaing the T streak technique, the bacteria was isolated into pure colonies for further study. The Gram Stain method was used to identity the morhphology of the bacteria such as the shape and whether the bacteria was Gram positive or Gram negative. Biochemical test were also used to help identify the unknown bacteria. The biochemical test used was the Triple Sugar Iron Agar, Sulfur Indole Motility test, Methyl Red test, Voges-Proskauer test, Citrate test, Urease test, and the Gelatin test. After observing the morphology of the bacteria using the Gram Stain method and utilizing all the possible biochemical test, the bacteria was identified to be Enterobacter aerogenes.

The Citrate Test indicates whether or not the bacteria contain the enzyme citrate permease, which is needed to bring citrate into the cell. The media used contains the pH indicator bromothymol blue which is green at a neutral pH level and blue at alkaline pH levels. If the top of the citrate slant has turned from green to blue, the culture is positive for citrate degradation producing alkaline byproducts. If not, the results are negative.