Essay On Unknown Bacteria

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.

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 purpose of this lab was to identify two unknown bacteria cultures using various differential tests. The identification of these unknown cultures was accomplished by separating and differentiating possible

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.

Citrobacter Freundii is a species of bacteria that can be potentially harmful to humans. It is known to cause meningitis by protruding into the brain and replicating itself (1). The Citrobacter species has also been found as a cause of some urinary tract infections, diarrhea, and even gastrointestinal diseases and symptoms (3). C. Freundii can be located in a wide variety of soils and water (3). Lastly, it is also the cause of many nosocomial infections due to its presence in water (1).

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

A Dichotomous Key was studied to identify bacteria and their relationships. Some of the organisms at the end of the Dichotomous Key had viable characteristics that separate them from different groups, and those that did not students learned how to further classify them. A Dichotomous Key is used to narrow down the search for the unknown organism tested. It is organized by phenotypic characteristics of organisms and conducts a systematic way of identifying the other unknowns. In the lab students were given a tube labeled with a number. Instructions were given to conduct a Gram stain to begin the search followed by the use of a Dichotomous Key and photos as resources to carry out the search. Instructions read to isolate and identify the unknown bacterium with both differential and selective tests to positively identify the given unknown organism. Differential tests used specifically for this unknown microorganism was BEA (Bile Esculin Agar), which interpreted results by the hydrolysis of esculin when the media is blackened around

were scrapped from the teeth and the second was an unknown given. It resulted that the unknown

After gaining some knowledge about bacteria, we were giving an investigating bacteria growth lab to do. Our objective was to observe the conditions required for bacteria to grow and to test the effectiveness of substances that may be antibacterial, disinfecting, and or sanitizing. My group and I began our procedure by gathering all the bacteria by swabbing our necks and mouths. After this, we inoculated the culture by rubbing the bacteria on the agar, a nutrient rich gel made from sea kelp, on the bottom side of the container where we grow bacteria, the Petridish. We hoped for the results to come back with little or even no colonies and an immense zone of inhibition around the tiny circle cut out of filter paper covered in toothpaste, Neosporin, and Chlorhexidine Gluconate 4% Solution.

The objective of these “unknown” experiments was to take a mixed culture, which contains two unknown species, and identify those species through a series of tests. The group was informed that one species of bacteria would be a gram-negative bacillus and the other would be a gram positive coccus. The tests to be conducted ranged from streak plate isolation to biochemical tests. Each test to be conducted was discussed and agreed upon by all group members. The results of each test were analyzed by the group and led to selection of the next test that would further narrow the possible identity of the unknown species.

MacConkey agar is a selective agar which is a good medium to use for E. coli since it does not contain bile salt and crystal violet, it contains a PH indicator which gives it colour red, it is also a disaccharide known as lactose. Lactose is a sugar molecule that is derived from Galactose and glucose . MRS agar was developed by de Man, Rogosa and Sharpe who decided it was best to have a different media which can be used for cultivating bacteria, this media is nonselective and lactobacillus can grow on it, they found out that acetate and citrate helps the growth of lactobacillus (De MAN, ROGOSA, and SHARPE, 1960). Gram staining was first used by Hans Christian Gram who devised this method to help identify bacteria, Gram positive bacteria have a bigger peptidoglycan and smaller lipid content in comparison to Gram negative bacteria. This was first tested in 1882 and later published in 1884, it the most common technique used by microbiologist. Being able to manipulate bacteria gives us an advantage to understand its structure, function, time taken to asexually reproduce etc. This information can be used to either coming close to curing the bacteria or changing the bacteria to

In this lab experiment, students had to create a growth curve for E. coli. The E. coli growth curve would illustrate the progression of the population of E. coli a set time period. In this case, the growth curve depicted the population of E. coli over a 12-hour period. The growth curve for E. coli was created from the absorbance levels, the optical density(OD), recorded from the spectrophotometer.

Determination of the bacteria being a lactose fermenter or non fermenter is done through the growth on the MacConkey agar. Knowing this allow for the student to perform the necessary tests to determine which lactose fermenter was present in the sample. The Indole test allows for the determination of whether the unknown bacteria is Escherichia coli because this genus and speices is the only lactose fermenter that will produce a positive result here. Moving onto the Methyl red test this indicates glucose fermentation, more specifically microbes that produce mixture of acids as a result of fermentation. The Voges-proskauer tests for glucose fermentation, specifically organisms whose acid is converted to acetoin. The Citrate test differentiates an organism’s ability to use citrate as its only carbon source. The urea broth culture detects the enzyme urease, which allows break down of urea producing acid, which causes a noticeable change in color. The final test is the motility test to determine if the bacteria has the capacity of movement beyond the point of

Organism one demonstrated irregular, flat, wavy, medium sized and cream coloured colony morphology when viewed on agar plate, however limited conclusive data can be obtained from these observations alone. In order to provide further information for diagnosis, additional culturing was conducted on a range of selective and differential media types including Horse Blood, MacConkey, Mannitol Salt and Brilliant chromogenic UTI agar’s. This demonstrated the organism was non-haemolytic, lactose fermenting, as evident through a red colony formation on the MacConkey agar, and unable to survive in high salt concentrations, as indicated through the lack of growth on Mannitol Salt agar. The

6. With one hand, take the inoculating loop and pass it through the flame until it is red- 7. With the other hand, open one of the Petri dishes slightly.