Use standard laboratory procedures, like cell staining, culturing and DNA sequencing to further narrow down your identification. Bacteria are generally grouped into species according to their physical and metabolic characteristics, rather than their genetic relationships to one another. Positive or Negative Eubacteria are the so-called true bacteria. They're distinct from archaea or archaebacteria, which form a separate kingdom.
The identification of these unknown cultures was accomplished by separating and differentiating possible bacteria based on specific biochemical characteristics. Whether the tests performed identified specific enzymatic reactions or metabolic pathways, each was used in a way to help recognize those specifics and identify the unknown cultures.
Each of the tests performed provided some key information about the bacteria in question and how it functions. The tests performed and what constitutes a positive and negative test are as follows. The oxidase test was performed only on gram - bacteria and was used to test for the presence of cytochrome oxidase.
Living bacteria were placed on a paper towel and saturated with a chromogenic reducing agent. Within seconds the reagent, acting as an artificial electron acceptor, will turn purple if oxidized cytochrome oxidase is present, indicating a positive test.
If no color change is observed, no cytochrome oxidase is present and the test is negative. This test is used to detect the presence of catalase, which helps to breakdown toxic hydrogen peroxide produced from the transport of high-energy electrons directly to oxygen.
Catalase is tested for by adding hydrogen peroxide to the culture, and looking for the production of gas bubbles. If gas bubbles appear immediately, the culture is catalase positive. However, if no bubbles are observed, the culture is negative for catalase. Lactose and sucrose sugar fermentation were tested using a broth containing the respective sugar compound, phenol red, and inverted Durham tubes.
The broths were inoculated with the unknown bacteria cultures and incubated for growth. If fermentation of the sugar molecules was carried out, the pH in the tube would be lowered, and the phenol red would be converted to yellow under the acidic conditions.
Thus, the conversion of the originally red broth to yellow signifies a positive test, indicating the bacteria can ferment using either lactose or sucrose.
If the broth remains red, fermentation on these sugars was not possible and the test is negative. The production of gas by the fermentation was monitored using the inverted Durham tubes. The iron agar slant was used to test for the fermentation of glucose and lactose, as well as the production of H2S.
Gas production was also monitored, looking for fissures produced by production of gas during fermentation. The conversion of the originally red slant and butt of the agar to yellow indicates that glucose fermentation took place.
H2S could have been produced by the reduction of thiosulfate contained in the media. Production of this compound will cause a reaction to occur with ferrous sulfate and will result in the production of a black precipitate.
Thus, the culture is positive for H2S production if a black precipitate is seen and negative if one is not observed. Nitrate reduction was tested for by inoculating a nitrate broth with the unknown cultures, and allowing growth to take place.
An inverted Durham tube was used again to test for the production of any gas. If nitrite is present, the medium turns red, indicating a positive test. However, if the medium does not change, a second test is performed to see if nitrite was further reduced.
In this second test, zinc powder is added to the broth to catalyze the reduction of any nitrate present to nitrite.UNKNOW BACTERIA LAB REPORT UNKNOWN 36 Introduction The purpose of this lab was to identify two unknown bacteria from a mixed culture.
The reason for identification of unknown bacteria was to help students recognize different bacteria through different biochemical tests and characteristics. HOW TO WRITE AN UNKNOWN LAB REPORT IN MICROBIOLOGY GENERAL Unknown reports in microbiology are written in scientific format. Scientific writing is written differently from other types of writing.
The results. Madelyn Barr. October 11, Unknown I Lab. Unknown # Unknown I Lab Report. Abstract The “Unknown I Lab” was performed in order to evaluate the student’s ability to identify an unknown organism based on a series of tests and observations. Accurately identifying microorganisms is important for a variety of reasons.
HOW TO WRITE AN UNKNOWN LAB REPORT IN MICROBIOLOGY GENERAL Unknown reports in microbiology are written in scientific format. Scientific writing is . unknown lab report for microbiology An unknown bacterium was handed out by the lab instructor.
The methods that have been learned so far in identifying bacteria were applied to this unknown. Example of a Microbiology Unknown Lab Report by Taylor Autry Introduction.
In this paper I will discuss the processes of how I came to find my two unknown bacteria.