The identification of the bacterial unknown was determined through a series of tests using differential media and a gram stain. These tests revealed information about the motility, the metabolism, and the enzymes of the unknown microorganism. The most basic technique for all tests is called the aseptic technique. This technique is “to prevent contamination of the sample” (Leboffe and Pierce, 2010). This is the first technique taught to students in the lab. Aseptic transfers were done with either an inoculating loop or needle between the stock of microorganisms to a sterile media. Sterile media included tryptic soy broth or tryptic soy agar. To prevent contamination, inoculating loops and needles are usually sterilized in the Bunsen burner flame, but in lab, a micro-incinerator was used instead. Other measures taken to avoid contamination include holding an open test tube at an angle and heating the tube’s lip and surrounding air (Leboffe and Pierce, 2010).
A microscopic examination was usually paired with a stain. For example, a Gram stain can be used to identify the shape of the microorganism and the number of peptidoglycan layers it has. The shape can be and type of cell can be used to determine which genera the unknown bacteria could be classified under.
Differential media was used to “distinguish different species of bacteria” (Madigan, Martinko, Stahl, Clark, 2012). While all species of the bacteria are able to survive on the medium, there are visible differences. Selective media was used to promote the growth of specific bacterial species by inhibiting others. Differential and selective media provide more information than a regular media would.
To distinguish a positive result from a negative result for a test, both positive and negative controls are required because results can be varied.
There is no correct species concept for bacteria. The most widely accepted concept groups species “based on overall genomic similarity and sharing of phenotypes deemed ecologically important” (Vos, 2011). This concept is different than the biological species concept used for eukaryotes. The biological species concept defines a species as a group of organisms in a population that is capable of interbreeding and producing viable offspring in nature. Bacteria species do not undergo sexual reproduction making the biological species concept inadequate to define a bacteria species. Another aspect of bacteria that makes it difficult to define a species concept is the ability of prokaryotes to perform horizontal gene transfer.
I identified the genus and species of an unknown bacterial culture, #16, and I applied the following knowledge of morphologic, cultural and metabolic characteristics of the unknown microorganism according to the laboratory manual as well as my class notes and power point print outs. I was given an incubated agar slant labeled #16 and a rack of different tests to either examine or perform myself; the tests are as follows: Gram Stain; Nutrient Gelatin Test; Carbohydrate Fermentation; Dextrose, Lactose and Sucrose; IMVIC tests; Citrate, Indole, Mythel-Red and Vogues Proskauer test; as well as a Urease and TSI Test.
After 5 days of growth each slant was tested using the gram staining technique to confirm the complete isolation of the bacteria. Both isolations were completely successful. Then each sample of bacteria was subjected to a series of tests for identification.
IDENTIFYING CITROBACTER FREUNDII THROUGH BIOCHEMICAL TESTING. Jebin Jacob November 15th, 14 Naghmeh Hassanzadeh Unknown - 10 Purpose The purpose of this study is to identify an unknown bacterium from a mixed culture, by conducting different biochemical tests. Bacteria are an integral part of our ecosystem.
...imary stain and not pick up the counterstain. Other human errors could have affected the results such as not inverting the plate before putting it into incubation would not allow for bacterial growth. Not pipetting the tube up and down to mix the bacteria that settled at the bottom of the tube before starting the Gram Stain would not allow for an accurate reading because there wouldn’t be many bacteria on the slide. Passing the slide over the bunsen burner too many times, hence killing the bacteria and not allowing for a Gram Stain. If this experiment had to be redone, one improvement would be to allow for more that one plate without a point deduction. Unexpected human errors might interfere with person’s results. Having more than one plate will allow for more accuracy in the results or allow for a person to determine were they went wrong during the experiment.
The purpose of this laboratory is to learn about cultural, morphological, and biochemical characteristics that are used in identifying bacterial isolates. Besides identifying the unknown culture, students also gain an understanding of the process of identification and the techniques and theory behind the process. Experiments such as gram stain, negative stain, endospore and other important tests in identifying unknown bacteria are performed. Various chemical tests were done and the results were carefully determined to identify the unknown bacteria. First session of lab started of by the selection of an unknown bacterium then inoculations of 2 tryptic soy gar (TSA) slants, 1 nutrient broth (TSB), 1 nutrient gelatin deep, 1 motility
Madigan, Michael T. et al. Brock biology of Microorganisms. 13th ed. California: Benjamin Cummings, 2012. Print.
The eighteenth exercise of the laboratory manual titled Unknown Identification and Bergey’s Manual is an experiment to identify an unknown bacterium. In this exercise, a student must randomly choose a numbered bacterium available to the class. The keys in Appendix H, located on the last pages of the book, are the major helpful tools in this exercise because it provides completed steps of tests that needs to be performed in order to distinguish certain bacteria. This means that in this exercise, various types of tests and techniques must be performed to identify the chosen unknown bacterium. The unknown bacterium that I selected was number thirty-nine in which I discovered as the Bacillus megaterium after conducting several tests.
I was given unknown organism #14, in order to find out what organism I had, I had to perform several different biochemical tests to identify it. Starting with the Gram stain test, which is performed to differentiate Gram-positive and Gram-negative cells. After staining, when observed through the microscope Gram-positive cells are a purple color with thick peptidoglycan cell walls. Gram-negative cells are a pinkish/red color with thinner cell walls. (handout G. s.) My organism was observed to be pinkish rod shaped meaning it is Gram-negative bacteria.
To perform this test we first did a Gram stain on our organism to determine if it was gram-positive or gram-negative. After this we performed a mixed Gram stain by incorporating our organism with a known bacteria that stained opposite of unknown. We were given the size of the known bacteria and performed a comparative analysis under the microscope to determine the size of our unknown. In my case the control was a gram-negative bacteria Escherichia coli.
Some bacteria are harmless and are part of our normal flora. While other bacteria are capable of causing diseases or death. In order to determine what type of bacteria is present, a set of biochemical test must be performed. With biochemical testing, the ability to identify the bacterium responsible for causing illnesses or diseases. Once this is determined, other tests can be performed to discover what treatments would work best in ridding the illness causing bacteria.
1. Living things can be either uni-cellular (one cell) or multi cellular. A bacteria is one type of unicellular.
Results from Gram staining procedures were provided a week later; hence, a dichotomous (a flowchart that is used to identify bacteria based on its taxonomic classification) was constructed based on a total of 10 possible unknown bacterium. The bacteria were then separated based on its Gram reaction; leading to two subcategories, including Gram positive and Gram negative. Both subcategories were then divided into two separate categories based on bacteria morphology, including rod and cocci shaped. A series of metabolic test were then selected strategically based on metabolic results provided by Dr. McLaughlin (See attached chart for possible results). The metabolic test for Gram positive rod
A scientist named Christian Gram invented a technique called gram staining by which is colorized that is separated into two groups Gram positive and Gram negative. In bacteria most have rigid cell walls in which is accountable for the shape of the organism. Within the cell wall of the bacteria it identifies whether the bacteria is gram positive or negative. In the cell wall there a lot of difference that determines the bacteria is gram is positive or negative for example the thickness and the amount of peptidoglycan later presences or absence of outer membrane and teichoic acids. Where gram positive have two later and negative has three layers. Gram positive the cell wall is a single layer, primarily composed of peptidoglycan, does not contain outer membrane and contains negatively charged teichoc acids, this result of a blue color indicator. For gram negative is more complex that the Gram positive, its membrane lies outside of th...
Individual colonies are better to work with because the organism can be aseptically transferred to another media, to create a pure culture. This helps narrow down specifically the type of organism of interest (Carson 19). During the culturing process, there are a lot of information that can help deduce the type of organism that are cultured. Some of the characteristic that are used in the identification of cultured organism are known as colony morphology (Carson 20). Colony morphology take in consideration the following characteristic of the culture: Size (small, medium, large), pigment (coloration), optical properties (opaque, translucent, transparent), surface (shiny, smooth, and mucoid) form (circular, irregular, and rhizoid), margin (lobate, undulate, filamentous or serrate), and elevation (flat, raised, umbonate, or convex) (Carson 20). In a more microscopic level, cellular characteristic may apply to the individual cell within a colony, otherwise known as cellular morphology. The agar plate were used during this experiment have selective and differential properties that help to differentiate between organism. A selective media will actively select for or against a particular
The term “microbiology” refers to the branch of study that deals with microorganisms. Microbiology is extremely important in today’s time for the crucial information that the study provides. Human’s have had a long and cruel history of disease and sickness, for example the bubonic plague, but microbiology gives scientists the ability to observe, study, and prevent sickness like the bubonic plague to ever happen again. At the center of microbiology lies the bacterial cell, one that differs from those of a plant or animal because it lacks a nucleus and membrane-bound organelles which, in turn are traded for pili, flagella, and in some cases a cell capsule. Bacteria that are capable of causing illness or disease are called pathogens, pathogens work by releasing toxins in the body or directly damaging the host’s cells. An article by Lise Wilkinson explains that the earliest categorizations of bacterial cells first occurred in the late eighteen-hundreds to the early nineteen-hundreds by scientists (at the time) O. Muller and C. Ehrenburg (Wilkinson, 2004). The observation and identification of unknown bacteria that emerge is crucial because these new bacteria might be pathogenic and cause illness so it is very important that the bacteria is identified as soon as possible in order to either prevent the upcoming illness or treat it. While the common person is unable to identify if they are carrying bacteria (which is very likely), specialized tests that are ran in a lab can identify different types of bacteria and can even help