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.
The isolate possesses some enzymes required for hydrolytic reactions. Hydrolytic enzymes found to be secreted from the bacterium, are -amylase, casein, and PYRase. In the starch hydrolysis and casein tests, there was a zone of clearing around the bacterium, which was indicative of the secreted enzymes necessary to break down starch and casein. In the PYR test, the presence of PYRase was detected by a color change to red on the PYR disc after the addition of the PYR reagent (p-dimethylaminocinnamaldehyde). Hydrolytic enzymes for which the EI tested negative were urease, gelatinase, and DNAse. In the Urea Hydrolysis test, it was observed that the urea broth did not have a color change, indicating that there was no urease secreted to break down urea in the broth. Similarly, there was no gelatinase present to break down gelatin in the Gelatin Hydrolysis test, so the nutrient gelatin remained solid. It was concluded that the EI does not possess DNase because there was no clearing zone around the bacteria, indicating that DNA had not been
The first day an unknown sample was assigned to each group of students. The first test applied was a gram stain to test for gram positive or gram-negative bacteria. The morphology of the two types of bacteria was viewed under the microscope and recorded. Then the sample was put on agar plates using the quadrant streak method for isolation. There were three agar plates; one was incubated at room temperature, the second at 30 degrees Celsius, and the third at 37 degrees Celsius. By placing each plate at a different temperature optimal growth temperature can be predicted for both species of bacteria.
In this lab project, the microbiology students were given 2 unknown bacteria in a mixed broth each broth being numbered. The goal of this project is to determine the species of bacteria in the broth. They had to separate and isolate the bacteria from the mixed broth and ran numerous tests to identify the unknown bacteria. The significance of identifying an unknown bacteria is in a clinical setting. Determining the exact bacteria in order to prescribe the right treatment for the patient. This project is significant for a microbiology students because it gives necessary skills to them for future careers relating to clinical and research work.
They can be found anywhere and identifying them becomes crucial to understanding their characteristics and their effects on other living things, especially humans. Biochemical testing helps us identify the microorganism present with great accuracy. The tests used in this experiment are rudimentary but are fundamental starting points for tests used in medical labs and helps students attain a better understanding of how tests are conducted in a real lab setting. The first step in this process is to use gram-staining technique to narrow down the unknown bacteria into one of the two big domains; gram-negative and gram-positive. Once the gram type is identified, biochemical tests are conducted to narrow down the specific bacterial species.
After the end of the experiment the unknown 10 sample was Staphylococcus epidermidis. Came to this conclusion by first beginning with a Gram Stain test. By doing this test it would be easier to determine which route to take on the man made flow chart. Gram positive and gram negative bacteria have a set of different tests to help determine the unknown bacterium. Based on the different tests that were conducted in lab during the semester it was determined that the blood agar, MSA, and catalase test are used for gram positive bacteria while Macconkey, EMB, TSI, and citrate tests are used for gram negative bacteria. The results of the gram stain test were cocci and purple. This indicated that the unknown bacteria were gram positive. The gram stain test eliminated Escherichia coli, Klebsiella pneumonia, Salmonella enterica, and Yersinia enterocolitica as choices because these bacteria are gram negative. Next a Blood Agar plate was used because in order to do a MSA or a Catalase test there needs to be a colony of the bacteria. The result of the Blood Agar plate was nonhemolytic. This indicated that there was no lysis of red blood cells. By looking at the plate there was no change in the medium. Next an MSA test was done and the results showed that there was growth but no color change. This illustrates that the unkown bacteria could tolerate high salt concentration but not ferment mannitol. The MSA plate eliminated Streptococcus pneumonia and Streptococcus pyogenes as choices since the bacteria can’t grow in high salt concentration. Staphylococcus aureus could be eliminated because not only did the unknown bacteria grow but also it didn’t change color to yellow. Lastly a Catalase test was done by taking a colony from the Blood Agar plate...
I also inoculated a tryptic soy broth (TSB), a nutrient gelatin deep, a motility agar deep, a fluid thioglycollate medium (FTM) tube, and a TSA plate with my unknown culture. All of these inoculated media were incubated until the next class period (about 48 hours). Then when I came to class most of my inoculated tubes and my streak plate appeared to have growth. The next step I took was making a gram stain to determine the gram reaction and cellular morphology of my unknown. I used my working slant to do this, after careful examination of the gram stain, I learned that my unknown was a gram-positive bacterium. I then preceded by making a negative stain to see the size of the cells of my unknown bacteria. The cell shape was cocci and the cells occurred in clusters of tetrads. After discovering that my unknown bacteria was gram-positive cocci, I turned to page 207 of the lab manual to narrow down my options, there was only four out of the gram-positive list that were
Phenotypic methods of classifying microorganisms describe the diversity of bacterial species by naming and grouping organisms based on similarities. The differences between Bacteria, Archaea and Eukaryotes are basic. Bacteria can function and reproduce as single cells but often combine into multicellular colonies. Bacteria are also surrounded by a cell wall. Archaea differ from bacteria in their genetics and biochemistry. Their cell membranes are made with different material than bacteria. Just like bacteria, archaea are also single cell and are surrounded by a cell wall. Eukaryotes, unlike bacteria and archaea, contain a nucleus. And like bacteria and archaea, eukaryotes have a cell wall. The Gram stain is a system used to characterize bacteria based on the structural characteristics of their cell walls. A Gram-positive cell will stain purple if cell walls are thick and a Gram-negative cell wall appears pink. Most bacteria can be classified as belonging to one of four groups (Gram-positive cocci, Gram-positive bacilli, Gram-negative cocci, and Gram-negative bacilli) (Phenotypic analysis. (n.d.).
The purpose of this project was to identify unknown bacteria species from a mixed culture. The two unknown species were initially plated onto Tryptic Soy Agar (TSA), Eosin Methylene Blue (EMB), Mannitol Salt Agar (MSA), and blood agar plates to distinguish between the two different bacteria using colony size, color, shape, and growth characteristics. By identifying and inoculating the differing types of colonies, the two unknown bacteria were purified and able to be tested
Bacteria are single celled microbes. Bacteria reproduce by binary fission. In this process, the bacterium, which is a single cell, divides into two identical daughter cells. Binary
For bacteria to be utilised to its full potential and to meet the demands of quantity need for the production of foods and medicines it is key that experts are able to firstly distinguish what type bacteria is need for a certain production and secondly, and very importantly, how to reproduce that bacteria to create enough of it needed for mass production of a certain product.
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
They also describe microbes as organisms that are often too small to be seen without the aid of a microscope. Microbes, also known as microorganisms, can be broken down into four classifications that are bacteria, viruses, fungi, and protozoa.
The abnormal presence of bacterial growth can be inspected under a microscope. If the organism inspected is not the bacteria used in the experiment, it means that the growth of the bacterial culture investigated is absent. By using this method, contamination by foreign substances in the surrounding air can be ruled out and the results would be more accurate.
It is a single-celled organism that is not visible to the human eye, which means it can only be seen with a microscope. Bacteria are classified as Prokaryotes. They make their own food from the sunlight and can absorb food from the materials that they live on.