1. Why are biochemical tests used to identify microbes? Biochemical tests are used to identify microbes in the laboratory to aid in pinpointing the different groups of bacteria. The bacteria vary in the cellular morphology and staining properties as well as structural and metabolic properties. Using biochemical testing, it permits a keener study at related organisms. In addition, the use of numerous color changes that occur with the test, allow to for a rapid identification of comparisons and variances of the bacteria that are tested. 2. What is mixed-acid fermentation? How Methyl red is used to determine if a microbe has undergone mixed-acid fermentation? Mixed acid fermentation is an anaerobic degradation of pyruvic acid that results in …show more content…
Why are methyl red and Voges-Proskauer tests often performed together? Methyl red (MR) and Voges-Proskauer (VP)tests are often performed together because MR is one half and VP is the other half for a complete test even though they are two separate tests. The principle of these two tests together, is to pinpoint the glucose, peptone and phosphate buffer. Various organisms will be able to conquer the buffering capability of the media by generating significant amounts of a stable acid end product, consequently reducing the pH. This requires at least a minimum of 48 hours of …show more content…
The methyl red (MR) test and the Vogues-Proskauer (VP) test. The MR test is used to reveal whether the E. coli or S. epidermidis produced high levels of acid during the glucose fermentation. When the high levels of acid are present it will turn the organism red. If it is low, it will remain yellow. It this experiment, both cultures turned red. The VP portion of the experiment is to identify acetoin. Next, drops of Barritt’s Reagent A and Barritt’s Reagent B are added to the E. coli and the S. epidermidis vials. Then, allow the vials to sit undisturbed for 30 minutes. A positive result can be observed in both vials which is a formation of a thin red surface layer. Concluding that the E. coli and S. epidermidis are competent enough to execute a mixed acid
One bacterium was gram negative. It underwent four different tests. These tests were the EMB test (Eosin Mehylene Blue), the Sulfur Indole Motility (SIM) test, the Urease test, and the Simmon’s Citrate Utilization test. The EMB test checks for a bacteria’s ability to ferment lactose. This test is accomplished by placing the bacteria on Eosin Methylene Blue agar. The agar is selective for gram negative bacteria and those bacteria that can ferment lactose will have colored growth, usually a metallic green sheen.
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...
These labels indicated the lactose solution that was be placed into the mini-microfuge tubes. The varying lactose ph solutions were obtained. The four miniature pipets were then used, (one per solution,) to add 1mL of the solution to the corresponding mini-microfuge tubes. When this step is completed there were two mini-microfuge tubes that matched the paper towel. Then, once all of the solutions contained their respective lactose solutions, 0.5mL of the lactase enzyme suspension was added to the first mini-microfuge tube labeled LPH4 on the paper towel, and 4 on the microfuge tube. As soon as the lactase enzyme suspension was added to the mini-microfuge tube, the timer was started in stopwatch mode (increasing.) When the timer reached 7 minutes and 30 seconds, the glucose test strip was dipped into the created solution in the mini-microfuge tube for 2 seconds (keep timer going, as the timer is also needed for the glucose strip. Once the two seconds had elapsed, the test strip was immediately removed, and the excess solution was wiped gently on the side of the mini-microfuge tube. The timer was continued for 30 addition seconds. Once the timer reached 7:32 (the extra two seconds accounting for the glucose dip), the test strip was then compared the glucose test strip color chart that is found on the side of the glucose test strip
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
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 independent variable for this experiment is the enzyme concentration, and the range chosen is from 1% to 5% with the measurements of 1, 2, 4, and 5%. The dependant variable to be measured is the absorbance of the absorbance of the solution within a colorimeter, Equipments: Iodine solution: used to test for present of starch - Amylase solution - 1% starch solution - 1 pipette - 3 syringes - 8 test tubes – Stop clock - Water bath at 37oc - Distilled water- colorimeter Method: = == ==
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
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
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. Materials and Methods/Results Upon receiving the Microorganism (M.O.) #16, I prepared a slide by cleaning and drying it. Then, using a bottle of water I placed a sterile drop of water on the slide and used an inoculating loop, flame sterilized, I took a small sample of the unknown growth in my agar slant and smeared it onto the slide in a dime sized circle and then heat fixed it for ten minutes.
Gram stain is one of the most important stains in determine the morphology and cell wall composition of the bacteria. The stain is positively charged and is attracted to the negatively charged surface of the bacteria; which produces the purple or red color of the gram stain. The gram stain results of unknown KK revealed that the bacteria species were gram-negative, red/pink, and rod shaped. Therefore, a MacConkey agar test will be conducted in order to differentiate two classes of gram negative
Their table had 15 mL glucose, 10 mL RO water, and 10 mL of yeast which they then placed in an incubator at 37 degrees Celsius. In conclusion, I feel that the absence of RO water in the flask made the enzymes work a little harder than when the RO water was in the mixture of the flask. Comparison #4 is between the Controlled Table and Table #5. The mixture for that table’s flask was 15 mL Sucrose, 10 mL of RO water and 10 mL of yeast, which the flask was then placed in an incubator at 37 degrees Celsius.
There were five test solutions used in this experiment, water being the control, which were mixed with a yeast solution to cause fermentation. A 1ml pipetman was used to measure 1 ml of each of the test solutions and placed them in separated test tubes. The 1 ml pipetman was then used to take 1ml of the yeast solution, and placed 1ml of yeast into the five test tubes all containing 1 ml of the test solutions. A 1ml graduated pipette was placed separately in each of the test tubes and extracted 1ml of the solutions into it. Once the mixture was in the pipette, someone from the group placed a piece of parafilm securely on the open end of the pipette and upon completion removed the top part of the graduated pipette.
Microbes are major key components in both are homes and industrial food preparation. There are number of lactic acid which is a form of bacteria which is a large group of beneficial bacteria used in certain foods while they are getting prepared such as yogurt, cheese, sour cream, butter milk and other type of fermented milk products. Things such as vinegars are produced by bacterial acetic acid fermentation. Yeast is also major use in the making of beer and wine and also for the leaving of breads. This also involves fermentations to convert corn and other vegetable carbohydrates to also make beer, wine or gasohol but also bacteria is the agents of are other foods. Other fermented foods will include things such as soy sauce, olives and cocoa. (Microbes and human life, 2013) Single cell proteins are known as dried cells of microbes which are used in protein supplement shacks. They are also called “novel food” and “minifood”. The production of this requires micro-organisms which then serve as the protein source and then the substrate which is biomass which they grow on them. There are a number of both these sources that we are able to use for the production of single cell protein (SCP). The micro-organisms used belong to the following groups of Algae, Fungi and bacteria. (Slide Share, 2012)