Microbiology Study Questions - ProProfs Quiz
image result-interpretation-of-catalase-test-and-examples- AC01A8. Bubbles= catalase positive. no bubbles= catalase negative. Oxidase test. Entry Quiz · Purpose · Structuring the Discussion Lactobacillus is a gram positive, catalase negative, oxidase negative, endospore forming, rod Pediococcus (3) is a gram positive, non-motile, catalase and oxidase negative, .. "Relationships between biochemical and quality-related characteristics of breads, resulting. Apr 29, Microbiology Quizzes & Trivia. Study quesitons for the production of: A. Indophenol oxidase. B. Nitritase. C. Lecithinase. D. Catalase.
It was also demonstrated by Hamad 18 that gram negative, catalase positive, rod shaped bacteria are also present but are contaminants from the air. Throughout the fermentation process a small number of Leuconostoc species are the first to grow. Leuconostoc creates an acidic environment through the slow production of lactic or acetic acid depending on whether conditions are either aerobic or anaerobic.
Enzymes - MCQ topic quiz - Lesson element (DOC, 896KB) 21/03/2016
This initiates the growth of a large number of species of Lactobacillus, between the pH range of 4. In the final stages of fermentation, a small number of species of Pediococcus starts to grow as they can tolerate highly acidic environments 13, Corsetti et al demonstrated 1 that by-products produced by Lactobacillus, in particularly, L.
As a result, sourdough breads have a longer shelf life. Species other than Lactobacillus and yeast can be found in sourdough bread. The majority of these include: Pediococcus, a gram positive, non-motile, catalase and oxidase negative, spherical bacteria that grow in pairs or tetrads 21 ; Lactococcus, which are non-spore forming, non motile, gram positive, catalase and oxidase negative spherical bacteria 18 ; and Weisella, which are, gram positive, catalase negative, non motile short rods that grow in pairs The conditions it is grown in need to be adjusted to promote Lactobacillus growth and inhibit the growth of other micro-organisms.
Acidity is also another important consideration, which, for optimal growth, should be maintained in a pH range of 4. This study was performed with the aim of isolating Lactobacillus from sourdough bread, as a pure culture. Sourdough is a good sample to use as it contains a large number of Lactobacillus species so there is a higher likelihood of isolating it as a pure culture. Also Lactobacillus metabolism alone will assist in inhibiting other bacteria from growing and in this way make it easier to isolateas a pure culture.
This was to be achieved by growing micro-organisms in aerobic conditions on nutrient agar and MRS plates. Lactobacillus was then to be isolated by conducting biochemical and morphological tests. Water was added to the tube to about 5mm above the bread. The sample was left to stand for about twenty-four hours at room temperature to allow any microorganisms present to enter the water.
Further water was added to ensure the bread did not absorb all the water. Preparation of sample in nutrient broth Two tubes containing nutrient broth were prepared according to Microbiological Methods A small amount of bread not from the crust about the size of a five cent piece was torn into small pieces. Using sterile techniques, the same amount of bread pieces were placed in each tube.
This promotes the growth of large amounts of different bacteria due to the nutritional content.
The lids were loosely placed on the tubes and the samples were incubated at room temperature for two days. Initial sub-culture of sample, growth conditions and media From the original bread and water suspension, four nutrient agar plates were subcultured. From the sample tube containing the bread in water, sterile methods were used to streak out onto four nutrient agar plates, prepared as stated in Microbiological Methods Using aseptic technique, each plate was inoculated with a bacteriological loop full approximately 10mL of original suspension, by smearing a small section of the plate.
To establish pure culture, single colonies were picked up with the bacteriological loop, and sub cultured onto nutrient agar NA and MRS de Man, Rogosa, Sharpe plates.
Microbiology and Immunology Overall Structure - Structure: Whole Paper
Two nutrient agar plates and twoMRS plates were used. These were labelled A increase in concentration of end-product B increase in substrate concentration C increase in enzyme concentration D increase in temperature towards the optimum Your answer 12 A a high temperature B an extreme pH C heavy metal ions D a low temperature D Which type of enzyme catalyses the conversion of a dipeptide into two separate amino acids?
A decarboxylase B dehydrogenase C hydrolase D oxidoreductase Your answer Version 1 A Which one of the following conditions is least likely to denature an enzyme?
Which of these bonds are not important in maintaining the shape of the active site? A ionic B hydrogen C disulfide D phosphodiester Your answer 15 D The diagram below represents reactions taking place in a bacterium in which amino acids are produced from other amino acids by the action of specific enzymes.
The numbers refer to different amino acids and the letters V and X refer to different enzymes. When an excess of amino acid 3 is added into the bacterium the rate of the reactions is reduced.
What is the cause of this? A third sample of the starch suspension was mixed with amylase and incubated at 30 oC for 10 minutes and then tested with Biuret reagent.
What was the resulting colour of the third sample? Curve X represents the relationship between an enzyme and the concentration of its substrate under optimal conditions and without an inhibitor. Your answer 18 A Which one of the curves A, B, C or D represents the result when the same experiment is conducted in the presence of a fixed, low concentration of an irreversible, non-competitive inhibitor?Catalase and oxidase tests
Your answer 19 When an enzyme is subjected to temperatures above the optimum, it denatures. Which of the following bonds are the first to be disrupted by high temperatures? In each graph, the scale on the x axis is from pH 2 to pH B Your answer This resource has been produced as part of our free Biology teaching and learning support package.
All the Biology teaching and learning resources, including delivery guides, topic exploration packs, lesson elements and more are available on the qualification webpages. If you are looking for examination practice materials, you can find Sample Assessment Materials SAMs and a link to the Practice Papers on the qualification webpages: Biology A, Biology B.
If you do not currently offer this OCR qualification but would like to do so, please complete the Expression of Interest Form which can be found here: Whilst every effort is made to ensure the accuracy of the content, OCR cannot be held responsible for any errors or omissions within these resources.
In this scheme, isolates were compared to the type strain of each of the 35 taxa for acceptance into the database. The results for the acceptable isolates were used to generate a fatty acid profile library and a biochemical test table to provide a practical system for identification.
Both are updated when new acceptable isolates are added to the database. On the basis of the test for coagulase, the enzyme causing coagulation of human and rabbit serum, the genus was originally divided into the coagulase-positive species S. Determination of coagulase activity is still the most frequently used test for the identification of S.
A number of methods are available for detecting coagulase. In the slide coagulase test for bound coagulase, a very heavy suspension of cells is placed on a microscope slide and a loopful of rabbit plasma is added; a positive reaction is indicated by clumping within 10 s. The results of the tube and slide coagulation tests are not always identical.
False-negative results in the tube and slide coagulase tests have been reported for 8 and 17 strains, respectively, of 87 strains of S. In the same study, false-positive results in the slide coagulase test were reported for 9 of 10 and 7 of 10 strains of S. Tests based on rapid latex agglutination and hemagglutination to detect clumping factor or protein A are also used extensively 79; however, Fournier et al. A new latex reagent, Pastorex Staph-Plus Sanofi Diagnostic Pasteurconsisting of a mixture of latex particles for the detection of fibrinogen-binding protein clumping factorprotein A, and S.
Comparison of five agglutination tests has shown sensitivities of Positive results in the tube or slide coagulase tests have been found for other Staphylococcus species, mainly S. Positive coagulase activity was reported for S. They have shown that staphylocoagulase activates the proenzyme prothrombin in a stoichiometric reaction between one molecule of prothrombin and one molecule of staphylocoagulase.
The substrate profile suggests arginine-specific endopeptidase activity. The identity of the amino acid adjacent to the arginine is also important since Bz-Phe-Val-Arg-p-nitroanilide was not hydrolyzed by the complex, suggesting that a proline but not a valine is required in that position.
The reaction with Chromozym-TH was done at pH 8. Raus and Love compared the activities of staphylocoagulases from S. They concluded that Chromozym-TH can be used to detect the enzyme in both species but that accurate detection of the activity of S.
In further studies, S. The studies suggested that the enzymes had structural differences