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What else can I help you with?
Biochemical tests for Salmonella and Shigella?
urease - negative ONPG - positive Lysine - positive
Why are some organisms positive in the ONPG Test but negative when tested for the ability to metabolize lactose?
In the ONPG test, organisms may be positive due to the presence of beta-galactosidase enzyme, which cleaves ONPG and produces a yellow color. However, in the lactose fermentation test, some organisms may lack other necessary enzymes or transport systems to fully metabolize lactose, resulting in a negative result despite having beta-galactosidase.
Why cant the ONPG test be substituted for the determination of lactose fermentation?
ONPG test detects only presence of beta galactosidase enzyme whereas lactose fermentation requires the presence of permease as well as beta galactosidase enzyme.
Motility is best seen with a?
Wet mount, hanging drop slide, or motility tube (SIMS, ONPG-PAM)
Why incubate ONPG?
too see transcription and translation speed - u plot it against time (A400 - A550*1.65) / 0.0075
Can shigella sonnei be a lactose non fermenter My tests are as followed TSI KA Methyl red VP - citrate - urea - NO3 degraded to NO2 H2S - motility -. all points to shigella but it's nonferm?
S.sonnei is not a true lactose fermenting bacteria (see.. http://www.pubmedcentral.nih.gov/picrender.fcgi?artid=271578&blobtype=pdf)But is a delayed lactose fermenter as it does not have the enzyme permease to transport lactose through its cell wall.However an ONPG lactose fermenting test does not require permease to allow the bacterium to ferment lactose so in an ONPG test the shigella sonnei will appear as lactose fermenting positive.Hope this helps!!2nd year BMS student
Is onpg harmful?
ONPG (o-nitrophenyl-β-D-galactopyranoside) is generally considered non-toxic and is commonly used in laboratory settings as a substrate for enzyme assays, particularly for measuring β-galactosidase activity. However, like any chemical, it should be handled with care, following appropriate safety guidelines, as exposure can lead to irritation or allergic reactions in some individuals. Ingestion or significant exposure may pose risks, so it is essential to use personal protective equipment and follow safety protocols. Always consult the material safety data sheet (MSDS) for specific information regarding handling and potential hazards.
Why beta Galactosidase produce yellow color?
Beta-galactosidase produces a yellow color when it acts on a substrate like X-gal because the enzyme cleaves X-gal to produce a galactose residue. The galactose further reacts with oxygen to form a yellowish compound, leading to the yellow color change as a visual indicator of enzyme activity.
How does an API test work?
The API 20E System is a miniatuized version of conventional tsts that is used for the identification of members of the family Enterobacteriaceae and other gram-negative bacteria. This system utilizes a plastic strip with 20 separated compartments. Each compartments consists of a depression, or cupule, and a small tube that contains a specific dehydrated medum. After you inoculated each compartment with an unknown bacteria, a reaction will occur within 24 hours. The results of each reaction are tabulated and then given a number based on the results. The unknown bacteria is identified by searching through a book, Analytical Profile Index (may be in other book), and searching for the number corresponding to your unknown.The test consists of the following:ONPG: galactosidaseADH: Arginine DiHydolaseLDC: LysineDeCarboxylaseODC: Ornithinine DeCarboxylaseCIT: Citrate utilizationH2S: Hydogen sulfide productionURE: UreaaseTDA: Tryptophane DeAminaseIND: Indole ProductionVP: acetoin production (Voges Proskauer)GEL: GelatinaseGLU: fermentaion / oxidation (Glucose)MAN: fermentaion / oxidation (Mannitol)INO: fermentaion / oxidation (Inositol)SOR: fermentaion / oxidation (Sorbitol)RHA: fermentaion / oxidation (Rhamnose)SAC: fermentaion / oxidation (Saccharose)MEL: fermentaion / oxidation (Melibiose)AMY: fermentaion / oxidation (Amygdalin)ARA: fermentaion / oxidation (Arabinose)Supplemental Test also may be done with the API testOXI:NO2:N2 GAS:MOT:MAC:OF-O:OF-F:The reactions of each compartment are given a (+) or (-). Each compartment has a corresponding points. If a reaction for a certain compartment, like GLU, is possible then the points are counted.Every 3 compartment (or test) is given a number. The points of every 3 set is 1, 2, and 4 (in order)... Do not get mixed up with points and number. Each test has a corresponding points and Every 3 tests is given a number based on the results...For example:ONPG (1), ADH (2), and LDC (4)If ONPG and LDC are positive and ADH reaction is negative, then the number given to this set is 5 (1pt from ONPG and 4pt from LDC; No point is given to ADH because the result is negative)THERE SHOULD BE 9 NUMBERS[27 tests/compartments divided into 3 groups each is 9]A test result for a specific bacteria of Eshcerichia coli (E. coli) is+ - + + - - - - + - - + + - + + - + - + - + - + + + +5 1 4 4 5 5 2 5 7The number is 514455257An important thing to remember is that they have a lot of bacteria. Some bacterias have different strains, so there may be more than 1 number that identifies to be E. coli. It's just they are different strains of E. coliInformation taken from Benson's MICROBIOLOGY APPLICATIONS Tenth edition by Alfred E. BrownPosted by 13K
