University:
Northwest College
Course:
MOLB-2210 | General Microbiology
Academic year:

2023
Views:

414

Pages:

6
Author:

Yesenia M.

exercise 4. (Fermentation Tests) Fenol (Phenol Red) mclusterts Fermentation Fermentation ollt red fermentation tube-used to detect acid and gas * production from carbohydrates. Fermentation media broth consistency yo contains peptone & Fermentation acid-base indicator phenol red* (Think: Fermin pees yellow and #sacidic) Yellow fermentation I inverted tube to trap gas (Durhamtube) y 10.5% 1.0% of the desired carbohydrate. red colored medium /nothing inoculated fermentation - Iarts. results Uninoculated tube: red color fermentation = acid production: yellow color change Øfermentation and production media stays red. = gas producion = you will see it trapped in the Durmam tube. * Fermentation occurs with or without of present BUT, during prolonged incubation (> 24 hrs), Bactena will grow Oxidatively using the Peptones after exhausting the carbohydrate Supplied, which will cause the indicator to neutralize and turn red due to ammonia production. Re Remember I this fest aud production = venow color in alkaline production Ibasic =red or) color Daced production MRVP test 2 Remember for me ve more red) boin tests: red (1) result. Fermentation processes can produce different end products depending on the substrate, the incubation, and the organism (the backena) Can be auds or neutral products (biothylene pathuwars) mixed acid Dathway, MRVP broth test: used to distinguish organisms that produce large amounts of acids from glucose and organisms that produce the neutral product ACETOIN* MRVP media: broth Acetoin is neutral! clear colored TP glucose supplemented (Remember MRVP used methyl id, & phenol red!!!!) IIf organism produces a large amount of organic acid from glucose, the media will remain red when methyl red is added. red result =(t) me test (UPH ditacid production) PH <4.4 Semi-red (orange red) = PH (44-6-0) some acid production. yellow color change = aeld production, neutral (acctoin) onduction PH>6. (BASIC/ALKALINE) production of acetoin (neutral producis) is detected by the 2 Indicators potassium Hydroxide -naphtol - used for 'VP' portion of the MRVP test. (Remember: MR only uses methyl red) →(+) vp test-top will change to red color after adding the 2 reagents = acetoin production- (-)rp test-ch color change acetoin production (or light brown) -hor: for this test 'MRUP', they can't both be(t) vo(+). or vice versa. VD He like they rule Citrate Test Some bactena are able to ferment citrate (as an alternate energy source) This ability can be used to identify certain bactenia. When citric acid of sodium citrate is in solution, it looses a proton or (Nat) to form a citfat ion. Bacteria that have the enzyme Citrate lyase can break & Citrate to form pyruvate, which can be reduced in fermentation. agar/media used Simmons citratu agar (Slant agar) • green colored media Indicator bromthymol blue Simmons eitrate agar can be used to determine eltrate ure when backend use Oltrate and ammonium, the medium is alkalanized because of ammonia (NH3) produced from NHist. (sodium lacarbonate) Indicator changes to blue (+) citrate test = blue color change (-) eltrate test = stays green. y