microbio lab practical

what is the purpose of a simple stain?

it stains negatively charged bacteria with basic stains that are positively charged

simple stains appears as..

dark object (the cell) on a white background

when is simple staining useful?

when trying to see cell shape/arrangment/size

what is a negative stains purpose?

use acidic dyes (negatively charged) to stain the background (bc the bacteria is also negative, so it rejects it staining the background)

what does a negative stain result in?

a uncolored/clear cell surrounded by a dark background

negative staining help when trying to observe resistant cell structures like..

endospores and capsules

negative stains are never…

heat fixed

Gram staining distinguishes between …

positive and negative bacterium

Gram Staining: Gram postive will..

stain purple, thick cell wall of peptidoglycan, no outer membrane

Gram Staining: Gram negative will..

stain pink, thin cell wall, have a outer cell membrane

Gram staining procedure

1. crystal violet

2. mordant Iodine

3. decolorizer alcohol

4. safranin

Endospore staining green means..

endosporee

endospore staining pink means

Vegetative cell

Acid Fast Staining is what kind of technique

differential

acid fast staining is used to identify ..

bacterium with a waxy cell wall

acid fast staining: why is the cell wall waxy?

it has a layer of mycolic acids

what can be diagnosed with acid fast staining?

Tuberculosis

when an acid fast stain is positive..

waxy cell wall and will stain pink

when an acid fast stain is negative..

no waxy cell wall and will stain blue

kirby baeur test determines..

the susceptibility of a specific bacterium to an antibiotic

whats ZOI in a kirby baeur test

zone of inhibition, it represents where bacterial growth is absent.

MSA plate is both,….

selective and differential

How is a MSA plate selective..?

because of it’s high salt, only allowing halophiles salt loving organisms to grow

How is a MSA plate differential

due to the mannitol plus the ph indicator phenol red

When a MSA plate changes colors red to yellow it means

it can ferment mannitol meaning it changed the made the medium acidic

A EMB plate is both..

selective and differential

EMB plate is used to indentify..

fecal coliforms

why is EMB selective

2 dyes: eosin and methlyene blue

Due to the dyes in EMB what cannot grow here

gram postive bacteria

how is EMB plate differential

due to the addition of lactose

what happens with the growth of gram negative in an EMB plate

it can change the plates color, showing signs that it can ferment lactose

if a bacterium on an EMB plate has both fermenting and negative it is

a true fecal coliform