Microbiology review

• 8. What does “parfocal” mean? Is the microscope used in the laboratory a “parfocal” microscope?

Parfocal is that a microscope stays in focus when you change the objective lens.

• Parcentric? • Stays center even after you change the focus.• Whats your TA’s Name and where to fid him.

• Know the difference between gram + and –

• Know what the different reagents in the gram stain and what they accomplish.

• Know what a basic (positive) and a acidic(negative) stain look like. And what they stain.

• Know all the media we used and what positive test means and what a negative test means. Also when a organism doesn’t grow what that means.

• Know selective and deferential definitions.

• Macconkey agar • Positive means• If it grows it means • EMB• If it grows ?• If is positive?

• MSA (mannitol salt agar )• Positive means ?• Growth Means ?• Mitis – salavarius • Colonies are blue?• If no growth?• PEA• Grow means?

Stains • Positive stain• Stains the cell also known as the basic stain• Negative stain• Stains all the back ground not the cells themselves.• Differential stain?• Differentiates the cells some how due to a structure or some type of

phenotype characteristics.• Capsule stain uses what 2 types of stains • Manevals stain • positive stain.• Congo red• Negative • Endospore stain uses what stains • Malachite green and safernin

Gram stain

• Gram stains • Primary stain • Crystal violet • Mordant• Grams iodine • Decolorizer• 95% ethanol alcohol • Counter stain • Saferin

Gram negative Media

• EMB

• Macconkey agar

• Hektoen

• Urea

EMB

• A positive test means what ?• growth of Gram + organisms. Additionally, the

medium contains lactose which can be utilized by lactose fermenters as a carbon and energy source.

• Grow means its what ?• That it’s a gram -.

EMB

Macconkey’s

• What does growth mean ?• That is a gram -• What does positive test mean?• above pH 8. Like EMB, this medium contains lactose

and those organisms that can utilize lactose produce acids. The acid production results in a lower pH in the medium and a change in the color of the medium to yellow. Neutral red is the ph indicator

• The selective molecule is bile salts

Macconkey agar

Hektoen enteric agar

• MacConkey’s agar. However, this differs from MacConkey’s agar because it also has ammonium sulfate and sodium thiosulfate in it.

• These chemicals are indicator molecules because they react with H2S released from the breakdown of peptones in the medium and turn the H2S producing colonies black (indicating that H2S was present).

• The pH indicator in this medium is bromothymole blue. • When bacteria use the lactose and sucrose in the medium acid

is produced and the medium’s color changes from a blue/green• It has bile salts as the selective indicator molecule

Hectoen enteric agar

Urea broth

• If its positive • the organism has urease .• If negative it doesn’t poses urease.• Has phenol red as a ph indicator

Urea broth

Gram positive

• MSA (man

• PEA

• Mitis-salavarius

Mitis-salavarius

• Grows up mainly gram positive mainly streptococcus.

• If the colonies turn blue what does this mean?• It incorporates the trypan blue from taking in

sucrose peptones and all the different carbohydrates.

Mitis- salavarius

PEA

• This is a selective media it doesn’t allow which type of bacteria to grow?

• Gram negatives.• What is incorporated in to this to allow only

gram positives to grow.

PEA

Mannitol salt agar

• IF an organims grows this means that the organism is a halophile.

• If it changes color which is a positive test this means that the organism uses mannitol as its main carbon source.

• has phenol red indicator.• It has NaCl as a inhibitory molecule.

Mannitol salt agar