quiz 1

i'm just putting whatever bro fr

simple stains

uses a single dye to visualize cells

• information we get from it

  • morphology

  • presence/absence of cells

    • e.g., methylene blue stain

      • cell has overall negative charge → methylene blue is pos (basic dye)

differential stain

uses two dyes to distinguish between cells based on physiology features/or differentially stain different cellular structures

basic dyes

upon ionization, chromogen has positive charge

acidic dyes

upon ionization, chromogen has negative charge

heat fixing

wave the slide (front facing away) in front of incinerator 4-5 times

• disadvantages

  • cells are dead → can’t see motility

  • cell shape may get distorted due to heat

cocci

spherical in shape

• diplococcus (pair)

• streptococcus (chain)

• staphylococcus (cluster)

tetrad

packet of 4

sarcina

packet of 8

bacilli

rod-shaped

• diplobacillus (pair)

• streptobacillus (chain)

coccbacilli

short rods or oval-shaped

• coccobacillus

• diploccoccbacillus

• streptococcobacillus

total magnification

magnification of eyepiece (10x) multiplied by magnification of objective (4x, 10x, 40x, 1000x)

resolution

ability of microscope to distinguish two adjacent objects as separate

• resolving power = wavelength/2NA

  • decreased wavelength: use blue light filter

  • increase NA: use highest objective on microscope

pure culture

a single bacteria representing a species

• necessary for identifying an unknown organism → allow us to study its morphology and biochemical properties

quadrant streak

dilution technique that spreads microorganisms over agar plate to isolate colonies

nutrient agar

rich medium that (mostly) all strains grow well on

gram stain

differentiates cells based on differences in cell wall structure

• primary stain

• decolorizing

• secondary stain

primary stain

• vegetative cell

  • basic stain penetrates negatively-charged cells → changes color

• endospore

  • without heat, stain is UNABLE to penetrate spore coat

  • with heat, spore coat opens to allow stain in → changes color

decolorizing

remove from heat and wash smear with water

• vegetative cell

  • malachite green water soluble → water easily washes stain from vegetative cells → turns invisible

• endospore

  • heat is removed → spore coat closes back up → traps stain within spore → stays primary coat color

secondary stain

apply safarin to smear

• vegetative cells

  • decolorized cells stained by safarin (basic, positively charged stain)→ appears red/pink under microscope

• endospore

  • because of closed spore coat, does not absorb secondary stain → continues to appear as primary stain

vegetative cell

metabolically active

endospore

metabolically inactive

• spore coat and certain spore contents confer increased resistence to stressful environment conditions

  • e.g., extreme temp. radiation, chemicals

  • spore coat resists penetration by stains

germination

occurs under favorable environmental conditions

• endospore spore coat ruptures → turns into vegetative cells

sporogenesis

occurs under unfavorable environmental conditions

• vegetative cell splits → turns into endospore

nigrosin stain

acidic and negatively charged → repelled by negatively charged cells

• appears as white cells on black background

  • advantages of using nigrosin over simple stain

    • no heat-fixing

    • undistorted by heat

complex media

media supplemented with nutritious ingredients (such as yeast extract) → supports growth of wide range of organism

• aka. nutrient agar

selective media

media used to select for the growth of specific types of bacteria

differential media

media used to differentiate between bacteria based on different physiological characteristics

mannitol salt agar plate

1. selective

• selects for: salt-tolerant microorganisms (halophiles)

  • 7.5% NaCl limits growth of non-tolerant organisms

2. differential

• differential for: mannitol fermentation

  • mannitol added as carbon source & phenol red added as pH indicator

eosin methylene blue plate

• selective

  • selects for: gram-negative bacteria

    • key ingredients: eosin & methylene blue dyes inhibitory toward gram-positive bacteria → only gram-negative can grow

• differential

  • differential for: lactose fermentation

    • key ingredients: lactose added as carbon source → organic acid produced as by-product of fermentation → causes dyes to precipitate out of media and onto cell surfaces

phenol red carbohydrate broth

tests for fermentation of glucose

• can test for fermentation of different sugars depending on what carbon source added

  • glucose (phenol red; higher pH) → organic acids (yellow; lower pH)

    • yellow positive; red negative

• glucose fermentation can also produce gases (H2 and CO2)

voges-proskauser test

detected by adding barritt’s reagents which reacts with acetoin to form red-colored product

• colorless negative

• red positive

kligler’s agar deep slant

tests for activity of enzyme cysteine desulfurize

• also tests for fermentation of glucose and lactose fermentation

  • and gas production

• turns black → positive reaction for cysteine desulfurize enzyme

indole production test

detected by adding kovac’s reagent which reacts with the indole to form a red-colored product at surface of the tube

• colorless/no change → negative

  • red colored surface → postitive

phenylalanine deaminase slant

detected by adding ferric chloride which reacts with the phenylpyruvic acid to form green-colored product

motility test

cells are stabbed into center of semi-solid agar

motile cells move from center stab line

non-motile cells stay in place

• TTC acts as indicator of activity

  • TTC (oxidized, colorless) → TTC (reduced, red)