MIC 103L Rogues' Gallery Bacteria

Pseudomonas putida

• gram: negative

• rod

• F agar: clear/white colonies obscured by fluorescent siderophores

• Nutrient agar: clear/white (same as EA, EC colonies)

• motile, obligate aerobic

• soil

• oxidase: positive

Bacillus cereus

• gram: positive

• rod

• Nutrient agar: flat, matte white colonies

• motile, facultative aerobic

• soil (endospores heat res)

Lactococcus lactis

• gram: positive

• coccus

• YGC agar: v small, white colonies w/ large zones of clearing (ferments glucose)

• aerotolerant, anaerobic

• dairy

• catalase: negative

Micrococcus luteus

• gram: positive

• coccus

• YGC agar: yellow colonies w/OUT zones of clearing (no glucose ferment)

• obligate aerobic

• skin, soil, water

• catalase: positive

Staphylococcus epidermidis

• gram: positive

• coccus

• YGC agar: cream colonies w/ zones of clearing (ferments glucose)

• Nutrient agar: cream colonies

• facultative aerobic

• skin

• catalase: positive

Enterobacter aerogenes

• gram: negative

• rod

• EMB agar: pepto bismol pink (eosin)

• Nutrient agar: clear/white colonies (similar to E. coli, Pseudomonas putida)

• facultative aerobic, non-endospore forming

• soil, enteric

• oxidase: negative

• IMViC: I-, M-, V+, C+

Escherichia coli

• gram: negative

• rod

• EMB agar: dark purple (eosin, methylene blue) w/ green metallic sheen

• Nutrient agar: clear/white (similar to Enterobacter aerogenes, Pseudomonas putida)

• facultative aerobic, non-endospore forming

• enteric

• oxidase: negative

• IMViC: I+, M+, V-, C-

Nutrient Agar

• all singing, non-selective media

YGC agar

• Yeast, Glucose, Calcium

• anything and everything grow on

EMB agar

• eosin + methylene blue dyes

• used to ID enteric:

  • differentiate based on lactose fermenting ability

  • Enterobacter aerogenes: weak lactose fermenter, small amt acid → pink

  • E. coli: strong lactose fermenter, lots of acid → dark purple, metallic green sheen

F Agar

• iron-free medium (stim. siderophore secretion)

  • many species secrete siderophores, Pseudomonas sp. fluorescent

Sodium benzoate agar

• selective media for Pseudomonas to grow on

Mac Conkey agar

• lactose, neutral red, crystal violet, bile salts

  • crystal violet + bile salts inhibit gram positive

• selective media for enteric bacteria

Catalase

• differentiate between gram + cocci

• question: produce catalase enzyme? (to break down H2O2)

• positive: Micrococcus luteus + Staphylococcus epidermidis (fizz, skin)

  • to differentiate? streak out on YGC

• negative: Lactococcus lactis (no rxn)

• transfer goober w/ sterile toothpick

• add couple drops H2O2 to each goober (ice)

Oxidase

• differentiate between gram - rods

• question: produce cytochrome c oxidase enzyme? (electron transport chain)

• positive: Pseudomonas putida (royal Thai purple)

• negative: Enterobacter aerogenes + Escherichia coli (colorless, latex)

  • to differentiate? IMViC

• filter paper on petri plate, transfer goober

• add couple drops of oxidase reagent (ice)

IMViC

• used to differentiate between Enterobacter aerogenes and Escherichia coli

• for gram negative, oxidase negative rods

• important in water testing

  • Enterobacter sp. normal in soil

  • E. coli presence = fecal contamination

• all 3 tubes 37º 48 hrs

Indole

• question: have enzyme tryptophanase?

• positive: E. coli (magenta ring)

• negative: E. aerogenes (no magenta ring)

• inoculation:

  • loop pick up bacteria to put in tryptone broth

  • move loop up and down at liquid air interface

• developing the test:

  • vortex broth

  • 4 drops Kovac’s reagent (ice) → rxn in sec

Methyl red

• question: mixed acid fermenter of glucose?

• positive: E. coli (red, v acid)

• negative: E. aerogenes (amber, slight acid)

• inoculating:

  • loop pick up small amount of bacteria

  • transfer to MR-VP broth

  • move loop up and down

• developing the test:

  • vortex

  • split broth in half

  • 4 drops methyl red → rxn in min

Vogues-Proskauer

• question: butanediol fermenter of glucose?

• positive: E. aerogenes (red layer)

• negative: E. coli (no red layer)

• developing the test:

  • 12 drops alpha-naphthol (ice)

  • vortex → milky

  • 4 drops KOH (ice)

  • vortex → not milky → 90 min

Citrate

• question: citrate as only carbon + energy source?

• positive: E. aerogenes (blue, slight basic)

• negative: E. coli (stays neutral green)

• inoculating:

  • loop small amount bacteria

  • transfer to citrate slant, zigzag btm to top

• developing the test:

  • look at slant, check streak marks