Lab Practical

Gram positive

Purple gram stain

Gram Negative

Pink gram stain

Cocci

sphere cell morphology

Bacilli

rod cell morphology

Spirilla

squiggle cell morphology

Vibrios

boomerang cell morphology

Corkscrew

spiral cell morphology

Endospore

a dormant extremely heat-resistant dehydrated structure

Resistant to chemicals and thus difficult to stain, as they are dehydrated and water-soluble dyes won't penetrate it

Capsule

Distinct, firm, and sticky polysaccharide layer

easiest to find towards the edge of the sample where the stain is the thickest

Flagella

specialized structures/appendages that many bacteria use for movement

Monotrichous

Single flagellus

Amphitrichous

has flagella at both ends

Lophotrichous

tuft of flagella at one of both ends

Peritrichous

has flagella surrounding the cell

Non-Motile

MTM has red precipitate with a small area beyond the stab line

Motile

MTM has red precipitate in a widespread area beyond the stab line

Motile

MTM has cloudiness spreading from the stab line

(# of colonies * total dilution factor)/ volume of culture plated (mL)

CFU/mL formula

Prodigiosin, Serratia marcescens

Red pigment on solid media

Pyocyanin, P. aeruginosa, water soluble

Blue-green pigment. Red in pH < 5.

Water Soluble

The pigment has spread into the water-based agar. Can be blue, green, or green-yellow pigments

Pyoverdine/Fluorescein, Pseudomonas aeruginosa and P. fluoresceus, water soluble

Yellow-green pigment

Canthaxantin/Cartenoid, Micrococcus roseus

Red-orange pigment. specific example produces pink colonies

Violacein, Chromobacterium violaceum

Purple pigment

Beta hemolysis

zone of clearing around the colony in SBA. Staph aureus and group A and B strep

Gamma hemolysis

no zone of clearing around colonies in SBA

Alpha hemolysis

produced by strep when the bacteria produce substances that oxidize the hemoglobin in red blood cells, turning the agar to a greenish brown.

Possessed by S. pneumoniae

staphylococci

If it grows on MSA, it is

Mannitol fermenter

yellow growth on MSA.

Non-Mannitol fermenter

No growth on MSA. red

Group A Strep

No growth in presence of bacitracin

Group B strep

Growth in presence of bacitracin

Gram negative, non-lactose fermenter

colorless or light lavender colonies on EMB

Gram negative, lactose fermenter

dark/dark purple colonies on EMB

Gram positive

No growth on EMB

E. Coli, lactose fermenter

green metallic sheened colonies on EMB

gram negative, lactose fermenter

red agar around colonies on MAC

gram negative, non-lactose fermenter

orange MAC agar

Citrate only carbon source

bright blue Simmon’s Citrate Agar

Citrate not only carbon source

green Simmon’s Citrate Agar

positive

pink Urea Broth

negative

yellow or peach colored urea broth

Glucose only fermenter

Red Slant Yellow Butt, TSIA

Glucose and Sucrose and/or Lactose fermenter

Yellow Slant Yellow Butt, TSIA

gas

TSIA agar lifted

hydrogen sulfate

Black precipitate butt, TSIA

EMB

positive lactose fermentors produce acid, which results in methylene blue + eosin Y dye complexes that form dark/dark purple colonies

E. Coli

Ferments lactose/produces acid quickly on EMB. The acid reacts with the media dyes and produces dark colonies with green metallic sheen.

MAC

Neutral red indicator reddens with agar around colonies in presence of acid from lactose fermentors. Non-lactose fermenters turn agar more orange.

Simmon’s Citrate Agar

bromothymol blue green at neutral pH but becomes blue as pH increases due to citrase metabolizing citrate, which forms alkaline product sodium carbonate.

Urea Broth

differentiates presence of Urease, which hydrolyzes urea into ammonia and carbon dioxide. phenol red indicator turns pink as ammonia increases the pH.

Phenol red

in TSIA slants and MSA. turns yellow when pH decreases (acid from bacteria fermenting carbohydrates). Positive is pink in urea brother as pH increases with ammonium production

Red, Yellow

Slant/Butt TSIA color that indicates an organism can only ferment glucose.

As the small concentration of glucose is fermented, organisms moves on to break down peptones aerobically releasing alkaline byproducts and turning the slant red

Anaerobic conditions in butt means glucose is not oxidizes, so as glucose fermentation acid builds up it turns butt yellow

Yellow, Yellow

Slant/Butt TSIA color that indicates an organism can ferment glucose and either lactose or sucrose or both.

Slant is yellow because lactose and sucrose are at 10x the concentration of glucose, meaning more production of acid.

After 24 hours the sugars may deplete and bacteria moves to peptones in the slant which produces basic ammonia turning slant the other color.

gas

bacteria that use thiosulfate as a terminal electron acceptor produce hydrogen gas which lifts agar up out of the tube. CO2 may also be produced through fermentation that may be visible as agar bubbles/cracks

Hydrogen Sulfate

Produced through bacteria’s reduction of thiosulfate. Combines with iron that produces a black precipitate visible in a TSIA butt. Requires an acidic environment, so it’s production assumes it’s covering a yellow/acidic butt.

positive

Yellow carbon fermentation test

negative

Red carbon fermentation test

gas

bubble in the inverted tube (Durham tube) in carbon fermentation test

Aspergillus. V, M, P, C

reproduces with asexual conidiophores that produce conidia.

Vesicle, V

Bulbous head containing conidia-producing cells in Aspergillus. Either uniseriate (one) or biseriate (two) layers of conidia-producing cells

Phialides

flask-shaped cells that arise from metulae. Structure in Aspergillus and Penicillium

Metulae, M

where phialides arise from, surround the vesicle. Structure in Aspergillus and Penicillium

Conidia, C

non-motile spores. Circular and structure in Aspergillus and Penicillium

Pencillum. M, P, C

blue-green molds that undergo asexual reproduction through branched conidiophores

Saccharomyces cerevisiae

budding yeast. Oval shaped and reproduce through asexual budding (“budding” yeast)

Rhizopus stolonifera. S, C, Sp, Sm

Reproduces asexually with sporangiospore contained within sporangia formation

Sporangiophore. S

aerial hyphae that emerge near the rhizoids.(the branched line) in Rhizopus.

Sporangium. Sm

contains the columella in Rhizopus.

Sporangiospore, Sp

surround the columella and capped by sporangium in Rhizopus

Columella, C

dome-shaped structure within each sporangium which supports spore development in Rhizopus

Ring stage

Mature Trophozoite

Schizont

Gametocyte