Lab Final

Catalase Test

• -The catalase enzyme breaks down the
• peroxides into non-toxic H20 and 02. Enzyme is needed in order for a cell to
• exist in the presence of o2

• Reagent-hydrogen
• peroxide

• Positive Result- bubble formation after placing a drop of hydrogen
• peroxide on colony

Negative Result-no bubble formation

Oxidase Test

• -Cytochrome oxidase
• is involved in the reduction of oxygen at the end of the ETC

Reagent-Kovac’s

• Positive result-purple color
• change after oxidase reagent is added

• Negative result-no color change
• after oidase reagent is added

O/F Carbohudrate Test

• -Used to determine whether an organism derives energy from
• sugars by fermentation or oxidation. Two
• tubes are used; one tube is covered while the other is not. If the bacteria has the ability to only grow in the presence of O2 it will grow only in the O tube. If the bacteria has the ability to only grow in the presence of no O2 it will only grow in the F tube with fermentation. If the bacteria grows in both tubes it is facultative and will grow with or with out O2

Left is (+) Middle indicates (+) with gas Right (-) test

Methel Red

• -Used to
• identify bacteria that produce stable acid end products by means of mixed acid
• fermentation of glucose

• Positive result-red color
• change indicating acid production

• Negative result-no color
• change

Nitrate Reduction Test

• -Test for
• the ability to reduce nitrate into nitrite. If the organism can reduce the
• nitrate, it will react with the reagent

Reagents-Paba, Zinc

• Positive result-nitrate(no30_____nitrite(NO2)-red
• color change after addition of reagent

• Negative result- nitrate(no30_____nitrite(NO2)-no
• color change after addition of reagent

Citrate Test

Left (-) no color change Right(+) color change to blue

• -Citrate
• agar tests for the ability of organisms to utilize citrate as a sole carbon
• source

• Positive Result-blue color
• change

• Negative Result- no color
• change

Indole Test

• -Checks
• for the presence of tryptophanase, which breaks down tryptophan into indole,
• ammonia & pyruvid acid

Reagent-Kovac’s

• Positive result-purple ring
• at the top of the media

• Negative result-brown or
• yellow ring at the top of the media

Urea Test

• Straw
• colored-uninnoculated Pink (+)
• test Yellow-orange (-) test

• -Checks
• for the presence of the enzyme Urease that breaks down urea to form two
• molecules of ammonia

• Positive result- bright
• pink color change

• Negative result-light
• orange to yellow color change

H2S Test

(-) no black (+) slight black (+) complete black

• -Tests
• the ability of an organism to produce hydrogen sulphide from thiosulphate

• Positive Result-production
• of black precipitate

• Negative Result-no
• production of black precipitate

MSA (Manatol Salt Agar)

• -Used for the isolation of Gram+ organisms. The high salt concentration of medium
• inhibits the growth of most other organisms(selective). Some organisms ferment
• the Mannitol into acid, this acid production turns the agar from red to
• yellow(differential)

• Positive Result-Growth of
• bacteria with media change to yellow

• Negative Result-Growth or
• no growth of bacteria without media color change

• (Bacteria unable to tolerate high
• salt or unable to ferment mannitol)

EMB (Eosin Methalane Blue Agar)

• -Medium
• used for isolation of Gram - rods. EMB inhibits the growth of Gram +
• organisms(selective). Differentiates bacteria between lactose fermenting and
• non-lactose fermenting organisms(differential)

• 1) Growth on plate indiacates
• organism is not inhibited(Gram – bacteria), green metallic sheen indicates
• organism is able to ferment lactose, producing strong acid end products

• 2) Growth on plate indiacates
• organism is not inhibited(Gram – bacteria), absence of color in growth
• indicates the organism is unable to ferment lactose

• 3) Growth on plate indiacates
• organism is not inhibited(Gram – bacteria), pink color indicates bacteria is
• able to ferment lactose to produce weak acid end products

• 4)No growth on plate indicates
• organism is(Gram+)

• Positive Result-Growth of
• bacteria, colonies have dark centers and clear borders or metallic green sheen

• Negative Result-Growth or
• no growth of bacteria without media color change

MAC (MacConkey Agar)

• -medium
• used for the isolation of (Gram- )organisms, it inhibits the growth of (Gram+)
• organisms(selective). Differentiates bacteria between lactose fermenting and
• non-lactose fermenting organisms(differential)

• Positive Result-Growth of
• bacteria, colonies have a pink appearance

• Negative Result-Growth or
• no growth of bacteria without media color change

Mueller-Hinton Agar

Standard growth medium used for antibiotic susceptibility testing

Sheeps Blood Agar (SBA)

Some microbes contain enzymes that can break open red blood cells (lyse host cells)

α -(alpha) - partial/greenish appearance

β - (beta) - complete cell lysis

ϒ - (gamma) - No cell lysis

• an engineered plasmid used as a vector for creating genetically modified organism
• contains reporter genes
• -green fluorescent protein
• -ampicillin resistance gene/codes for exoenzyme(ampicillinase)
• Arabinose(sugar)-makes the organism fluoresce under UV light

commonly used bacteria indicator of sanitary quality of food and H20 of the coli family

Used to masure potential fecal contamination of environmental samples (present in human waste in high enough numbers to be readily detected)

Responsible for causing disease in the host as they inhibit curtian host functions

Small extra-chromosomal elements that can exist in some bacteria. The bacterial genome is made of bacterial chomosome and any plasmids that the organism may contain.

Usualy carry the genes for antibiotic resistance

Plasmids may have up to 300 copies of itself in any one bacterial cell it can produce up to 300 copies of gene product that it caries in that bacterial cell.

Circle around the disk where the antibiotic noticeably affected cell viability

Chemicals that have the ability to kill bacteria

Produced by microorganisms (fungi), used as a defense mechanism

Derived from microoganisms or Synthetically produced

Chemicals used on living tissue to kill microbes

Mouthwash

Chemicals used on the surface of inanimate objects to kill microbes

Bleach

Used to determine the effectiveness of antibiotics on certain bacteria

Is a method, to detect coliforms in two stages

Presumptive test- test for acid and gas production

Confirmed test - uses EMB agar

# of coliforms in sample detemined by MPN method

• 1. Obligate aerobe
• 2. Obligate Anarobe
• 3. Facultative anaerobic organism
• 4. Microaerophile
• 5. Aerotolerant

Parts of a Microscope