Lab Exam 2

The nutrient preparations used to grow (culture) microorganisms in lab

Used to obtain actively growing populations of bacteria to carry out biochemical tests or observe movement etc.

Such as nutrient agar is used to observe colony appearance, to isolate pure cultures , and to carry out certain biochemical tests. May be prepared in a petri plate or in a tube.

Used for routine lab work as it supports a wide variety of heterotrophic bacteria. This includes nutrient broth and nutrient agar. Contain yeast extract, beef extract or a similar complex material containing proteins, complex carbohydrates and fats.

contain known amounts of specific chemicals. They may be used to grow organisms with special requirements or to exclude certain organisms. Must contain a source of energy, and also sources of carbon, nitrogen, sulfur, phosphorus and any other growth factor that an organism cannot manufacture

Media designed to supress the growth of unwanted bacteria or other microorganisms while favoring the growth of the target bacterium

Allow you to distinguish visually between 2 bacterial bacterial species growing on the same plate

Provide added nutrients to favor growth of terget bacteria. Ex: Blood agar and chocolate agar

methods to help prevent microorganisms from the environment contaminating our experiments, or our experimental bacteria contaminating the environment.

The complete removal or destruction of all forms of microbial life-is most achieved by physical methods such as autoclaving, falming, filtration or radiation. The method of choice will depend on the substance to be sterilized.

Most effective method for sterilizing glassware and media in lab. These items are exposed to steam at high temperature and pressure in a sealed chamber. The heat denatures proteins. All vegetative cells plus bacterial endospores and viruses will be killed in about 15 minutes.

uses dry heat to destroy contaminated material. Also how flame sterilization works.

used to sterilize media that are inactivated by high heat, such as many antibiotic solutions. These media can instead be passed through a filter or screen with pores small enough to exclude microorganisms.

Lethal to many microorganisms because it damages their DNA. A UV lamp can be used to sterilize surfaces, or the air in a room, but it does not penetrate glass or travel far through liquid in a container.

Ethylene oxide gas is a chemical method of sterilizing heat-sensitive items such as plastic Petri plates and other plastic equipment. Denatures the proteins of microorganisms, killing both vegetative cells and endospores in 4-18 hours

Reduce microbial numbers on surfaces. These DO NOT complete chemcical sterilization. Some examples are vesphene, hand soap or alcohol gel.

It contains proteins, complex carbohydrates and fats

200 ml of ultra pure water and 4.6 grams of nutrient agar in powder form

It is used to observe colony appearance, to isolate pure cultures and to carry out certain biochemical tests

Must contain a source of energy and also sources of carbon, nitrogen, sulfur, phosphorus and any other growth factor that an organism cannot manufacture for itself.

So it doesn't solidify

The heat denatures proteins and all vegetative cells plus bcterial endospores and virsues wll be killed.

To observe colony morphology and to isolate single colonies

The shape, color, size and general appearance of the bacterial colonies

Shape, Margin, Elevation, texture, color, optical properties and size

• Contains animal blood
• Enriched medium and differential medium (distinguishes between bacteria on the basis of their ability to break down RBCs (hemolysis))
• Used to culture pathogenic organisms from clinical samples,

• partial breakdown of RBCs
• Results in a production of a greenish discoloration (the pigment biliverdin)

• complete breakdown of RBCs.
• Results in a zone of clearing around bacterial colonies

no breakdown of RBCs

• Enriched medium
• Used to culture certain bacteria that require the nutrients in blood in order to grow but cannot lyse RBCs. The blood cells are lysed by heating during the preparation of this medium and the resulting agar is chocolate colored.

• Selective for Gram negative bacteria.
• Contains bile salts and crystal violet dye both of which inhibit the growth of Gram positive bacteria.
• DIfferential as well cuz it distinguishes lactose fermenting bacteria from non lfb. Bacteria that can ferment lactose in the medium produce acid that changes the color of the colonies from whitish to pink. Bacteria that cannot ferment lactose remain white.

Microorganisms that are permanent residents of the human body, but do not produce disease under normal circumstances 10-100x for abundant than our human cells.

Used to determine whether a bacterium is resistant or susceptible to a particular drug and helps doctors to make decisions about which drugs to use in treating a patient's infection.

The area where bacteria were unable to grow.

During aerobic respiration toxic oxygen byproducts are formed, including hydrogen peroxide. Aerobic, and some facultative anaerobic bacteria synthesize the enzyme catalase, which breaks down hydrogen persoxide to harmless water and oxygen, but obligate anaerobic bacteria and some facultative anaerobes do not possess this enzyme.

• Used to isolate and differentiate Staphylcoccus aureus from other bacteria.
• MSA contains carbohydrate mannitol, plus 7.5% NaCl and the pH indicator phenol red. Phenol red is yellow below pH 6.8, red at pH 7.4 to 8.4 and pink above 8.4.
• Sa ferments mannitol and produces acid, which turns the pH indicator yellow. Non-pathogenic staphylcocci produce no color change.

It ferments it which produces an acidic solution

If it is greater than 6.8, it stays pink. If it is lower tjam 6.8, it ferments and turns yellow.

• Used to distinguish between enteric bacteria. In this test the bacteria are grown on Triple SUgar Iron agar.
• Has a peptone base and contains the pH indicator phenol red, which is yellow below 6.8.
• Also contains glucose (0.1%) sucrose and lactose (1%) and FeSO4

No carbohydrate fermentation means no acid produced so the pH of the agar is not reduced. Aerobic respiration of peptone in the slant produces alkaline products. (No fermentation of sugars-pink slant/red butt)

If the bacteria can only ferment glucose, but not the other sugars, the acid produced by fermentation will turn the agar yellow at first. However the bacteria will run out of glucose after about 10 hours and will then catabolize peptone aerobically in the slant. Only glucose fermente-pink slant/yellow butt)

If the bacteria can ferment lactose or sucrose in addition to glucose, they will continue to produce acid, and as these sugars are present in higher concentrations in the medium, the whole slant will turn yellow. (Yellow slant/yellow butt)

To test for glucose, lactose, sucrose and Iron and how it is fermented.

Peptone base, pH indicator phenol red, glucose (0.1%), sucrose and lactose (1% each) and FeSO4

Just in case the bacteria can only ferment glucose. Once it is used up, the break down of peptone (proteins) occur

FeSO4

It means having e coli like characteristics (Gram negative, non spore forming, rod shaped and able to ferment lactose with formation of acid and gas.

The first part of the coliform analysis. Water samples are inoculated into tubes of lactose broth. The lactose is the sole carbon and energy source in the organic acids and CO2 gas. The gas collects in a small inverted tube, called a Durham tube. Presence of gas in the Durham tube after 48 hours of incubation represents a positive presumptive test.

If the P Test is a positive 2nd test, the C test is carried out. Other bacteria can also ferment lactose and produce gas, including bacillus and Clostridium species, and these must be ruled out.

Bacteria from the P test are transfered to a tube of BGLBB. This broth is selective for Gram negative bacteria and again gas production is monitored using a Durham tube. After incubation, gas in the Durham tube provides a positive confirmed test indicating the presence of a Gram negative, lactose-fermenting gas former. Now part 3 of the test, called the Complete test is carried out

The bacteria growing in the BGLBB are streaked onto EMB agar plates. The 2 dyes in the agar continue to supress growth of gram positive bacteria and the color of the colonies helps to identify bacterium present. E coli colonies on EMB plates are blueish-black with dark centers when viewed by transmitted light. When viewed by reflected light, they have a distinctive green metalic sheen. These colonies represent a positive completed test.

The lactose is the sole carbon and energy source in the broth so only lactose fermenting organisms can grow.

It provides a positive confirmed test indicating the presence of gram negative, lactose fermenting gas.

It is selective for gram negative bacteria

It should have a greenish metallic coloring and it proves that there is fecal matter in the water

E Coli is used as a bacterial indicator because it is found in large numbers in human feces

No it just concludes that gas is formed.

It indicates the presence of a gram negative, lactose fermenting gas former

Is is both selective and differential. It is selective for gram negative bacteria and gas production is monitored by the Durham tube. After incubation, the Durham tube provides a positive confirmed test indicating the presence of gram negative lactose fermenting gas former.