07-Microbial Culturing

Amino acids, salts, and nutrients needed for microbial growth.

A single distinct colony.

EMB (Eosin Methylene Blue) Agar, which provides a color indicator distinguishing between organisms that ferment lactose (e.g., E. coli) and those that do not (e.g., Salmonella, Shigella).

To isolate a pure strain from a single species of microorganism.

Bubbles of oxygen gas are produced when peroxide is added to a smear of culture.

Organic growth factors are compounds that the organism cannot synthesize on its own and must obtain from the environment, such as vitamins, amino acids, and nucleotides.

A non-selective media that contains additional factors needed to grow microbes with particular needs. An example is Chocolate Agar.

To produce viral particles for study or for vaccine production.

Clumping of the plasma when a drop of rabbit plasma is added to a smear of culture.

The media and everything used to manipulate it.

Factors such as pH, temperature, oxygen levels, and nutrient availability must be considered to provide optimal growth conditions for specific microbes.

Because a clear ring is seen around colonies of bacteria which are capable of hemolysis (lysing red blood cells).

12 - 15 hours

Water exits the cell.

A media that only supports the growth of specific microbes. It is often used to isolate a particular species. An example is Pseudomonas Isolation Agar, which allows Pseudomonas aeruginosa to grow while inhibiting E. coli.

Because viruses lack the cellular machinery to reproduce.

Chickenpox virus and polio virus.

To determine what antibiotic therapies may be effective against the identified organism.

Trace elements are inorganic elements required in small amounts, mostly for specific enzymes, such as iron, copper, zinc, magnesium, and calcium.

Partial hemolysis, e.g., Streptococcus pneumoniae.

A secreted invasin enables the bacteria to penetrate host cells and move to other tissues.

40°C

As biofilms and communities.

They will be clones, genetically identical.

H2O2 (peroxide) → H2O + O2 (gas)

Because they help ensure that the culture remains uncontaminated and safe for workers.

Viruses are cultured using host cells, such as animal cells, bacterial cells, or plant cells, because they require a living host to replicate.

Oxygen makes energy generation more efficient but can be lethal to some organisms. Microorganisms can be obligate aerobes, obligate anaerobes, or facultative anaerobes.

Non-hemolytic, e.g., Group D Strep (Enterococcus).

Acidic pH levels (pH 5-6).

37°C

Agar, a carbohydrate extracted from seaweed.

To keep the culture pure and uncontaminated, and to protect workers and the lab from contamination.

Bacterial lawns are used to study the effects of antibiotics, bacteriophages, and other antimicrobial agents on bacterial growth.

Needle aspiration from the subarachnoid space of the spinal column.

Nitrogen is found in amino acids (proteins) and nucleotides (DNA, RNA).

Because the neutral red dye becomes red in the presence of the waste products of lactose metabolism.

17 - 20 minutes

Helicobacter pylori.

34°C

Bacteria, yeast, and some protists.

To differentiate staphylococci (catalase-positive) from streptococci (catalase-negative).

Influenza virus for flu shots.

Quickly identifying many medically relevant organisms using holders or tubes with various types of media and colored indicators.

Catheter or 'clean catch' urine sample.

Phosphorus is found in DNA, RNA, ATP, and phospholipids (membranes), and makes up 4% of the dry weight of a cell.

5-10% whole sheep blood.

27 - 30 minutes

There is no water movement.

The chemical composition is precisely known. An example is Minimal Media, which contains the minimum nutrients possible for colony growth, allowing only certain species to grow.

MacConkey agar is both selective and differential, used to isolate Gram-negative bacteria and differentiate them based on lactose fermentation. Blood agar is enriched and differential, used to grow fastidious organisms and differentiate bacteria based on hemolytic activity.

Sulfur is found in amino acids, thiamine, and biotin, and makes up 4% of the dry weight of a cell.

To isolate pathogens with complex nutritional requirements and to detect hemolytic activity.

Because the severity of the disease is dependent on the host’s immune system.

30°C

As pure cultures.

On bacterial lawns, where they appear as 'plaques' or clearings.

Proteus species.

Liquid media are nutrient-rich solutions used to grow bacteria in a liquid environment, while solid media contain agar and are used to grow bacteria on a solid surface. They are used to culture and isolate microorganisms.

For isolation of Gram-negative bacteria.

Complete hemolysis, e.g., Streptococcus pyogenes (GAS) and Streptococcus agalactiae (GBS).

18 - 24 hours

Salt curing process.

A non-selective media that encourages the growth of a range of microbes. Examples include Nutrient Agar and TSA (Tryptic Soy Agar).

Staphylococcus aureus.

It produces ammonia and raises the pH.

Carbon is used for structural organic molecules and as an energy source.

Because the crystal violet prevents Gram-positive bacteria from growing.

Ready to eat (RTE) foods such as deli meats, soft cheeses, and sprouted vegetables.

To provide microorganisms with the nutrients and media to multiply under laboratory conditions.

30°C

The presence of the enzyme coagulase, which converts fibrinogen to fibrin.

HIV in genetically modified mice.

Needle aspiration from a vein.

Biopsy.

Crystal violet, lactose, protein, and neutral red dye.

A Gram-positive bacillus.

33 hours

37°C

Embryonated eggs, tissue/cell culture, and living animals.

Sterilization is necessary to eliminate any contaminating microorganisms that could interfere with the growth and study of the target microbes.

Intubation.

Bell jars, GasPak™ jars, and glove boxes may be used to provide oxygen-free environments. Reducing media, which contains chemicals that react with and remove O2 from the media, is often used.

Listeriosis.

Neutral pH levels (pH 6-8).

Halotolerant organisms, such as Staphylococci.

Because the blood supports the growth of additional microbes.

Clinical features range from mild flu-like symptoms to meningitis and bacteremia.

The time period in which bacteria will double in number under proper nutrients and growth conditions.

Sputum from a cough or catheter.

It supports the growth of many species, but some will have a different appearance due to the characteristics of the medium.