By Maleeha Fatima 

• The observable growth that appears in or on the medium is known as a culture. • The substances & environment which is provided to the microorganisms for their growth is called as media. • Culture media are contained in test tubes, flasks, or Petri dishes . • Media are extremely varied in nutrient content & consistency & can be specially formulated for a particular purpose. INTRODUCTION By Mf 

TYPES OF MEDIA Media can be classified on three primary levels  Liquid  Semisolid  Solid (can be converted to liquid)  Solid (cannot be liquefied)  Synthetic (chemically defined)  Non-synthetic (not chemically defined) •General purpose •Enriched •Selective •Differentiation •Miscellaneous Physically Chemically Functionally By Mf 

PHYSICAL STATES OF MEDIA Liquid media It is defined as water-based solutions that do not solidify at temperatures above freezing & that tend to flow freely when the container is tilted. These media termed broths, milks, or infusion, are made by dissolving various solutes in distilled water. Growth occurs throughout the container & can then present a dispersed cloudy or particulate appearance. Examples: • Luria broth • Nutrient broth By Mf 

Luria broth By Mf 

Semisolid media It exhibit clot-like consistency. It contain solidifying agent (agar or gelatin) that thickens the media but does not produce a firm substrate. This media is used to determine the motility of bacteria & to localize a reaction at a specific site. Example: • Both motility test medium & Sulfide Indole Motility (SIM) contain a small amount of agar. The medium is stabbed carefully in the center & later observed for the pattern of growth around the stab line. By Mf 

SIM agar By Mf 

Solid media It provide a firm surface on which cells can form discrete colonies & are advantages for isolating & sub-culturing bacteria & fungi. They come in two forms: 1. Liquefiable 2. Nonliquefiable By Mf 

Liquefiable solid media  also called reversible solid media  contain a solidifying agent that is thermoplastic  include agent such as agar (complex polysaccharide isolated from the red alga Gelidium)  agar is solid at room temperature & it melts (liquefies) at 100˚C Non-liquefiable solid media  have less versatile applications than agar media because they are not thermoplastic  include materials such as rice grains (used to grow fungi), cooked meat media (good for anaerobes), & potato slices  all of these media start out solid & remain solid after heat sterilization By Mf 

Nutrient agar By Mf 

CHEMICAL STATES OF MEDIA Synthetic media Media whose compositions are chemically defined are termed as synthetic media. These media contain highly pure organic & inorganic compounds that vary little from one source to another & have a molecular content specified by means of an exact formula. Examples: • Glucose-salt agar • Inorganic synthetic broth By Mf 

Glucose salt agar By Mf 

Non synthetic media Media whose compositions are not chemically defined are termed as nonsynthetic media. It contain at least one ingredient that is not chemically definable. Most of these substances are extracts of animals, plants, or yeasts including such materials as ground-up cells, tissues, secretions, milk, yeast extract, soybean digests, peptone. Examples: • Nutrient broth • Blood agar • EMB agar By Mf 

Blood agar By Mf 

FUNCTIONAL TYPE OF MEDIA These are designed to grow as broad a spectrum of microbes as possible. They are nonsynthetic & contain a mixture of nutrients that could support the growth of pathogens & nonpathogens alike. Examples: • Nutrient agar • Nutrient broth • Brain-heart infusion • Trypticase soy agar General purpose media By Mf 

Trypticase soy agar By Mf 

Enriched media It contain complex organic substances (blood, serum, hemoglobin or special growth factors) that allow certain species to grow. Examples: •Streptococcus pneumoniae is cultured on blood agar, which is made by adding sterile sheep, horse or rabbit blood to a sterile agar base •Neisseria can grow on Thayer-Martin medium or chocolate agar, which is essentially cooked blood agar. By Mf 

Chocolate agar By Mf 

Selective media It contain one or more agent that inhibits the growth of certain microbes thereby encourages the growth of desired microbe. These type of media are very important in primary isolation of a specific type of microorganism from samples containing a highly mixed population. Examples: • Mannitol Salt Agar (MSA) • MacConkey agar • Eosin-Methylene Blue (EMB) agar By Mf 

MacConkey agar By Mf 

Differential media A differential media can grow several types of microorganisms, but it is designed to highlight differences among these microorganisms. Its ability of differentiation is due to the type of agents added. Examples: • Sulfide Indole Motility (SIM) agar • Xylose Lysine Deoxycholate (XLD) agar • Triple Sugar Iron (TSI) agar By Mf 

Xylose Lysine Deoxycholate agar By Mf 

Miscellaneous media A reducing medium contains a substance (thioglycollic acid or cystine) that absorbs oxygen or slows the penetration of oxygen in a medium thus reducing its availability. These media are important for growing anaerobic bacteria or determining oxygen requirements. Example: • Thioglycolate broth Reducing media By Mf 

Thioglycolate broth By Mf 

Carbohydrate fermentation media It contain sugars that can be fermented (converted to acids) & a pH indicator to show this reaction. By Mf 

Transport media It is used to maintain & preserve specimens that have to be held for a period of time prior to clinical analysis or to sustain delicate species that die rapidly if not held under stable conditions. Example: • Stuart’s & Amies transport media contain salts, buffers & absorbants to prevent cell destruction by enzymes, pH changes & toxic substances but will not support growth. By Mf 

By Mf 

Assay media Assay media are used by technologists to test the effectiveness of antimicrobial drugs & by drugs manufacturers to assess the effect of disinfectants, antiseptics, cosmetics & preservatives on the growth of microorganisms. By Mf 

Enumeration media This media is used by industrial & environmental microbiologists to count the number of microorganisms in milk, water, food, soil & other samples. By Mf