Microbiology Portage - Module 4 Microbial Growth and Control Already Passed

Microbiology Portage - Module 4 Microbial Growth and Control Already Passed Expanding a given microbial population allows researchers to do what? to detect and assess the microorganism more easily What is Growth Media? Growth media is a liquid or solid formulated to support microbial growth. What does Growth Media contain? The media contains essential nutrients to provide the microbe with a source of carbon/energy. The nutrient composition often includes a rich source of sugars, amino acids and vitamins. What else can Growth Media also be called? Such media can also be referred to as a nutrient broth and is commonly used to grow microbes in a suspension. Describe LB media Perhaps the most common nutrient broth in the lab, LB media (lysogeny broth) is a nutritionally rich liquid known for its ability to grow a vast array of microbes. What is Selective Media? Selective media allows for only the growth of certain microbes and, by extension, restricts the growth of all others. How can Selective Media be accomplished? Such an approach can be accomplished in a variety of ways including: using limiting amounts of nutrients, varying degrees of pH (being either very acidic or very basic media), or various chemical additives that limit unwanted microbial growth (i.e.) antibiotics. Describe how Selective Media works with Gram-Positive versus Gram-Negative bacteria. If a plate is selective for Gram-Negative then it will only grow Gram-Negative bacteria on it. It will not grow Gram-Positive bacteria on it. What is Differential Media? Differential media distinguishes between two, often related, microbes. What is one way that a Differential Media can distinguish between Escherichia coli and Salmonella? They are both Gram negative but can be distinguished by the presence (or absence) of lactose fermentation. If grown on the same differential media, E coli ferments lactose and turns the culture red. In contrast, Salmonella does not ferment lactose and the culture remains white/tan in color. (This above example is probably on MacConkey agar) What is a fastidious microorganism? an organism with complex growth requirements such that if absent it will not grow What are Enriched Medias used for? Enriched media is used to grow fastidious microorganisms Enriched Medias contain what? enriched medias contain the essential nutrients required for the growth of this subset of microorganisms Can a plate be a combination of selective, differential and enriched? Yes Growth Media comes in what 2 forms? liquid and solid What is Solid Growth Media? Solid growth media, often contained within a sterile petri dish, is in its simplest form liquid growth media that has had a hardening agent added. What makes agar? The addition of a polysaccharide derived from seaweed (algae) extract added to the liquid growth media creates a solid medium called agar. What is a colony? As they grow, microbes form colonies that take on the appearance of individual isolated dots. Why does dehydrated agar (and other necessary components) get mixed with water and heated to a high temperature? to dissolve the agar into solution. The high temperature also ensures sterility as it will kill most, if not all, foreign microbes. What is LB agar also known as? lysogeny broth What color is LB agar? pale yellow What types of microorganisms can grow on LB agar? it is a multi-purpose media capable of growing a wide variety of microorganisms How is LB agar classified as far as Non-Selective, Selective and Differential? LB is classified as a non-selective and non-differential media. LB agar is commonly used for growing what specific bacteria? E. coli Trypticase Soy Agar is also known as what? TSA or TSAYE What kind of media is Trypticase Soy Agar? it is another multi-purpose media capable of growing a wide variety of microorganisms What color are Trypticase Soy Agar plates? TSA plates are virtually identical in color to LB plates (pale yellow) How is TSA media classified as far as Non-Selective, Selective and Differential? it is non-selective and non-differential What does TSA serve as the base of? it serves as the base when formulating specialized (enriched) medias. Blood agar is also known as what? BAP (blood agar plates) Blood agar is a derivative of what? It is a derivative of TSA whereby mammalian blood, often from sheep, is added to the plate. What color is Blood agar? Red How is Blood agar classified as far as Non-Selective, Selective and Differential? BAP is an enriched, non-selective yet differential media. What do the red blood cells in Blood agar promote the growth of? fastidious microorganisms such as various strains of Streptococcus. Blood agar is a differential media used to detect what? hemolytic activity. Hemolysis, or the lysis (breakdown) of red blood cells is classified as what three types? alpha, beta or gamma. When grown on Blood agar microbes capable of alpha hemolysis present as what? greenish-brown color colonies due to the incomplete (partial) lysis of red blood cells. Beta hemolysis is classified as what? the capacity of a microbe to completely lyse red blood cells. The resulting lysis of Beta hemolysis presents as what? a distinct zone of clearing around the growing colony. Gamma hemolysis designates what? the absence or lack of hemolytic activity Gamma hemolysis shows what on the Blood agar? the resulting colonies are often white/tan in color growing on the red background color of the unaffected blood agar plate What color is Columbia CNA agar? Red How is Columbia CNA agar classified as far as Non-Selective, Selective and Differential? enriched, selective and differential media What antimicrobial agents does Columbia CNA agar contain? colistin and Nalidixic acid What do colistin and Nalidixic acid suppress the growth of on Columbia CNA agar? they suppress the growth of Gram-negative bacteria What is Columbia CNA agar used for the isolation of? It is used for isolation of Gram-positive microbes What else is Columbia CNA agar enriched with? It is also enriched with blood Because