Flashcards in Quiz 3 Deck (97)
What is Sticky test/KOH lysis test based on?
Based on the difference between the structure and thickness of the cell wall in Gram positive and Gram negative organisms and how it affects the ease of entry of chemicals into cells.
What does KOH do?
causes the lysis of cells by breaking down the cell wall and the cell membrane.
What happens if the cell wall gets thicker?
the thicker the cell wall, the harder it is for the KOH to penetrate
Purpose of Sticky test/KOH lysis test?
it will help you confirm whether or not your organism is Gram + or Gram -
What happens to Gram - under KOH test?
They lyse more quickly when treated with base and when they lyse, DNA is released and its viscous
What happens to Gram + under KOH test?
Gram positive cells take a lot longer to lyse because they have thicker cell walls which makes the KOH harder to penetrate.
What errors can occur in Sticky Test/KOH test?
If you leave the KOH on a slide with gram + too long or use old cultures of Gram + organisms, you are going to see lysis and this leads till a false interpretation of Gram -
What type of media is MacConkey?
it is both selective and differential
What is the purpose of using MacConkey medium?
its used to isolate and differentiate between members of the Enterobacteriaceae ( Gut Bacteria )
How is MacConkey like Levine EMB?
it allows a quick preliminary indication of whether a specimen contains enteric pathogens.
What does MacConkey include? and is it defined or undefined?
Its undefined ; and includes
3. Bile salts
4. Neutral Red
5. Crystal Violet
What 2 ingredients make MacConkey a selective media? and what do they select against?
1. Bile salts
2. Crystal violet
Both of them inhibit growth of Gram +
What 2 ingredients make MacConkey a differential Media?
1. Neutral Red
What is neutral red and what color to they exhibit and low and high pH
Neutral Red is a pH indicator.
1. it is red at pH less than 6.8
2. it is Colorless to yellow as pH increases
Explain the process of how neutral red works
A gram negative will ferment lactose -> this causes acid to build up -> The acid will decrease the pH --> the pH indicator will respond to this acid build up and change to a different shade of red depending on how much lactose is fermented
MacConkey results for COLONIES that are Gram Negative, Strong Lactose fermenter?
1. these organisms produce a LOT of acid
2. Neutral red dye taken up by these organisms turn pink due to the decrease in pH, coloring the colonies RED/PINK
MacConkey results for AREA AROUND colonies that are Gram Negative, Strong lactose fermenters?
Acid that is excreted into the medium turns the neutral red dye in the medium around the colonies pink.
What happens when theres so much acid in the MacConkey medium?
this results to a large decrease in pH resulting in an opaque Bright pink halo due to precipitation of bile salts.
MacConkey results for COLONIES that are gram negative and regular lactose fermenters
Colonies are pink/red dude to decrease in pH
MacConkey results for COLONIES that are Gram Negative, NON-lactose fermenters?
Colonies are White or transparent that often turns into a brownish color.
Why are colonies a brownish color in the MacConkey results for a gram negative, non lactose fermenter?
it is due to a slight increase in pH. These organisms dont use lactose in the medium and uses the amino acids in peptone instead. Amino acid metabolism results in the release of ammonia, resulting in rise of pH
What is nutrient recycling?
The ability to break down large organic molecules such as nucleic acids, proteins, lipids, and polysaccharides that are released from dead plants/animal cells and reincorporate them into cellular material
What is required to break down large organic molecules?
It requires the production of extracellular enzymes
What are extracellular enzymes and what do they do?
They are enzymes that are made in the cells and released into the surrounding medium. These enzymes break down large molecules by HYDROLYZING the bonds and are known as hydrolytic enzymes
What is hydrolysis
Breaking bonds through the addition of a water molecule
Different types of Extracellular enzymes?
What does Glycosidase do?
Hydrolyze the glycosidic bond that binds monosaccharides
What are monosaccharides?
They are monomeric subunits of polysaccharides
What are exampls of polysaccharides
What do proteases do?
hydrolyze peptide bonds that links amino acids
What do esterases do ? ( also known as lipases)
hydrolyze ester bond between glycerol and fatty acids in fats/oils
What do nucleases do?
Hydrolyze Phosphodiester bond between nucleotides of nucleic acids such as DNA and RNA
Even after Large organic molecules are broken down, can they still get into the cell membrane?
not necessarily. the cell membrane is a selectively permeable membrane that allows only certain molecules to enter.
How can the smaller components of nutrients enter the cell if it cannot go through the cell membrane?
The cell needs Special binding proteins on or in the membrane that recognizes and binds to these specific nutrients
What happens to the molecule once it binds to these special binding proteins? Whats this process called?
it is transported across the membrane into the cell, this is known as translocation
True or False, Translocation proteins are often specific to the particular molecule they are able to transport across the membrane
U is right...
Once the molecule is translocated, what conditions must it have to be able to contribute energy to the cell
1. There has to be an appropriate metabolic pathway and
2. all the enzymes pertaining to the pathway are produced in the cell
What are carbohydrates?
Compounds containing Carbon, Hydrogen, and oxygen
What are Hydrocarbons
They are lipids.
They contain carbon and hydrogen but little oxygen and differs in structure
What are the basis for classifying carbohydrates?
They are classified according to their complexity and size, type of glycosidic bond, or fucntion
What are Simple carbohydrates?
Composed of one or two monomers and include monosaccharides and disaccharides.
What are monosaccharides?
simple sugars. that are either pentose (5C) or hexose (6C)
Examples of Pentose?
What are Dissacharides?
Two monosaccharide units connected by glycosidic bonds.
Sucrose, Lactose, Maltose
what are Complex Polysaccharides. What are its branches?
Composed of chains of more than two monosaccharides joined by glycosidic bonds
what are Oligosaccharides? and example?
contains between 3 - 10 monosaccharides .
example would be 3-unit raffinose
What are Polysaccharides and examples?
Contains more than 10 monosaccharides
example would be cellulose and starch
Where can you find Alpha (1->2) glycosidic bond?
Where can you find Alpha (1->4) glyocsidic bond?
Where can you find Beta (1->4) glycosidic bond?
Lactose and cellulose
Which glycosidic bond (alpha or beta) can humans digest?
Alpha glycosidic bonds
What is a galactosidic bond?
Any glycosidic bond in which at least one of the sugars is a galactose
Examples of structural polysaccharides?
Example of Storage polysaccharides?
Starches in plants and glycogen in animals
What are the two starches made in plants?
Why is cellulose important? What organism does not produce cellulose?
Its necessary for the rigid structure for all plants
Animals do not make cellulose.
Structure of cellulose?
Long chains of glucose linked by Beta-Glycosidic bonds, unbranched and packed in parallel bundles in plant fibers
True or false? Cellulose is insoluble in water.
What enzyme is used to hydrolyze cellulose
Cellulase hydrolyzes cellulose and releases its monomers before the glucose can be used for energy production
Where is cellulase production most prevalent?
What main role does fungi play?
Fungi serve as the main biological agents in aerobic recycling of plant materials
Difference of Gylcogen and Starch?
Glycogen: Made in animals, Highly branched polysaccharide
Starch: made in plants, can be found in the amylose or the amylopectin form
What is the characteristic of the amylose form?
It is a straight chain polymer of glucose molecules
What is the characteristic of amylopectin form?
Contains chains of glucose that are branched at frequent intervals
What are Amylases?
Glycosidases That hydrolyzes starch
What is end product of starch hydrolysis?
What is maltose?
Highly soluble disaccharide that is easily taken and used by bacteria cells
What is Starch Agar used for?
It provides a simple way to evaluate bacteria for the ability to produce diffusible extracellular amylases.
What happens once amylase is produced?
It diffuses into the medium and hydrolyzes the starch in an increasing radius from the point of growth.
How do you make the starch visible since its not visibly different from the products of its hydrolysis?
The addition of iodine which reacts with starch to produce either
1. Blue color or
2. Reddish brown color
What does blue color in starch indicate?
what does reddish-brown color in starch indicate?
True or false, Iodine reacts with any of the products of starch hydrolysis
False, it does not
Zone of hydrolysis
An organism is capable of hydrolyzing starch, and is irrespective of whether or not it is capable of utilizing the maltose, it will grow on a starch plate and show an unstained zone around the growth area when the plate is treated with iodine
Positive Reaction of Starch Hydrolysis?
Clear Colorless zone surrounds growth of colony or streak. Remainder of starch agar stains deep blue to red-brown
Negative reaction of Starch hydrolysis?
Entire plate stains deep blue or red brown with no clear or colorless zone
What are proteins composed of?
Composed of chains of amino acids linked by peptide bonds and folded into complex shapes through H-bonding, Hydrophobic interactions, and disulfide bonds
Which part of the protein provides valuable nutrients to the microorganisms?
What must happen to protein first before taken into cell
Must be broken down because its too large and complex
Protein breakdown is carried out by a number of microorganisms, which one is predominant?
Common examples of bacteria that breaks down protein?
What are Extracellular proteinases?
What do proteases or proteolytic enzymes do?
Hydrolyzes protein into smaller chains of amino acids known as peptides
what are Intracellular peptidases?
they take up peptides if they are small enough to pass through the cell to be digested
What are extracellular peptidases?
These enzymes further digest peptides if they are still too large after being broken down
What is Casein
Its primarily a phosphoprotein found in milk as the insoluble calcium salt, calcium caseinate
Qualities of calcium caseinate in media?
Large and insoluble in aqueous media
and small enough not to precipitate out of suspension
How does casein effect the characteristics of milk?
the casein in milk exists as a colloidal suspension that gives milk its characteristic of turbidity and white color
What is casein in the form of?
Skim Milk powder
What are the requirements of incubation of an organism in a casein medium?
optimal temperature at
Positive reacton of Casein medium?
If organism is capable of digesting casein
1. itll produce extracellular proteinases that will hydrolyze casein into peptides or amino acids
2. These products of the hydrolysis are soluble and no longer visible in the medium
3. Thus manifesting the proteolytic activity through the production of a clear zone around the growth
Negative reaction of Casein in medium?
No clearing of the casein under or around the growing microorganisms
2 Disadvantage of Gelatin in solidifying agent (agar)?
1. It liquefied at 28 degrees celcius ( close to room temp)
2. it was degraded by fungi and SOME bacteria
its the breakdown product of the animal protein collagen, which is found in connective tissue, cartilage, and organic matrix of bone