Microbiology Lab Exam 2

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Labs 8-13

Noncellular elements that must rely on other cells to replicate

Viruses

What are viruses made up of?

Infective DNA or RNA (Viron) + a protein coat (Capsid)

Viruses that infect bacteria

Bacteriophages

Lytic Cycle

During the lytic cycle, the phage's genome is immediately replicated and new phage particles are synthesized. The phage, T4, will actually digest the bacterial cell's own DNA in an effort to focus the cell's energy to make its own DNA and phage particles. Once the phage particles are complete, the host cell will lyse, releasing the newly synthesized phage, which will then infect neighboring cells

Lysogeny

During lysogeny, the phage's DNA becomes integrated into the host's genome, called a prophage, and is then replicated along with the bacterium's genome. The prophage will remain latent until a 'cue,' usually environmental, cues triggers it to excise from the host genome. When the phage genome exits the host's DNA, it will then enter the lytic cycle and destroy the cell.

Phages that reproduce by both the lytic cycle and lysogeny

Temperate phages

Phages that replicate by only the lytic cycle

Virulent phage

Which type of phage is T4? Temperate or Virulent?

Virulent- it replicates by only the lytic cycle

What is a clearing in a lawn of bacterial growth called?

Plaque

After incubation of a bacteriophage and its appropriate host, what can be counted on an agar plate? What is assumed?

Plaque-forming units. It is assumed that one phage infects one bacterial cell, so the plaques can be counted to give an accurate statistical estimate of the amount of phage in a sample.

What technique is used to perform the plaque assay?

Pour-plate technique

Pour Plate Technique

Used to perform the plaque assay. Broth cultures of phage and bacteria are added to a tube of molten (liquified) top agar. The inoculated top agar is then poured on top of an agar plate. The top agar is allowed to solidify and then incubated. The bacteria that were added to the top agar grow as a uniform lawn over the agar plate

How does T4 replicate?

only by the lytic cycle

Plaques

If a phage is incubated along with its appropriate host on an agar plate, it produces plaques. Plaques clear the lawn of bacterial growth

Plaque-forming units

Can be counted on an agar plate. It is assumed that one phage infects one bacterial cell, so the plaques can be counted to give an accurate statistical estimate of the amount of phage in a sample

Fungi

Eukaryotic heterotrophs that have cell calls made up primarily of chitin (a polysaccharide that is very strong)

What are mushrooms and molds made up of?

Filaments of hyphae that grow from the tip. This is accomplished by cytoplasmic vesicles fusing to the tips cell membrane providing material for expansion enhanced by turgor pressure resulting in wall formation

What is the collective growth of hyphae called?

Mycelium

Submerged mycelium

Mycelium that grows on or into the medium

Aerial mycelium

Mycelium that begins to grow upward. Spores can be released from the arial hyphae.

Yeasts

unicellular, spherical/oval in shape, and grow without forming hyphae. They can reproduce sexually by fusion of sexual spores or asexually by budding

Do fungi ingest their food?

No, they excrete enzymes into the environment which breakdown organic substrates. The fungus can then absorb these nutrients

Saprotrophs

Fungi that are decomposers and cycle essential nutrients back into the environment from decaying material

Necrotrophs

Fungi that prey on living cells

Biotrophs

Fungi that utilize nutrients from living cells not killing them

Anamorphs - What are they? Give some examples.

Fungi that reproduce by mitotic cell divisions producing asexual mitospores directly from the hyphae.
Penicillium
Aspergillus

Fungi that can sexually reproduce by alteration of generations

Rhizopus

How do you know whether the telomorph stage is represented?

The presence of zygospores. They germinate to produce meiospores

Mushrooms

The multicellular fruiting bodies of some fungi. They can be grown for human consumption (portobellos) or antibiotics can be produced from them (penicillin)

Mycology

The study of fungi

What type of agar should fungi be grown on?

Potato dextrose (PDA) or Sabouraud agar because they have a slightly lower pH compared to other agars, which inhibits bacterial growth

Chemicals or processes that reduce or kill microbes on a substance and can be achieved through physical or chemical means

Antimicrobial agents

___________ are used to either decrease or kill microbes in a certain environment

Physical Methods

Name the the 4 physical antimicrobial methods

Using very high or very low temperatures (Pasteurization)
Changes in pH
Irradiation (Electromagnetic radiation using x-rays, gamma rays, or UV rays)
Filtration

_______ is a process that allows us to "disinfect" milk or other beverages that contain microorganisms

Pasteurization

______ involves heating milk to a specific temperatures for a given amount of time to kill most of the mircoorganisms present

Pasteurization

What are 2 bacteriums that pasteurization kills?

Mycobacterium tuberculosis (Tuberculosis)
Coxiella burnetii (Q fever)

_____ are chemical compounds that are used on non-living objects. Name 3 examples.

Disinfectants
Lysol cleaner, bleach, detergents

______ are chemical compounds that are used on living tissue. Name 3 examples

Antiseptics
rubbing alcohol, hydrogen peroxide, neosporin

______ are chemical compounds that will selectively kill or inhibit pathogens inside the individual without causing harm to the host (selective toxicity). They can be taken internally or applied to living tissue

Antimicrobials

________ are antimicrobial substances that are derived from microorganisms. Give 3 examples.

Antibiotics
Penicillin, streptomycin, neomycin

______ are man-made drugs that resemble antibiotics on the molecular level. Give 3 examples.

Synthetic drugs
Amoxicillin, ampicillin, nalidixic acid

Which of the following are antibiotics and which of the following are synthetic drugs?

Amoxicillin
Penicillin
Neomycin
Nalidixic Acid
Ampicillin
Streptomycin

Synthetic
Antibiotic
Antibiotic
Synthetic
Synthetic
Antibiotic

What does -cidal mean?

Destroy

What does -static mean?

Inhibit

Sterilization

When all viable organisms (Fungi, bacteria, viruses) and spores are killed

A process that only destroys pathogens from non-living substances is called _________

Disinfection

______ refers to the removal of pathogens from living tissue

Antisepsis

Disk diffusion method

The most common method used in hospitals to test a pathogen's suseptibility to an antimicrobial agent. The organism to be tested is inoculated on a Mueller-Hinton plate as a lawn and filter paper disks having known concentrations of an antibiotic are placed over the bacterial lawn using a dispenser (stamper)

Zone of inhibition

A clearing around the disks caued by the antibiotic if the pathogen is susceptible to it.

Kirby-Bauer Test

The disk diffusion method combined with the comparison of zones of inhibition diameters to a standardized chart to determine the susceptibility of the pathogen.

What type of plate is used for all Kirby-Bauer tests in order for the results to be consistant? What depth must the plate be?

Mueller-Hinton agar
5 mm

_________ inhibits protein synthesis by interrupting the transfer of amino acids to ribosomes in the cell

Chloramphenicol

Spectrum of Activity for Chloramphenicol

Bacteriostatic against a variety of gram-negative and gram-positive organisms that cause ocular infections

___ inhibits protein synthesis during translation

Neomycin

____ impetes DNA replicationb by interferring with DNA gyrase and inhibits ATPase activity

Novobiocin

_____ inhibits cell wall development by preventing peptidoglycan synthesis in the cell

Penicillin

______ increases the permeability of the cell wall membranes in bacteria

Polymyxin B

_______ Interferes with the binding between tRNA and mRNA during protein synthesis

Tetracycline

Neomycin is bactericidal against what?

Gram-negative rods and some gram-positive bacteria

Novobiocin is affective against what type of bacteria?

Gram-positive

Penicillin is bactericidal mainly agains what type of organisms?

Gram-positive

Polymyxin B is bactericidal against what type of bacteria?

Gram negative bacilli (NOT Proteus species)

Gram-negative cocci and gram + organisms are resistant

Tetracycline is bacteriostatic against what type of bacteria?

Many gram-negative and gram-positive bacteria

Streptomyces venequelae is the source of what antibiotic?

Chloramphenicol

Streptomyces fradiae is the source of what antibiotic?

Neomycin

Streptomyces niveus is the source of what antibiotic?

Novobiocin

Penicillum notatum is the source of what antibiotic?

Penicillin

Bacillus polymyxa is the source of what antibiotic?

Polymyxin B

Streptomyces aureofaciensis is the source of what antibiotic?

Tetracycline

A ___________ turbidity standard is used to standardize how much bacteria is inoculated on the plate.

McFarland

__________ media is used to isolate specific types of bacteria by containing chemical substances that allow the growth of a particular organism, while inhibiting the growth of other organisms

Selective

____ media contains chemical compounds that allow bacteria to be distinguished between eachother based on their reactions to the compounds on the media. This type of media produces a characteristic change in the appearance of the bacterial growth and/or the media it is growing on (Usually a color change)

Differential

Selective/Differential media

combines the properties of selective and differential media into one medium. It contains ingredients that inhibit/select for a certain type of bacteria and also has components that will allow you to differentiate between the bacteria that grow

_______ are incorporated into the medium to allow changes in pH to be observed as color changes to the medium

pH indicators

Staphylococci
Gram + or -?
Shape and arrangement?
Colony morphology and color?
Where is it found?

Gram +
cocci arranged in grape-like clusters
Pinhead colonies with a slightly golden color
Found on skin surfaces and upper respiratory tract

______ is generally an avirulent organisms but is capable of producing skin lesions if given the opportunity, such as a break in the skin

Staphylococcus epidermidis

Avirulent strains of __________ can produce numerous types of diseases that range from skin infections, inflammation of internalk organs, and MRSA

Staphylococcus aureus

Streptococci
Gram + or -?
Shape and arrangement?
Colony morphology and color?
Where is it found?

Gram +
Cocci arranged in chains or pairs
Pinpoint colonies on solid media

Infection with ________ can lead to strep throat or scarlet fever

Streptococcus pyogenes

_______ is a major cause of pneumonia

Streptococcus pneumoniae

______ is the breakdown of red blood cells by the production of _________

Hemolytic Activity is the breakdown of red blood cells by the production of hemolysins

_______ organisms produce no lysis of red blood cells, with no change to the surrounding medium. These organisms are generally avirulent.

Nonhemolytic

____ Hemolysis is the incomplete lysis of red blood cells

Alpha

What does a positive result of alpha hemolysis look like?

A greenish halo around the colony which is caused by the oxidation of the heme iron in the red blood cells in the agar

Organisms that are part of the normal flora of the mouth exhibit _______ hemolysis

Alpha

____ hemolysis is the complete lysis of red blood cells. The organism completely utilizes the released hemoglobin from the red blood cells using hemolysins

Beta

What does a positive result for beta hemolysis look like?

A clear halo surrounds the colonies

Which type of hemolysis is typical of pathogenic forms of staphylococci and streptococci

Beta

Blood agar is ____ type of medium

Differential but not selective

______ is an enzyme that converts hydrogen peroxide into water and oxygen gas

Catalase

Positive vs negative result for catalase

Positive causes bubbles to form
No bubbles if negative

Which types of bacteria produce catalase and which do not? (Which are positive and which are negative for catalase?)

Staphylococci
Streptococci do NOT.

Mannitol Salt agar is _____ type of agar

Both selective and differential

Which type of bacteria can tolerate the MSA?

Staphylococcus can tolerate the high salt concentration and will grow on it

What type of pH indicator does MSA have? What color is it at an acidic pH and what color is it at higher pH's?

Phenol red
Yellow at an acidic pH
Pink at basic pH

When mannitol is fermented, ____ is produced which causes the medium and colonies to turn _____

Acid
Yellow

Streptococcus pneumoniae: alpha, beta, or nonhemolytic?

Alpha

Staphylococcus aureus: alpha, beta, or nonhemolytic?

Beta: Halo around large, pinhead colony

Streptococcus pyogenes: alpha, beta, or nonhemolytic?

Beta: halo around small, pinpoint colony

Staphylococcus epidermidis: alpha, beta, or nonhemolytic?

Nonhemolytic

_______ produce catalase (+ reaction, bubbling)
_______ do not

Staphylococci produce catalase
Streptococci do not

Staphylococcus epidermidis
Gram stain
Hemolysis patterns
Catalase
NaCl Tolerant
Mannitol fermentation

Gram +
nonhemolytic
+
+
-

Staphylococcus aureus
Gram stain
Hemolysis patterns
Catalase
NaCl Tolerant
mannitol fermentation

Gram +
beta
+
+
+

Streptococcus pyogenes
Gram stain
Hemolysis patterns
Catalase
NaCl Tolerant
mannitol fermentation

Gram +
Beta
-
-
-

Streptococcus pneumoniae
Gram stain
Hemolysis patterns
Catalase
NaCl Tolerant
mannitol fermentation

Gram +
alpha
-
-
-

E coli
gram stain
lactose fermentation
H2S production
Citrate utilization

G -
+
-
-

Klebsiella pneumoniae
gram stain
lactose fermentation
H2S production
Citrate utilization

G -
+
-
+

Salmonella enterica
gram stain
lactose fermentation
H2S production
Citrate utilization

G -
-
+
+

Yersinia enterocolitica
gram stain
lactose fermentation
H2S production
Citrate utilization

G -
-
-
-

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