Essay Questions
1. Gram Positive vs. Gram Negative & Procedure (2 Part Question, list 5 things, they should
match, should start with smear preparation)
• First: Smear Preparation Steps
1. Organism growing in liquid = small drop of broth on surface of slide
2. Organism growing on solid surface = mixed into small drop of water
3. Spread organism on slide in circular motion
4. Let air dry, then pass through flame
• Second: Gram Staining Procedure
1. Flood the smear with basic dye crystal violet for 1 minute and rinse with water. Crystal violet is the
primary stain
2. Flood the smear with an iodine solution for 1 min and then rinse with water. Iodine is a mordant, a
substance that binds to a dye and makes it less soluable. After this step all cells remain purple
3. Rinse the smear with a solution of ethanol and acetone for 10-30sec, then rinse with water. This solution is a
decolorizing agent, breaks down the thin cell wall of gram negative cells, allowing the stain and mordant to
be washed away. Gram negative cells are colorless. Gram positive remain purple
4. Flood the smear with safranin for 1 min, then rinse with water. Red counterstain provides a contrasting
color to primary stain.
• **Most Critical Step is washing with alcohol b/c that tells the difference between gram
positive and gram negative**
2. 5 Scientist and their Contribution to Microbiology (2-3sentences each, bullets are fine too)
Antoni Leeuwenhoek Carolus Linnaeus Robert Koch Alexander Louis Pasteu
Fleming
-Consider him the father - Developed a - Developed Heat - Pasteur con
of Microbiology taxonomic Fixation a series of
- Began making and system for - Germ Theory experiments
using simple naming plants - Proved that tha addresse
microscopes and animals and microorganisms the cause of
-Often made a new grouping similar can cause fermentation
microscope for each organism disease -Led to the
new specimen together - A bacterium development
-Examined water and causes anthrax pasteurizatio
visualized tiny animals, - Postulates - Process of h
fungi, algae, and single- - Direct link of a liquids just e
celled protozoa; specific to kill m
“”animalcules” microbe to a bact
▪ By the end of specific disease - Began the fi
the 19th century, industrial
these organisms microbiology
were called - Intentional
microorganisms. microbes for
o Leeuwenhoek’s manufacturin
microorganisms can products
be grouped into six - Pasteurizati
categories: (Apply high h
▪ Bacteria a short per
▪ Achaea o times
▪ Fungi Kills m
organisms
, multicellular
animals
3. Stages of Bacterial Growth (2-3 Characteristics)
• Lag phase is no increase in number of living bacterial cells.
▪ Cells are adjusting to their new environment
▪ Most cells do not reproduce immediately but instead actively synthesize enzymes
to utilize novel nutrients in the medium
▪ The lag phase can last less than an hour or can last for days, depending on the species and
the chemical and physical conditions of the medium
• Log Phase is an exponential increase in number of living bacterial cells.
▪ Population increases logarithmically, and the reproductive rate reaches a constant as
DNA and protein syntheses are maximized.
▪ Populations in log phase are more susceptible to antimicrobial drugs that interfere with
metabolism and to drugs that interfere with the formation of cell structures
▪ Populations in log phase are preferred for Gram staining because most cells’ walls
are intact—an important characteristic for correct staining.
• Stationary phase is a plateau in number of living cells; rate of cell division and death roughly
equal.
▪ The metabolic rate of surviving cells declines
▪ Cells in this phase are stress tolerant because they are adapted for challenging
conditions, such as heat, high salt concentrations, and the presence of antibiotics
• Death or decline phase is an exponential decrease in number of living bacterial cells.
▪ Some cells remain alive and continue metabolizing and reproducing, but the number
of dying cells exceeds the number of new cells produced so that eventually the
population decreases to a fraction of its previous abundance
4. Prokaryotes vs. Eukaryotes (5 characteristics each)
Prokaryotes Eukaryotes
• Bacteria & Archea • Algae, protozoa, fungi, animals and plants
• No Nucleus & multicellular parasites
• Can Read DNA and make protein simultaneously • Has nucleus
• Lack various internal structures bound • DNA bound to protein
w/ phospholipid membranes • Has organelles
• No organelles • Larger in size
• Smaller in size • 80s Ribosomes
• Circular DNA • Mitosis and Meiosis
• 70s Ribosomes • Complex structure
• Binary Fission • Chromosomes paired (diploid or more)
• Single Chromosomes
5. Parts of Virus
6. 5 Stages of Viral Replication ( Lytic Stage)
1. Attachment
• Contact w/ bacteria occurs by random collision
• Molecular currents move Virons through environment
• Tail fibers responsible for attachment
• Phage attachment specific
2. Entry
• Must get past cell wall/membrane
, • Lysozyme released to weaken cell wall
• Phage injects genome through tube into bacterium
3. Synthesis
• Stops synthesizing own material, only viral aspects from genome
4. Assembly
• Phages spontaneously attach to one another to form new capsid heads
• Little or no enzyme help
• For some viruses enzymes pump genome into assembled capsid under high pressure
5. Release
• Virons are release from the cell as lysozyme completes its work on cell wall
and bacterium disintegrates
7. Intercellular vs Extracellular
• Extracellular
-Called virion
-Protein coat (capsid) surrounding nucleic acid
-Nucleic acid and capsid, also called nucleocapsid
-Some have phospholipid envelope
-Outermost layer provides protection and recognition sites
for host cells
• Intercellular
-Capsid removed
-Virus exists as nucleic acid
8. Viroid , Virion,Prion
Viroids Prions Virion
- Extremely small, circular pieces - Proteinaceous infectious - consists of a protein coat,
of agents
RNA that are infectious - Cellular PrP a capsid, surrounding a nu
and pathogenic in plants - Made by all mammals acid core
- Similar to RNA viruses but - Normal, functional - Together, a viral nucleic
lack capsid structure has α- helices acid its capsid are also
- May appear linear because - Prion PrP called a nucleocapsid, whic
of hydrogen bonding - Disease-causing form has β-sheets in many cases can
- Viroidlike agents affect some - Prion PrP causes cellular PrP crystallize like crystalline
fungi to refold into prion PrP chemicals
-Prion diseases - Some virions have a
phospholipid membrane
call
-
Spongiform encephalopathies an envelope surrounding
the
-
Large vacuoles form in brain nucleocapsid.
-
Characteristic spongy - The outermost layer of a v
appearance (capsid or envelope)
-
BSE, vCJD, kuru provide
- Transmitted by ingestion, the virus both protection
and
transplantation, or contact of recognition sites that bind
mucous membranes with infected complementary chemicals
tissues surfaces of their specific h
- Prions are destroyed by
incineration or autoclaving in
concentrated sodium
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