44 terms

Advanced Microbiology Exam I

How are facilitated diffusion and passive diffusion similar list two.
movement of molecules are not energy-dependent; Direction of movement from high concentration to low concentration; Size of concentration gradient impacts rate of uptake
How are facilitated diffusion and passive diffusion different? List two.
Facilitated diffusion use carrier molecules (permeases), passive diffusion does not; Facilitate diffusion is more efficient: smaller concentration gradient is required for significant uptake of molecules; Effectively transport compounds that facilitated diffusion can not transport e.g. glycerol sugars and aminoacids
List 4 reasons that make a bacterial endospore resistant to environmental conditions
1. Dipicolinic acid (15% of dry weight of the spore complexed with Ca ions), located in the core: thought to be involved in heat resistance (however, heat resistant mutants has been isolated)
2. Calcium: help increase resistance to wet heat, dry heat, and oxidizing agents.
3. Calcium - dipicolinic acid complexes: might stabilize spores nucleic acid
4. Small acid-soluble, DNA-binding proteins (SASPs): saturate spore DNA and protect it from heat, radiation, desiccation, and chemicals
5. Dehydrated core: cortex can remove water from the core protect it from heat and radiation damage
6. Spore coat: thick, impermeable, protects against enzymes and chemicals
7. DNA repair enzymes: repairs DNA once spores germinate.
List 3 differences between archaeal and bacterial membrane lipids
1. Polar head: Phosphorylated ethanolamine in Bacteria, variable in Archaea
2. Nonpolar tail: Glycerol ester of various fatty acids in Bacteria. Glycerol ether of C20 hydrocarbons in Archaea (e.g. Phytanol)
3. Non polar tail can dimerize to form a membrane monolayer in Archaea but not in the Archaea
4. Additional nonpolar lipids in Archaea are called Squalene, and tetrahydrosqualene while in Bacteria they are called Hopanoids
Define "Origin of Replication"
A specific site within the bacterial genome where DNA replication begins
Define "Terminus"
A specific site within the bacterial genome where DNA replication ends
Define "Replisome"
The group of proteins needed for DNA synthesis; most important of which is DNA polymerase, these proteins attach to the origin of replication to initiate chromosome replication phase of the prokaryotic cell cycle
Define MreB
A protein present in eukaryotic cells, similar to the eukaryotic protein actin. It plays a role in determination of the cell shape and movement of chromosomes to opposite cell walls
Define and list the function of "Carboxysome"
Definition: Non-storage inclusions bodies that are present in carbon fixing bacteria
Function: Contain the enzyme ribulose-1,5,-bisphosphate carboxylase (Rubisco), enzyme used for CO2 fixation
Define and list the function of "Magnetosome"
Definition: Non-storage inclusions bodies that are present in some aquatic bacteria, are formed of magnetite (Fe3O4), and are usually arranged in chains (magnetosome chain)
Function: magnetite particles for orientation in Earth's magnetic field, which is thought to help the cells move downwards towards more organic compound rich sediments.
Define and list the function of "Gas Vacuoles"
Definition: A gas Vacuole is an aggregate of thousands of hollow, cylindrical single protein structure called gas vesicles. Gas vacuoles are present in many photosynthetic and aquatic bacteria.
Function: Vacuoles provide buoyancy to a cell: by synthesizing more vacuoles or collapsing existing ones, cells can adjust their location and position themselves where optimum environmental conditions for their growth exists
Choose the Correct Answer:
The cytoplasmic membrane of bacteria
A. retains the cytoplasm and its contents.
B. acts as a selectively permeable barrier, allowing some molecules to pass while preventing the movement of others.
C. is the major site of ATP synthesis and respiratory process in bacteria.
D. all of the above
D. All of the above
Choose the correct answer:
Which of the following is/are true of capsules?
A. They help bacteria escape phagocytosis by host cells.
B. They protect the cell from harsh environmental conditions e.g. desiccation
C. They prevent entry of many bacterial viruses.
D. all of the choices
D. All of the choices
Choose the Correct Answer:
Chemotaxis is a process by which bacteria
A. move toward an attractant or away from a repellent.
B. avoid phagocytosis.
C. respond metabolically to the presence of autoinducer molecules.
D. move on solid surfaces by means of type IV fimbriae.
A. Move toward an attractant or away from a repellent.
Choose the Correct Answer:
Organisms that can use carbon dioxide as their sole or principal source of carbon are
A. auxotrophs.
B. autotrophs.
C. prototrophs.
D. heterotrophs.
B. Autotrophs
Choose the Correct Answer:
Mannitol salt agar (MSA) only allows the growth of halophiles; nonhalophiles will not grow. Among the halophiles, mannitol fermenters will produce acid that turns the pH indicator yellow; mannitol nonfermenters leave the medium red. Onto MSA you inoculate a halophilic mannitol fermenter and a halophilic mannitol nonfermenter. In this case, the medium is acting as (a) __________ medium(s).
A. selective
B. differential
C. selective and differential
D. enrichment
B. Differential
Choose the Correct Answer:
The movement of molecules across a membrane from an area of lower concentration to an area of higher concentration with the expenditure of energy is called
A. facilitated diffusion.
B. osmosis.
C. passive diffusion.
D. active transport.
D. Active Transport
Choose the Correct Answer:
Which of these methods can be used to determine the number of viable microorganisms in a sample?
A. light scattering in a spectrophotometer
B. measuring total cell mass
C. measuring colony forming units per ml
D. counting a known volume of cells in a hemocytometer
C. measuring colony forming units per ml
Choose the Correct Answer:
The actin-like protein that seems to be involved in determining cell shape and chromosome movement is
A. MreB.
B. ActA.
C. SpnC.
D. FtsZ.
A. MreB
Choose the Correct Answer:
Which of the following is a reason for the occurrence of a lag phase in a bacterial growth curve?
A. The cells may be old and depleted of ATP, essential cofactors, and ribosomes that must be synthesized before growth can begin.
B. The medium may be different from the previous growth medium so that the cells must synthesize new enzymes to use different nutrients.
C. The organisms may have been injured and require time to recover.
D. All of these are potential reasons.
D. All of these are potential reasons.
Choose the Correct Answer:
Organisms that grow near deep-sea volcanic vents are likely to be
A. alkylophilic.
B. acidophilic.
C. barophilic or barotolerant.
D. picrophilic.
C. barophilic or barotolerant
Choose the Correct Answer:
Organisms that are damaged by the normal atmospheric levels of oxygen (20%) but require oxygen at levels of 2-10% for growth are called
A. facultative anaerobes.
B. microaerophiles.
C. aerotolerant.
D. anoxygenic.
B. Microaerophiles.
Choose the Correct Answer:
A growth medium that distinguishes among different groups of bacteria on the basis of their biological characteristics is called a __________ medium.
A. selective
B. differential
C. enrichment
D. transport
B. Differential
True or False:
Sterol-like molecules called hopanoids are thought to be important for the structural integrity of many bacteria because of their suspected role in membrane stabilization.
True or False:
A given medium can be either selective or differential but not both.
True or False:
The primary mechanism by which DNA is damaged by ultraviolet radiation involves the formation of thymine dimers.
True or False:
During the assembly of the bacterial flagellar filament, the flagellin protein monomers assemble at the cell proximal base of the flagellum.
True or False:
When a young, vigorously growing culture of bacteria is transferred to fresh medium of the same composition, the lag phase is usually short or absent.
True or False:
FtsZ protein is important in Cytokinesis (septation) since it mediate the formation of a Z ring which is essential for septation
True or False:
Although the cell cycle of E. coli (i.e. chromosome partitioning and cyokinesis) requires 60 minutes to be completed, E. coli cell could have a generation time (i.e. can double) in a much shorter time (e.g. 20-30 minutes)
True or False:
Obligate haophilic microorganisms (e.g. Halophilic Archaea) adapt to the high salt levels in an environment by synthesizing and uptaking organic compounds called compatible solutes, while halotolerant microorganisms adapt to the high salt levels by accumulating high levels of intracellular potassium
True or False:
When using a spectrophotometer to measure cell growth (turbidity), a dense cell suspension will result in more light being detected at the detector, while a dilute cell suspension will result in less light being detected at the detector
True or False:
Gram-positive bacteria have a structurally and chemically more complex cell wall than gram-negative bacteria.
Fill in the Blank:
The three domains of life are ________, ________, and __________.
Bacteria, Archaea, Eukaryotes
Fill in the Blank:
Examples of organic inclusion bodies include __________, __________, _____________, ___________. ____________, while examples of inorganic inclusion bodies include ____________.
Organic: Cyanophycin, Carboxysome, Poly Beta Hydroxybutyrate (PHB), Glycogen, gas vacuoles
Inorganic: Polyphosphate sulfur granules
Fill in the Blank:
The three main structural parts of the flagella are the _________, _________, and ___________.
Filament, Basal Body, Hook
Fill in the Blank:
Lipopolysaccharide part of the cell wall of gram negative bacteria is formed of three parts: ___________, ____________, and _____________.
Lipid A, O side chain (O antigen), Core Polysaccharide
Fill in the Blank:
Growth Curve has four phases: ______, ________, _________, _________.
Lag, Log (exponential), Stationary, Death
Fill in the Blank:
A _________ is a polysaccharide layer that lies outside the cell wall and is not easily removed, while a _________ consists of diffuse unorganized polysaccharide material that lies outside the cell wall and is easily removed.
Capsule, Slime layer
Fill in the Blank:
Colonies grow most rapidly at the ______ where oxygen and nutrients are readily available; however, they grow less rapidly at the _______ where these materials have been depleted.
Edge, Center
Fill in the Blank:
Organisms with growth temperature maxima above 100°C are referred to as __________________.
Fill in the Blank:
Many bacteria facilitate the uptake of iron by secreting low molecular weight molecules, called ___________ to form complexes with the iron that can then be readily transported into the cell.
Fill in the Blank:
The _________ is the length of time it takes for a population of microorganisms to double in number.
Doubling time or generation time
Fill in the Blank:
Organisms that can grow in habitats in high osmotic pressure by maintaining a high internal salt concentration are called _______ organisms, while those that can grow in habitats with low high osmotic pressure by accumulating compatible solutes are called ______________.
Halophilic (osmophilic), Halotolerant (osmotolerant)