MicroBio Review Chapter 2
swimming speeds are determined by
a combination of factors, including microbial species, size, environmental conditions, and chemotactic factors.
pili
filamentous proteins extending from the cell with various functions such as conjugation, transformation, and twitching motility
polar arrangement flagellum
flagella at one or both ends of the cell, respectively.
lophotrichous
flagella located in a tuft on one end
amphitrichous
flagella located in tufts on both ends
Differences in the energy-coupling mechanisms and the flagellar protein structure suggests that
flagellar motility evolved separately in Archaea and Bacteria after the domains diverged over 3.5 billion years ago.
Despite the different possibilities of flagellar arrangements, they all
function primarily to propel a microorganism through its environment to reach nutrients or other similar microorganisms
Which of the following structures enable a Bacterial or Archaealcell to adjust its position in a water column?
gas vacuoles
periplasm
gel-like space with hydrolytic enzymes for nutrient transport and chemoreceptors to direct movement
Predict which type of organism would be more difficult to treat with antibiotics and why.
gram-negative organisms -- extra layer of LPS
CCCC0------
hypha - budding and appendaged bacteria
Staining of microbial samples before microscopy is used to __________.
increase sample contrast for better visibility
S-Layer
interlocking molecules of protein or glycoprotein that prevents osmotic lysis and acts as a semipermeable barrier
A glycoprotein
is a type of peripheral protein above that can be used as a receptor or in enzymatic functions.
slime layer
loose, easily deformed, sticky matrix of either polysaccharide or protein that allows prokaryotes to form biofilms and avoid dehydration
thick cell wall
made of peptidoglycan, enables prokaryotes to withstand high pressures without lysing
similarities or differences between archaeal and bacterial flagella
may contribute to, but do not ultimately determine swimming speeds of microorganisms.
Which of the following is an essential tool in the study of microorganisms?
microscope
Once equilibrium is reached,
molecules move, but there is no net movement in a particular direction.
Taxis is
movement towards or away from a stimulus.
pertrichous
multiple flagella, all over the cell
fibriae
numerous filamentous proteins extending from cell that aid in adhesion and pellicle or biofilm formation
Two types of light microscopy that do not use stains but are able to increase the contrast of samples being viewed are __________.
phase contrast and dark-field microscopy
Lophotrichous and amphitrichous arrangements are types of
polar arrangement
A student observed a stained specimen of bacteria using bright-field microscopy. At 100x magnification, there appeared to be only one cell in the field of view, but at 1000x it was clear that there were two cells close together. The ability to distinguish these two cells as separate entities is called __________.
resolution resolution <==> magnification
In microscopy, what is the limiting factor in our ability to see microorganisms clearly?
resoultion
-------
rod
As a bacterium approaches a food source, one would expect
runs to become more frequent.
Peritrichous arrangement
shows flagella extending from all over the cell.
The cytoplasmic membrane is termed "semi-permeable" because some substances, like water and alcohols, can pass freely through while others, like sugars, amino acids, and ions, cannot. What molecular characteristics largely determine whether or not a substance can pass through the membrane?
size and hydrophobicity
~~~ ~~ ~~~ thin waved
spirochete
~~~~~~~ thick wave or slight curve
spirriulum
CCCCO----*
stalk - budding and appendaged bacteria - has "foot"
Which of the following cell inclusions resides in the periplasm of gram-negative bacteria?
sulfur globules
An example of a differential stain is __________.
the Gram stain
Regardless of size, organisms in all three domains are capable of motility. However...
the differences in the mechanisms behind their motility point to evolutionary adaptations by each domain.
capsule
tight, sticky matrix of either polysaccharide or protein that allows prokaryotes to attach to solid surfaces and protect from dessication
Integral proteins are mostly involved in
transport function.
scanning electrion microscopy (SEM)
with SEM the electrons scan the surface of a specimen to give a three-dimensional view
Which structural feature of Gram-positive bacteria enhances their ability to retain the crystal violet dye?
* a thick peptidoglycan layer * a thin peptidoglycan layer * an outer membrane
shape/morphology of the microbial cell
* coccus * spirochete * rod * spirillum * filamentous bacteria * hypha and stalk (budding and appendaged)
Identify the pieces of the cytoplasmic membrane correctly.
* hydrophobic groups - outside * hydrophilic groups - inside * integral membrane protein - span over membrane * layer of phospholipid molecules coat * 6--8nm wide
How does motility relate to flagellation?
* polarly flagellated organisms move more quickly than peritrichously flagellated organisms * Bacteria with peritrichously arranged flagella change direction by changing the flagellar rotation and "tumbling." * Peritrichously arranged flagella may only rotate counterclockwise. * Certain flagellated prokaryotes exhibit gliding motility, a slower and smoother form of movement along the long axis of a cell. * Bacteria with amphitrichously arranged flagella change direction by periodically stopping to reorient themselves or by changing the flagellar rotation.
bacterial flagella
* powered by a proton-motive force * flagellin proteins are unrelated to those seen in bacterial flagella * twice as small as archaeal flagella * double the width of archaeal flagella
Archael flagella
* powered directly by ATP * made of flagellin proteins unrelated to those seen in bacterial flagella. * about twice as long as bacterial flagella. * are about half as wide as bacterial flagella.
This question highlights the structure of the Gram-positive cell wall.
* wall-associated protein * teichoic acid * peptidoglycan * lipgoteichoic acid
prokaryotes have developed a number of cell surface structures that promote their survival and reproduction...such as...
*thick cell walls *lipopolysaccharide layers * periplasm *S-layers, capsules *slime layers * fimbriae, * pili
In what size range is the diameter of a typical prokaryotic cell?
0.5 to 2 μm
PROCEDURE STEP 4. Counterstain with safranin for 1-2 minutes
4. Counterstain with safranin for 1-2 minutes RESULT --> gram negative cells are pink/red and gram positive cells appear purple
Motility and flagellation
A bacterium does not continuously swim at one speed in one direction. Different arrangements and structures of flagella contribute to changes in speed and direction when necessary.
Why is ATP necessary for active transport?
ATP provides energy to transfer material against its concentration gradient.
What would you expect to see if you forgot to perform step 2 of the Gram stain procedure?
All bacteria would appear pink.
What would you anticipate seeing if you accidentally switched crystal violet and safranin while performing a Gram stain?
All bacteria would appear purple.
Which type of active transport protein uses one protein to pump two different molecules?
Antiport and Symport
Why is a specimen smaller than 200 nm not visible with a light microscope?
Anything smaller than 200 nm cannot interact with visible light.
Which molecule shown in the animation, the square or the circle, is moving against its concentration gradient?
Both the circle and the square
How does water enter and exit a cell?
By simple diffusion or by use of an integral transport protein
Which of the following statements best describes how fimbriae and capsules differ from each other?
Fimbriae are filamentous structures whereas capsules are not.
Which of the following statements about bacterial flagella is true? FLAGELLA MOVEMENT
Flagella can rotate 360 degrees.
Archaeal vs. bacterial flagella
Flagellar motility is widespread in both Archaea and Bacteria. * some archaeans (Methanocaldococcus) swim faster than E.coli bacteria * some (Halobacterium) are slower. wide range of speeds may indicate that flagellar motility is an example of convergent evolution.
Porins are present in ______________bacteria because, in these organisms, molecules entering the cell must pass through an extra layer of ___________.
Gram-negative; membrane
Which statement best illustrates the importance of a high surface-to-volume ratio that is found in microorganisms?
If a cell has a high surface-to-volume ratio, there will be enough surface area to get the needed nutrients in to support cellular metabolism and the accumulated waste out.
Cell surface structures
In addition to flagella that allow for motility, prokaryotes have developed a number of cell surface structures that promote their survival and reproduction.
Predict why dipicolinic acid is only found in endospores and not vegetative cells.
It binds free water and aids in dehydration, which would be detrimental to vegetative cells.
What is meant by light rays being divergent?
It is spreading out
Which of the following molecules is shared by both Gram-positive and Gram-negative organisms?
N-acetylmuramic acid
What is the most likely outcome for the treatment of a suspension containing equal numbers of bacterial and archaeal cells in a hypotonic solution with lysozyme?
Only the Bacteria will be lysed.
Which of the following terms refers to a bacterium moving towards a light source?
Positive phototaxis
Which of the following would not move freely across the cytoplasmic membrane?
Positively charged hydrogen ions
PROCEDURE STEP 3. Decolorize with alcohol briefly -- about 20 seconds
RESULT --> Gram-negative cells are colorless and gram positive cell remain purple
PROCEDURE STEP 2. Add iodine solution for 1 min
RESULT --> all cells remain purple
PROCEDURE STEP 1. flood with heat - fixed smear with crystal violet for 1 min
RESULT --> all stains remain purple
Which type of active transport protein moves two molecules into the cell at the same time?
Symport
transmission electron microscopy (TEM).
TEM electrons show the details inside the cell in a thinly sliced specimen.
There is no solid evidence that swimming speeds are solely determined by flagella width or length, flagellin protein, or the number and arrangement of flagella.
TRUE -- >The relationship of structure and function in microbial flagella
Why is no energy required in passive transport?
The concentration gradient drives the movement.
Flagellar arrangement
The number and arrangement of flagella can be different for different microorganisms. For instance, flagella arrangement can be described as: amphitrichous, monotrichous, peritrichous, lophotrichous, or polar.
In a typical brightfield microscope (seen in the animation), at which point does magnification begin?
The objective lens
Why are receptors on the cell surface necessary for bacterial movement?
The receptors sense the stimulus and send signals to the flagella.
Explain why the presence of a capsule or slime layer would benefit a bacterial cell.
These outer layers can aid in attachment to solid surfaces.
What happens to the light rays when they hit the specimen?
They are reflected, refracted, or absorbed by the specimen.
Which of the following is the best explanation for how membranes conserve energy?
They develop proton motive force, which drives the activity of ATP synthase.
What makes phospholipid membranes good at keeping some molecules out, and allowing others to freely pass?
They have both hydrophilic and hydrophobic regions.
What is the role of the ocular lens?
To recreate the image in the viewer's eye
Wide range of speeds may indicate that flagellar motility is an example of convergent evolution.
True
Which transport protein employs transporters that move molecules only in one direction?
Uniport and Symport
the speed of Bacteria and Archaea is determined by:
a combination of structural, functional, and environmental factors...The relationship of structure and function in microbial flagella
An ABC transporter refers to __________.
a transporter that employs an ATP-binding cassette
While staining a mixed culture of Gram-positive and Gram-negative bacteria, switching the order of steps 2 and 3 would result in ______________________.
all bacteria appearing pink
Teichoic acid molecules in Gram-positive cell walls include phosphate groups. Therefore, they will __________.
bind positive ions like Mg2+ and Ca2+
Amoxicillin is an antibiotic that inhibits the formation of peptide cross-links. Amoxicillin, therefore, would most likely inhibit the growth of __________.
both Gram-positive and Gram-negative organisms
O
coccus
Which of the following terms refers to a bacterium with a spherical shape?
coccus
In terms of structure, the flagella of all microorganisms are.
composed of multiple subunits of the same protein.
lipopolysaccharide layer
confers strength and protection and is toxic to many animals because of its lipid A component
This type of microscopy allows you to see microbial cells and communities in three dimensions.
confocal laser scanning microscopy
the number and arrangement of flagella can be
different for different microorganisms.
Which of the following is NOT a type of light microscopy?
electron micsroscopy
Which list contains the correct components of a bacterial flagellum?
filament, hook, basal body
------- thin long , hair like
filamentous bacteria