Chapter 3.6-3.9 (quiz 3)
What are the two types of cell walls among bacteria?
Gram-positive and Gram-negative
What are the two parts of the LPS molecule?
Lipid A and O-specific polysacchride
What species of bacteria lack a cell wall?
Mycoplasma, one of which causes a mild form of pneumonia
glycan chain
NAM and NAG covalently joined to one another
Describe endospore formation
Sporulation: it is a complex, highly order sequence of changes that initiates when sporeforming bacteria are grown in low amounts of carbon or nitrogen. Apparently the cells sense starvation conditions and therefor begin the 8 hour process that prepares them for rough times ahead (69)
Dental plaque is an example of what? and how does it damage teeth?
a biofilm on teeth, Streptococcus mutans uses sucrose to synthesize a capsule, which enables it to adhere to and grow in the crevices of the tooth. Acid production by bacteria in the biofilm damages the tooth surface
peptidoglycan
a macromolecule found only in the cell wall of bacteria, which contributes to the rigidity of its cell wall
endosymbiont
a partnership of the intracellular bacterium (77).
teichoic acids
a prominent component of the Gram-positive cell wall, these are chains of a common subunit, either ribitol-phosphate or glycerol phosphate. Joined to the peptidoglycan molecule through covalent bonds to N-acetylmuramic acid.
The cell wall of most prokaryotes is:
a rigid structure that determines the shape of the organism. Prevents lysis
Biofilm
a slime layer, a polysaccharide encased mass of bacteria coating a surface. ei: dental plaque.
fimbriae
a type of pili which enable attachment of cells to specific surfaces. At the tip or along the length of the molecule is located another protein, an adhesion, that adheres by binding to a very specific molecule.
Chemotaxis
a way by which motile bacteria sense the presence of chemicals and responds by moving in a certain direction.
tumble
after a brief period, the direction of rotation of the flagella is reversed, this abrupt change causes the cell to stop and roll, called a tumble (66).
what is the basic structure of peptidoglycan?
an alternating series of two major subunits: N-acetylmuramic and N-acetylglucosamine (NAM and NAG); theses subunits are related to glucose.
Lysozyme
an enzyme found in many body fluids including tears and saliva, breaks the bond that links the alternating NAM and NAG molecules of peptidoglycan. Destroys the structural integrity of the glycan chain, the backbone of the peptidoglycan molecule.
cytoskeleton
an interior protein framework. Involved in cell division and controlling cell shape (68)
basal body
anchors the flagellum to the cell wall and cytoplasmic membrane
How do antibiotics and antibacterial substances affect bacteria?
antibiotics interfere with synthesis of peptidoglycan or alter its structure causing cell lysis
lipoteichoic acids
are a type of teichoic acid, are linked to the cytoplasmic membrane of gram positive bacteria.
Storage granules
are accumulations of high molecular weight polymers synthesized from a nutrient that a cell has in relative excess (68)
Plasmid
are circular, supercoiled, double stranded DNA molecules. A cell generally does not require the genetic information carried by a plasmid. Many plasmids code for the production of one or more enzymes that destroy certain antibiotics.
Ribosomes
are intimately involved in protein synthesis, where they serve as the structures that facilitate the joining of amino acids.
Why don't antibiotics affect eukaryotic cells?
because they don't have peptidoglycan
what are the characteristics of mycoplasma?
because they lack a rigid cell wall they are variable in shape, neither penicillin nor lysozyme affects these organisms, their cytoplasmic membrane is stronger than that of most other bacteria. They have sterols in their membrane; rigid planar molecules stabilize membranes, making them stronger.
How is germination triggered in endospores?
by a brief exposure to heat or certain chemicals. Since one vegetative cell gives rise to one endospore, sporulation is not a means of cell reproduction. (70).
What are the internal structures of prokaryotic cells?
chromosome, plasmid, ribosomes, cytoskeleton, storage granules, gas vesicles, and endospores
hook
connects the filament to the cell surface
In Gram-negative bacteria, tetrapeptides are joined _____.
directly (61), from NAM to NAM
What are the three basic parts of the flagella?
filament, hook, and basal body
What is a type of pili?
fimbriae
What are the components of the outer membrane of gram-negative cells?
has porins, has secretion systems, lipopolysaccharide layer (LPS), the O.M is joined to peptidoglycan by means of lipoprotein molecules.
repellent
in chemotaxis, the bacteria will detect the toxin/repellent causing cells to move away
attractant
in chemotaxis, the bacteria will move toward the nutrient/attractant
In Gram-positive bacteria tetrapeptides are joined _____.
indirectly by a series of amino acids, a peptide interbridge. connecting from NAM to NAM.
Flagellum
is a long protein structure responsible for most types of bacterial motility. Spins like a propeller, using proton motive force as energy (65).
Endospore
is a unique type of dormant cell produced by a process called sporulation within cells of certain bacterial species, such as genera Bacillus and Clostridium (69)
Penicillin
is the most thoroughly studied of a group of antibiotics that interfere with peptidoglycan synthesis (62)
filament
is the portion extending into the exterior environment , it is composed of identical subunits of a protein called flagellin
sex pilus
is used to join one bacterium to another as a prelude to a specific type of DNA transfer.
What does "S" stand for in terms of ribosomes?
it is a distinct unit which determines the relative size and density of ribosomes and thier subunits, that reflects how fast they settle when spun at very hight speeds in an ultracentrifuge.
What is glycocalyx and where is it found?
it is found in capsules and slime layers of bacteria, it composed of polysaccharides.
Describe the chromosome of prokaryotes
it resides as an irregular mass within the cytoplasm, forming a gel-like region called the nucleoid. Chromosomal DNA is typically a single, circular double stranded DNA molecule. It is tightly packed and is supercoiled, which appears to be stabilized by the binding of positively charged proteins (67).
how does the flagella move?
it runs and tumbles
lipopolysaccharide layer (LPS)
on the outside layer of the outer membrane
Outer membrane
only in gram-negative bacteria, serves as a barrier to the passage of most molecules.
secretion systems
proteins produced by the cell that are destined for secretion are moved across the outer membrane by this mechanism
Ribosomes are composed of:
ribosomal proteins and ribosomal RNAs
O-specific polysaccharide
side chain is the portion of LPS directed away from the membrane, at the end opposite that of lipid A.
Porins
small molecules and ions can cross the membrane through porins, which are specialized channel-forming proteins
Gas vesicles
some aquatic bacteria produce gas vesicles, small, rigid, protein-bound compartments that provide buoyancy to the cell. Gasses flow freely into the vesicles thereby decreasing the density of the cell.
endosymbiont theory
states that the ancestors of mitochondria and chloroplasts were bacteria residing within other cells in a mutually beneficial partnership (77)
what is the difference between a capsule and slime layer?
the capsule has an organized distinct and gelatinous layer whereas a slime layer has a diffuse and irregular layer.
How do gram positive and gram negative differ when they are stained?
the gram positive cell retain the CV-I complex within the cell even when subjected to acetone-alcohol treatment, whereas the gram negative cell wall cannot (63)
what part of the cell wall gets stained with the Gram stain?
the inside of the cell is stained by the crystal violet-iodine complex
Lipid A
the portion that anchors the LPS molecule in the lipid bilayer (61).
Periplasm
the region between the cytoplasmic membrane and the outer membrane of gram-negative bacteria, it is filled with a gel-like fluid called periplasm. All secreted proteins are found here.
Describe the layers of the endospore
the spore coat is thought to function as seive, excluding molecules such as lysozyme. The cortex helps maintain the core in a dehydrated state, prevent heat damage (70)
What are pili?
they are shorter and thinner than flagella, a string of protein subunits arranged helically to form a long cylindrical molecule with a hollow core.
what are the characteristics of endospores?
they can remain dormant for 100 years or longer, they are resistant to heat, desiccation, toxic chemicals, and UV irradiation. They become activated if they survive these treatments (69)
Describe the cell wall of Archaea
they have a greater variety of cell wall types than bacteria. They do not contain peptidoglycan, but some do have a similar molecule, pseudopeptidoglycan.
What are characteristics of the Gram-negative cell wall?
thin layer of peptidoglycan, has outer membrane, and periplasm. It is resistant to many medications (61)
True or false: In some cases flagella are important for bacteria to cause disease
true, for example Helicobacter pylori, the bacterium that causes gastric ulcers, has powerful multiple flagella at one end of its spiral-shaped cell.
How are the movements of pili characterized?
twitching motility: short, jerking movement gliding motility: smooth sliding motion
germinate
when endospores exit the dormant stage
run
when flagella rotate counterclockwise, the bacterium is propelled in a forward movement called a run (66).
endotoxin
A lipopolysaccharide molecule, a part of the cell elicits symptoms of infections caused by bacteria.
after a dormant endospore cell germinates, what does it become?
A vegetative cell, a typical multiplying cell
Name the bacteria: It has peritrichous flagella, bacillus shaped, common in colon of warm blooded mammals, thin layer of PG, gram negative
E. coli
What are some characteristics of Gram-positive bacteria?
Thick layer of peptidoglycan, presence of teichoic acids, sensitive to lysozyme, purple, more susceptible to penicillin, represented in Bacillus, staphylococcus, streptococcus
What are some characteristics of Gram-negative bacteria?
Thin layer of peptidoglycan, have an outer membrane, lipopolysaccharide, porin proteins, periplasm, less susceptible to penicillin, not sensitive to lysozyme, represented in Escherichia, Neisseria, Pseudomonas
True or false: Some capsules enable bacteria to infect
True,the capsule acts a defense system therefore unecapsulated cells are quickly engulfed and killed by phagocytes