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