Bacterial Structure, Function, and Growth Flashcards
Lipopolysaccharide (LPS) contains lipid A, ____, and O side chain oligosaccharides.
core polysaccharide
What are pili?
long, slender, hair-like structures on the bacterial surface that help adhesion
What is a virus that infects bacteria?
bacteriophage
Name the 7 characteristic bacterial cell shapes.
1) coccus 2) bacillus 3) coccobacillus 4) fusiform bacillus 5) vibrio 6) spirillum 7) spirochete
How does isoniazid work?
it inhibits lipid synthesis in Mycobacteria
What is the electron transport system and where is it located in a bacterium?
the principal source for generating the proton motive force during respiration; the cytoplasmic membrane
_____ appears to function like intermediate filaments in eukaryotes.
CreS
During exponential growth, the rate of cell division is _____.
maximal
In nature, bacteria spend most of their time in the ____ phase.
stationary
How do chloramphenicols work?
bind to the 50S ribosomal subunit and inhibits peptidyl transferase and peptide bond formation
What is the exponential/logarithmic phase?
when the rate of increase of cell number is proportional to the number of cells already present
What is respiration?
ATP generated by an e- transport chain using O2 as the terminal e- acceptor
What do the O side chain oligosaccharides do?
function as somatic antigens (O antigen)
What are flagella?
organs of motility that originate in the cytoplasmic membrane
How do tetracyclines work?
bind to the 30S ribosome and inhibit binding of aminoacyl tRNA
FtsZ resembles _____ in eukaryotes.
tubulin
The _____ of gram-negative bacteria is located on the outer leaflet; the inner leaflet contains _____.
lipopolysaccharide (LPS); phospholipids
In gram-positive bacteria, the tetrapeptides are cross-linked from ____ to D-ala with an intervening peptide such as pentaglycine.
L-lys
What is the internal osmotic pressure for a gram-positive bacterium?
about 20 atm
What is another name for pili?
fimbriae
What is the death phase?
a decrease in the number of viable bacteria
Which drugs inhibit nucleic acid synthesis?
1) quinolones 2) rifampicin
____ and ____ resemble actin in eukaryotes.
MreB; ParM
In gram-negative bacteria, the tetrapeptides are cross-linked from DAP to ____.
D-ala
Which drug inhibits RNA polymerase and interferes with transcription initiation?
rifampicin
Most capsular polysaccharides are _____, and some are used as vaccine components.
antigenic
How does vancomycin work?
inhibits the utilization of lipid-linked intermediate in peptidoglycan synthesis
What does polycistronic mean?
encode for more than one protein product
Bacterial mRNAs may be _____.
polycistronic
What is the lag phase?
when the bacteria are “adjusting” by inducing new enzymes and establishing a proper intracellular environment
_____ consists of a polymer of repeating units of 2 hexose sugars, N-acetylglucosamine (GlcNAc) and N-acetylmuramic (MurNAc) acid.
Peptidoglycan
Heterotrophic bacteria obtain both ____ and _____ by subjecting nutrients to fermentation and respiration.
energy; reducing power
Lipoteichoic acids are attached to _____ and help _____.
the underlying cytoplasmic membrane; anchor the cell wall to the membrane
What is another name for the bacterial cytoplasmic membrane?
inner membrane (in gram-negative bacteria)
What is the purpose of the cytoplasmic membrane?
it’s the barrier btw the inside and outside of the bacterial cell
Which drug interferes with folate metabolism by inhibiting dihydrofolate reductase?
trimethoprim
Lipopolysaccharide (LPS) contains lipid A, core polysaccharide, and _____.
O side chain oligosaccharides
If the environment remains favorable, bacteria are capable of _____ growth and division.
unlimited
What is selective toxicity?
using a drug concentration that affects the bacteria and is tolerated by the host
What drugs binds to the 50S ribosomal subunit and inhibits peptidyl transferase and peptide bond formation?
chloramphenicols
_____ are structural analogs of p-aminobenzoic acid (PABA), which is a component of folic acid.
Sulfonamides
Which drug inhibits alanine racemace, preventing the formation of muramyl pentapeptide in the peptidoglycans?
cycloserine
____ have a thick, extensively cross-linked peptidoglycan layer that also contains teichoic acids.
Gram-positive bacteria
Which drug inhibits the utilization of lipid-linked intermediate in peptidoglycan synthesis?
vancomycin
What is sporulation?
generation of spores because of a lack of C, N, or P
What is phage conversion?
a change in the phenotype of a host bacterium as a consequence of gene expression encoded by a bacteriophage
Sulfonamides are structural analogs of _____, which is a component of folic acid.
p-aminobenzoic acid (PABA)
How do the macrolides and lincomycins work?
bind to the 23S ribosomal RNA and the 50S subunit and inhibit peptidyl transferase
The lipopolysaccharide (LPS) of gram-negative bacteria is located _____; the ______ contains phospholipids.
on the outer leaflet; inner leaflet
Describe the bacterial chromosome.
usually a single, double-stranded, circular DNA molecule (but can be linear or multiple)
In gram-positive bacteria, the tetrapeptides are cross-linked from L-lys to ____ with an intervening peptide such as pentaglycine.
D-ala
What is peptidoglycan made of?
a polymer of repeating units of 2 hexose sugars, N-acetylglucosamine (GlcNAc) and N-acetylmuramic (MurNAc) acid
What is fermentation?
organic compounds serve as both e- donors and acceptors; no net oxidation of substrates; usu anaerobic conditions
Teichoic acid, found in gram-positive bacteria, has a repeating _____ backbone covalently attached to the peptidoglycan layer.
polyglycerol-P or polyribitol-P
Counterclockwise flagellar motion results in ____; clockwise results in _____.
swimming; tumbling
What drug binds to the 30S ribosome and inhibits binding of aminoacyl tRNA?
tetracyclines
_____ have a thin, sparsely cross-linked peptidoglycan layer and other major components located exterior to it.
Gram negative bacteria
How does cycloserine work?
inhibits alanine racemace, preventing the formation of muramyl pentapeptide in the peptidoglycans
Gram-positive bacteria have a thick, extensively cross-linked peptidoglycan layer that also contains ____.
teichoic acids
What are the 2 forms of energy currency in the bacterial cell? What enzyme interconverts them?
1) ATP 2) electrochemical gradients (proton motive force) — membrane ATPase
Which drug is a cationic surfactant that disrupts the outer and cytoplasmic membrane?
polymyxins
How is trimethoprim selective?
bacteria are 50,000 times more sensitive to it than the host
What are the functions of the cytoplasmic membrane? (5)
1) electron transport system 2) transport of metabolites 3) biosynthesis of lipids 4) DNA replication 5) flagellar rotation
Plasmids in pathogenic bacteria often encode _____; _____ carry genes that determine resistance to antibiotics.
virulence factors; R-factors
What are capsules?
loose, gelatinous outer surface layers consisting of complex polysaccharides that enhance virulence
_____ play a role in bacterial conjugation.
Sex pilli
Where does lysozyme cleave the peptidoglycan?
the glycosidic bond between MurNAc and GlcNAc
What is the nucleoid?
a distinct region of the cytoplasm where the DNA of bacteria is located
The ____ phase is when the bacteria are “adjusting” by inducing new enzymes and establishing a proper intracellular environment .
lag
The _____ is typically much greater in gram-positive bacteria.
extent of cross-linking
What drugs target the outer and cytoplasmic membrane?
polymyxin
What are obligate intracellular bacteria?
bacteria that can only grow within a eukaryote
Teichoic acid, found in _____, has a repeating polyglycerol-P or polyribitol-P backbone covalently attached to the peptidoglycan layer.
gram-positive bacteria
Lipopolysaccharide (LPS) contains _____, core polysaccharide, and O side chain oligosaccharides.
lipid A
What are polyribosomes?
several ribosomes interacting with a single mRNA
What enzyme hydrolyzes peptidoglycan?
lysozyme
These residues are linked to tetrapeptide chains that contain aas only found in bacterial cell walls.
N-acetylmuramic (MurNAc)
_____ forms a rigid mesh that surrounds the cytoplasmic membrane.
Peptidoglycan
In gram-negative bacteria, the tetrapeptides are cross-linked from ____ to D-ala.
DAP
What drug inhibits lipid synthesis in Mycobacteria?
isoniazid
How does metronidazole work?
interferes with anaerobic metabolism
What does peptidoglycan do?
it surrounds the cytoplasmic membrane and forms a rigid mesh
MreB and ParM resemble ____ in eukaryotes.
actin
How do capsules enhance virulence?
they enable the bacteria to resist phagocytosis
What drug interferes with anaerobic metabolism?
metronidazole
What are the 4 distinct phases of the bacterial growth curve?
1) lag phase 2) exponential/logarithmic phase 3) stationary phase 4)
What organelles/cellular components do bacteria have, as opposed to eukaryotes?
- cell wall (peptidoglycan) 2. 70S ribosome
What are the bacterial 70S ribosomes related to?
eukaryotic mitochondria
The DNA genomes of _____ can integrate into bacterial chromosomes and often carry genes that encode bacterial toxins, virulence factors, or resistance to antibiotics.
temperate bacteriophages
What is a plasmid?
an extra-chromosomal, self-replicating DNA molecule usu not essential for bacterial viability
Name 3 bacterial cytoskeletal structural elements.
1) FtsZ 2) MreB 3) CreS
Which drugs bind to the 23S ribosomal RNA and the 50S subunit and inhibit peptidyl transferase?
macrolides and lincomycins
What is the stationary phase?
when cell growth decreases dramatically or stops bc of nutrient consumption and accumulation of toxic metabolites; growth is balanced by death; increased resistance to antibiotics is seen
How do quinolones work?
inhibit DNA gyrase and topoisomerase
_____ distribution means the flagella are on one end of the cell.
Polar
The distinct region of the cytoplasm where the DNA of bacteria is located is called the ____.
nucleoid
What ribosomes do bacteria have?
70S
Most flagella are antigenic, and the _____ used to classify enteric bacteria are flagellar antigens.
H antigens
What are the minimum requirements for growth for most bacteria?
nutrient medium containing inorganic ions, a carbon source, and an energy source
Why does a bacterium have a rigid cell wall?
- to resist osmotic lysis 2. to maintain cell shape
What is the generation time?
doubling time
The outer membrane of gram-negative bacteria contains _____, _____, and _____.
lipopolysaccharides; lipoproteins; porins
Name 3 amino acids found only in bacterial cell walls.
- meso-diaminopimelic acid (DIP) 2. D-glutamic acid 3. D-alanine
_____ flagellar motion results in swimming; _____ results in tumbling.
Counterclockwise; clockwise
What do antibodies to pili do?
block bacterial adherence and confer resistance to infection
_____ are important for bacterial chemotaxis.
Flagella
What is an extra-chromosomal, self-replicating DNA molecule usu not essential for bacterial viability called?
a plasmid
What is the internal osmotic pressure in a gram-negative bacterium?
about 5 atm
What are autotrophic bacteria?
bacteria that obtain their C exclusively from CO2
Which drugs bind to target proteins on the 30S ribosome to inhibit protein synthesis?
aminoglycosides
Name 4 drugs that inhibit metabolism in bacteria.
1) sulfonamides 2) trimethoprim 3) isoniazid 4) metronidazole
How is the cytoplasmic membrane different than the plasma membrane of animal cells?
- usually contains no sterols 2. has a much higher protein content (60-70%)
What is N-acetylmuramic (MurNAc)?
a hexose sugar that makes up peptidoglycan; is linked to tetrapeptide chains that contain aas that are only found in bacterial cell walls
______ is determined by both intracellular cytoskeletal elements and by rigid components of the cell wall.
Bacterial cell shape
Which drug inhibits the final transpeptidation rxn in cross-linking peptidoglycan?
beta-lactam
How do beta-lactams work?
inhibit the final transpeptidation rxn in cross-linking peptidoglycan
How does trimethoprim work?
interferes with folate metabolism by inhibiting dihydrofolate reductase
What is the inoculum?
the starting cells
What are the components of the bacterial cytoplasm? (3)
1) ribosomes 2) nucleoid 3) chromosome (plasmids)
Where is the genetic material found in a bacterium?
in the cytoplasm
Organisms that grow in the presence of O2 produce _____, such as ____ or _____.
toxic oxygen metabolites; hydrogen peroxide; superoxide
What is N-acetylglucosamine (GlcNAc)?
a hexose sugar that makes up peptidoglycan
What are porins?
transmembrane channels that allow hydrophilic molecules of
How does rifampicin work?
inhibits RNA polymerase and interferes with transcription initiation
Sulfonamides are structural analogs of p-aminobenzoic acid (PABA), which is a component of _____.
folic acid
What organelles/cellular components do bacteria lack, as opposed to eukaryotes?
- a nuclear membrane 2. ER 3. mitotic spindle 4. mitochondria 5. chloroplasts
The ____ phase is when cell growth decreases dramatically or stops bc of nutrient consumption and accumulation of toxic metabolites; growth is balanced by death; increased resistance to antibiotics is seen.
stationary
In gram-positive bacteria, the tetrapeptides are cross-linked from L-lys to D-ala with an intervening peptide such as ______.
pentaglycine
Bacterial cell shape is determined by both_____ and by _____.
intracellular cytoskeletal elements; rigid components of the cell wall
What does the cytoplasmic membrane consist of?
a lipid bilayer of phospholipids and proteins
How do aminoglycosides work?
bind to target proteins on the 30S ribosome to inhibit protein synthesis
Gram negative bacteria have a _____ and other major components located exterior to it.
thin, sparsely cross-linked peptidoglycan layer
How do bacterial cells divide?
binary fission
The extent of cross-linking is typically much greater in _____.
gram-positive bacteria
Which drugs target the peptidoglycan?
1) beta-lactams 2) vancomycin 3) cycloserine
What is Lipid A?
the toxic component of endotoxin
What are fastidious bacteria?
bacteria that need growth factors like aas, vitamins, purines, pyrimidines, and inorganic ions
Heterotrophic bacteria obtain both energy and reducing power by subjecting nutrients to _____ and _____.
fermentation; respiration
What is anaerobic respiration?
bacteria using inorganic substrates such as nitrate or nitrite as the terminal e- acceptor
There is no ____ surrounding the bacterial DNA.
nuclear membrane
What is a change in the phenotype of a host bacterium as a consequence of gene expression encoded by a bacteriophage called?
phage conversion
Name 5 major antibacterial targets.
1) cell walls (peptidoglycan) 2) outer and cytoplasmic membrane 3) protein synthesis at the ribosome 4) nucleic acid synthesis 5) metabolic inhibition
CreS appears to function like _____ in eukaryotes.
intermediate filaments
How do sulfonamides work?
inhibit the formation of folic acid, preventing nucleic acid synthesis
How does polymyxin work?
it’s a cationic surfactant that disrupts the outer and cytoplasmic membranes
____, found in gram-positive bacteria, has a repeating polyglycerol-P or polyribitol-P backbone covalently attached to the peptidoglycan layer.
Teichoic acid
During sporulation, bacteria differentiate to form _____ that have no _____.
highly resistant, dehydrated forms (spores); metabolic activity
Bacteria that grow in the presence of O2 produce ______ or ______ that protect them against toxic ROS.
catalase/peroxidase, superoxide dismutase (SOD)
Which drug inhibits DNA gyrase and topoisomerase?
quinolones
Flagella can be ____ or ____ in their distribution.
peritrichous; polar
_____ are attached to the underlying cytoplasmic membrane and help anchor the cell wall to the membrane.
Lipoteichoic acids
How are sulfonamides selective?
bacteria cannot utilize pre-formed folic acid (humans can) and synthesize folic acid on their own (humans do not)
Because there is no nuclear membrane, _____ can occur in bacteria.
transcription and translation can occur as a coupled process
______ distribution means the flagella are all over the surface.
Peritrichous
What are heterotrophic bacteria?
bacteria requiring an organic carbon source
What drugs are inhibitors of protein synthesis at the ribosome?
1) aminoglycosides 2) tetracyclines 3) chloramphenicol 4) macrolides
____ resembles tubulin in eukaryotes.
FtsZ
