3. GENERAL CHARACTERISTICS OF BACTERIA Flashcards
[Prokaryotes or Eukaryotes] contain nucleic acids, proteins, lipids, and carbohydrates
Both
[Prokaryotes or Eukaryotes] metabolize food, build proteins, and store energy
Both
[Prokaryotes or Eukaryotes] DNA is found in the cell ‘s nucleus, which is separated from the cytoplasm by a nuclear membrane, and the DNA is found in multiple chromosomes
Eukaryotes
[Prokaryotes or Eukaryotes] DNA is consistently associated with chromosomal proteins called histones and with nonhistone
Eukaryotes
[Prokaryotes or Eukaryotes] Have a number of membrane-enclosed organelles
Eukaryotes
[Prokaryotes or Eukaryotes] Cell walls, when present, are chemically simple
Eukaryotes
[Prokaryotes or Eukaryotes] Cell division usually involves Mitosis
Eukaryotes
[Prokaryotes or Eukaryotes] DNA is not enclosed within a membrane and is usually a singular circularly arranged chromosome
Prokaryotes
[Prokaryotes or Eukaryotes] DNA is not associated with histones; other proteins are associated with the DNA.
Prokaryotes
[Prokaryotes or Eukaryotes] Lack membrane-enclosed organelles
Prokaryotes
[Prokaryotes or Eukaryotes] Usually divide by Binary Fission
Prokaryotes
[Prokaryotes or Eukaryotes] Cell walls almost always contain the complex polysaccharide peptidoglycan
Prokaryotes
→DNA is copied, and the cell splits into two cells
→involves fewer structures and processes than eukaryotic cell division
Binary Fission
How is DNA organized in prokaryotes?
Circular chromosome
Are prokaryotic DNA associated with histones?
No histones
What is a key characteristic of prokaryotic cell walls?
Peptidoglycan
Why is binary fission simpler than eukaryotic cell division?
Fewer processes
Where is DNA located in eukaryotes?
Nucleus
How is eukaryotic DNA organized?
Multiple chromosomes
What proteins are associated with eukaryotic DNA?
Histones
Do eukaryotes have membrane-enclosed organelles?
Yes
What is the chemical nature of eukaryotic cell walls?
Chemically simple
How do eukaryotes typically divide?
Mitosis
What key molecules are found in both prokaryotic and eukaryotic cells?
Nucleic acids, proteins, lipids, carbohydrates
What processes are similar in both prokaryotic and eukaryotic cells?
Metabolism, protein synthesis, energy storage
What is a main structural difference between prokaryotic and eukaryotic cells?
Cell walls and membranes
What specialized structures are absent in prokaryotes but present in eukaryotes?
Organelles
→unicellular organisms that lack a nuclear membrane and true nucleus
BACTERIA
prokaryotes meaning
before kernel [nucleus]
classified as prokaryotes, having no mitochondria, endoplasmic reticulum (ER), or Golgi bodies
BACTERIA
Bacterial cell wall differences provide the basis for the
Gram stain
What characteristics vary in bacterial morphology?
Size, shape, arrangement
What is the typical size range for clinically relevant bacteria?
0.25 to 1 μm (width), 1 to 3 μm (length)
How does a bacterium compare in size to a virus?
Hundreds of times larger
How does a bacterium compare in size to a eukaryotic cell?
Ten times smaller
What can cause variation in size and shape within a bacterial population?
Asymmetric growth of the cell wall
What do you call bacteria that are circular in shape?
Cocci
What do you call bacteria that are ovoid in shape?
Coccobacilli
What do you call rod-shaped bacteria?
Bacillus
What do you call bacteria with tapered, pointed ends?
Fusiform
What do you call helical, corkscrew-shaped bacteria?
Spiral
What do you call bacteria that vary in length and number of helical turns?
Spirochetes
What do you call bacteria with no defined shape?
Pleomorphic
Bacterial Arrangements
a. Pairs
b. Chains
c. Grape-like clusters
d. Group of four
e. Packets of eight
f. Palisades
g. Chinese characters
Bacterial shapes
Cocci
Coccobacilli
Bacillus
Fusiform
Curved
Spiral
Pleomorphic
What do you call the outermost structure in bacteria?
Cell envelope
What membrane is found only in gram-negative bacteria?
Outer membrane
What is the bacterial cell wall composed of?
Peptidoglycan (murein layer)
What structure, found only in gram-negative bacteria, lies between the outer membrane and the cell membrane?
Periplasm
What membrane encloses the cytoplasm of bacterial cells?
Cytoplasmic (or cell) membrane
What type of bacteria has an outer membrane?
Gram-negative bacteria
What is the primary function of the outer membrane in gram-negative bacteria?
Initial barrier to the environment
What does the outer membrane serve as a primary barrier to?
Hydrophilic and hydrophobic compounds
What is the outer membrane composed of?
Lipopolysaccharide (bilayered structure)
What charge does the surface of gram-negative bacteria have due to the outer membrane?
Net negative charge
What role does the outer membrane play in bacterial disease?
Significant role in pathogenicity
facilitate the attachment of the outer membrane to the next internal layer in the cell envelope, the cell wall
Murein Lipoproteins
→protein structures scattered lipopolysaccharide macromolecules throughout the
→water-filled structures that control the passage of nutrients and other solutes, including antibiotics, through the outer membrane
→influence the extent to which various substances pass through the outer membranes of different bacteria
Porins
What is the cell wall also known as in bacteria?
Peptidoglycan (or murein layer)
What does the cell wall provide to the bacterial cell?
Shape and strength
What does the cell wall protect against?
Osmotic pressure changes and mechanical disruption
What is a primary target for the development of antimicrobial agents?
Cell wall synthesis and structure
What is the structure of the cell wall composed of?
Disaccharide-pentapeptide subunits
What are the alternating sugar components in peptidoglycan?
N-acetyl-D-glucosamine and N-acetyl-D-muramic acid (moieties)
How do polymers of peptidoglycan subunits cross-link?
peptide bridges
What is formed by the cross-linking of peptidoglycan sheets?
Multilayered, cross-linked structure
What is the peptidoglycan structure surrounding the entire bacterial cell called?
Murein sacculus (or sack)
How are different types of cell wall structures traditionally categorized?
According to staining characteristics
What are the major types of cell walls?
Gram-positive and gram-negative
What type of cell wall do mycobacteria have?
Acid-fast cell wall
stain gram-positive, have a modified cell wall called an ACID-FAST CELL WALL
Mycobacteria
microorganisms that have no cell wall
Mycoplasmas
What is the primary component of the gram-positive cell wall?
Thick peptidoglycan layer
What are the polysaccharide chains in the gram-positive cell wall made of?
N-acetyl-D-glucosamine (NAG) and N-acetyl-D-muramic acid (NAM)
How do many antibiotics affect gram-positive bacteria?
By preventing peptidoglycan synthesis
How does the peptidoglycan layer in gram-negative bacteria compare to gram-positive bacteria?
Thinner
Why are gram-negative bacteria less affected by certain antibiotics?
Different cell wall structure, thinner peptidoglycan
What component of the gram-positive cell wall is anchored to the peptidoglycan?
Teichoic acid
What are the polymers in teichoic acid composed of?
Glycerol or ribitol phosphate combined with sugars, amino acids, and amino sugars
What is lipoteichoic acid anchored to?
Plasma membrane (PM)
What components are unique to the gram-positive cell wall?
Teichoic acid and lipoteichoic acid
What other components may be present on the surface of the peptidoglycan layer of gram positive cell walls?
Antigenic polysaccharides
→ similar polymers, but the repeat units include sugar acids (eg, N-acetylmannosuronic or d-glucosuronic acid) instead of phosphoric acids
→ synthesized in place of teichoic acids when phosphate is limiting
Teichuronic acids
What are the two layers of the gram-negative cell wall?
Inner peptidoglycan layer, Outer membrane
What is found outside the peptidoglycan layer in gram-negative bacteria?
Outer membrane
What components make up the outer membrane of gram-negative bacteria?
Proteins, phospholipids, lipopolysaccharide (LPS)
What are the three regions of lipopolysaccharide (LPS)?
O-specific polysaccharide, Core polysaccharide, Lipid A
What is the antigenic region of LPS called?
O-specific polysaccharide
What are the components of the core polysaccharide in LPS?
Ketodeoxyoctanoic acid (KDO) and heptose
What is the inner, major constituent of LPS also known as endotoxin?
Lipid A
How does LPS contribute to the bacterial surface?
Negative charge stabilization
What is LPS considered to be due to its effects?
Endotoxin
LPS main function
Vital in evading the host defenses
→consists of phosphorylated glucosamine disaccharide units to which are attached a number of long-chain fatty acids
→responsible for producing fever and shock conditions in patients infected with gram-negative bacteria
Lipid A moiety
What does the lipid A moiety consist of?
Phosphorylated glucosamine disaccharide units with long-chain fatty acids
What conditions can the lipid A moiety produce in patients infected with gram-negative bacteria?
Fever and shock
What is one function of the outer membrane as a barrier?
blocks hydrophobic compounds and harmful substances
How does the outer membrane act as a sieve?
Allows water-soluble molecules through porins
What does the outer membrane provide that enhances attachment to host cells?
Attachment sites
What role does the strong negative charge of the outer membrane play?
Evading phagocytosis
What does the outer membrane act as a barrier to?
Toxic substances
Outer membrane of the cell wall function:
barrier
sieve
evading phagocytosis
What bounds the periplasmic space in gram-negative bacteria?
Internal surface of the outer membrane and external surface of the cellular membrane
What does the periplasmic space contain besides the thin peptidoglycan layer?
Murein layer, gel-like matrix with nutrient-binding proteins
What is the function of nutrient-binding proteins in the periplasmic space?
Assist in the capture of nutrients
Found in the periplasmic space that assists in the capture of nutrients
nutrient-binding proteins
What type of enzymes are found in the periplasmic space?
Enzymes involved in degradation of macromolecules and detoxification
What does the periplasmic space help detoxify?
Environmental solutes and antibiotics
What type of cell wall structure do acid-fast bacteria have?
Gram-positive
What does the acid-fast cell wall contain that is bound to the exterior of the cell wall?
Waxy layer of glycolipids and fatty acids (mycolic acid)
What percentage of the acid-fast cell wall is lipid?
More than 60%
What is the major lipid component in the acid-fast cell wall?
Mycolic acid
How does mycolic acid affect the permeability of the cell wall?
Forms a hydrophobic lipid shell, affecting permeability
Why is Mycobacterium spp. difficult to stain with the Gram stain?
Due to its lipid-rich cell wall
What color do Mycobacterium and Nocardia stain with the Gram stain?
Faint blue (gram-positive)
What type of stain is best for Mycobacterium and Nocardia?
Acid-fast stain
What do organisms that lack a cell wall contain in their cell membranes?
Sterols
How does the absence of a cell wall affect the rigidity of these organisms?
They lack rigidity
What are some examples of organisms without a cell wall?
Mycoplasma, Ureaplasma
Gram-positive and gram-negative cells can lose their cell walls and grow as_________ in media supplemented with serum or sugar to prevent osmotic rupture of the cell membrane
L-forms
What is used in media to prevent osmotic rupture of L-forms?
Serum or sugar
What is the deepest layer of the cell envelope in both gram-positive and gram-negative bacteria?
Cytoplasmic (inner) membrane
What is the composition of the cytoplasmic membrane?
Phospholipid bilayer, proteins (70%)
What is a primary function of the cytoplasmic membrane?
Osmotic barrier
Which organism incorporates sterols like cholesterol into their cytoplasmic membranes?
Mycoplasma
What functions are performed by the cytoplasmic membrane?
Transport, enzyme housing, ATP generation, cell motility, chromosomal segregation, molecular sensing, electron transport, excretion
What type of transport relies on diffusion and uses no energy?
Passive transport
What is an example of passive transport?
Simple diffusion, facilitated diffusion
What is facilitated diffusion?
Selective, no energy, solute concentration outside is never exceeded inside
form selective channels that facilitate the passage of specific molecules
Channel proteins
accounts for the entry of very few nutrients, including dissolved oxygen, carbon dioxide, and water itself
Simple diffusion
What does active transport move across the cell membrane?
Molecules against a concentration gradient using energy
What type of transport uses ion gradients for moving molecules?
Ion-coupled transport
What are the three basic types of ion-coupled transport?
Uniport, Symport, Antiport
What is the function of uniport transport?
Transport of a substrate independent of any coupled ion
What does symport transport involve?
Simultaneous transport of two substrates in the same direction
What does antiport transport involve?
Simultaneous transport of two like-charged compounds in opposite directions
Which vital cellular processes occur on the cytoplasmic membrane related to the cell wall?
Housing enzymes for outer membrane synthesis, cell wall synthesis, and assembly/secretion of extracytoplasmic substances
How does the cytoplasmic membrane generate energy for the cell?
Through ATP generation
What is the role of the cytoplasmic membrane during bacterial replication?
Mediates chromosomal segregation
How does the cytoplasmic membrane help bacteria respond to environmental changes?
It houses molecular sensors that monitor chemical and physical changes
What is the function of the cytoplasmic membrane in aerobic species?
Electron transport and oxidative phosphorylation
What does the cytoplasmic membrane excrete to aid in the breakdown of macromolecules?
Hydrolytic exoenzymes
What type of transport uses ATP directly to move solutes into the cell?
ABC transport
In gram-negative bacteria, what facilitates the transport of many nutrients?
Specific binding proteins in the periplasmic space
In gram-positive bacteria, where are binding proteins located?
Attached to the outer surface of the cell membrane
What type of metabolism allows bacteria to use energy efficiently by coupling transport with metabolism?
Group translocation
Why is group translocation not considered active transport?
It does not involve a concentration gradient
What compounds chelate iron and promote its transport as a soluble complex?
Siderophores
How do some pathogenic bacteria acquire iron from the host?
By binding to host proteins like transferrin and lactoferrin
Cytoplasmic structures
Ribosomes
Genome
Plasmid
Inclusion Bodies
Endospores/ Asexual spores
What is the site of protein biosynthesis in bacteria and gives the cytoplasm a granular structure?
Ribosomes
What size are bacterial ribosomes?
70S (50S, 30S)
What antibiotics attach to the 30S ribosomal subunit and interfere with protein synthesis?
Streptomycin and Gentamicin
What antibiotics attach to the 50S ribosomal subunit and interfere with protein synthesis?
Erythromycin and Chloramphenicol
What is the bacterial genome made of?
A single, circular chromosome
What structure is the bacterial chromosome attached to?
Mesosome
What does the bacterial nucleoid test positive for?
Feulgen stain
Which bacteria have dissimilar chromosomes compared to the typical single circular genome?
Vibrio cholera and Brucella melitensis
Extrachromosomal, double-stranded DNA elements associated with virulence
plasmids
What role do plasmids play in bacterial cells?
Code for antibiotic resistance and toxin production
Large plasmid provides resistance to what antibiotics
β-lactam antibiotics like penicillin
Small plasmid is responsible for resistance to
tetracyclines and chloramphenicol
→Not essential for bacterial growth so a bacterial cell may or may not contain a
→Sometimes disappears during cell division and it can make bacteria (mostly Gram-neg) pathogenic
Plasmid
Consists of a single continuous circular molecule ranging in size from 0.58 to almost 10 million base pair Exeptions:
Borrelia burgdorferi and Streptomyces coelicolor
→Serve as the energy source or food reserve of the bacteria or as a reservoir of structural bulding blocks
Inclusions Bodies
What is the role of inclusion bodies in bacteria?
Serve as energy source or food reserve
What are inclusion bodies primarily composed of to lessen osmotic pressure?
Polysaccharides
What is the storage form of glucose in bacteria?
Glycogen
What is the storage form for inorganic phosphates in bacteria?
Polyphosphate granules
What are the phosphate granules in Corynebacterium diphtheriae called?
Babes-Ernst bodies
What inclusion bodies are found in Yersinia pestis?
Bipolar bodies
What are the granules found in Mycobacterium tuberculosis called?
Much granules
→Lipid like compound consisting of chains of B-hyroxybutyric acid units connected through ester linkages →Produced when the source of nitrogen, sulfur or phosphorus is limited and there is excess carbon in the medium
Poly-B-hydroxybutyric acid (PHB)
Under what condition is poly-B-hydroxybutyrate produced by bacteria?
When nitrogen, sulfur, or phosphorus is limited, but carbon is in excess
What are PHB and glycogen used as when protein and nucleic acid synthesis resume?
Carbon source
What kind of granules store hydrogen sulfide and thiosulfate?
Sulfur granules
Which bacterium has Babes-Ernst bodies?
Corynebacterium diphtheriae
Which bacterium has bipolar bodies?
Yersinia pestis
Which bacterium has Much granules?
Mycobacterium tuberculosis
What are small, dormant structures inside bacterial cells that aid survival?
Endospores
What substance is an endospore composed of?
Calcium dipicolinate
Calcium dipicolinate is made of
dipicolinic acid and calcium ions
Which bacterial genus produces terminal spores?
Clostridium tetani
Which bacterial genus produces subterminal spores?
Clostridium botulinum
Which bacterial genus produces central spores?
Bacillus anthracis
Endospores are produced in what type of bacterial cells?
Vegetative cells of some Gram-positive bacteria
Endospores are responsible for?
perpetuation, but not muliplication
Endospores Core are called
Spore protoplast
What does the core of an endospore contain?
A complete nucleus and protein-synthesizing apparatus
What is the innermost layer of an endospore that becomes the cell wall of the germinating vegetative cell?
Spore wall
What is the thickest layer of the spore envelope that contains an unusual type of peptidoglycan?
Cortex
What is the layer of the endospore composed of keratin-like protein that provides resistance to antibacterial agents?
Coat
What is the outermost layer of the endospore composed of proteins, lipids, and carbohydrates?
Exosporium
Exosporium consists of
paracrystalline basal layer
hairlike outer region
Which bacteria have an exosporium?
Bacillus anthracis and Bacillus cereus
Cellular Appendages
Glycocalyx
Flagella
Pili (Fimbria)
What is the outward complex of polysaccharide on the bacterial surface called?
Glycocalyx
What role does the glycocalyx play for bacteria?
Helps the bacteria attach to the surface of solid objects or tissues.
How does a capsule differ from a slime layer?
A capsule is organized and firmly attached to the cell wall, while a slime layer is unorganized and loosely attached.
Where is the capsule located in gram-positive and gram-negative bacteria?
Immediately exterior to the murein layer in gram-positive bacteria and
the outer membrane in gram-negative bacteria.
What exception exists to the typical polysaccharide capsule composition in bacteria?
Bacillus anthracis and Bacillus licheniformis have capsules made of Poly-D-glutamic acid.
How does the capsule protect bacteria?
It acts as a virulence factor by resisting phagocytosis and desiccation.
Why might a capsule need to be removed in laboratory identification?
To detect the somatic (cell wall) antigens present.
How is capsule removal typically accomplished?
By boiling a suspension of the microorganism.
Why doesn’t a bacterial capsule stain with common laboratory stains like Gram or India ink?
It doesn’t ordinarily stain and appears as a clear “halo”-like area.
It can inhibit phagocytosis or aid in the adherence of bacteria to host tissues or synthetic implants.
slime layer
→Unorganized material that is loosely attached to the cell
wall
→Made up of polysaccharide
→Can either inhibit phagocytosis or aid in the adherence
of the bacteria to the host tissue or synthetic implants
→facilitates and maintains bacterial colonization of
biologic (e.g., teeth) and inanimate (e.g., prosthetic
heart valves) surfaces through the formation of biofilms
Slime Layer
How does the slime layer contribute to biofilm formation?
It facilitates and maintains bacterial colonization on biological (e.g., teeth) and inanimate (e.g., prosthetic heart valves) surfaces.
It helps cells attach to their environment and each other, protects the cells, facilitates communication, and enables survival.
Extracellular Polymeric Substance (EPS) in biofilms
→exterior protein filaments that rotate and cause
bacteria to be motile
→complex structures, mostly composed of the protein
flagellin, intricately embedded in the cell envelope
Flagella
What protein primarily makes up flagella?
Flagellin
What is the role of flagella in bacteria?
Motility and aiding in disease-causing ability
What is the diameter of bacterial flagella?
12–30 nm
What antigen type is found in flagella?
H antigens
Which bacteria exhibit gliding motility?
Capnocytophaga, Cyanobacteria, Myxobacteria
What is the function of the hook in flagella?
It connects the basal body to the flagellum.
How does the basal body differ between gram-positive and gram-negative bacteria?
Gram-positive has one pair of rings, gram-negative has two pairs.
What is the filament of the flagellum made of?
Flagellin arranged in a helical structure.
What is bacterial motility?
Movement through “runs” and “tumbles.”
What causes a “tumble” in bacterial movement?
Reversal of flagellar rotation
What unique movement ability does Proteus have?
Swarming across solid media.
endowed with many flagella
→ can “swarm,” or show rapid wavelike movement
across a solid culture medium
Proteus
bacterium moves in one direction
for a length of time
“Run” or “Swim”
What is the term for bacteria without flagella?
Atrichous
What is the term for bacteria with a single flagellum at one end?
Monotrichous
What is the term for bacteria with a single flagellum at both ends?
Amphitrichous
What is the term for bacteria with a tuft or group of flagella at one or both ends?
Lophotrichous
What is the term for bacteria with flagella covering the entire surface?
Peritrichous
What are the bundles of fibrils that spiral around a spirochete cell called?
Axial filaments
What is the location where axial filaments are anchored in spirochetes?
One end of the spirochete
What type of movement is produced by the rotation of axial filaments in spirochetes?
Spiral motion
What bacterial movement is similar to how a corkscrew moves through a cork?
Axial filament movement
What group of bacteria move using axial filaments or endoflagella?
Spirochetes
Which method is best for observing true motility and Brownian movement?
Hanging drop method
What term describes bacteria moving in a definite direction?
True motility
What type of movement occurs when bacteria bounce back and forth due to water molecules?
Brownian movement
What is the term for bacterial movement toward or away from a stimulus?
Taxis
What method is best for observing motility and includes using a hanging drop?
Hanging drop method
Ways of demonstrating motility in the Lab:
✓Hanging Drop Method
✓SIM
✓Flagellar staining
✓Serologic test
✓Fluorescent Antibody Technique(FAT)
✓Swarming Phenomenon
✓Darkfield Microscopy
What laboratory test is used for motility and involves sulfur, indole, and motility testing?
SIM
Which technique uses stains to visualize bacterial flagella?
Flagellar staining
Which test involves antibodies to detect bacterial motility?
Serologic test
What method uses antibodies tagged with fluorescent dyes to detect bacteria?
Fluorescent Antibody Technique (FAT)
What phenomenon involves the movement of bacteria across solid media?
Swarming phenomenon
Which microscopy method helps visualize bacterial motility in the lab?
Darkfield microscopy
What are hairlike structures that help bacteria attach to host cells called?
Pili (Fimbriae)
What protein makes up the structural subunits of pili?
Pilin
What is the type of motility involving jerky, intermittent movements due to pilus retraction?
Twitching motility
What kind of pili are involved in bacterial adherence to surfaces and contribute to virulence?
Common pili (Ordinary pili)
What is the term for the specialized pilus that transfers DNA during bacterial conjugation?
Sex pilus
Which bacterial cells produce the protein F factor for conjugation?
F-positive cells
In which bacteria are fimbriae the site of the M protein, the main surface antigen?
Streptococci
What acid associated with fimbriae helps group A streptococci adhere to epithelial cells?
Lipoteichoic acid
What bacteria can produce pili of different antigenic types?
Neisseria gonorrhoeae
→hairlike, proteinaceous structures that extend
from the cell membrane into the external
environment; some may be up to 2 μm long
→Hair-like microfibrils usually produced by
flagellated Gram-negative bacteria observable
by electron microscopy
→serve as adhesins that help bacteria attach to
animal host cell surfaces, often as the first step in
establishing infection
Pili (Fimbria)
Examples of bacteria with twitching motility due to powerstroke
Pseumdomons aeruginosa, Neisseria gonorrheae,
and some strains of E. coli
→present only in cells that produce a protein referred to
as the F factor
Sex pilus
