Chapter 4: Prokaryotes Flashcards
Prokaryotes
-no nucleus
-nucleoid contains DNA
-ribosomes present
-3 basic shapes
-most bacteria are monomorphic (one or single shape)
-few are pleomorphic
-1 circular chromosome, not in a membrane
-no histone proteins associated with w/ their DNA
-no sterols in plasma membrane
-reproduce by binary fission
-peptidoglycan in cell walls
Structures of external to prokaryotic cell wall?
-flagella
-pilus (plural: pili)
-glycocalyx
-capsule
-slime layer
-fimbriae
-axial filaments (only in spirochetes; function: motility)
Glycocalyx
-viscous
-gelatinous
-made of polysaccharide and/or protein
-a capsule (very tightly bound; organized; ex. Streptococcus pneumoniae)
-a slime layer (loosely bound; disorganized; ex. Streptococcus mutans- dental plaque)
-virulence factor
Functions of glycocalyx
-adherence to host and to surface
-antiphagototic
-contributes to biofilm (medical device)➡️ resistant to antibiotic, disinfectants, and host defenses
Flagella
-made of chains of flagellin
-anchored to the wall and membrane of basal body
-important in identification of bacteria
-motility
-H antigens- identification
-rotate, composed of flagellin
Flagella stain can show
1) # of flagella
2) arrangement of flagella
-peritrichous- around entire bacteria
-very motile
-ex. Proteus
Monotrichous and polar
Phototaxis
Move toward or away from light
Chemotaxis
WBC release chemical for bacteria to come toward WBC
Axial filaments
-“endofagella”
-wrap around cell between plasma membrane and cell wall
-In spirochetes
-anchored at one end of a cell
-corkscrew rotation causes cell to move
Fimbriae
-hair-like appendages
-functions:
1) adherence to surfaces and other cells
2) colonization of bacteria in a host
-E. coli: UTI
-N. gonorrhoeae
Pili (sex)
-shorts appendages made of pilin
-function of DNA transfer between bacteria (conjunction- bridge- transfer of DNA across appendage to another bacteria (plasmid))
Which structures of the prokaryotes are used for attachment to a host cell?
-fimbriae
-glycocalyx
-slime layer
-capsule
Cell wall functions
1) maintain cell structure
2) protection from changes in osmotic pressure
3) site of action of certain antibiotics (ex. Penicillin- acts on cell wall)
4) identification of bacteria
In bacteria, cell wall is made of
Peptidoglycan
Peptidoglycan
-Polymer of repeating disaccharide of N-acetylglucasmine (NAG) and N-acetelmuramic acid (NAM)
-linked by polypeptides
Gram-(+) cell wall
-Peptidoglycan (thick layer)
-teichoic acids (wall teichoic acids and lipoteichoic acids)
-regulate movement of ions and stabilize cell wall
-periplasmic space: absent
-out membrane: absent
-lipopolysaccarhide (LPS) content: absent
-lipid and lipoproteins acids content: absent
-toxin produced: exotoxins
-cell wall distribution by lysozyme: high
-susceptibility to penicillin: high (➖peptidoglycan synthesis)
Gram-(-) cell wall
-more intricate
-peptidoglycan (thin layer)
-outer membrane- where lipopolysaccharide (endotoxin) (“LPS”, “lipid A”) and o-polysaccharide, core polysaccharide are located- responsible for toxic properties
-porin proteins
-periplasmic space: present- rich in degradative enzymes
-stain pink
-teichoic acids: absent
-lipid and lipoprotein content: present
-toxin produced: endotoxin and exotoxin
-cell wall distribution by lysozyme: low
-suseptibility to penicillin: low (tetracycline sensitive- ➖ protein (ribosomes) synthesis)
Basic shapes of bacteria
Cocci (spherical)
-ex. Streptococci
-tetrads
-pairs
-chains
Bacilli (rod)
-random arrangement
Spiral
Bacterial arrangements
-pairs: Diplococci, Diplobacilli
-clusters: Staphylococci
-chains: Steptococci, Streptobacilli
Atypical cell walls
-archae lack peptidoglycan- walless; no gram stain
-Mycoplasma- lack cell wall
-sterols(help maintain the membrane fluidity and structural integrity)in plasma membrane
Endotoxin cause
fever and shock
Damage to cell wall
-lysozyme (enzyme in human secretions) digests peptidoglycan
-antibiotics (ex. Penicillin), interfere w/ cell wall synthesis
-penicillin ➖ peptide bridges in peptidoglycan
Cytoplasmic membrane/plasma membrane
Structure: phospholipid bilayer
Functions:
-selective permeability
-enzymes for ATP production
-photosynthetic pigments
Destruction of plasma membrane by alcohol, ammonium quartenary detergents (QUATS), and polymyxin antibiotic (causes leakage of cell contents (lyse))
Isotonic solutions
-0.85% NaCl solution
-effect on cell: no change
Hypotonic solution
<0.85% NaCl solution
Effect on cell: osmotic lysis (swelling- weak cell wall➡️ burst)
Hypertonic solution
> 0.85% NaCl solution
Effect on cell: plasmolysis (shrink)
Group translocation
-prokaryotes only
-uses ATP (type of active transport)
-involves chemical changes in a substance as it is being transported
Cytoplasm
Substance inside plasma membrane
Aqueous
Contains nuclear area, ribosomes, and inclusions (non-living substances found w/in a cell that are not bound by membranes and act as storage sites for nutrients, secretory products, or pigment granules)
Nuclear area (nucleoids)
-DNA
-a single, circular chromosomes
-DNA lacks histones
-no nuclear membrane or nuclei
Plasmids
-closed, circular, 2x-stranded DNA extrachromal, self-replication
-encode for R-factors and enzyme penicillinase (ex. Antibiotic resistance)
Ribosomes
Protein synthesis
70S
Site of antibiotics (ex. Tetracycline)
Smaller than eukaryotic ribosomes
Inclusions
-reserve deposits- store substances
-ex. Sulfur granules, metachromatic granules (phosphate storage), lipid granules, polysaccharide granules, carboxysomes, magnetosomes (iron storage), gas vacuoles
Endospores
-resting, inactive or dormant thick-walled structure
-resistant to desiccation (moisture), heat, chemicals
-usually produced by gram-(+) bacteria
-survives in harsh conditions to preserve genetic material
Sporulation/spirogenesis
-endospore➡️lysis-not for reproduction
-endospore formation by gram-(+) bacteria
Endospore germination
-inactive endospore➡️active vegetative
- the process by which the spores of the bacterium Clostridium botulinum produce new bacteria that can cause botulism
-Environmental stimuli
-Endospores are triggered to germinate by environmental stimuli, such as low acidity, moisture, and the absence of oxygen.
-Amino acid interaction
-Amino acids interact with a germinant receptor, which starts a series of events that lead to germination.
-Vegetative growth
-The endospore germinates into a -vegetative cell that multiplies.
-Botulinum neurotoxin production
The vegetative cell produces botulinum neurotoxin (BoNT), which is responsible for botulism
Endospores are important from a clinical viewpoint and in food industry:
1) food intoxication- (canned food) not sterilized properly➡️ ingest exotoxin
2)persistence of endospores
3) toxins being released during germination- signs and symptoms of disease
Cell division
Binary fission; no sexual reproduction
Chromosomes
Circular chromosome, not enclosed w/in a nuclear envelop
Bacterial structures that are likely to be antigens, to which host antibodies bind, marking the invader for phagocytosis
-capsule
-flagella
-cell wall
-fimbriae
Members of which genus of bacteria are best stained using the acid-fast method?
Mycobacterium
Bacterial structures that are likely to be antigens, to which host antibodies bind, marking the invader for phagocytosis
-capsule
-flagella
-cell wall
-fimbriae
If antibacterial drugs were not selectively toxic…
Then they would kill or interfere w/ the hosts’ cells as well as bacterial cells
Antibacterial strategies that would likely be selectively toxic for bacteria
-interfering w/ translation at 70S ribosomes
-➖ of fimbriae synthesis
-➖of peptidoglycan synthesis
Why can prokaryotes be smaller than eukaryotes and still carry on all the functions of life?
because they lack complex internal organelles, meaning all necessary processes occur within a single, relatively small space, while the smaller size gives them a higher surface area to volume ratio, allowing for efficient nutrient uptake and waste removal compared to larger eukaryotic cells.
Spheroplast
Gram-(-) bacteria that are exposed to lysozyme but retain some of the outer membrane
define endospore. what us the advantage of a n endospore to a bacterial cell?
dormant, highly resistant structure produced by certain bacteria that allows them to survive harsh environmental conditions like extreme heat, desiccation, radiation, and chemicals, essentially acting as a protective “resting stage” for the cell when conditions become unfavorable; the main advantage of an endospore to a bacterial cell is its ability to endure extreme environments where the vegetative cell would otherwise die, enabling the bacteria to survive and reproduce when conditions improve again.
What evidence about eukaryotes supports endosymbiosis?
1) size and shape of mitochondria and chloroplasts resemble bacteria
2) mitochondria and chloroplasts contain circular DNA like bacteria
3) ribosomes of mitochondria and chloroplasts are 70S like bacteria
Why is botulism more common when home-canning)?
Botulism can occur in all low-acid foods that have been inadequately processed. The botulism bacteria are heat resistant and require a temperature of 115 degrees Celsius to destroy, which can only be reached by using a pressure canner. Botulism is a serious and life threatening condition.
