Intro To Prokaryotes Flashcards
Describe a Coccus/Cocci bacterium/bacteria
A single round cell
Describe a diplocpccus/diplococci bacterium/bacteria
A pair of cocci
Describe a tetrad (pl. tetrad) bacterium/ bacteria
Group of four cocci
Describe a Streptococcus(pl. streptococci)
A chain of cocci
Describe a Staphylococcus (pl. stsohylococci ) bacterium/ bacteria
Cluster of cocci
Describe a Bacillus(pl. Bacilli)
Single-rod shape
Describe a Streptobacillus(pl. streptobaccilli)
A chain of rods
Why is smaller better for prokaryotes?
- More surface area relative to volume (higher surface area to volume ratio)
- Substance enter and diffuse quickly(absorb nutrients faster)
- Growth rate is affected by nutrients( small cells can grow faster than big ones)
What is the function of the Capsule slime layer of the bacteria?
- Prevent bacteriophage attachment
- Evade phagocytosis
- prevent bacteria from getting dried out
What is the function of Pili Fimbriae for bacteria?
Allows bacteria to :
- Attach to surfaces or tissues
- Attach to each other
What is the function of the cell wall of the bacteria?
- Keep cell rigid
- Contain all cellular components
What is function of the cytoplasmic membrane of bacteria?
- Control access in/out site
- Site of metabolism
- Enzyme functions
What is the function of endospores inclusion vacuoles in bacteria?
To assist bacteria in surviving environmental changes
What is the function of flagellae in bacteria?
- To allow bacteria to change location in liquid environment
- Move towards something good
- Move away from something bad
What are the key layers of a Gram negative bacterial cell?
- Cytoplasm ( ribosomes, DNA, lots of enzymes)
- Cytoplasmic/cell membrane
- Peptidoglycan
- Periplasmic space
- Outer membrane
What are the key cell layers of a gram positive bacterial cell?
- Cytoplasm (ribosomes, DNA, lots of enzymes)
- Cytoplasmic/cell membrane
- Peptidoglycan
- Periplasmic space
Describe the cytoplasm of the prokaryotic cell?
- Water
- DNA and Ribosomes
- Enzymes
- Proteins
- Inclusion bodies e.g. storage granules
- Endospores
- NO organelles( no mitochondria, ER, Golgi apparatus, nucleus etc.)
- site of many cellular processes(others take place at cytoplasmic membrane)
Describe the cytoplasmic membrane in prokaryotes
Fluid mosaic model-interface with the external environment (outside of the cell)
- phospholipids- 30%-40%
- proteins- 60%-70%
Phospholipid belayer :
polar heads - hydrophilic
Fatty acyl heads- hydrophobic
What are the functions the prokaryotic cell membrane ?
- Transport - from the inside to the outside of the cell and vice versa
- Energy production-
a. Proton motive force
b. Oxidative phosphorylation
c. Phosphorylation - Metabolic processes
- Motility- energy for flagella movement.
- Communication- receptors for sensing if environment is favorable or unfavorable (detecting and sending signals)
What function does Cell wall have in controlling what enters and leaves a prokaryote?
While present in both gram positive and gram negative, cell wall does not control the flow of what goes in or out
Differentiate simple diffusion and passive diffusion
Simple diffusion: Materials pass through a membrane without the help of proteins
Passive diffusion: materials diffuse across the plasma membrane with the help of membrane proteins
Explain what is Bulk Transport
Consists of endocytosis and exocytosis
Endocytosis: absorption of larger molecules that are polar in charge and unable to diffuse through hydrophobic cell membrane
Exocytosis: expulsion of larger molecules that are polar in charge and unable to diffuse through hydrophobic cell maybe
What is the peptidoglycan cell wall of prokaryotes?
“The bacterial exoskeleton”
A multi-layered mesh around the cell
What is the function of the peptidoglycan cell wall?
Defines cell shape- coccus, bacillus, vibrio etc.
Maintains osmotic integrity inside of the cell
-it is necessary in order to maintain a high intracellular osmotic pressure(prevents lysis of the cell)
What is a prokaryotes’ gram staining character defined by?
Thickness, how the layers are cross linking and gram positive bacteria much thicker peptidoglycan layer
Between gram positive and gram negative cell walls, which is thicker?
Gram positive bacteria are much thicker
What is a peptidoglycan?
A large molecule that is unique only to bacteria
Describe the contents of the peptidoglycan Layer
Polysaccharide:
N-acetylglucosamine( NAGj
N-acetylmuramic acid(NAM)
-some amino acids
- Long chains made next to each other that are then cross-linked
- Mesh-like net around the cell
Gram negative and gram positive have different….
Cross links
What type of linkage occurs between NAM and NAG ?
B 1-4 linkage
What are the differences between teichoic acids and lipoteichoic acids?(Gram positive bacteria )
Teichoic acid= acidic polysaccharide
- Polymer of phosphate plus ribitol or glycerol - If anchored into cell membrane= lipoteichoic acid
What are the functions of teichoic acids and lipoteichoic acids?
- Can be a substantial component cell wall
- Anchor other proteins; bind molecules for transport e.g. Mg 2+
- Responsible for overall negative charge of cell surface
- Targets for vaccine and drug development
Where are teichoic and lipoteichoic acids?
Gram positive bacteria
Bacterial endospores enable resistance to:
- Drying
- Chemicals
- Heat
- Radiation
What are the functions of bacterial endospores?
- Survival adaptations from unfavorable environments
- Released when the producing cell dies
- help with long term survival(>100-1000s of years
- Dehydrated, no active protein synthesis or metabolism, unique layers and components
What is sporulation?
Formation of endospores
What is germination?
Return to vegetative growth when the conditions are favorable
Describe the 2-phase life cycle of bacterial endospores
Vegetative cell- bacterial cell is metabolically active and growing
Endospores-in unfavorable environments the cell stores its DNA in the core of the cell and when the timing is right, and conditions are favorable it will become metabolically active again
Describe bacterial endospores and their special features
- Unique cellular structure
- Chemical and enzymatic resistance
- Specialized peptidoglycan
- Germ cell wall
- Major permeability barrier
- house’s cell’s DNA
- Dipicolinic acid(10% of spore, dry weight)
What is the function of the core layer of the endospores?
Mostly dehydrated and metabolically inactive ; contains dipicolinic acid; chromosomal DNA and ribosomes
What is the function of the cortex layer of endospores?
Occupies most of the spore volume;- made up from a unique thick layer of special type of peptidoglycan
What is the function of the coat layer of endospores?
Contains keratin; impermeable to most toxins and chemicals(contributes to resistance)
What is the function of the exosporium layer of the endospores structure?
Thin outer glycoprotein layer
What is the periplasm in gram negative bacteria?
The area between the outer membrane and cytoplasmic membrane
What is the periplasm of gram positive bacteria?
Space between the cytoplasmic membrane and peptidoglycan
What is the function of periplasmic space?
- Transport(binding proteins)
- Breakdown of food molecules (hydrolysis enzymes)
- Chemoreceptors (chemotaxis: detecting chemical signals)
Describe the periplasmic space/ periplasm
Gel-like rather than true space
High concentration of proteins
What type of bacteria has an outer membrane?
Gram negative
What is the purpose of the outer membrane?
Part of the bacterial defense against the action of antibiotics: some don’t penetrate the cell because their entry is blocked by the outer membrane
Describe the porins of the outer membrane of gram negative
Outer membranes contains porins
- proteins that form channels/tunnels through the outer membrane
- Porin size vary, blocking or allowing the entry of certain products
Describe the permeability of the outer membrane of gram negative bacteria
Not permeable to proteins or large molecules (traps proteins in periplasmic space -e.g. degradation enzymes, binding proteins, chemoreceptors)
What is the outer most layer of gram negative outer membrane?
Lipopolysaccharides
What are the layers of the endospores?
Core layer
Cortex layer
Coat layer
Exosporium layer
Lipopolysaccharide is also known as …
“Endotoxin”
What are the 3 components of lipopolysaccharides?
- O-specific polysaccharides
- Core. Polysaccharide
- Lipid A
Describe the O-specific polysaccharides in lipopolysaccharides
- Very variable between different species
- “O antigenl
Describe the core polysaccharide in lipopolysaccharides
Comprised of 10-15 different sugars
Describe Lipid A in lipopolysaccharides
It anchors the lipopolysaccharide in the phospholipid layer. The active “toxic” component
Why are lipopolysaccharides medically important?
- Important antigen
- Contributes to some of the symptoms for some gram-negative infections
- Immune system responds to the lipopolysaccharides (good in small amounts, bad in higher)
- Fever and chills
What happens when a bacterium is in a harsh environment?
Sporulation (6-8 hours)
How is sporulation done?
- bacteria copies it’s genome and pinches the plasma membrane
- spore septum forms
- a double membrane forms around spore septum
- peptidoglycan fills the spore to finalize the spore forming
- endospores is released from the spore with the copier genome and finds a favorable environment to germinate
Differentiate slime layer and capsule
Slime layer- less of it, relatively easy to move, loosely organized
Capsule- thick, not easy to remove, highly organized, Capsular Polysaccharides (CPS)/ K Antigen
How can bacteria change the color of an algae plate?
-If bacteria are producing a capsule, it changes hows the colonies appear when they are grown on an agar plate
What is a function of the capsule in prokaryotes?
-Some capsules can be used to create vaccines to protect against infections e.g. meninges
What is the size fimbrae?
- 2-10 nm diameter
- 1-2 microns long
What is the fimbrae known as?
Short attachment, common pili
What is the size of the Pillus?
- 2-10 nm in diameter
- from 10 - over 20 microns long
The pillus is involved in_____________
Conjugation
A prokaryote has atrichous flagella, what is this?
No flagella
A Prokaryote has a polar flagella, what is this?
Single flagella at one or both ends
A prokaryote has a lophotrichous flagella, what is that?
Bunch at the end
A prokaryote has amphitrichous flagella, what does this mean ?
Bunched flagella at one point
A prokaryotic cell has Peritrichous flagella, what is that?
Flagella all around cell
Differentiate spirillum and spirochete bacteria
Both are spiral but spirilium is shorter and thicker than spirochete
What is a coccobacillus?
Mix of a rod and circular bacteria
Describe the difference in staining in gram positive and negative bacteria
Gram positive- thick peptidoglycan and will stain purple
Gram negative- thin peptidoglycan and will stain punk by Safarin counter stain
Explain the mesh work of gram positive bacteria
NAG and NAM alternating
Each NAM has a tetrapeptide sticking out connecting to another tetrapeptide via pentagon INR bridge
Describe the mesh work of the gram negative cell wall
Alternating chains of NAM and NAG
with a different tetrapeptide than gram positive
Tetrapeptide from NAM connected by a peptide bond
Name 2 medically important endospores ?
Clostridia( tetanus) and bacillus (B anthracis)
What is a terminal endospores?
Endospore at the end of the cell
What is a sub terminal endospore?
Endospore is between the terminal and central
What is a central endospore?
Spore in the center of the cell
What part of lipopolysaccharides cause symptoms?
The toxic lipid A
What 3 structures are external to cell wall?
Capsule, flagella and fimbrae pilli
How do bacterial capsules help their bacteria ?
Helps evade the immune system
Why is motility important?
- gain access to different areas/body sites
- moves in response to stimulus
- chemotaxis
- move around body in a clockwise or anti clockwise motion
Not all bacteria are motile via flagella
A bacteria moves around in a clockwise motion, also known as…
Tumbling motion
A Bacteria moves around in an anti clockwise motion, also known as…
Linear. Motion
What is the H antigen?
The hair like antigen- flagella antigen
