Unit 5 Flashcards
Eukaryotes and Prokaryotes main difference
Eukaryotes Have a clearly defined nucleus
Eukaryotes ribosome
80S
Prokaryotes ribosome
70S
Division of prokaryotes
Binary fission
Size bacteria
10⁻⁶ m
Where are located the sterols
Plasma membrane of eukaryotes
Size virus
10⁻⁹m
Shapes bacteria
Coccus
Bacillus
Coccobacillus
Vibrio
Spirillum
Spirochete
Pleomorphism
Bacteria changes the size and shape according to environment (pH)
Arrangement Cocci
Single (coccus)
Pair ( diplococci)
Tetrads
Irregular cluster (Staphylococci)
Chains ( streptococci)
Cubical (Sarcina)
Which type of bacteria has the greatest variety in arrangement
Coccus
Sarcina
Cubical
Staphylococci
Irregular clusters (grapes)
Streptococci
Chains
Bacilli arrangement
Bacillus
Diplobacilli
Streptobacilli
Palisades
Streptobacilli
➖➖➖
Chain
Palisades
/\/\/
Arrangement spirilla
Sometimes in chains
Bright field microscope
Bright background
Dark image
Dark field
Black background
Bright specimen
Black background
Bright specimen
Dark field
Phase contrast microscope
Bright structures
Green background
To see internal components
Bright structures
Green background
To see internal components
Phase contrast microscope
Fluorescence microscope
Black background
Fluo stained structures
Black background
Fluo stained structures
Fluorescence microscope
Electron microscope
Grey background
White structure
3D
To see viruses and organelles
Why staining
Increase contrast
Smear technique
Take sample of the cells, spread in crystal slide and air dry it
Heat fixation so that the cells are not removed when washing
Or chemicals to preserve subcellular structures and morphology
3 types procedures for microscope
Direct fresh preparations
Stained smears
Special procedures ( electron microscope)
Differential or complex stain
Primary dye and counterstain
- Gram staining
- Ziehl Neelsen
Gram stain procedure function
Differentiate the structure and chemical composition of the cell wall
➡️identification and classification of bacteria
Steps Gram stain procedure
1st dye, crystal violet, wash
Mordant (lugol): help fixation
Decolorizer : ethanol-acetone. Critical step. Removed the first dye in some bacteria
Conterstain : Safranin
Gram - color
Pink red
Gram + color
Dark purple
Obligated structures in Prokaryotes
Cell wall (except mycoplasma)
1 Chromosome
Plasma membrane
Cytoplasmic matrix
Where is the bacterial chromosome located
Nucleoid
Cell wall properties
Exclusive to bacteria
Semi-rigid layer outside the plasma membrane
Target of some antibiotics
Determine type of stain used Gram/Ziehl-Neelsen
Contains antigenic components ( LPS, teichoic acids
What bacteria doesn’t have a cell wall
Mycobacteria
Composition cell wall
Main : peptidoglycan=murein
Peptidoglycan
- Peptides
- Glycan: NAM-NAG-NAM
Overall : NAM and NAG are linked by glycosidic bonds
1 Tetrapeptide ( peptide cross links) on each NAM, link NAMs together form a chain to another
Peptide
Small protein
Synonym glycan
Polysaccharide
NAM and NAG are linked by
Glycosidic bonds
Why are lysozymes effective
They break the glycosidic bonds between NAM and NAG
Gram + cell wall
Thick and rigid wall of peptidoglycan
Lots of techoic acids crossing the peptidoglycan
No outer membrane
No lipopolysaccharide
Gram - cell wall
Thin peptidoglycan layer
Outer membrane (only for gram -)
Periplasmic space
Transmembrane proteins (porins)
Outer membrane Compo
Made of phospholipids, proteins (porins), and Lipopolysaccharide LPS endotoxin
Lipopolysaccharide compo
Lipid A
Core polysaccharide
O side chain
Periplasmic space
Between the outer membrane and the plasma membrane
Function porins
Diffusion hydrophilic molecules
Mycobacterias are also called
Acid fast bacteria AFB
Structure mycobacteria cell wall
Great amount of lipids
Mycolic acid layer (wax like lipid coat)
Arabino galactan polymer
What type of stain is used on mycobacteria
Ziehl-Neelsen stain
Ziehl-Neelsen stain stages
Heat 3 times to melt the wax
Carbol fuchsine (pink)
Decolorizer : HCl + alcohol
Methylen blue
Acid fast bacteria get stained the first time and don’t get discolored because of the wax
Functions of cell wall
Gives shape, rigidity and elasticity
Protection from osmotic lysis
Protection from toxic substances
Anchor for flagella
Support for glycocalyx when present
Involved in adhesion (to infect a cell) and aggregation
Plasma membrane composition
Phospholipidic membrane
Bilayer of lipids contains most of the time hopanoids
Proteins crossing the membrane
PBPs on the outer side
PBP function
Involved in peptidoglycan synthesis
How are mycoplasma genus different
They have sterols instead of hopanoids in their plasma membranes (like eukaryotes)
What is the name of the bacteria that has sterol in its membrane
Mycoplasma genus
Function plasma membrane
Retains cytoplasm
Protection from osmotic stress
Transport : Selective permeable barrier ( waste, secretions, nutrient intake)
Location of metabolic processes ( respiration, photosynthesis, synthesis of wall constituents)
Contains receptor molecules to detect and respond to chemical signals
Cytoplasmic matrix synonym
Cytosol
Cytoplasmic matrix definition
No organelles, just soluble components like enzymes, vitamins, DNA, etc
Largely water
Cytoskeleton
Ribosomes 70S
Ribosomes
Made of ribosomal RNA and protein
2 sub units
Bacterial chromosome
Prokaryotes are haploid
No nucleus
Single circle of double stranded DNA
Supercoiled DNA due to enzymes like topoisomerase, gyrase or HU proteins
Fibrillar appearance
Haploid
1set of chromosomes
Facultative structures for Prokaryotic cells
Plasmids
Glycocalyx (capsule & slime layer)
Flagella
Fimbriae/pili
Endospore
Plasmids
Double stranded circle of DNA
Exist independently of the chromosome
Not required for growth and reproduction
Confer selective advantage such as drug resistance, toxin production
Moves horizontally or vertically between bacteria
Not attached to plasma membrane ➡️sometimes lost during division
Glycocalyx
Supplementary coat, mucus
Protects the cell and help for adhesion to environment
2 types
What are the two types of glycocalyx
Slime layer
Capsule
Description Slime layer
Loose shield
Unorganized layer of extra cellular material
Easily removable
Description Capsule
Bound more tightly to the cell
Denser, thicker, more organized
Not easily washed off
Function Capsule
Anti-phagocytic structure
Helps to adhere to surfaces
Protects from bacterial viruses and most hydrophobic toxic materials
Protects from desiccation cells and anti microbial agents
Function Slime layer
Can enclose many bacterias into a biofilm
Protects from environment (dessiccation, antibiotics)
Protects from loss of nutrients
Allows bacteria to adhere to smooth surfaces (like medical devices)
Dessiccation
Loss of water
Flagella Function
Cell mobility
Role in pathogenesis
Antigenic properties
Flagella description
Helical filament appendage
Attached to plasma membrane
Made of the protein flagellin
Types of bacteria according to flagella
Monotrichous
Lophotrichous
Amphitrichous
Peritrichous
Monotrichous
1 flagella
Amphitrichous
1 Flagella located on opposite sides of bacteria
Lophotricous
Several flagella on one side
Peritrichous
Several flagella everywhere on the plasma membrane
Where is the flagella attached
Plasma membrane
Fimbrae and pili
Filament appendages shorter and thinner than flagella
Attached to plasma membrane
Made of the protein pilin
Don’t provide locomotion (except twitching mvt of pseudomonas)
Where are attached Fimbriae and pili
Plasma membrane
Types of Fimbriae and pili
Fimbriae (common pili)
Sex pili
Fimbriae
Short, thin, hair like appendages
Involved in bacterial adherence
Sex pili
Larger than Fimbriae
Required for bacterial mating
Synonym bacterial mating
Bacterial conjugation
Meaning bacterial conjugation
Transfer of plasmids
Endospores
In some gram+ bacteria
Special resistant, dormant structures
Resistance to environmental stresses such as lack of nutrients, UV, gamma radiation, chemical disinfectant, dessiccation.
Difference spirochete and spirilla
Spirilla is more rigid
Function of hopanoids
Similar to sterols
Fluidity
