2016/17 -SAQ Flashcards
List four features of bacterial cells that distinguish them from eukaryotic cells
1.No membrane bound nucleus
2.Simper cell structure
3.Lack of membrane-bound organelles
4.Presence of cell wall
Absence of membrane bound nucleus
bacterial cells that distinguish them from eukaryotic cells
Lack true membrane bound nucleus
eukarotic cells: well defined nucleus enclosed by nuclear membrane
Simpler cell structure
bacterial cells that distinguish them from eukaryotic cells
Bacterial cell: relatively small, simpler cell structure
Eukaryotic: larger, more complex
Lack of membrane-bound organelles
bacterial cells that distinguish them from eukaryotic cells
Bacteria; lack this
Eukaryotic cells: Mitochondria, ER, Golgi Apparatus, lysosomes, peroxisomes
Presence of Cell Wall
bacterial cells that distinguish them from eukaryotic cells
Most bacterial cell: Peptidoglycan
Absent in eukaryotic cells except some fungi and algae
Major Components of biofilm extracellular matrix (ECM)
- Extracellular polymeric substances (EPS)
- Water
- Ions and mineral
- DNA
- Proteins
Extracelllarpolymeric substances
Major Components of biofilm extracellular matrix (ECM)
- complex mixture: polysaccharides, proteins, nucleic acids, and lipidsmake up the bulk of the ECM
- Structural integrity
- Protects the resident microbial community from external stresses
Water
Major Components of biofilm extracellular matrix (ECM)
A lot of water
Hydrated environment
For microbial growth and metabolic activity
Ions and Minerals
Major Components of biofilm extracellular matrix (ECM)
Calcium
Magnesium
Iron
- For microbial growth and metabolic activity
DNA
Major Components of biofilm extracellular matrix (ECM)
extracellular DNA (eDNA)
From lysed cells
Structural component
Source of nutrients and genetic material for th resident microbial community
Protein
Major Components of biofilm extracellular matrix (ECM)
Enzymes
Adhesins
Structural proteins
Diverse roles in biofilm formation, stability and function
Explain what thee Gram stain is used for?
Laboratory technique
Differentiates bacterial cellsinto 2 major groups based on cell wall structure
>Gram- positive
>Gram- negative
Gram stain- series of sequential steps
Application of crystal violet, iodine, alcohol, and safranin to bacterial cells
The Gram Stain
What components of the bacterial cell membrane determines the outcome of the staining procedure?
Outcome
- depends on chemical and physcial properties of bacterial cell wall
Physical
- thickness of peptidoglycan layer
Chemical
-Composition of peptidoglycan layer
Gram-positive bacteria
What components of the bacterial cell membrane determines the outcome of the staining procedure?
Thick layer of peptidoglycan
traps crystal violet-iodine complex
Cells appear purple/blye under light microscope
Gram-negative bacteria
What components of the bacterial cell membrane determines the outcome of the staining procedure?
Thinner layer of peptidoglycan
Surrounded by outer membrane that contains lipopolysacchararides (LPS)
>Negatively charged
Staining procedure
- Alcohol: dissolves outer membrane, removes crystal violet-iodine complex from the thin peptidoglycan layer> cell appear pink or red after adding safranin
Why is gram stain useful?
Identifying and classifying bacterial species
Determining antibiotic treatment
Gram negative bacteria generally more resistant to antibiotics
Why> presence of the outer membrane
What is the regressive theory?
Q: Key aspect of the regressive theory of virus origin?
- suggests virus evolved from free-living
- Cellular organisms lost their cellular machinery
- Became parasitic
- Viruses originated from intracellular parasites that lost abbility to replicate independently
- Became dependent on host cells for survival and reproduction
Key aspect of the regressive theory of virus origin?
- virus evolved from more complex cellular organisms
- Rather than emerging spontaneously from non-living materials
- Proposes that viruses evolved from once free-living cells that lost ability: metabolic functions
- became dependent on other cells for their survival and replication
- Hypothesis supported by large genome viruses: mimiviruses
- > complex replicaation cycles that resemblethose of cells
What do mamavirus, pandovirus and pithovirus have in common?
Giant viruses
1. Large genome size
2. Complex viral structure
3. Ability to infect ameoba
4. Controversial classification
5. Environmental reservoirs
Large genome size
What do mamavirus, pandovirus and pithovirus have in common?
Larger tha typical viruses
Mamavirus - 600 kilpbases(kb)
Pandoravirus -over 2.5 megabases
