Bacteria Flashcards
1
Q
Two cell shapes
A
Cocci - round
Bacilli - rod
2
Q
Features of Gram positive bacteria
A
- Bounded by single cytoplasmic lipid membrane.
- Thick peptidoglycan layer, multilayers
- Periplasmic space
- Low lipoprotein content
- Primarily exotoxins produced
- More susceptible to antibiotics
3
Q
Staining characteristics of Gram positive
A
- Thick peptidoglycan later retains the Gram stain
- Retains crystal violet dye
- Remains coloured blue or purple when washed with absolute alcohol and water
4
Q
Features of Gram negative bacteria
A
- Inner cell membrane is present
- Thin peptidoglycan layer
- Outer membrane with lipopolysacharides and phospholipids
- Primarily endotoxins produced
- More resistant to antibiotics
5
Q
Staining characteristics of Gram negative
A
- Due to thin peptidoglycan layer, can be decolourised and accept counterstain
- Doesn’t retain Gram stain when washed with absolute alcohol or water
6
Q
What culture to use for Gram negative and Gram positive
A
- MacConkey agar
7
Q
How to determine DNA species
A
PCR
8
Q
Capsule
A
- In Gram +ve and -ve bacteria
- Polysaccharide layer that lies outside the cell envelope bacteria
- Difficult to stain but can appear as a halo under a microscope
- Raise virulence factor as they prevent phagocytosis
- Not all bacteria have these
9
Q
Flagellum
A
- In Gram +ve and -ve
- Lash-like appendage
- Allow for different types of motility
- Not all bacteria have these
10
Q
Fimbriae
A
- In many Gram -ve and some Gram +ve
- Adherence main job
- Carry adhesins that attach to the substratum so bacteria can handle shear force and get nutrients
- Create virulence for E.coli, Bordetella pertussis, staphyloccus and streptococcus bacteria
11
Q
Cytoplasm
A
Material or protoplasm within a living cell, excluding nucleus
12
Q
Ribosomes
A
Minute particle consisting of RNA and associated proteins
13
Q
Cell wall
A
Rigid layer of polysaccharides lying outside the plasma membrane
14
Q
Peptidoglycan
A
- Polymer consisting of sugars and amino acids, forms a mesh-like layer outside the plasma membrane of most bacteria
15
Q
Chromosome
A
- Packaged and organised structure that contains most of the DNA of a living organism
- DNA organised in prokaryote into nucleoid
16
Q
Penicillin binding proteins
A
- Group of proteins characterised by their affinity for and binding of penicillin
- All β-lactam antibiotics bind to PBPs which are essential for bacterial cell wall synthesis
17
Q
Lipopolysaccharides
A
- Known as lipoglycans and endotoxins
- Found in the outer membrane of Gram negative bacteria
- Can be released during lysis of the cell
- They illicit a strong immune response in animals
18
Q
Exotoxins
A
- Toxin secreted by bacteria
- Can be secreted or released during lysis of the cell
- Can cause damage to the host by destroying cells or disrupting normal cellular metabolism
19
Q
Plasmid definition
A
- Small DNA molecule within a cell that is physically separated from a chromosomal DNA and can replicate independently
20
Q
How plasmid is transmitted from one bacterium to another
A
- Transformation: direct uptake and incorporation of exogenous genetic material. Taking up DNA
- Transduction: Foreign DNA from a phage introduced into a cell wall by a virus or viral vector.
- Conjugation: Transfer of genetic material between bacterial cells by direct cell-to-cell contact by bridge-like connection between 2 cells
21
Q
Transduction mechanism in plasmids
A
Phage injects DNA Phage enzyme breaks down host DNA Cell creates new phages Transducing phage inserts donor DNA Donor DNA included in recipients chromosome due to recombination
22
Q
Bacteriophage
A
- Virus that infects and replicates within a bacterium
- Bacteriophages are composed of proteins that encapsulate a DNA or RNA genome
- Phages replicate within the bacterium following the injection of their genome into its cytoplasm
23
Q
Spore
A
- Small, round body inside bacterial cells
- When conditions become adverse, these are important for survival
- They are extremely resistant: can tolerate extreme dryness, some cannot die at subzero temps, some can spread poisonous chemicals
24
Q
Staphylococcus
A
Grapelike clusters
25
Q
Streptococcus
A
Chains of cocci
26
Q
Acinetobacter spp.
A
Non-motile
