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Flashcards in Bacteria Deck (26):
1

Two cell shapes

Cocci - round
Bacilli - rod

2

Features of Gram positive bacteria

- Bounded by single cytoplasmic lipid membrane.
- Thick peptidoglycan layer, multilayers
- Periplasmic space
- Low lipoprotein content
- Primarily exotoxins produced
- More susceptible to antibiotics

3

Staining characteristics of Gram positive

- Thick peptidoglycan later retains the Gram stain
- Retains crystal violet dye
- Remains coloured blue or purple when washed with absolute alcohol and water

4

Features of Gram negative bacteria

- Inner cell membrane is present
- Thin peptidoglycan layer
- Outer membrane with lipopolysacharides and phospholipids
- Primarily endotoxins produced
- More resistant to antibiotics

5

Staining characteristics of Gram negative

- Due to thin peptidoglycan layer, can be decolourised and accept counterstain
- Doesn't retain Gram stain when washed with absolute alcohol or water

6

What culture to use for Gram negative and Gram positive

- MacConkey agar

7

How to determine DNA species

PCR

8

Capsule

- 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

Flagellum

- In Gram +ve and -ve
- Lash-like appendage
- Allow for different types of motility
- Not all bacteria have these

10

Fimbriae

- 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

Cytoplasm

Material or protoplasm within a living cell, excluding nucleus

12

Ribosomes

Minute particle consisting of RNA and associated proteins

13

Cell wall

Rigid layer of polysaccharides lying outside the plasma membrane

14

Peptidoglycan

- Polymer consisting of sugars and amino acids, forms a mesh-like layer outside the plasma membrane of most bacteria

15

Chromosome

- Packaged and organised structure that contains most of the DNA of a living organism
- DNA organised in prokaryote into nucleoid

16

Penicillin binding proteins

- 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

Lipopolysaccharides

- 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

Exotoxins

- 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

Plasmid definition

- Small DNA molecule within a cell that is physically separated from a chromosomal DNA and can replicate independently

20

How plasmid is transmitted from one bacterium to another

1. Transformation: direct uptake and incorporation of exogenous genetic material. Taking up DNA
2. Transduction: Foreign DNA from a phage introduced into a cell wall by a virus or viral vector.
3. Conjugation: Transfer of genetic material between bacterial cells by direct cell-to-cell contact by bridge-like connection between 2 cells

21

Transduction mechanism in plasmids

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

Bacteriophage

- 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

Spore

- 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

Staphylococcus

Grapelike clusters

25

Streptococcus

Chains of cocci

26

Acinetobacter spp.

Non-motile