Animal and Plant Pathogens Flashcards Preview

BIO - 4.1.1 Communicable Diseases > Animal and Plant Pathogens > Flashcards

Flashcards in Animal and Plant Pathogens Deck (8)
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1
Q

What are pathogens?

A
  • Infectious organisms which spread communicable diseases.
  • Includes bacteria, viruses, fungi and protoctista. The type of pathogen determines how it spreads.
  • A vector is something which carries a pathogen from one organism to another.
2
Q

Bacteria

A
  • They are prokaryotes so they have v. different ultrastructure to the organisms they infect. Most bacteria are not pathogens.

They can be identified in 2 main ways:

1) Cell walls: bacterial cell walls react differently to a process called gram staining because of their different structures - gram pos. bacteria appears purple whereas gram neg. bacteria appears red.
- This is useful as bacteria with diff. cell walls respond differently to antibiotics.
2) Basic shapes: Bacillus (rod), Streptobacillus, Coccus (sphere), Streptococcus, Staphylococci, Vibrio (comma), Spirillum (spiral), Spirachaete (corkscrew)

3
Q

Viruses

A
  • Non living infectious agents, 0.2-0.3um in diameter. All viruses are pathogens.
  • Basic structure is some DNA/RNA surrounded by protein.
  • They invade living cells where the genetic material takes over the host to make more viruses. They reproduce rapidly and evolve by adapting to the host.
  • Bacteriophages are viruses which attack bacteria and use them to replicate, destroying them at the same time, and can be used to identify and treat disease.
4
Q

Protoctista

A
  • A group of eukaryotic organisms with a variety of feeding mechanisms, which can be uni- or multicellular. Only a small amount of protoctista are pathogens.
  • Parasitic, so use animals as their host organism. They may need a vector to transfer them from one organism to another, or enter directly.
5
Q

Fungi

A
  • Generally multicellular eukaryotic organisms which are major problem in plants, but can affect animals.
  • Digest their food extracellularly and then absorb the nutrients, meaning they feed on decaying matter.
  • Fungal infections kill plants by attacking leaves and stopping them from photosynthesising.
  • Reproduce by releasing millions of spores which can travel long distances.
6
Q

Pathogenic modes of action: Damaging host directly

A
  • Viruses take over cell metabolism as the viral DNA/RNA is inserted into host DNA, causing new viruses to be synthesised. When viruses burst out to spread to another cell, the cell dies.
  • Some protoctista take over cells and kill them as a new generation emerges like viruses. They don’t take over the genetic material but they only digest cell contents as they reproduce.
  • Fungi digest living cells and destroy them.
7
Q

Pathogenic modes of actions: Producing toxins

A
  • Bacteria produce toxins which poison or damage the host in some way, causing disease. Such as breaking down membranes, inactivating enzymes or interfering with genetic materials. Toxins are a by-product of normal functioning.
  • Fungi can also produce toxins.
8
Q

How bacteriophages work

A

1) Attach to host.
2) Insert viral DNA/RNA
3) Replication of DNA/RNA
4) Assembly of viral protein
5) Assembly of virus
6) Lysis of host