12.1 - Animal & Plant Pathogens Flashcards
Define communicable disease and give 3 examples of pathogens.
Diseases that are passed from one organism (of the same or different species) to another through infective organisms called pathogens.
Pathogen examples: bacteria, viruses, fungi and protoctista
In plants, are communicable disease passed directly or indirectly between them?
Directly
Define vector and give some common examples.
A living or non-living factor that transports pathogens from one organism to another.
- Common vectors are water and insects
What are the different types of bacterial cell walls?
And what is the purpose of staning them?
- 2 types of cell wall - different structures and react differently when they undergo ‘Gram Staining’
- Gram-positive bacteria are bacteria with cell walls that stain purple-blue (e.g. MRSA)
- Gram-negative bacteria are bacteria with cell walls that stain red (e.g. E.coli)
- The purpose of Gram Staining is to identify how different types of bacterial cell walls will react with different antibiotics (a chemical/compound that kills or inhibits the growth of bacteria)
Give the characteristics of protoctista.
- Group of eukaryotic organisms with a variety of feeding methods
- Consist of unicellular organisms and colonial cell groups
- A small proportion of Protista are pathogenic, and thus cause disease. That proportion are parasitic
- Pathogenic protists may use vectors to transfer to hosts – e.g. malaria** and **sleeping sickness
They may also enter the body directly through polluted water
What is the general structure and function of a virus?
- Non-living infectious agents
- 50 times smaller than average bacterium
Basic structure: DNA/RNA surrounded by protein
- Viruses attack living cells, their genetic material takes over the biochemistry of the cell to reproduce rapidly and evolve to develop adaptations to their host – making them successful pathogens
All naturally occurring viruses are pathogens
What are bacteriophages and what is their function?
Bacteriophages: Viruses that invade bacteria
- They attack bacteria, use them to replicate and subsequently destroy bacteria.
- Bacteriophages are used to identify and treat some diseases
- They are referred to, as the ultimate parasites (an organism that uses a host for nourishment, whilst simultaneously depleting the host of its nourishment. The parasite benefits, the host loses out)
What is the structure and function of a fungal cell?
- Fungal disease is not a large problem in animals, is detrimental to plants.
- Eukaryotic, often multicellular organisms
- Cannot photosynthesise, food is digested extracellularly before absorbing nutrients
- Fungi are saprophytes – organisms that acquire nutrients by absorption of decaying material
- Some fungi are parasitic
- Fungal infection affects leaves of plants, stopping them photosynthesising – killing the plant
- Fungi can reproduce very fast to produce millions of tiny spores that spread distances and can kill crop
What is a direct mode of action pathogens take?
DIRECT HOST TISSUE DAMAGE – damage the tissue, causing symptoms from the disease
- Viruses take over cell metabolism, viral genetic material is inserted in host cell DNA. Virus uses host cell to reproduce viruses and bursts out of cell destroying and infecting other cells
- Protista over take cells, breaks open cell to make new generation emerge – don’t take over genetic material. They digest and use cell contents to reproduce. Protists that cause malaria are an example of this
- Fungi digest and destroy living cells. This combined with body’s immune response gives the symptoms of the disease
What is an indirect mode of action pathogens take?
PRODUCING TOXINS THAT DAMAGE HOST TISSUE
- Bacteria produce toxins that poison or damage host cells, causing disease. Some bacterial toxins break down cell membranes, some damage inactive enzymes and some interfere with genetic material – so they can’t undergo mitosis. Toxins are by products of functioning bacteria
- Fungi produce toxins which affect host cells causing disease.
