4.1 Flashcards
I have not included all the ‘did you know’ boxes in this deck.
😉
What is the organism in which a pathogen lives called?
The host.
What does a host body create for a pathogen?
A good habit in which microorganism can live.
What is a pathogen?
A microorganism that causes disease.
How do pathogens live?
By taking nutrition from their host, but also cause damage in the process. This damage can be considerable.
Where do numerous types of microorganism live in or on?
The body of another organism.
What kingdom does bacteria belong to?
The kingdom Prokaryoate.
How does the size of eukaryotic cell’s compare bacteria cells?
Bacteria cells are smaller than eukaryotic cells.
How often do bacteria reproduce?
In the right conditions, some types of bacteria can reproduce every 20 minutes. Once in the hosts body, they can multiply rapidly.
What can the presence of bacteria cause?
Their presence can cause diasease by damaging cells or by releasing waste products and/or toxins that are toxic to the host. In plants, the bacteria often live in the vascular tissues and cause blackening and death of these tissues .
What are the problems caused by fungi?
Fungi can also cause a variety of diseases in both plants and animals. There are common fungal infections where the fungus lives in the skin of an animal, and where its hyphae, which form a mycelium, grow under the skin surface.
How does fungi grow across the skin surface?
The fungus can send out specialised reproductive hyphae, which grow to the surface of the skin to release spores. This causes redness and irritation.
Where do fungi live in pants?
In plants, the fungus often lives in the vascular tissue, where it can gain nutrients.
What do fungi cause in a plant?
The hyphae release extracellular enzymes, such as cellulases, to digest the surrounding tissue, which causes decay. Leaves will often become mottled in colour, curl up and shrivel, before dying. Fruit and storage organs, such as tubers (potatoes) will turn black and decay.
How do viruses reproduce?
Viruses invade cells and take over the genetic machinery and other organelles of the cell. They then cause the cell to manufacture more copies of the virus. The host cell eventually bursts, releasing many new viruses which will infect healthy cells.
Describe protoctista.
There are a number of diseases caused by animal-like protoctists. These organisms usually cause harm by entering host cells and feeding on the contents as they grow.
What parasite feeds on haemoglobin inside red blood cells?
The malarial parasite Plasmodium has immature forms that feed on the haemoglobin inside red blood cells.
What are the characteristics of tuberculosis?
A disease that affects many parts of the body killing the cells and tissues: the lungs are most often affected.
What is the organism that causes tuberculosis?
Bacteria Mycobacterium tuberculosis and M. bovis
What are the characteristics of bacterial meningitis?
Infection of the meninges - the membranes that surround the brain and spinal cord; the membranes become swollen and may cause damage to the brain or nerves
What is the organism that causes bacterial meningitis?
bacteria Neisseria meningitidis or Streptococcus
What are the characteristics of ring rot (in plants) ?
Ring decay in the vascular tissue of a potato tuber or tomato, accompanied by leaf wilting.
What is the organism that causes ring rot (in plants) ?
bacterium Clavibacter michiganensis subsp. sepedonicus
What are the characteristics of HIV/AIDS?
attacks cells in the immune system and comprises the immune response.
What is the organism that causes HIV/AIDS?
virus; human immunodeficiency virus
What are the characteristics of influenza?
attacks respiratory system and causes muscle pains and headaches.
What is the organism that causes influenza?
virus from family Orthomyxoviridae - ‘flu’ viruses
What are the characteristics of tobacco mosaic virus?
causes mottling and discolouration of leaves.
What is the organism that causes tobacco mosaic virus?
virus tobacco mosaic virus.
What are the characteristics of black sigatoka (bananas)?
causes leaf spots on banana plants reducing yield
What is the organism that causes black sigatoka (bananas)?
fungus Mycosphaerella fijiensis
What are the characteristics of blight (tomatoes and potatoes) ?
affects both leaves and potato tubers
What is the organism that causes blight (tomatoes and potatoes) ?
protoctistan phytophthora infestans
What are the characteristics of ringworm (cattle)?
growth under skin of feet - particularly between the toes
What is the organism that causes ringworm (cattle)?
fungus Trichophyton rubrum
What are the characteristics of athlete’s foot (humans)/
growth under skin of feet - particularly between the toes
What is the organism that causes athlete’s foot (humans)/
fungus Trichophyton rubrum
What are the characteristics of malaria?
parasite in the blood that causes headache and fever and may progress to coma and death.
What is the organism that causes malaria?
protoctistan Plasmodium falciparum, P. vivax, P. ovale, P. malariae
Give an example of a organism that causes diasease that is hard to classify.
Phytophthora (blight) has been classified as a fungus for many years. Recently, it was moved to the kingdom Protoctista, before being placed in a new kingdom (stramenopila), because it has many features that do not fit with other fungi (it does not fit the mould).
What is direct transmission?
passing a pathogen from host to new host, with no intermediary.
What is indirect transmission?
passing a pathogen from host to a new host, via a vector.
What is a vector?
an organism that carries a pathogen from one host to another.
What is transmission?
passing a pathogen from an infected individual to an uninfected individual. (remember it is the pathogen that is transmitted not he disease)
Pathogens have life cycles that involves living in or on other living things. What is the by-product of this life cycle?
That they cause harm to their host.
What are the stages of the life cycle of a pathogen?
Travel from one host to another (transmission) entering the host’s tissues reproducing leaving the hosts tissues
Pathogenic organisms can be transmitted between animals in a variety of ways, which is the most common?
direct transmission.
What are the different methods of transmission?
Direct physical contact, faecal - oral transmission, droplet infection and transmission by spores.
Describe direct physical contact as a means of transmission.
such as touching a person who is infected or touching contaminated surfaces (including soil) that harbour the pathogens.
What are some examples of diseases caught through direct physical contact?
For example, HIV, bacterial meningitis, ringworm, athlete’s foot.
What are factors that cause transmission through direct physical contact?
Hygiene: washing hands regularly - especially after using the toilet. Keeping surfaces clean - especially door handles. Cleaning and disinfecting cuts and abrasions. Sterilising surgical instruments. Unsing condoms during sexual intercurse.
Describe faecal - oral transmission as a means of transmission.
usually by eating food or drinking water contaminated by the pathogen.
What are some examples of diseases caught through faecal - oral transmission?
For example, cholera and food poisoning.
What are factors that cause transmission through faecal - oral transmission?
Using human sewage to fertilise crops is a common practice in some parts of the world. Treatment of waste water and treatment of drinking water are important ways to reduce the risk. Thorough washing of all fresh food (using treated water). Careful preparation and thorough cooking of all food.
Describe droplet infection as a means of transmission.
in which the pathogen is carried in tiny water droplets in the air.
What are some examples of diseases caught through droplet infection?
tuberculosis and influenza
What are factors that affect transmission through droplet infection?
Catch it - bin it - kill it. Cover your mouth when coughing or sneezing. Use a tissue and ensure the tissue is disposed of correctly.
Describe transmission by spores as a means of transmission.
Transmission by spores, which are a resistant stage of the pathogen. These can be carried in the air or reside on surfaces or in the soil.
What are some examples of diseases caught through transmission of spores?
anthrax and tetanus
What are factors that affect transmission through transmission of spores?
Use of mask. Washing skin after contact with soil.
What social factors affect transmission of a pathogen?
Overcrowding - many people living and sleeping together in one house. poor ventilation poor health - particularly if a person has HIV/AIDS, as they are more likely to contract other diseases poor diet homelessness living or working with people who have migrated form areas where a disease is more common.
How are diseases transmitted indirectly?
Via a vector. A vector is another organism that may be used by the pathogen to gain entry to the primary host.
Use malaria to give an example of indirect transmission.
For example, the Plasmodium parasite that causes malaria enters the human host via a bite from a female Anopheles mosquito. The life cycle of Plasmodium, which uses a vector
What is the life cycle of Plasmodium?
-> a person with malaria -> gametes of plasmodium in blood -> female mosquito sucks blood -> plasmodium develops and migrates to a mosquito’s salivary glands -> an uninfected person is bitten -> PLasmodium migrates to the liver -> PLasmodium migrates to the blood ->
How can plant pathogens be spread?
Plant pathogens can also be spread by direct and indirect means. Many pathogens are present in the soil and will infect plants by entering the roots - especially if these havent
How does fungi reproduce?
Many fungi produce spores as a means of sexual or asexual reproduction. These spores may be carried in the wind - airborne transmission.
What course of action does the pathogen take when inside a plant?
Once a pathogen is inside the plant, it may affect all the vascular tissue.
How do pathogens spread?
Pathogens in the leaves are distributed when the leaves are shed and carry the pathogen back to the soil where it can grow and infect another plant/ Pathogens can also enter fruit and seeds, and will the be distributed with the seeds - so that many or all the offspring are infected.
Describe how indirect transmission often occurs in plants.
Indirect transmission of plant pathogens often occurs as a result of insect attack. Spores or bacteria become attached to a burrowing insect, such as a beetle, which attacks an infected plant. When that beetle attacks another plant, the pathogen is transmitted to the uninfected plant. The beetle is acting as a vector. For example, the fungus that causes Dutch elm disease is carried by the beetle Scolytus multistriatus.
In what climates are protoctists most common?
Many protoctists, bacteria and fungi grow and reproduce more rapidly in warm and moist conditions. Therefore they tend to be more common in warmer climates.
Why are protoctists most common in warm climates?
In cooler climates, these pathogens may be damaged or even killed by cold winter weather - such weather will reduce their ability to grow and reproduce. As a result, there is a greater variety of diseases to be found in warmer climates, and animals or plants living in these regions are more likely to become infected.
What is making Europe more appealing to pathogens?
As Global warming alters our climate, these pathogens will be able to survive more easily in Europe. Tropical diseases may become more common in Europe as a result.
What is callose?
a large polysaccharide deposits that blocks old phloem sieve tubes.
Plants manufacture sugars in photosynthesis and convert those sugars to a wide range of compounds such as proteins and oils. Therefore what does it represent to a pathogen?
Therefore they represent a rich scource of nutrients for many organisms such as bacteria, fungi, protoctists and viruses may be pathogenic.
What do plants have as an immune system?
Plants do not have an immune system comparable with animals. But they have developed a wide range of structural, chemical and protien-based defences which can detect invading organisms and prevent them from causing extensive damage. This includes both passive defences to prevent entry and active defences which are introduced when the pathogen is detected.
What is a passive defence?
These are defences present before infection, and their role is to prevent entry and spread of the pathogen. Passive defences include physical barriers and chemicals.
Why are the physical defences of a plant against pathogens?
cellulose cell wall, lignin thickening of cell walls, waxy cuticles, bark, stomatal closure, callose and tylose
Describe cellulose cell wall as a physical plant defence against pathogens.
this not only acts as a physical barrier but most plant cell walls contain a variety of chemical defences that can be activated when a pathogen is detected.
Describe lignin thickening of cell walls as a physical plant defence against pathogens.
lignin (a phenolic compound) is waterproof and almost completely indigestible.
Describe as a physical plant defence against pathogens.
these prevent water collecting on the cell surfaces. Since pathogens collect water and need water to survive, the absence of water is a passive defence.
Describe waxy cuticles as a physical plant defence against pathogens.
these prevent water collecting on the cell surfaces. Since pathogens collect in water and need water water to survive, the absence of water is a passive defence.
Describe bark as a physical plant defence against pathogens.
most bark contains a variety of chemical defences that work against pathogenic organisms.
Describe stomatal closure as a physical plant defence against pathogens.
stomata are possibly points of entry pathogens. Stomatal aperture is controlled by the guard cells. When pathogenic organisms are detected, the guard cells will close the stomata in that part of the plant.
Describe callose as a physical plant defence against pathogens.
callose is a large polysaccharide that is deposited in the sieve tubes at the end of growing season. It is deposited around the sieve tubes and blocks the flow in the sieve tube. This can prevent a pathogen spreading around the plant.
Describe tylose as a physical plant defence against pathogens.
a tylose is a balloon-like swelling or projection that fills the xylem vessel. When a tylose is fully formed, it plugs the vessel and the vessel can no longer carry water. Blocking the xylem vessel prevents spread of pathogens through the heartwood. The tylose contains a high concentration of chemicals such as terpenes that are toxic to pathogens.
When chemical deferences do plant tissues contain?
Plant tissues contain a variety of chemicals that have anti-pathogenic properties. These include terpenoids, phenols, alkaloids and hydrolytic enzymes.
When are chemical defences used within plant tissue?
Some of these chemicals, such as terpenes in tyloses and tannins in bark, are present before infection. However, because the production production of chemicals require a lot of energy, many chemicals are not produced until the plant detects an infection.
How does a plant know a pathogen is attacking?
When a pathogen attacks, specific chemicals in their cell walls can be detected by the plant cells. These chemicals include specific proteins and glycolipids.
How does a plant respond to attack of pathogens?
The plant responds by fortifying the defences already present. This includes increasing the physical defences and producing defensive chemicals.
What are the active defences of a plant?
Cell walls become thickened and strengthened with additional cellulose. Deposition of callose between the plant cells wall and cell membrane near the invading pathogen. Oxidative bursts that produce highly reactive oxygen molecules capable of damaging the cells of invading organisms. An increase in production of chemicals.
Active defences; What is the action of the chemical terpeniods?
A range of essential oils that have antibacterial and antifungal properties. They may also create scent, for example, the menthols and menthones produced by mint plants.
Active defences; What is the action of the chemical phenols?
These have antibiotic and antifungal properties. Tannins found in bark inhibit attack by insects. These compounds bond to salivary proteins and digestive enzymes such as trypsin and chymotrypsin, deactivating the enzymes. Insects that ingest high amounts of tannins do not grow and will eventually die. This helps to prevent the transmission of pathogens.
Active defences; What is the action of the chemical alkaloids?
Nitrogen-containing compounds such as caffeine, nicotine, cocaine, morphine, solanine. These give a bitter taste to inhibit herbivores feeding. They also act on a variety of metabolic reactions via inhibiting or activating enzyme action. Some alkaloids inhibit proton synthesis. If the plant can reduce grazing by larger animals, then it will suffer less damage that can allow pathogens to enter the plant.
Active defences; What is the action of the chemical defensive proteins (defensins)?
These are small cysteine-rich proteins that have broad anti-microbial activity. They appear to act upon molecules in the plasma membrane of pathogens, possibly inhibiting the action of ion transport channels.
Active defences; What is the action of the chemical hydrolytic enzymes?
These are found in the spaces between cells. They include chitinases (which break down the chitin found in fungal cell walls), glucanases (which hydrolyse the glycosidic in glucans) and lysozymes (which are capable of degrading bacterial cell walls.
What is necrosis?
Deliberate cell suicide. A few cells are sacrificed to save the rest of the plant.
Why do plant cells undergo necrosis?
By killing cells surrounding the infection, the plant can limit the pathogens access to water and nutrients and can therefore stop it spreading further around the plant.
How is cell suicide activated?
Necrosis is brought about by intracellular enzymes that are activated by injury. These enzymes destroy damaged cells and produce brown spots on leaves or dieback.
What is a canker?
A sunken necrotic lesion in the woods tissue such as the main stem or branch. It causes death of the cambium tissue in bark.
What is inflammation?
Swelling and redness of tissue caused by infection.
What is a mucous membrane?
Specialised epithelial tissue that is covered by mucous.
What are primary defences?
Those that prevent pathogens entering the body.
What is a macrophage?
Macrophages are larger cells manufactured ion the bone marrow. They travel in the blood as monocytes (look at the picture) before settling in the body tissues.
What does a macrophage do when it englufs a pathogen?
Describe the role of an antigen presenting cell?
Describe an investigation looking at blood cells.
- Blood cells can be viewed in a blood smear.
- A thin layer of blood is spread out o a slide, and is stained to make the white blood cells more visible.
- The red blood cells are pink in colour.
- Note that red blood cells do not always look like a perfect bioconcave disc.
- Monocytes are the largest white blood cells and usually have a large kidney shaped nucleus.
- Neutrophils have a multilobed nucleus. Lymphocytes are smaller, and the nucleus alomost fills the cell.
Thye specifc immune response involves the co-ordinated action of a range of cells. In order to work togther effectively they need to communicate, this is known as cell signalling. How is this communication achieved?
Give three examples of communication using cytokines.
The causes of autoimmune disease are unknown, but seem to include both genetic and environmental factors. What are some examples?
- Artritus is a painful inflammation of a joint. The cause is uncertain, but it starts with antibodies attacking the membrane around the joint.
- Lupus can affect any part of the body, causing swelling and pain. It may be associated with antibodies that attack certain portions in the nucleus in cells and affected tissues.
Describe how the concentration of antibodies changes over time for primary and secondary immune responses.
Discribe controll of epidemics in vaccination.
What are the dangers relaxing a routine vaccination?
