Module 4 bio communicable diseases

pathogens

bacteria, viruses, fungi, protocista

through directly damaging the tissue or through the release of toxins

tuberculosis, bacterial meningitis and ring rot

HIV/AIDS, influenza and tobacco mosaic virus

black sigatoka, ring worm and athlete’s foot

malaria and potato/tomato late blightq

their shape and cell wall

rod (bacillli), spherical (cocci), comma (vibrio), spiralled (spirilla), and corkskrew (spirochaetes)

Gram-positive of Gram-negative

the bacteria Mycobacterium tuberculosis (M.bovis in cows)

humans, deer, cows, pigs, and badgers

causes harm by damaging the lung tissue and surpressing the immune system

using antibiotics and can be prevented by vaccination

Streptococcus pneumoniae or Neisseria meningitidis and infects the brain the meninges protective layers around the brain

very serious and spreads through the body very quickly causing septicaemia and death

antibiotics can cure it is it is diagnosed before too much damage is caused

some forms can be vaccinated against

clavibacter michiganesis

potatoes tomatoes and aubergines

Gram-positive

causes damage in leaves, tubers and fruit

non-living and A-cellular

smaller than bacteria

consist of only genetic material (DNA or RNA) a capsid and attachment proteins

inside the host cell and involves the injection of nucleic acid into the cell

a virus that infects bacteria

capsid - the outer protein

core consists of the genetic material (RNA) and the enzyme reverse transciptase, which are needed for viral replication

envelope - an extra outer layer made out ofmlipids taken from the host cells membrane

protein attachments - on the exterior of the envelope to enable the virus to attach to the host cell’s T helper cell

in the blood and uses the attachment proteins (CD4 proteins) to attach onto the host’s T helper cells

the HIV protein capsule then fuses with the T helper cell membrane

enabling the RNA and the reverse transcriptase enzyme from the HIV to enter the host cell

once in the host cell the reverse trancriptase copies the virus's RNA into a DNA copy and that DNA copy will then move to the T helper cell’s nucleus

retrovirus because it can convert RNA to DNA

once the DNA copy of the virus’s RNA is moved into the T helper cell’s nucleus it is transcribed into mRNA (because it’s in the nucleus) and the the T helper cells will begin to create the viral proteins from the transcribed mRNA

they are infected with the virus

when the replicating viruses in the T helper cells interfere with the normal functioning of the immune system

with the help of the T helper cells being destroyed by the virus, the host is unable to produce an adequate immune response to other pathogens and is left vulnerable to infections and cancer

the destruction of the immune system causes death

Orthomyxoviridae

it infects the ciliated cells lining gas exchange surfaces

the infection can kill these ciliated cells and cause harmful secondary infetions such as pneumonia is caused by a bacterium that infects the airways and if sufferers develop this as a secondary infection it ca result in death

children and the elderly and those with a lowered immune system

tobacco plants

mainly the leafs though it can cause damage to flowers and fruits

damage prevents the plant from growing as it stops it from photosynthesisng effectively

there is no cure but scientists have been able to develop resistant plant strains to this virus

eukaryotes

single celled or cells grouped into colonies

very few are pathogenic but those that are can cause extremely dangerous symptons

parasites

via a vector

Plasmodium

spread to humans through mosquitoes (vectors)

sexually and asexually in the mosquitoes and within the human hosts

when mosquitoes bite and take blood from humans

in humans the Plasmodium will then infect red blood cells, the liver and the brain

no vaccine or cure but there are some preventative medicines

phytophthora infestans - a fungus-like protoctista

it has hyphae which enter the plant and cause damage to the leaves and fruit

no cure but resistant strains have been developed

eukaryotes that mainly cause diseases in plants

they can be either multi-cellular or single-celled

pathogenic fungi are parasitic and able to release enzymes to digests the host tissue which the fungi then feed off of

Mycosphaerella fijiensis

bananas

the fungal hyphae cause damage to the leaves causing them to turn black preventing growth

fungicides can kill the fungus and resistant stains have been developed

Trichophyton verrucosum

many mammals including humans

causes white crusty circles on the skin

not harmful but can cause itching and discomfort

Tinia pedia

only infects humans

it’s a type of ring-worm that thrives in warm damp places between the toes

antifungal creams

increased heat provides more kinetic energy for chemical reactions and reproduction

poverty /developing countries- could result in poorer sewage infrastructure, a lack of fresh water and food, poorer sanitation and overcrowded living quarters medecines and vaccines being less readily available to prevent spread

direct and indirect transmission

direct contact, inoculation and ingestion

touching, kissing, contact with cuts in skin, sexual contact

animal bites, sharing needles and cuts in skin

drinking and eating contaminated water and food

vectors, droplets and fomites

usually animals that pass the pathogens to humans such as mosquitoes transmitting malaria

pathogens transmitted in droplets of water e.g. saliva and mucus expelled when sneezing

dirty bedding, socks and cosmetics are examples of inanimate objects that can carry and transmit pathogens

direct contact

direct contact between different plants e.g. ring-rot, tobacco mosaic virus, black sigatoka, blights

contaminated soil and vectors

pathogens and their spores can remain in the soil and infect the roots of subsequent plants

wind, water animals and humans can all carry pathogens and spores from one plant to another

they do not have blood or an immune system instead they have:

• barriers to prevent entry such as bark or waxy cuticles

• antibacterial chemicals and proteins as a defence against bacterial infections can repel insects (vector) and kill pathogens

• physical defences to prevent pathogens from spreading between their cells oncethey become infectedsuch as producing callose

there is a primary and secondary line of defence against pathogens

the primary line of defence in non-specific

that the same response will occur regardless of the pathogen

skin - acts as a barrier and contains the skin flora (healthy microorganism) which outcompete the pathogens for space and resources on the skin

blood clots - will form if the skin is cut to form a new barrier

mucous membranes - line many body tracts the mucus produced traps pathogens and the cilia sweep the mucus away from the lungs

lysozymes - hydrolytic enzymes which digest pathogens

expulsive reflexes such as sneezing coughing and vomiting mechanisms to force pathogens out of the body

inflammation - occurs in the localised areas where damage is detected. when cells are damages it causes mast cells to release histamines and cytokines

cause the blood vessels in the inflamed area to dilate therefore blood is flowing in the area - the increased temperature from blood can kill pathogens

histamine also makes the walls of blood vessels more permeable so that more white blood cells can be delivered to the site of damage

attract phagocytes which can engulf and destroy the pathogens

an example of the 1st line of defence done by white blood cells (phagocytes- macrophages or neutrofils

phagocytes (neutrofils or macrophages) travel in the blood and squeeze out of capillaries to engulf and digest pathogens

it is a non-specific response

damaged cells and pathogens release cell-signalling chemicals (cytokines) thet attract the phagocytes to the site of infection

a protein that can attach to a pathogen and mark them making it easier for the neutrophils and macrophages to engulf them

phagocytes have receptors that can attach onto chemicals on the surface of proteins

the phagocyte then engulfs the pathogen into a vessicle to create a phagosome

within the phagocytes there are lysosomes which contain hydrolytic lysozyme enzymes

the lysosome then fuses with the phagosome to expose the pathogen to the lysozyme

the lysozyme hydrolyses the pathogen and any soluble useful molecules are absorbed into the cytoplasm of the phagocyte

the phagocyte will present the antigen of the digested pathogen on their surface - they are called antigen-presenting cells

specific and will respond toparticularly shaped antigens

it involves lymphocytes

B lymphocytes

T lymphocytes

in the bone marrow

b lymphocytes mature in the bone marrow

whereas

t lymphocytes mature in the thymus

T lymphocytes

cells that present a non-self antigen on their surface

infected body cells presenting viral antigens on their surface

a macrophage which has engulfed and destroyed a pathogen presenting the antigens on their surface

cells of a transplanted organ will have different shaped cells on their surface compared to your self cell antigens

cancer cells will have abnormally shaped self cell antigens

once the pathogen has been engulfed and destroyed by a phagocyte the antigens are positioned on the cell surface now called an APC

T helper cells have receptors on their surface which can attach to the antigens on the APC

once attached interleukins are produced which activates the T helper cells to divide by mitosis to replicate and make a large number of clones

cloned T helper cells then differentiate into different cells that are needed

some will remain T helper cells and produce interleukins to activate the B lymphocytes

some will produce interleukins to stimulate macrohphages to perform more phagocytosis

T memory cells are produced

T killer cells (cytotoxic cells) are produced

and T regulator cells are produced which surpress the immune response to ensure that the cell mediated response only occurs when the pathogens are detected

Tcells that will retain that particular shaped receptor for that antigen in case of reinfection

cells that can destroy abnormal or infected cells that have those antigens on their surface

release a protein (perforin) which embeds in the cell surface membrane and makes a pore so that any substances can now enter or leave the cell and this causes death

most common in viral infections because viruses infect body cells which ahve to be destroyed and sacrificed to prevent any further damage

B lymphocytes

T helper cells stimulating the B cells by producing interleukins

antibodies

globular quarternary structure protein with 4 polypeptide chains, two heavy polypeptide chains and two light polypeptide chains

the binding site is known as the variable region where the antibody binds to the complentary-shaped antigen

the rest of the antibody is the constant region

agglutination, marking pathogens and acting as antitoxins

the clumping together of pathogens to make it easier for phagocytes to locate and engulf them