Pathogens

Feature Prokaryotes Eukaryotes

Size and shape

Nucleus Present

Ribosomes Present

Organelles Present

Examples

Copy and Complete this table in your books **make the table the width of your notebook)

The Differences between Prokaryotes and Eukaryotes

Cell Types and Structures

Bacteria• Cell type: Prokaryotes• Shape: 3 basic shapes

– Round (Coccus)– Rod (Bacillus)– Spiral (Spirochaete – pronounced spy-row-keet)

• Classification– Live singularly or in groups which is used in their classification e.g. Cocci that live together

in bunches (like grapes) are called Staphylococci, where as if they live together in a line they are called Streptococci.

• Structures• Flagella – some bacteria have falgella – thin appendages that

allow a bacteria to move. Bacteria without flagella are unable to move and are called non-motile.

• Capsule – many bacteria have a layer called a capsule outside their cell wall, this slimy layer may have long ‘fingers’ called Pili. The capsule makes the bacteria more difficult to be captured and destroyed by our body’s defences.

• Spores - some bacteria form spores which are reproductive structures resistant to heat and drying out. They can survive if the environment becomes unsuitable for the bacteria. Generally one spore is formed per bacteria.

• Cell Wall Structures – strains bacteria have chemical differences in their cell walls. This causes them to react differently to our cells and medications (antibiotics). When tested with Gram Stain, Gram Positive bacteria will turn a violet colour. Gram Negative will not, they will later be stained pink.

• Oxygen Requirements– Bacteria can be classified based on their oxygen requirements.

• Some grow in the presence of oxygen (Aerobes) such as those that cause external ear infections

• Others grow in the absence of oxygen (Anaerobes) such as those that cause tetanus

• Note, some Anaerobes with grow in either the presence or absence of oxygen such as those that cause tonsillitis.

• Nutritional Requirements– Different bacteria have different energy and nutritional needs.

In a laboratory different culture media (Agar Plates) are used to target different bacteria.

• Reproduction– In order to reproduce bacteria require an

environment with sufficient nutrients and water, with an appropriate temperature and pH. When conditions are favourable bacteria multiply quickly. Bacteria multiple by Binary Fission – this is an example of ‘Asexual reproduction.

Disease causing Bacteria• Bacteria can cause disease in humans if:

– They can enter a person, who acts as a host– They can reproduce in their host– They damage the hosts tissues in some way.

• Virulence – the disease causing capabilities of bacteria. E.g. if a bacteria causes significant disease in humans it is said to be virulent. Note: the presence of a capsule can make bacteria more virulent.

• Transmission – Bacteria can be transmitted from person to person directly (sneezing, coughing, through blood or body contact), by ingesting contaminated food and water, or carried by another animal or insect such as a tick (vector).

• Effects – bacteria can damage tissues by:– causing tissue to die due to a lack of blood supply (Gangrene)– Many bacteria secrete poisonous toxins that can:

• Inhibit protein synthesis in host cells• Damage host cell membranes or prevent transfer of materials

across them• Interfere with normal nerve function.

Examples of Bacterial Pathogens

• Some examples of Bacterial Pathogens include:– Tetanus, Botulism, Golden Staph, E. Coli, Cholera,

Tuberculosis, Bacterial Meningitis, Pertussis (Whooping Cough), Foot Rot, Syphilis, Meningococcal Disease, Food Poisoning (Salmonella)

– There are many, many more!!

• Good Bacteria, examples– In the Digestive Tract: Many types of bacteria live in the

human digestive system. Many of these bacteria types are good bacteria — they help the digestive system to do its job. Good bacteria, like acidophilus and bifidobacterium, may also prevent disease by making an unfavourable environment for less desirable bacteria. Good bacteria can do several things to promote health. For example, it helps to break down plant starches and other foods that the human body has difficulty digesting. This allows the body to convert more food into energy.

– In soil: Some bacteria are decomposers which break down dead organisms and their wastes.

– In our food: Yoghurt is made by fermenting milk, sugar and a culture of specific bacteria.

Activity

• Read pages 267-269 of the Biology 2 textbook, complete questions 2-8 on page 269 in your books.

Single Celled, Eukaryotic Pathogens• Protozoa

– Cell Type: Eukaryote, Heterotrophs (can’t make own food), small – only a few micrometres in diameter.

– Examples include Giardia lamblia, which is a mobile protozoa (with flagella), that forms cysts (enclosed ‘packages’ carrying the organism) and is generally harmless. However, under certain conditions (i.e. pH change in the intestines) it becomes a pathogen and causes Giardiasis (diarrhoea). It also produces toxins that can damage the cells and may persist for years.

– Another example is Malaria, which is caused by Plasmodium falciparium which affects the liver and read blood cells. Malaria is transmitted via a vector, in this case a Mosquito

Amoeba and Disease• Some are relatively harmless if ingested,

others are fatal. E.g. • Naegeleria flowleri is a pathogen that

reproduces in stagnant water and is able to infect the brain and spinal cord causing one type of meningitis.

• Dysentery (travellers diarrhoea) is caused by ingesting Entamoeba histolytica from contaminated food and water.

Malaria

• Caused by Protozoan Plasmodium falciparium• Is spread by mosquitos (Anapheles), which are Vectors.• The parasite infects the liver and blood cells, where it

reproduces and ultimately ruptures the cell (the cell dies).

• The parasite can remain dormant for many years in the liver before becoming active again.

• Many strains are becoming resistant to treatments• Mosquito populations are become more difficult to

control as they become resistant to insecticides

Activity

• Read pages 283-285 of Biology 2 textbook • Answer the following in your books:– Why is it difficult to cure Malaria– If the Anopheles mosquito could be eliminated,

explain the impact this might have on the incidence of Malaria

Fungi

• Cell Type: Eukaryotes• Structure: Most consist of thread like structures call

hyphae which form a Mycelium. • Obtain nutrients from the other living organisms

(parasites) or decomposition of dead organic matter (decomposers).

• Fungal spores are everywhere and will grow on any organic matter with suitable temperature and moisture.

• Some fungi are edible – yeast in bread, mushrooms. Some fungi are pathogenic.

• Most fungal infections are superficial – effecting the skin, hair and nails.

• Some can cause life-threatening illness if they enter the body of someone who is already ill.

• Fungi can effect plants and can interfere with our food supply.

• Examples

• Tinea (athletes foot), ringworm, thrush (candida albicans)

• Aspergillus flavus is a fungus that produces aflatoxin which has been linked to some cancers. It is transmitted by fungal food poisoning.

Complete the following:

Read pages 286-287 of the Biology 2 textbook and complete the following:

1. Explain why most fungal infections are not serious infections

2. Describe 2 common fungal diseases.

Practical Activity 1

• Bacteria can be found in all fresh food, including milk.

• Milk can be treated to reduce the number of bacteria (e.g. Pasteurisation – milk heated to specific temperature for a specific time, then rapidly cooled and stored in fridge)

• All milk sold for consumption in Australia has been Pasteurised

• Pasteurisation does not remove all bacteria, some remain which can multiply rapidly in ideal conditions

House keeping

• Work in groups of 2 or 3 – there needs to be a total of 8 groups.

• Each group will be assigned a number, groups 1-4 will use fresh milk, groups 5-8 will use older milk.

• Safety: Wear a lab coat, hair tied back. Handle glass with care. Do not ‘sniff’ the samples directly.

Bacteria in Milk

• Aim: to determine at what temperatures bacteria multiply in pasteurized milk causing spoilage

Materials

• 3 x 20ml test tubes • Test tube rack• 250ml Beaker• Marker Pen• Cling wrap• Full Cream Milk (fresh or old)• Indicator Paper

Method – Part 11. Collect equipment2. Using a 250ml Beaker, collect 50ml of milk (groups 1-4 use the fresh milk,

groups 5-8 use the older milk)3. Label each test tube with your group number, and letter A, B and C4. Using a 25ml measuring cylinder, measure 10ml of milk into each test tube5. Describe the milk samples – smell, colour, consistency, etc, record this

information in your notes6. Using the indicator paper, determine the pH of the milk

• Using the forceps, dip a piece of Indicator Paper in the milk• Match the colour on the strip to the closest match on the Indicator

Paper Pack• Record the pH in your notes

7. Cover your samples with plastic wrap and return samples in racks to the front of the classroom.

8. Empty the remaining milk down the sink, thoroughly rinse the beaker, measuring cylinder and sink. Return equipment to the trolley and wipe over your bench

9. The samples will be stored at three different temperatures:– Sample A will be stored in the fridge– Sample B will be stored at room temperature– Sample C will be stored at 40oC in an incubator

10.Samples will be checked for changes on Tuesday and during your the lesson of week 1

Practical Activity 1: Questions

• How can you tell if the milk has spoilt and therefore the number of bacteria have increased?

• What do you predict will happen to each of your three samples?

• What differences do you predict between the fresh and older samples?

• What other factors can influence the growth of bacteria in milk? How might these factors affect the ‘shelf life’ of the milk??

ResultsSample: Observations

Day 1 Day 2 Day 3 or 4

Fresh Milk A: stored in FridgeFresh Milk B: Stored at Room TempFresh Milk C: Stored at 40oCOlder Milk A: stored in FridgeOlder Milk B: Stored at Room TempOlder Milk C: Stored at 40oC

Method – Part B

1. On day 2, Collect you samples2. Describe the samples (smell, colour,

consistency, pH), Record this in your notes3. Cover the samples and return them to the

appropriate racks– A to Fridge Rack– B to Room Temp Rack– C to Incubator Rack

4. Repeat steps 1-3 on Day 3 (or 4)

Practical 1: Questions

• What do the results suggest?• Which temperature provide the best

environment for the bacteria to multiply?• What were the Independent, Dependent and

Controlled variables in the Practical?• What are the possible sources of error in the

Practical?• How could you investigate other factors that

could affect the ‘shelf life’ of milk

Tuesday Tutorial Activities

1. Complete Practical 1 – Part B and answer the questions (this should only take 15 minutes)

2. Using the White Book and Biology 2 complete the Cardiovascular Disease Worksheet and • Describe the benefit to an individual of four lifestyle

choices that could reduce the risk of non-infectious disease.

• Describe the possible impacts of 2 non-infectious diseases on a persons life.

Multicellular Eukaryotic Organisms

Macroparasites • members of 2 groups of invertebrates (no

backbone), the Arthropods and Worms.

• Arthropods – insects, spiders, etc– Examples include:

• Sarcoptes scabiei, which causes Scabies (the ‘itch’)• Pediculus capitis – Head Lice

– Arthropods can cause itching, which if over scratched can cause a wound vulnerable to secondary infection

– Arthropods can be vectors for other pathogens

Worms

• Examples include:

• Thread worm (round worm/pin worm), which generally live in the intestines and their eggs (layed in anus) cause itching. It is easily transferred from person to person.

• Hydatid Worm (e.g. tapeworms) involve multiple hosts during their life cycles. They can form cycts which can grow to a size that damages or prevents surrounding tissues and organs from functioning correctly.

Activity

1. Copy the diagram on page 289 (Biology 2) into your notes.

2. Read pages 288-2903. Answer:– What is a parasite?– What is an ectoparasite?– What is an endoparasite?– What factors lead to the spread of tape worms

from one host to others?

Viruses

• Viruses are the smallest known reproducing things • They are not cells, they have no cytoplasm and cannot

survive without a host. They need a host cell to reproduce

• Contain DNA or RNA surrounded by 1 or more coats of protein

• Each virus will infect specific cell type• Bacteriophages are viruses that infect bacterial cells

(Bacteria Eaters). • Viruses can remain inactive in the body for years

Activity

• Read Pages 277-282 (Biology 2)• Answer questions 19-24 in your books