6: Microbiology

Question 1

What conditions and nutrients are needed to culture microorganism?

Answer 1

Have to grow large numbers of microorganisms so they can be measured in some way. Need to be provided with right nutrients and oxygen a well as the ideal pH and temperature

Question 2

Why is it important to take great care while culturing microorganisms?

Answer 2

Always risk of a mutant strain arising that may be pathogenic, even if the bacteria is harmless, there is this this risk.

Risk of contamination of the culture by pathogens microorganisms form the environment

When you grow a pure strain of microorganism, there is a risk of the air or skin contaminating it.

Question 3

Why must it be sterile?

Answer 3

Shouldn’t leave the lab. To ensure it isn’t contaminated.

Question 4

How should the microorganisms be disposed of?

Answer 4

Safety sealed in plastic bag and sterilised at 121 degrees for 15 minute under high pressure.

Question 5

What is nutrient medium?

Answer 5

Can be in the form of nutrient broth, or in solid form as nutrient agar. These contain the right nutrients for the microorganisms.

Question 6

Where is the agar from?

Answer 6

seaweed. Very useful as it sets as jelly at 50 degrees and doesn’t melt until 90.

Question 7

What is selective medium?

Answer 7

Growth medium for microorganisms that contain very specific mixture of nutrients, so only a particular type of microorganisms can grow.

Question 8

What can selective medium be used for?

Answer 8

For identifying microorganism that have been genetically modified, because the antibiotic resistance or the requirement for a particular nutrient is ofte engineered along to desired gene.

Question 9

How do you introduce the bacteria to the culture?

Answer 9

Called inoculation. Need inoculating loop, scape the bacteria off one solid medium surface either into liquid medium or steaming it along a solid medium plate.
Inoculating broth can be used.

Question 10

What’s an inoculating broth?

Answer 10

Making a suspension of the bacteria to be grown and mixing a known volume with the sterile nutrient broth in the flask. Flask is then stoppered again as quickly as possible with Cotton wool to prevent contamination from air, and label it. Incubated at suitable temperature and shaken or agitated regularly. For aeration.

Question 11

How do you grow a pure medium?

Answer 11

Need to isolate it. Need to use information about its specific needs, or about the requirements of possible contamination organisms.
Eg if anaerobic conditions only anaerobic bacteria will survive. Different nutrient- favour growth of specific bacteria’s. Indicator medium which causes certain types fo bacteria to change colour tc

Question 12

How do you cell count?

Answer 12

Can use a haemocytometer. Grid of lines on the visual site.
If nutrient broth is diluted by half of its plume of trypan blue, the dye stains dead cells, so you can identify the living.
Means can be calculated.

Question 13

What is turbidity?

Answer 13

Specialised form of colorimetry.
As the number of bacteria cells increase, the culture becomes increasingly cloudy or turbid. It absorbs more light and hence can record how much light passes through it using a colorimetry.
Calibration curve produced. Gives a relationship between turbidity of culture ns the number of bacteria cells.

Question 14

What is dilution plating?

Answer 14

Finds the total viable cell count. Each colonies on agar grow from a single viable microorganism. Eg, 30 patches: 30 original cells. However, if too many, very hard to see how many there was. So yo dilute it with water, 0.1 dilution then 0.01 etc. Until you can see the cel counts

Question 15

What is the generation time?

Answer 15

Time between bacterial divisions.

Question 16

Why do we use logs when considering the numbers of bacteria?

Answer 16

Th numbers are massive. Logs are to the power of 10 therefore make them easier to follow. Much easier to manage.

Question 17

Wha is exponential growth rate constants?

Answer 17

Allow you to work out the number of bacteria in a colony. Ca calculate the number of bacteria in a population using a formula.
K= log10Nt-log10N0 divided by log10(2)X t

Nt is N0 times 2^kt
Nt is the number of organisms at time t
N0 is the number of organisms a time 0 (beginning)
K is the exponential growth rate constant
T is the time the colony has been growing

Question 18

What is the lag phase?

Answer 18

Where the bacteria is adapting to their new environment and are not yet reproducing at max rate

Question 19

What is the log phase?

Answer 19

Or exponential phase
When the rate of bacterial reproduction is close to or at its theoretical maximum, repeatedly doubling in a given time period

Question 20

What is the stationary phase?

Answer 20

When the total growth rate is zero as the number ones cells form by binary fission is equal to the number of cells dying

Question 21

What is the death phase?

Answer 21

Or decline phase

When reproduction has almost ceased and the death rate of cells is increasing

Question 22

What happens to the bacteria if there is reduction in the amount of nutrients available?

Answer 22

Slows the rate of growth down. Unless fresh nutrients are available, they will become insufficient to support further growth and reproduction and so will limit growth of organisms.

Question 23

What happens to bacteria is there is a build up of waste products?

Answer 23

At the beginning, waste products are minimal, but as the cell numbers rise, the build up of toxic materials comes sufficient to inhibit further growth and could even poison and kill the culture.
Of CO2 builds up by respiration, the pH of the colony falls.

Question 24

How do bacteria cause disease?

Answer 24

Invade and destroy host tissues. Most make the human unwell through toxins made as a by product of their metabolism
Toxins may incapacitate the whole host organism or just the immune system.
Ends toxins or exotoxins

Question 25

What are endotoxins?

Answer 25

Lipopolysachhcarides that are a integral part of the cell wall outer layer of gram NEGATIVE bacteria.
The lipid part acts as the toxin, while polysaccharide stimulates immune response.

Question 26

Where does endotoxins have effects?

Answer 26

Around the site of infection by the bacteria.
Fever, vomiting, diarrhoea etc
To fatal themselves but symptoms can lead to death.

Question 27

What is the example of endotoxins bacteria?

Answer 27

Salmonella.

Question 28

How does salmonella bacteria work?

Answer 28

they invade the lining of the intestine and the endotoxins cause inflammation. Cells no longer absorb water, so faeces become liquid and th gut goes into spasms of peristaltic that result in diarrhoea

Question 29

How is salmonella in the body?

Answer 29

Spread by infection of food and water which contain infected faeces.
Also live in the guts of many of the foods from animals, and ca easily contaminate the meat.
If food isn’t cooked properly, the bacteria survives and pass into your gut wen you eat the food.
If someone handles raw meat and doesnt wash their hands, the bacteria can be transmitted.
Salads washed in contaminated water can claps cause infection.

Question 30

How does the bacteria salmonella travel in the body?

Answer 30

They survive the stomach acid that destroys many pathogens, passing into the small intestines where they invade the lining of the cells, and the endotoxins produce the symbols of the disease.

Question 31

How can salmonella be treated?

Answer 31

Treating them with antibiotics isn’t very effective unless the patient is young, very old, or has weak immune system. I most people, antibiotics just reduce symptom, allowing the person to feel better by act as a carrier for longer

Best wat to treat is to AVOID. Cook all meat all the way through, wash hands always.

Question 32

What are exotoxins?

Answer 32

Usually soluble proteins, that are produced and released into the body by bacteria as they metabolise and reproduce in the cells of their host.

Question 33

What cells produce exotoxins?

Answer 33

Gam negative and gram positive.

Question 34

What cells produce endotoxins

Answer 34

Gram negative only

Question 35

What are the effects of exotoxins?

Answer 35

Very more widespread than endo. Often act at sites at a distance from bacterial infection.
Many different effects.
Some damage cell membranes causing breakdown or internal bleeding, some act as competitive inhibitors to neurotransmitters, while others directly poison cells.
Rarely cause fevers, but they include some of the most dangerous bacterial diseases.

Question 36

What is an example of exotoxins bacteria?

Answer 36

Staphylococcus bacteria. Gram positive bacteria.

Question 37

What cells do staphylococcus affect?

Answer 37

Live in the gut flora and in the skin. Only cause disease if they get inside the tissues of the body. Or if the person have a compromised immune system due to another disease.

Question 38

What do the exotoxins cause from staphylococcus

Answer 38

Cause anything from mild cell disease to rapid death.

Question 39

What are the 2 strands of staphylococcus

Answer 39

Staphylococcus aureus and staphylococcus epidermis

Question 40

What do s. aureus cause?

Answer 40

Cause skin infections such as styles, boils and impetigo. Causes infections of the joints, infection o them membranes around the heart, gastroenteritis and diseases such as toxic shock syndrome

Question 41

what do both strands of staphylococcus cause?

Answer 41

Bacterial meningitis. If they get access to the brain.

Question 42

How is staphylococcus treated?

Answer 42

By antibiotics if they are diagnosed quickly. But the exotoxins are very powerful and can cause death very quickly.
Are becoming increasingly resistant.

Question 43

What is hot tissue invasion?

Answer 43

Invading host cells an damaging the cells. Response of the host organism to the cell damage that causes the symptoms of disease. Often this cell damage is also linked o the production of exotoxins or the presence of endotoxins.

Question 44

What is mycobacterium tuberculosis?

Answer 44

One of the most common human infections on a global scale.

Question 45

How is TBspread?

Answer 45

TB is caused my mycobacterium tuberculosis. And is spread by droplet infection. Crowded living or working conditions increase this likelihood.
People who are malnourished, ill or have problems with immune system are more vulnerable. People with HIV are more vulnerable.

Question 46

What else other than humans does tuberculosis bacterium invade?

Answer 46

Cattle. People become affected by drinking milk fro infected cows, or working in close contact wit cattle.

Question 47

What does TB affect?

Answer 47

The respiratory system.damaging and destroying lung tissue. Also suppresses the immune system, making body less able t fight ideas.

Question 48

What are the symptoms of TB?

Answer 48

Coughing up blood and weakness. They come at the end of the process.

Question 49

What happens in TB after the bacteria has been inhaled?

Answer 49

They invade the cells in the lungs and multiply slowly. This is PRIMARY INFECTION. Causes of symptoms.

Question 50

If you have a healthy immune system, what will be. A sign of TB?

Answer 50

Localised inflammatory response forming a mass of tissue called a TUBERCLE.

Question 51

What is a tubercle?

Answer 51

Contains dead bacteria and macrophages in a mass of tissue.

Question 52

What happens to the primary infection in TB?

Answer 52

About 8 weeks the inflammation dies Dow and the lung tissue heals. Often take place in children and the majority get better by themselves

Question 53

What adaptation. Does mycobacterium tuberculosis have to avoid being detected by immune system?

Answer 53

Bacteria produce think wax outer layer that protects them from the enzymes of the macrophages. Bacteria with an effective coping wil remain deep in the tubercles n the lungs, slowly growing/

Question 54

What happens to the dormant bacteria in TB when someone becomes malnourished?

Answer 54

Cause ACTIVE TB. The most effective bacteria are selected and will be passed on once they become active again, they can grow and reproduce very rapidly, causing serious damage.