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Flashcards in Bacteria Deck (13):

What are bacteria

They are microscopic

Single celled

They have a cell wall

Do not have a nucleus or membrane enclosed organelles

Single loop of DNA


What are the types(Shapes) of bacteria

Rod - Shaped e.g Tetanus, TB

Round- shaped e.g Pneumonia, Food poisoning

Spiral shaped e.g. syphilis collera


Explain Bacterial reproduction

Reproduce asexually by binary fission

DNA strand replicates itself

Cell elongated with DNA strand attached to each end

Cell splits to two simillar sized cells

Bacteria can reproduce every 20 minutes in suitable conditions

Short life cycle means that mutations e.g resistance to antibiotic spread fast


What are endospores

Endospores are tough walled spores capable of surviving harsh conditions

Form when a bacterial chromosome replicates

one of the new strands becomes included in an endospores inside the parent cell

The parent cell then breaks down and the endospores remains dormant

When conditions are suitable endospore absorbs water and tough wall breaks down


What is nutrition in bacteria

Autotrophic ( make their own food )
- photosynthetic (Use light as energy source to make food )

- Chemosynthetic ( Use chemical reactions as an energy source to make food)

Heterotrophic ( takes in food )
- saprophytic ( live on and take food from dead sources )

- parasitic ( take in food from a live host and usually cause harm to the host )


What factors affect bacterial growth

Temperature - affects bacterial activity by influencing rate of enzyme action
- most bacteria 20- 30 by disease causing bacteria prefer 37

Oxygen concentration - "Aerobic bacteria need oxygen for respiration .Aerobic bacteria do not require oxygen for respiration"
- obligate anerobes - must have oxygen for respiration
- Facultative anerobes - can respite with or without oxygen

- most bacteria prefer PH 7

External solute concentration
- environment outside a bacteria has a lower solute concentration than so water will pass in and out by osmosis

- if the environment has higher solute concentration water will pass ou they osmosis

- bacteria will not be able to grow and reproduce due to shortage of water

- basis of preserving foods by salting


Economic benefits of bacteria

Manufacture products like yogurt and cheese ( lactobacilli)

Use of genetically engineered bacteria to make insulin, drugs and enzymes


Economic disadvantages of bacteria

Cause human, plant and animal diseases

Cause food decay


What are pathogens

Pathogens are micro organisms that cause disease


What are antibiotics

"Antibiotics are chemicals made by fungi or bacteria to kill or stop the growth of bacteria"

Bacteria can develop immunity to antibiotics by mutations

Multi resistance bacteria have evolved that are not affected by most anti biotics


Describe bacterial growth

The lag phase - no increase in numbers

The log phase - numbers increase very rapidly

The stationary phase - no increase in numbers

The decline phase - rapid fall in numbers

The survival phase - some bacteria survive as spores


What is batch culture

A certain amount of nutrients is added to the micro organisms in the bioreactor

The bioreactor is closed

The bacteria go through the lag, log and stationary phases of growth

The process is stopped

The bioreactor is emptied and sterilized so the process can be repeated

Advantages: - simple process
- Allows small volume of product to form


What is continuous flow culture

Nutrients are continuously added to the bioreactor

Bioreactor is left open

Bacteria, culture medium and product are continuously removed

Bacteria are maintained at the log stage of growth

Conditions in the bioreactor are kept constant

- productions is continuous ( No time wasted )
- productions is formed more rapidly ( bacteria very active in log phase )