Bacteria Flashcards
Who were the ancestors of current bacteria?
Unicellular micro-organisms that were the first forms of life to develop on earth, about 4 billion years ago.
For about 3 billion years ____ and ___ were the dominant forms of life.
Bacteria
Archaea
Define archaea.
Archaea are single-celled microorganisms with a structure similar to bacteria. They are evolutionarily distinct from bacteria and eukaryotes and form the third domain of life. Archaea are obligate anaerobes living in environments low in oxygen.
However, it was not until fairly recently that bacteria were discovered by humans. The possibility that something very small (______) might exist was discussed for many centuries before their actual discovery in the ___ century.
Micro-organisms
17th
What were people warned about during the Roman times (about 400AD) ?
People were warned against ‘certain minute creatures which cannot be seen by the eyes, which float in the air and enter through the mouth and nose and there cause serious diseases.
What was proposed in the 1500s?
That epidemic diseases were caused by transferable ‘seed-like entities’.
It was only in the 1600s after the development of the ____ that _____ were proven by being observed and accurately described.
Microscope
Micro-Organisms
Which kingdom do bacteria belong to?
Kingdom Monera
Who were the first organisms to evolve?
Bacteria
Name the general characteristics of bacteria. (8)
- Bacteria are the most diverse and abundant group of organisms
- Bacteria inhabit practically all environments
- Bacteria are mostly useful, but some cause diseases
- Bacteria are unicellular and are among the smallest organisms
- Bacteria vary in shape
- Bacteria can exist singly, in chains or. in clumps
- In favourable conditions bacteria produce very rapidly by binary fission
- In unfavourable conditions, e.g. high temperatures and dryness, bacteria may still survive by becoming dormant
True or False
Practically all surfaces which have not been sterilised are covered in bacteria.
True
True or False
The number of bacteria in the world is estimated to be around five trillion.
False, it is estimated to be around five million trillion trillion.
Where are bacteria found?
They are found in sea water, soil, air, animals gastrointestinal tracts and deep beneath the Earth’s crust in rocks.
Extremophile definition.
An extremophile is an organism that thrives in extreme environments.
Where do extremophiles live?
Thrive in climatic or environmental extremes such as the intense heat of a boiling sulphur pool or the intense cold of Artic permafrost.
How big are bacteria?
A bacterium is about a thousand times bigger than a typical virus but is very much smaller than the cells of eukaryotes. They can be observed under the light microscope and range in size from one to ten micrometers/microns.
What shapes can bacteria be classified into?
- Spherical bacteria are called cocci
- Rod-shaped ones, bacilli
- Spiral shaped ones, spiralla
- Comma-shaped ones, vibrios
- Example of the bacteria which exist in chains.
2. Example of the bacteria which exist in clumps.
- Streptococcus
2. Staphylococcus
What is binary fission?
An asexual process whereby a single cell divides into two with identical DNA. In binary fission DNA replication and segregation occur simultaneously.
How fast can some bacteria divide under favorable conditions?
Some may divide every 10-15 minutes- a doubling of the population at these time intervals producing billions of bacteria with identical DNA within 24 hours.
How do some bacteria remain dormant during unfavorable conditions?
They form spores with a thick protective coat around themselves. When favorable conditions return the spore coat splits open to release the bacterium.
What are endospores?
A small group of bacteria produces special spores called endospores that can withstand heat, desiccation, pressure, high levels of UV light, determents and disinfectants.
How long can bacteria which produce endospores survive?
For thousands of years
Can bacteria that produce endospores cause disease?
Yes, for example, the inhalation of Bacillus anthracis endospores can cause anthrax and deep puncture infected with Clostridium tetani endospores can cause tetanus.
