Bacteria (i/bktri/; singular: bacterium) constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a number of shapes, ranging from spheres to rods and spirals. Bacteria were among the first life forms to appear on Earth, and are present in most of its habitats. Bacteria inhabit soil, water, acidic hot springs, radioactive waste, and the deep portions of Earth's crust. Bacteria also live in symbiotic and parasitic relationships with plants and animals. They are also known to have flourished in manned spacecraft.

There are typically 40 million bacterial cells in a gram of soil and a million bacterial cells in a millilitre of fresh water. There are approximately 51030 bacteria on Earth, forming a biomass which exceeds that of all plants and animals. Bacteria are vital in recycling nutrients, with many of the stages in nutrient cycles dependent on these organisms, such as the fixation of nitrogen from the atmosphere and putrefaction. In the biological communities surrounding hydrothermal vents and cold seeps, bacteria provide the nutrients needed to sustain life by converting dissolved compounds, such as hydrogen sulphide and methane, to energy. On 17 March 2013, researchers reported data that suggested bacterial life forms thrive in the Mariana Trench, which with a depth of up to 11 kilometres is the deepest part of the Earth's oceans. Other researchers reported related studies that microbes thrive inside rocks up to 580 metres below the sea floor under 2.6 kilometres of ocean off the coast of the northwestern United States. According to one of the researchers, "You can find microbes everywhere they're extremely adaptable to conditions, and survive wherever they are."

1. What is the singular tense of bacteria?
2. What does it constitute?
3. How many cells are in a gram of soil?
4. and in a millitre of fresh water?
5. Do they have different shapes?
6. what kind?
7. Can you find it most places?
8. like what?
9. anywhere else?
10. anywhere else?
11. HAve they been around a while?
12. What happened in 2013?
13. what was the depth?
14. Is that a shallow part?
15. what is it?
16. Where else can they thrive?
17. where are they?
18. What are bacteria vital in?
19. What is dependent on bacteria?
20. such as?

Numbered answers:
1. bacterium
2. a large domain of prokaryotic microorganisms
3. 40 million
4. a million
5. yes
6. spheres to rods and spirals
7. yes
8. soil, water, acidic hot springs, radioactive waste, and the deep portions of Earth's crust.
9. symbiotic and parasitic relationships with plants and animals.
10. in manned spacecraft.
11. among the first life forms to appear on Earth
12.
esearchers reported data that suggested bacterial life forms thrive in the Mariana Trench
13. up to 11 kilometres
14. no
15. the deepest part of the Earth's oceans.
16. inside rocks
17. 580 metres below the sea floor under 2.6 kilometres of ocean
18. recycling nutrients,
19. stages in nutrient cycles
20. the fixation of nitrogen from the atmosphere and putrefaction