What are bacteria?
A: Bacteria are ubiquitous, mostly free-living organisms often consisting of one biological cell.
Typically a few micrometers in length, bacteria were
among the first life forms to do what?
A: To appear on Earth, and are present in most of its habitats.
Bacteria inhabit soil, water, acidic hot springs,
radioactive waste, and the deep biosphere of what?
A: Earth's crust.
Bacteria are vital in many stages of the nutrient cycle
by doing what?
A: Recycling nutrients such as the fixation of nitrogen from the atmosphere.
The nutrient cycle includes the decomposition of dead
bodies; bacteria are responsible for what?
A: The putrefaction stage in this process.
In the biological communities surrounding hydrothermal
vents and cold seeps, extremophile bacteria provide the nutrients needed to
sustain life by doing what?
A: By converting dissolved compounds, such as hydrogen sulphide and methane, to energy.
Bacteria also live in symbiotic and parasitic
relationships with what?
A: Plants and animals.
Most bacteria have not been characterized and there are
many species that cannot be grown where?
A: In the laboratory.
The study of bacteria is known as what?
A: Bacteriology, a branch of microbiology.
Humans and most other animals carry how many bacteria?
Most bacteria on humans are where?
A: In the gut, and there are many on the skin.
Most of the bacteria in and on the body are harmless or
rendered so by the protective effects of what?
A: The immune system, though many are beneficial, particularly the ones in the gut.
However, several species of bacteria are pathogenic and
A: Infectious diseases, including cholera, syphilis, anthrax, leprosy, tuberculosis, tetanus and bubonic plague.
What are the most common fatal bacterial diseases?
A: Respiratory infections.
What are used to treat bacterial infections and are
also used in farming?
A: Antibiotics, making antibiotic resistance a growing problem.
Once regarded as plants constituting the class
Schizomycetes ("fission fungi"), bacteria are now classified as what?
Unlike cells of animals and other eukaryotes, bacterial
cells do not contain what?
A: A nucleus and rarely harbor membrane-bound organelles.
Although the term bacteria traditionally included all
prokaryotes, the scientific classification changed after the discovery in
the 1990s that prokaryotes consist of what?
A: Two very different groups of organisms that evolved from an ancient common ancestor.
These evolutionary domains are called what?
A: Bacteria and Archaea.
The ancestors of bacteria were unicellular
microorganisms that were the first forms of life to appear on Earth, about
how long ago?
A: 4 billion years ago.
For about 3 billion years, most organisms were
microscopic, and bacteria and archaea were the what?
A: The dominant forms of life.
The most recent common ancestor of bacteria and archaea
was probably a what?
A: A hyperthermophile that lived about 2.5 billion–3.2 billion years ago.
Bacteria were also involved in the second great
evolutionary divergence, that of what?
A: Archaea and eukaryotes.
Bacteria are ubiquitous, living in every possible
habitat on the planet including soil, underwater, deep in Earth's crust and
even such extreme environments as what?
A: Acidic hot springs and radioactive waste.
There is approximately 2×1030 bacteria on Earth,
forming a biomass that is only exceeded by what?
Most do not cause diseases, are beneficial to their
environments, and are essential for what?
The soil is a rich source of bacteria, and a few grams
contain how many of them?
A: Around a thousand million of them.
They are all essential to soil ecology by doing what?
A: By breaking down toxic waste and recycling nutrients.
They are even found in the atmosphere and one cubic
meter of air holds how many?
A: Around one hundred million bacterial cells.
The oceans and seas harbor around 3 x 1026 bacteria
which provide up to 50% of what?
A: The oxygen humans breathe.
How many bacterial species have been fully studied?
A: Around 2%.
Among the smallest bacteria are members of the genus
Mycoplasma, which measure only 0.3 micrometers, as small as what?
A: The largest viruses.