22.1 Prokaryotic Diversity

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They live on and inside virtually all living things, and they cover every surface where there is enough water.
In the human body, prokaryotic cells outnumber human body cells by about ten to one.
They are the majority of living things.
inhospitable environments for most living things are where prokaryotes thrive.

Carbon and nitrogen are essential substances and they drive the evolution of new ecosystems, some of which are natural and others man-made.

Since long before multicellular life appeared, prokaryotes have been on Earth.
The descendants of ancient prokaryotic communities are thought to be eukaryotic cells.

The first forms of cellular life on Earth were prokaryotes, and they existed for billions of years before plants and animals appeared.

The Earth is 4.54 billion years old.
Evidence from dating of meteorite material together with other material from Earth and the moon leads to this estimate.
The first organisms probably flourished where they were more protected, such as in the deep ocean or far beneath the surface of the Earth, because Early Earth had a very different atmosphere than it does today and was subjected to strong solar radiation.
It is likely that the first organisms were adapted to high temperatures because of the strong volcanic activity of this time.
Because early Earth was prone to geological upheaval and volcanic eruption, the first organisms must have withstood these harsh conditions.

Microbial mats or large biofilms are believed to be the earliest forms of prokaryotic life on Earth.

It is remarkable that cellular life appeared on Earth only a billion years after the Earth formed, suggesting that pre-cellular life that could replicate itself had evolved earlier.
Microbial mats are only a few centimeters thick and grow on moist surfaces.
There are different types of prokaryotes that carry out different pathways and that is the reason for their different colors.
The prokaryotes are held together by a glue-like sticky substance.

The first mats probably got their energy from chemicals.

About three billion years ago, some prokaryotes in the mats came to use a more widely available energy source--sunlight--whereas others were still dependent on chemicals from the hydrothermal vents.

The mat has a colony ofbacteria.

The arrow shows a chimney that allows gases to escape.

Fossilized mats are the earliest record of life on Earth.

Stromatolites are rocks made of carbonate or silicate.
There are places on Earth where stromatolites are still forming, even though most stromatolites are artifacts from the past.
Stromatolites have been found in the Anza-Borrego Desert State Park.

Only those organisms that can grow without oxygen were able to live.

Increased atmospheric oxygen allowed the evolution of more efficient O2 using catabolic pathways.
Ozone and O2 convert into O3 and Ozone, respectively, and they effectively absorb the ultraviolet light that could have caused fatal genetic defects.
The evolution of other life forms may have been aided by the increase in O2 concentrations.

There is a hot spring in the park.

As water flows down the gradient, the intensity of the green color increases as the cell density increases.
The edges of the stream appear green because the water is cooler at the edges than in the center.
Some organisms are able to survive harsh conditions.
A cell wall is a protective structure that allows prokaryotes to survive in both hypertonic and hypotonic conditions.
The organisms can survive until favorable conditions come back, because some soilbacteria are able to form resistance to heat and water.

The most abundant life form in the land and water is the bacterium.

Some prokaryotes thrive in environments that would seem normal to us, while others thrive in environments that would kill a plant or animal.

Extremophiles have been found in a wide range of environments, from the depths of the oceans, to hot springs, to harsh chemical environments, to high radiation environments.
Extreme conditions are what allow them to live in extreme ways.
Several habitats are extreme in multiple ways, and there are many different groups of extremophiles that are identified by the conditions in which they grow best.
The organisms that live in a soda lake must be both alkaliphiles and halophiles because the lake is salty and alkaline.
Organisms like these give us a better understanding of prokaryotic diversity and can lead to the discovery of new therapeutic drugs or industrial applications.

This false color transmission electron micrograph shows Deinococcus radiodurans, a prokaryote that can tolerate very high doses of ionizing radiation.

Even if it has been broken into hundreds of pieces by radiation or heat, it has developed mechanisms that allow it to reconstruct its chromosomes.

The Dead Sea is a hypersaline basin that is located between Jordan and Israel.

Hypersaline environments are composed of water.

The water in the Dead Sea has high levels of magnesium, which is toxic to most living things.
What is commonly referred to as "hard" water is produced by elements such as iron, calcium, and magnesium.
The Dead Sea is unique and hostile due to its high concentration of divalent cations, acidic pH, and intense solar radiation.

The Dead Sea has several salt- tolerant bacterial mats, including the archaean Haloarcula marismortui.

There are salt- tolerantbacteria in the sea.

One of the greatest discoveries of modern science is the process of culturingbacteria.

Koch discovered techniques for pure culture, including staining and using growth media.

Microbiologists use an appropriate culture medium to grow prokaryotes in the laboratory.
The medium can be liquid or solid.
There should be evidence of growth after the right temperature has been reached.
The Petri dish is still used in today's laboratories.
Koch's postulates are used in the medical community.
Koch's postulates state that an organisms can be identified as the cause of disease when it is present in all samples and absent in all healthy samples and that it can reproduce the disease after being cultured multiple times.
Cultures are still a primary diagnostic tool in medicine.

There are blood agar plates.

Red blood cells are added to the growth medium in these agar plates.
Blood agar becomes transparent when red blood cells are destroyed by Streptococcus.
The plate on the left is inoculated with non-hemolytic Staphylococcus, while the plate on the right is inoculated with hemolytic Streptococcus.
The agar surrounding thebacteria has turned clear if you look closely at the right plate.
Some prokaryotes can't grow in a lab.
Almost all of thebacteria and archaea are unculturable.
This is due to a lack of knowledge as to what to feed these organisms and how to grow them; they may have special requirements for growth that remain unknown to scientists.
Somebacteria cannot be cultured because they are obligate intracellular parasites.

In other cases, culturable organisms become unculturable even though they could have been cultured previously.

Prokaryotes enter a dormant state that allows their survival when they respond to environmental stressors.

The criteria for entering into the state are not fully understood.

Most of the prokaryotes living in the soil or in the ocean are non-culturable.

It has been said that only a small percentage of prokaryotes can be cultured in a laboratory.

Microbiologists use techniques such as the polymerase chain reaction to amplify parts of the prokaryotes' genes.

Some prokaryotes need the presence of other prokaryotic species to beculturable.

Microbiologists used to think of prokaryotes as separate entities.
The model does not reflect the true ecology of prokaryotes, who prefer to live in communities where they can interact.
Films grow on surfaces.
Some of the best-studied biofilms are composed of prokaryotes, while some are also composed of a mixture of fungi andbacteria.

Most of the time, biofilms are present: they can cause pipes to fail and colonize surfaces in industrial settings.

In recent large-scale outbreaks of food-borne illnesses, the role of biofilms has been important.

They colonize household surfaces, such as kitchen counters, cutting boards, sinks, and toilets, as well as places on the human body, such as the surfaces of our teeth.

The protective exopolysaccharidic environment of the organisms that populate a biofilm makes them more robust than planktonic, prokaryotes.

The sticky substance that holdsbacteria together makes them harder to kill than planktonic ones.
biofilms are resistant to many forms of sterilizing, so they are difficult to destroy.

The stages of development are shown.

The weak van der Waals interactions are produced by electrical interactions between atoms.
Hairlike appendages called pili anchor the bacteria to the surface during stage 2.
The biofilm grows through cell division and recruitment of otherbacteria during stage 3.
The biofilm is held together by an extracellular matrix.
The biofilm continues to grow and take on a more complex shape during stage 4.
Somebacteria can escape and colonize another surface during stage 5 of dispersal.
Micrographs of a Pseudomonas aeruginosa biofilm are shown.