Учебное пособие Кожарская Е. Э., Козлова О. Н., Колесников Б. М., Даурова Ю. А., Сурганова Т. В., Секретева О. А. 2011


НазваниеУчебное пособие Кожарская Е. Э., Козлова О. Н., Колесников Б. М., Даурова Ю. А., Сурганова Т. В., Секретева О. А. 2011
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Дата публикации10.03.2013
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ТипУчебное пособие
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Extreme Bacteria


Imagine life in the environment without oxygen or with an extremely high salt concentration or with boiling hot acid. How could any organism live there? All of the animals and plants with which we are familiar would find these conditions uninhabitable. How could a cell's plasma membrane and large molecules remain stable and functional under these conditions? How can these very different, extreme environments be home to a unique group of microorganisms, the Archaea?

This interesting group of microbes is unique; they have thrown the whole classification system for living organisms upside down. Some characteristics of Archaea are closely related to bacteria, whereas other characteristics show a relationship to eukaryotes. But archeans have many distinctive properties that set them apart from bacteria or eukaryotic organisms. Their cell wall and plasma membrane compositions are unique, as is their ribosomal RNA. What does this mean from an evolutionary perspective? The dilemma arose when scientists were deciding where to place these organisms in relation to all other organisms on Earth. Where do they belong, with the bacteria or in their own group? Dr. Carl Woese made the suggestion that the Archaea should be one of three new superkingdoms or domains of organisms, with all bacteria making up the second domain and all eukaryotic organisms making up the third. Does this suggestion make sense? Why or why not?

Archaeans are classified into three main groups, depending on their habitat: methanogens, halophiles, and thermoacidophiles. The methanogens are rod-shaped, live in strictly anaerobic environments, and produce large quantities of methane (CH4) from carbon dioxide and hydrogen. They live in marshes, lake bottoms (causing the rotten-egg smell that occurs when you poke a stick into the mud at the bottom). The halophiles require high concentrations of salt, such as the Great Salt Lake in Utah. The thermoacidophiles normally grow in hot (100oC), acidic (pH 1.0) environments.
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Light from Life


You can see some of the coolest lights ever being produced by an array of lifeforms, ranging from bacteria to fish. The word that describes these cool chemical lights is bioluminescence. "Cool" is correctly used here. In this amazing chemical reaction, nearly 100% of the energy is released as light, compared with only 10% for an electric light bulb. Just imagine if Thomas Edison could have accomplished this efficiency with the electric light bulbs he invented! The bulb in the lamp by which you are reading this article would then emit only light and not wasteful heat.

The biochemical "recipe" for cool light is much the same among the numerous types of organisms that can produce bioluminescence. The ingredients are luciferin, luciferinase, ATP, calcium or magnesium, and oxygen. Biologists think that bioluminescence evolved many times during the existence of life on Earth. Some scientists speculate that bioluminescence may have evolved when Earth's atmosphere began to accumulate oxygen. The free oxygen was toxic to some of the early inhabitants, and bioluminescence might have provided a pathway for detoxification.

Although the significance of bioluminescence is not always apparent in a particular organism, many uses have been demonstrated. Fireflies in the family Lampyridae use their cool tail lights for attracting the opposite sex. These cool lights can also be deceptive and can lead to a rendezvous with death for unsuspecting male fireflies. Female fireflies of the genus Photuris prey on males of different firefly genera by mimicking their flashing mating signals. When the amorous male responds to a female's return flash and arrives for the mating, he becomes her meal instead.

Bioluminescence can be used to startle or confuse, perhaps by temporarily blinding a potential predator. The flashlight fish has small cavities under its eyes that are jam-packed with bioluminescence bacteria. Some fungi use bioluminescence to advertise their presence and thus call attention to themselves.

Many species of marine plankton are also bioluminescent. While swimming or walking on the beach at night, you may have noticed a glow around you. Although it is not always understood why some organisms are bioluminescent, the simple fact that they are can have wide-ranging implications. The military is especially interested in understanding and predicting the locations of these bioluminescent plankton. Secret beach landings and silent-running submarines are easily revealed by the glow of these bioluminescent organisms.

Many genetic engineers are very interested in bioluminescence. What if it were possible to transfer genes that produce bioluminescence into organisms that do not bioluminesce? For example, what if pumpkins could be engineered to glow in the dark? Or if the bioluminescence gene could be used as a marker for tracking antibiotic resistance in various pathogenic bacteria? Bioluminescence is cool and can light up your life; it just depends on what species you are.

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14. Text for translation into English.

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