The most famous bacterium – a vermicelli-shaped organism found in the shallow mangrove swamps of the Caribbean Sea that is large enough to be seen with the naked eye – redefines what is possible for the oldest life form on Earth, the bacterium. doing.

Scientists noted on Thursday that a bacterium called Thiomargarita magnifica is not only huge for unicellular organisms up to about 2 cm in length, but also because its internal structure is different from other bacteria. Said it was worth it.

DNA, the blueprint for living organisms, is not suspended inside cells like most bacteria, but it is contained in a number of small membrane-bound sac. The intracellular membrane-bound structure is called the organelle.

“Thousands of times larger than a normal-sized bacterium. Discovering this bacterium is like meeting a human as tall as Mt. Everest,” said the US Department of Energy’s Joint Genome Research Institute and Institute marine biologist Jean-Marie Boland said. Co-leader of research published in the journal Science at Complex Systems, California.

This bacterium has been found in several parts of Guadeloupe, the French archipelago of the Caribbean. It was first discovered in the sulfur-rich seawater of the Guadeloupe wetlands by Olivier Gros, a microbiologist and co-leader of the study at Université des Antilles.

“In 2009, I found long white filaments on the sunken leaves of a mangrove tree. Such filaments were intriguing. I returned to the lab to analyze them. “It was,” Gross said. “I was very surprised to see the giant bacteria inhabiting the mangroves of Guadeloupe.”

The length of a normal bacterial species is 1-5 micrometers. This species averages 10,000 micrometers (1 cm), and some Thiomargarita magnifica are twice as long.

“This is an order of magnitude larger than what we thought was the largest possible size for a single bacterium,” Volland said. “It’s about the same size and shape as eyelashes.”

The maximum length of the largest bacterium known to date was about 750 micrometers.

Bacteria are unicellular organisms that live almost everywhere on the planet and are essential to their ecosystems and most organisms. Bacteria are the first organisms to inhabit the Earth and are thought to remain very simple in structure after billions of years. People’s bodies are full of bacteria, but relatively few cause illness.

Thiomargarita magnifica is not known as the largest unicellular organism. Its honor is given to the algae Caulerpa, which can reach 15-30 cm in length.

The Caribbean Mangrove Wetlands are clogged with organic matter, which is broken down by microorganisms in the sediments to produce high levels of sulfur. The sulfur-rich environment provides an energy source for bacteria such as Thiomargarita Magnifica.

Researchers named the organelle containing its DNA “pepin” after the French word for small seeds in fruits.

“With two exceptions, no other bacterium was known to retain DNA in organelles bound to the membrane, which means that in reality, the membrane, such as human cells or animals. It is a characteristic of more complex cells with nuclei attached to. Plant cells. “


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Mapping its genome showed that thiomargarita magnifica lost some genes essential for cell division and had more copies of the genes involved in cell elongation.

“This may explain some of the reasons why cells grow into such elongated filaments. The genome is also very large and contains three times the average number of genes normally found in bacteria. I don’t know what half of these genes are, because they are. “

This bacterium shows that life on Earth still has a surprise awaiting discovery, he said.

“Life is fascinating, very diverse and very complex,” Volland added. “It’s important to be curious and open.”

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