Happy Nice Mall

In a mangrove forest in the Caribbean, scientists have discovered a strain of bacteria that reaches the size and shape of human eyelashes.

These cells are the largest bacteria ever observed, and are thousands of times larger than more familiar bacteria such as Escherichia coli. “It would be like meeting another human the size of Mount Everest,” said Jean-Marie Volland, a microbiologist at the Joint Genome Institute in Berkeley, California.

Dr. Volland and colleagues published Their study on the bacterium Thiomargarita magnifica, published Thursday in the journal Science.

Scientists once thought bacteria were too simple to produce large cells. But Thiomargarita magnifica turned out to be quite complex. While much of the bacterial world has yet to be explored, it’s entirely possible that even larger, even more complex, bacteria await discovery.

Nearly 350 years have passed since Dutch lens grinder Antonie van Leeuwenhoek scraped his teeth and discovered bacteria. When he put dental plaque under a primitive microscope, he was surprised to see single-celled organisms floating around. Over the next three centuries, scientists found many more types of bacteria, not all of which were visible to the naked eye. For example, an E. coli cell measures approximately: two micronor less than ten thousandths of an inch.

Each bacterial cell is its own organism, meaning it can grow and divide into a pair of new bacteria. But bacterial cells often live together. Van Leeuwenhoek’s teeth were covered with a jelly-like film containing billions of bacteria. In lakes and rivers, some bacterial cells stick together and form small filaments.

We humans are multicellular organisms, our bodies are approx. 30 trillion cells. Although our cells are not visible to the naked eye, they are typically much larger than those of bacteria. A human egg cell is approx. 120 micron diameter or five thousandths of an inch.

Cells of other species can grow even larger: The green algae, Caulerpa taxifolia, produce blade-shaped cells that can grow for a long time. foot long.

As the gap between small and large cells emerged, scientists looked to evolution to figure it out. Animals, plants, and fungi all belong to the same evolutionary lineage called eukaryotes. Eukaryotes share many adaptations that help them form large cells. The scientists decided that without these adaptations, the bacterial cells would have to remain small.

To begin with, a large cell needs physical support so that it does not collapse or rupture. Eukaryotic cells contain rigid molecular wires that function like poles in a tent. Bacteria do not have this cellular skeleton.

A large cell also faces a chemical challenge: As its volume increases, it takes longer for molecules to circulate and meet the right partners and perform precise chemical reactions.

Eukaryotes have come up with a solution to this problem by filling cells with tiny compartments where different forms of biochemistry can take place. They wrap their DNA in a sac called the nucleus, along with molecules that can read genes to make proteins, or when a cell replicates, proteins produce new copies of DNA. Each cell produces fuel inside sacs called mitochondria.

Bacteria do not have the compartments found in eukaryotic cells. Without a nucleus, each bacterium typically carries a freely floating DNA loop around its interior. They also do not have mitochondria. Instead, they typically produce fuel with molecules embedded in their membranes. This arrangement works well for small cells. But as a cell’s volume increases, there isn’t enough room on the cell’s surface for enough fuel-producing molecules.

The simplicity of the bacteria seemed to explain why they were so small: They just didn’t have the complexity necessary to grow.

However, the founder of the Complex Systems Research Laboratory in Menlo Park, California, and Dr. According to Shailesh Date, co-author with Volland, this conclusion was reached too hastily. Scientists made sweeping generalizations about bacteria after examining only a small part of the bacterial world.

“We’ve only scratched the surface, but we’ve been very dogmatic,” he said.

This dogma began to crack in the 1990s. Microbiologists have found that some bacteria develop their own compartments independently. They also discovered species visible to the naked eye. epulopiscium fishelsoniFor example, it appeared in 1993. The bacteria living inside the surgeonfish grows larger than a grain of salt, up to 600 microns in length.

Olivier Gros, a biologist at Antillean University, discovered Thiomargarita magnifica while researching mangrove forests in 2009. Guadeloupe, a cluster of Caribbean islands that are part of France. The microbe looked like miniature pieces of white spaghetti that formed a fold on the dead tree leaves floating in the water.

At first, Dr. Gros didn’t know what he had found. He thought spaghetti might be mushrooms, tiny sponges, or some other eukaryote. But when he and his colleagues took DNA from samples in the lab, it turned out to be bacteria.

Dr. To get a closer look at the strange organisms, Gros joins Dr. He joined forces with Volland and other scientists. They wondered if bacteria were microscopic cells stuck together in chains.

It turned out that this was not the case. When the researchers looked inside the bacterial noodles with their electron microscope, they realized that each one had its own giant cell. The average cell was about 9,000 microns long, and the largest was 20,000 microns – long enough to cover the diameter of a penny.

Work on Thiomargarita magnifica progressed slowly because Dr. Vallant and his colleagues have yet to figure out how to grow the bacterium in their lab. For now, Dr. Gros has to collect a new source of bacteria every time the team wants to run a new experiment. You can find them not just in leaves, but in oyster shells and plastic bottles sitting on sulfur-rich sediments in the mangrove forest. But bacteria seem to follow an unpredictable life cycle.

Dr. “I haven’t been able to find them in the last two months,” Gros said. “I don’t know where they are.”

Researchers have discovered a strange, complex structure inside the cells of Thiomargarita magnifica. Their membranes have many different types of chambers embedded within them. These compartments are different from those in our own cells, but they can allow Thiomargarita magnifica to grow to enormous sizes.

Some of the compartments look like fuel-producing factories, where the microbe can use energy from nitrates and other chemicals that it consumes in the mangrove.

Thiomargarita magnifica also has other pods that are quite similar to the human core. Each of the compartments, which scientists call the pepin after the tiny seeds in fruits like kiwis, contains a DNA loop. While a typical bacterial cell has only one loop of DNA, Thiomargarita magnifica has hundreds of thousands of DNA, each packed into its own pepin.

Even more remarkable, each pep contains factories for creating proteins from its own DNA. “Cells are essentially small cells inside,” said Petra Levin, a microbiologist at the University of Washington in St. Louis, who was not involved in the study.

Thiomargarita magnifica’s huge DNA supply may allow it to create the extra proteins it needs to grow. Each pepin can make the specific set of proteins the bacterium needs at its site.

Dr. Volland and colleagues hope they can confirm these hypotheses once the bacteria start growing. They will also unravel other mysteries, such as how the bacterium managed to become so tough without a molecular skeleton.

Dr. “You can take a single filament of water with tweezers and put it in another container,” Volland said. “How it is held together and how it takes shape – these are questions we have yet to answer.”

Dr. Maybe even bigger than Thiomargarita magnifica, there may be more giant bacteria waiting to be found, Date said.

“We really don’t know how big they can get,” he said. “But now, this bacterium has shown us the way.”