A bacterium from the mangrove sumps on the Guadeloupe island is around one centimeter long-and thus about 50 times longer than the next largest bacterium. The organism christened by a working group around Jean-Marie Volland from the Lawreley Berkeley National Laboratory, which is christened Thiomargarita Magnifica, forms white, around one centimeter long and about a tenth of millimeter thick cords, which are attached to sunken mangrove leaves with one end. As the team reports in a publication in "Science", Thiomargarita has several adjustments that could explain its enormous size growth. For example, the bacterium not only has an extraordinarily large genome, but also contains around half a million copies. It is unclear why the organism is so large - and whether there may be even larger bacteria.
Thiomargarita belongs to the group of large sulfur bacteria, which previously represented the largest known bacterial cells. For example, Thiomargarita namibiensis can grow up to 750 micrometers in length under special circumstances. Even this species is usually only around 200 micrometers long, so the newly discovered bacterium is around 50 times longer. Actually, such a large bacterium should not be viable at all, because in such a large cell, nutrients, signaling molecules or newly produced proteins take far too long to reach all places of the cell.
Thiomargarita Magnifica solves the problem with several tricks. On the one hand, the cell is not as big as it appears. Your inside is almost completely filled with a membrane bubble in which the cell stores nitrate - it can use it as an oxygen source for energy generation. The actual cell outside the nitrate bubble is just about two to three micrometers thick layer of cell plasma, in which countless membrane bubbles are also stored with sulfur and also used for energy generation. They give all major sulfur bacteria their typical bright white color. In addition, all the membrane bubbles reduce the cell plas masonation, which must actually be supplied.
An important role for the unusual size is played by the hundreds of thousands of copies of the genetic material. Each of them is enclosed in its own membrane bubble, which also contains some ribosomes. These structures are called pepins. They serve as protein factories distributed throughout the bacterium. In addition, thiomargarita is permeated with a whole network of membranes in which ATP-producing enzymes are anchored, which are driven by differences in proton concentration and produce energy for cell processes. However, how the cell generates the differences in proton concentrations is still completely mysterious.
Other important questions are also unclear. So there must be a kind of long -distance communication in the cell, because the protein factories do not all produce randomly and with the same rate of biomolecules. Rather, the activity focuses in a few places, reports the working group around Volland. How the cell selects these places and what signals the pepine activate is uncertain. It is still open as the reaction to harmful environmental influences works for a bacterium of this size. However, there are initial clues to how it reproduces: the experts interpret the approximately 0.2 millimeter long constrictions at the loose end of the cell as possible daughter cells by Thiomargarita Magnifica. Last but not least, a considerable part of the metabolic activity seems to be playing there.
However, it is most interesting for further research that the curious cell threads are perfectly clean. Bi -films actually form on every surface, especially since hundreds of thousands of normal bacteria fit on the surface of Thiomargarita Magnifica. The cause of the sterile shells are probably antibiotic substances that produce the bacterium. About a quarter of its genome consists of enzymes that produce different natural substances that serve in other organisms of chemical warfare. Which fabrics the giant bacterium actually excretes is so far unknown - but there may be new antibiotic candidates for medicine.
