Thiomargarita magnifica

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Thiomargarita magnifica
Scientific classification Edit this classification
Domain: Bacteria
Phylum: Pseudomonadota
Class: Gammaproteobacteria
Order: Thiotrichales
Family: Thiotrichaceae
Genus: Thiomargarita
Species:
T. magnifica
Binomial name
Thiomargarita magnifica
Volland et al., 2022[1]

Candidatus Thiomargarita magnifica is a species of sulfur-oxidizing gammaproteobacteria, found growing underwater on the detached leaves of red mangroves from the Guadeloupe archipelago in the Lesser Antilles.[2] This filament-shaped bacteria is the largest known bacterium, with an average length of 10 mm and some individuals reaching 20 millimetres (0.79 in),[3] making the bacteria visible to the naked eye.[1]

Discovery

The bacterium was originally discovered in the early 2010s by Olivier Gros from the University of the French Antilles at Pointe-à-Pitre, but initially it did not attract much attention as Gros thought his find to be a fungus;[4] it took Gros and other researchers five years to determine that it is a bacterium, and a few more years until Jean-Marie Volland, a graduate student working under the supervision of Gros, figured out its unusual properties.[3] The bacterium was formally described in a 2022 publication.[1]

Name

Thiomargarita means "sulfur pearl" in Latin. This refers to the appearance of the cells; they contain microscopic sulfur granules that scatter incident light, lending the cell a pearly lustre. The name magnifica means "magnificent" and was chosen by researcher Silvina González Rizzo, who identified T. magnifica as a bacterium.[5]

Structure

In bacteria, both nutrients and waste products of metabolism reach the interior of the cell by diffusion, which places an upper limit on the size of these organisms. Cells of the large sulfur bacterium T. namibiensis, discovered in 1999, contain a large sac (vacuole) filled with water and nitrates, pushing most of the cytoplasm into close to the cell wall, so that the distances required for diffusion are relatively small; life processes occur only "along the edge" of the cell. Ca. T. magnifica's cell includes a similar vacuole[3] that occupies most of the cell (65–80% by volume) and pushes the cytoplasm to the periphery of the cell (the thickness of cytoplasm varies from 1.8 to 4.8 microns).[1]

The size of this bacterium and its extreme polyploidy are partially explained by its genome, which lacks many common bacterial cell division genes.[1]

The outside of the cell lacks epibiotic bacteria; their "surprising absence" can be explained by Ca. T. magnifica possibly producing biologically active or even antibiotic chemical compounds.[1]

Encapsulated DNA

Another sac or compartment within the organism contains its DNA. Researchers have named these compartments "pepins". This structure is very different from the free-floating DNA found in most other bacteria.[6] This arrangement is important, in as much as it blurs the boundary between prokaryotes, primitive single-cell organisms that do not have a cell nucleus (their DNA is left in the cytoplasm), and eukaryotes, where the DNA is surrounded by the nuclear envelope. With Ca. T. magnifica being a bacterium, it is a prokaryotic organism, but its cell includes membrane sacs that encapsulate the cell's DNA.[1]

Reproduction and life cycle

Like all prokaryotes, Ca. T. magnifica reproduces asexually. However, there are slight differences in reproduction compared to other Thiomargarita species. Instead of dividing into equally sized daughter cells, its life cycle is dimorphic.[1] Researchers observed a process of reproduction similar to budding. During this process, Ca. T. magnifica shares only some of its “pepins” with the much smaller daughter cell. It is believed that the smaller daughter cell serves as a method of dispersion; and helps it to spread over longer distances.[1]

See also

References

  1. ^ a b c d e f g h i Volland, Jean-Marie; Gonzalez-Rizzo, Silvina; Gros, Olivier; Tyml, Tomáš; Ivanova, Natalia; Schulz, Frederik; Goudeau, Danielle; Elisabeth, Nathalie H.; Nath, Nandita; Udwary, Daniel; Malmstrom, Rex R.; Guidi-Rontani, Chantal; Bolte-Kluge, Susanne; Davies, Karen M.; Jean, Maïtena R.; Mansot, Jean-Louis; Mouncey, Nigel J.; Angert, Esther R.; Woyke, Tanja; Date, Shailesh V. (24 June 2022). "A centimeter-long bacterium with DNA contained in metabolically active, membrane-bound organelles". Science. 376 (6600): 1453–1458. bioRxiv 10.1101/2022.02.16.480423. doi:10.1126/science.abb3634. eISSN 1095-9203. ISSN 0036-8075. PMID 35737788. S2CID 249990020.
  2. ^ "Record bacterium discovered as long as human eyelash". BBC News. 23 June 2022. Retrieved 23 June 2022.
  3. ^ a b c Pennisi, Elizabeth. "Largest bacterium ever discovered has unexpectedly complex cells". Science. science.org. Retrieved 24 February 2022.
  4. ^ Rogers, Peter. ""Impossibly big" bacteria rattle the field of microbiology". BigThink. Retrieved 22 March 2022.
  5. ^ Ansede, Manuel (1 March 2022). "Scientists discover one-centimeter long bacterium that's visible to the naked eye". El País. Retrieved 23 June 2022.
  6. ^ Ferreira, Becky (23 June 2022). "Government Scientists Discover Biggest Bacteria Ever, Visible to Naked Eye". Vice.