The Sulfur Pearl of Namibia

Thiomargarita namibiensis (which means “the sulfur pearl of Namibia”) is a colorless sulfur bacteria found in ocean sediments off the coast of Namibia. While an E. coli bacterium is about 2 mm long T. namibiensis has a diameter of 750 mm. When it was discovered it was 100 times larger than the previous record for bacterial size. Usually bacteria remain small because of the need to optimize molecular diffusion into the cell. Staying small helps them transport the molecules they need with more ease. So why does T. namibiensis grow to be so much larger than many of its bacterial counterparts?
 

Part of the answer lies in the chemical reactions T. namibiensis uses to survive. T. namibiensis uses nitrate as an electron acceptor and oxidizes hydrogen sulfide (H₂S) into elemental sulfur (S). This reaction helps provide the energy that the cell needs, similar to how our cells use oxygen. The sulfur is deposited in the cytoplasm as granules that appear as opalescent pearls within the cell, giving the bacteria its name. T. namibiensis lives in hydrogen sulfide rich sediments (hydrogen sulfide is produced by many other bacteria) but nitrate rich ocean water doesn’t reach the bacteria very often. To combat this problem, T. namibiensis stores large amounts of elemental sulfur and nitrates within the cell. The cell’s large size is a result of the need for storage of essential elements.

         Personally I find bacteria to be super interesting so I was fascinated to learn about T. namibiensis. However, they’re existence also has important scientific implications. These bacteria push the known limits of bacterial cell size and expand our knowledge of cellular adaptations on this planet. They also couple the sulfur and nitrogen cycles in a way we haven’t seen before. This might sound like a small thing, but bacteria are essential to global biogeochemical cycles and improving our understanding of how they process nutrients could have profound implications for our understanding of ecosystems and global nutrient cycles.

-Laura Spielman

https://sciencepolicyivh.wordpress.com/2015/02/24/bacterial-giants-the-pearl-of-namibia/

https://www.independent.co.uk/news/worlds-largest-bacteria-found-off-namibia-1087496.html