All about the world’s largest bacterium

Despite forming an integral part of our daily lives, microorganisms, as you all know, cannot be seen with the naked human eye. That’s why you may be surprised to find that scientists have finally discovered a bacteria species that can be seen without any microscopic support. This rare and unique bacterium is called Thiomargarita magnifica. It was found in a Caribbean mangrove swamp in 2009. Scientists now largely regard it as the world’s largest bacterium. 

Here’s what’s known about this giant microorganism. 

A sneak peek at the world’s largest bacterium
Jean-Marie Volland, a marine biologist affiliated with the Lawrence Berkeley National Laboratory, co-authored the paper that announced the discovery of Thiomargarita magnifica. Recently, Volland stated that this bacterium resembles a long, thin and translucent white filament. It’s said to measure approximately 0.9 centimetres; so, it’s nearly as big as a human eyelash. This discovery was published in the journal Science.  

Thiomargarita magnifica can be quite a mouthful, right? That’s why, these days, it’s popularly referred to as magnificent sulfur pearl. That’s simpler, isn’t it? There’s also an interesting story associated with this bacterium’s discovery. As it turns out, when biologist Oliver Gros, of the University of the West Indies and Guiana, first came upon it in the Guadeloupe mangroves, he didn’t know it was a bacterium. This was because of its unconventionally large size. Later, a genetic experiment proved that it was, in fact, a single bacterial cell. 

Now, thanks to this amazing discovery, the scientific community is wondering if there are more giant bacteria out there.  

Characteristics of the world’s largest bacterium
Apart from mangroves, it has been found that the magnificent sulfur pearl also attaches itself to oyster shells, rocks and glass surfaces. Although it hasn’t been developed in a laboratory yet, researchers have started analysing its characteristics. For instance, it has a predictable life cycle.  

However, its most important characteristic is its unusual cell structure. Unlike other bacteria, the magnificent sulfur pearl has a large central compartment or vacuole that enables restricted cell functions to be isolated to that space, in contrast to the overall cell. Scientists believe that this one-of-a-kind feature aids the bacterium to overcome physical limitations.  

Scientists are still trying to pin down a specific reason for its humongous size, which is nearly 5000 times larger than most known bacteria. Interestingly, the common presumption is that the large size is the bacterium’s way of protecting itself from other tiny organisms. 

Another surprising characteristic is the bacterium’s organised DNA. While the DNA of other bacteria remains free and floating within the cytoplasm of the cell, the giant bacterium’s DNA is contained within a structure that has its own membrane. It also possesses thrice as many genes as other bacteria, and almost 12 million pairs of genomes.   

But why is it called the magnificent sulfur pearl? Well, for the simple reason that it’s a sulfur-oxidising prokaryote. A prokaryote is an organism that doesn’t have a nucleus. Additionally, the bacterium is white like most pearls. On the other hand, its scientific name, Thiomargarita magnifica, was chosen by molecular biologist and co-founder Silvina Gonzalez-Rizzo. After she carried out gene sequencing to identify and classify the bacterium, she found that it belonged to the genus Thiomargarita. She then added ‘magnifica’ to it owing to its large size—in Latin, ‘magnus’ means big.