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Scientists discover the largest known bacteria on record

Measuring roughly the length of an eyelash, Thiomargarita magnifica is 50 times larger than any bacteria we’ve previously discovered. This challenges long held basics about our understanding of bacterial cells.

Germaphobes, get ready to squirm. ‘We’re going to need a bigger dish.’

Government scientists have discovered the first form of bacteria that is instantly visible to the naked eye, as reported in the journal Science.

Resembling white filaments around a centimetre in length, the strange organism is 50 times the size of the largest previously known bacterium and reportedly ‘challenges our concept of a bacterial cell’ altogether.

Discovered on decaying mangrove leaves in a Guadeloupe swamp (in the eastern Caribbean Sea), Thiomargarita magnifica has microbial biologists absolutely stumped for several reasons… other than the obvious.

It was previously thought that bacteria simply couldn’t grow this big, and scientists had confidently asserted that the absolute size limit – according to established models of cell metabolism – would be around 100 times smaller than this new species.

‘To put it into context, it would be like a human encountering another human as tall as Mount Everest,’ said Jean-Marie Volland, a scientist at the Lawrence Berkeley National Laboratory. That’s not a terrifying prospect, at all.

Also, when categorising the Earth’s dizzying array of bacteria, which have all existed for billions of years and occupy a multitude of different roles, they usually have one common characteristic: they’re composed of simple cells, measuring up to around two microns in diameter.

In this extraordinary case, however, Thiomargarita was found to contain three times the number of expected genes with many of them duplicates. It also had these complex sequences contained within membrane like casings, while most bacteria have DNA floating around freely.

‘These cellular features likely allow the organism to grow to an unusually large size and circumvent some of the biophysical and bioenergetic limitations on growth,’ Volland and his team concluded.

Technically, Thiomargarita belongs to a single-celled organism group called prokaryotes – this indeed includes bacteria – but its sheer size more closely resembles eukaryotes, such as plants and even animals.

In the initial days of study, scientists suggest that this bacterium may have grown to this size to prevent being preyed on by larger organisms.

‘If you grow hundreds or thousands of times bigger than your predator you cannot be consumed by your predator,’ said Volland. Shrewd observation, that.

But, aside from the obvious novelty factor of the thing being freakishly big, why else is this considered a major milestone for microbiologists?

The team has suggested that the presence of Thiomargarita may well point to other large and complex forms of bacteria hiding in plain sight, though the original discovery zone for this particular organism has apparently now dried up.

Volland remains convinced that unearthing more eukaryote-like forms of bacteria (if they exist) could fundamentally reshape our understanding of evolution.

Delving into the ‘biology, energy metabolism, formation, and nature’ of such organisms may well bring us closer to answering life’s big existential question of how everything came to be.

Sounds plenty worthwhile to me.