One variety of bacteria has only ever been isolated from the wreck of the RMS Titanic; another type of bacteria has only ever been found inside clean rooms used to assemble spacecraft.
It is often said that we know more about the Moon than we do about the bottom of the ocean. That’s true, but we know a lot more about both than we do about bacteria.
Biologists have classified more than nine thousand different species of bacteria, but that’s not even scratching the surface of this branch of life. We think that those nine thousand species represent less than one percent of the total number of bacteria species on the planet… but we’re not even certain of that. Estimates of the total number of species range from a hundred million or so up into the quadrillions.
There are a few reasons for this knowledge gap. It can be quite tricky to isolate and identify bacteria. Usually they need to be grown in a lab, but many bacteria species just don’t grow in that artificial environment. (I’ve read one estimate that only about 2% of bacteria species can be cultured in a lab. The bacterium that causes syphilis, Treponema pallidum, was only successfully cultured in 2018!) And there are just so many species of bacteria that the task to identify them all is an impossible one.
All this is to say that bacteria have to do something really special in order to stand out. Halomonas titanicae achieved this feat by appearing inside rust on the RMS Titanic. We have never seen it anywhere else; this bacteria is literally eating the most famous shipwreck in the ocean.
And then there’s Tersicoccus phoenicis. We discovered this bacteria when it showed up inside the clean room where the Phoenix Martian lander was being assembled. Spacecraft clean rooms are supposed to be sterile – so that we don’t spread our germs to other planets. So you can imagine our surprise when the same bacteria showed up in another spacecraft clean room in French Guiana. Tersicoccus phoenicis resists our most rigorous sterilization procedures, and that’s the only reason we ever discovered it. All the other bacteria was already gone.