Microbes: new life forms on Earth and perhaps beyond

Bacteria, microbes, single-cell organisms - the planet is teeming with them, literally in the billions. There are tens of thousands in a single drop of seawater and, worldwide, they constitute the greatest biomass on Earth. If their numbers are an indication of success then perhaps that success is due to both the simplicity of their existence and their ability to adapt to changing environments.

Two recent announcements regarding these tiniest of creatures caught my eye (no pun intended) because they had to do with the aquatic world and involved places I've been or would very much like to be.

Bacteria that challenges our notions of life
In the arid, alien-like landscape of Mono Lake, researchers have found bacteria that has adapted to an arsenic-rich environment. What is most unusual in this adaption was that the bacteria incorporated arsenic into its basic metabolic structure, replacing phosphorus. This is rather unique as phosphorus is one of nature's building blocks for all living things. Scientists have long held that carbon, hydrogen, nitrogen, oxygen, sulfur, and phosphorus are the basic elements of life as they help make up nucleic acids, proteins, lipids, and other fundamental components of all living matter.

However, researchers from Arizona State University have found in the water of Mono Lake, in east central California, bacteria that has exchanged phosphorus for the more prevalent arsenic, thereby challenging our notions of what constitutes what or where life can exist either here on Earth or elsewhere.

"At the moment we have no idea if life is just a freak, bizarre accident which is confined to Earth or whether it is a natural part of a fundamentally biofriendly universe in which life pops up wherever there are Earth-like conditions," said Paul Davies, the Arizona State University and NASA Astrobiology Institute researcher.

The researchers are very cautious not to draw too many conclusions from this preliminary research. Though the implications are tantalizing, with the possibility of life forms on other planets based on a totally different structure than what exists on Earth, there is still a considerable amount of work to be done before scientists decide to re-define our established notions of what constitutes life. Still, it makes you wonder just what our planetary probes in space should be looking for.

John Elliot, a UK researcher who has been involved in the search for extraterrestrial life, said, "It starts to show life can survive outside the traditional truths and universals that we thought you have to use... this is knocking one brick out of that wall."

Microbes that went down with the ship, way down
Ever since I read my parent's original copy of A Night to Remember by Walter Lord when I was a child, I have had a soft spot for anything Titanic. I'm not alone in this fascination with the great ocean liner that epitomized both man's industrial might and arrogance. But while the name and the vessel represent all things huge, scientists also study some of the wreck's smallest features - like a new form of iron-eating bacteria.

The genus Halomonas covers salt water bacteria that slowly breakdown metals, typically leaving behind evidence of their handiwork in the form of long, trailing icicle-like structures known as rusticles. Covering the Titanic along its hull and decaying metal superstructure, rusticles form a bizarre wintry scene to remind us of the cold depth 2.5 miles below the surface where the ship lies in two great pieces.

Reported in the International Journal of Systematic and Evolutionary Microbiology, researchers from universities in Ontario, Canada and Seville, Spain have discovered a new bacteria, named Halomonas titanicae, by studying rusticle samples taken by the Russian submersible, Mir 2, back in 1991. Cultured in the lab from the 19-year old samples, these bacteria are of interest beyond just the fascination in lifeforms that are able to survive in some of the planet's harshest environments. The fate of offshore oil and gas pipelines at the hands of these metal-devouring microbes is an important area of research, particularly in the aftermath of this year's Gulf of Mexico oil spill. Additionally, understanding how these smallest of creatures can breakdown and possibly "recycle" some of mankind's largest structures could assist in developing safe and effective disposal methods of ships and oil rigs.

From the deepest depths of the ocean to perhaps beyond the stars, life continues to show scientists that it has a tenacious drive to survive, adapting to its surroundings sometimes in the most fundamental of ways.

Read about the arsenic bacteria in BBC News.
Read Titanic microbe study in the IJSEM journal.