Scientists discover smallest lifeforms in existence

Scientists have taken the first ever extensive microscopy images of ultra-small bacteria, which are so far thought to be the smallest life forms in existence.

The bacteria have an average volume of 0.009 cubic microns (a micron is one millionth of a meter), 150,000 of which could be placed on the tip of a human hair.

Ultra-small bacteria's presence has been under debate for some twenty years, but until now they lacked a comprehensive electron microscopy and DNA-based description.

The research was carried out by a group of scientists from the US Department of Energy's Lawrence Berkeley National Laboratory and the University of California, Berkeley, and was published in the February 27 edition of the journal .

"These newly described ultra-small bacteria are an example of a subset of the microbial life on earth that we know almost nothing about," said the co-corresponding author of the research, Jill Banfield, a senior faculty scientist in the earth sciences division of Berkeley Lab.

The diverse microbes are discovered in groundwater and are believed to be rather common. They are the smallest a cell can be but still harbor sufficient material to sustain life.

"They're enigmatic. These bacteria are detected in many environments and they probably play important roles in microbial communities and ecosystems. But we don't yet fully understand what these ultra-small bacteria do," said Banfield.

The bacterial cells are compromised of densely packed spirals which are thought to be DNA and a low number of ribosomes, and hair-like appendages which could aid the cell to connect with other microbes and obtain required resources.

Their metabolism is stripped down probably making them dependent on other bacteria.

"There isn't a consensus over how small a free-living organism can be, and what the space optimization strategies may be for a cell at the lower size limit for life. Our research is a significant step in characterizing the size, shape, and internal structure of ultra-small cells," said the other author of the research Birgit Luef.

The research was carried out by filtering groundwater obtained at Rifle, Colorado, down to 0.2 microns. The remainder was enriched with ultra tiny microbes, which were flash frozen and transported to Berkeley laboratory, where they underwent cryogenic transmission electron microscopy imaging.