The bacteria are very, very small, with the cells having average volume of 0.009 cubic microns (this is a very tiny one micron is one millionth of a meter). To put the size in context, around 150,000 of these ultra-small bacteria would fit onto the tip of a human hair. in the laboratory, the isolated bacteria passed through 200-nanometer filters (these are filters with a pore size of equal to one billionth of a meter.)
There has been a longstanding debate within microbiology about the existence of nanobacteria, with different sides arguing the existence of of such minuscule organisms. To be classed as a “nanobacterium” the organism must be of a size much smaller than the generally accepted lower limit for life (about 200 nanometres for bacteria). The newly discovered ultra-small bacteria fall within a slightly larger category, leaving the idea of nanobacteria remaining something still to be proved.
The ultra-small bacteria were discovered in groundwater. The sample was taken from Rifle, Colorado. The cells take on the appearance of tightly-coiled spirals. The bacterial cells are thought to be the smallest that a cell can be and still hold sufficient material to sustain life.
To view the bacteria, the researchers were flash frozen to -272 degrees Celsius using a specially created device called a cryo plunger. The microbiologists then used 3-D cryogenic transmission electron microscopy to view and photograph the bacteria (what is termed “cryo-electron tomography.”) Later, the genomes of the bacteria were analysed. The genomes were found to be one million base pairs in length.
The examination of the bacteria suggests that they have tiny appendages (pili). Because the bacteria are relatively simple, they rely on interactions with other larger and more complex bacteria in order to function. Nonetheless, the images caught the bacteria in the process of dividing.
With the bacteria, initial results suggest that there are several different species. Little is known about the different species and they are an enigma to scientists. What is apparent, however, is that they are surprisingly abundant. Here it is a strange event: the presence of the bacteria was unknown, however, now scientists now where and how to look, they seem to be everywhere. Researchers hope that the new bacteria will reveal some information about the Earth’s ecosystem.
The bacteria and accompanying images have been reported to the science journal Nature Communications. The research paper is titled “Diverse uncultivated ultra-small bacterial cells in groundwater.”
