The beginning of life can be viewed from different angles. How did our planet, that formed from space debris come to harbor life? How have Earth's dwellers grown from single-celled organisms to complex multi-cellular creatures?
The beginning of life: Possible culprits
No matter where we go, bacteria can be found in every ecosystem in our planet. They can naturally be found even in our bodies where they outnumber our cells. They are often considered as single-celled organisms.
For the longest time, since bacteria are considered to be ancient organisms, many believe that they are the first life form to ever "walk" our planet. However, a recent work conducted by an international research team that was published in Molecular Biology and Evolution posits a different view on the beginning of life.
Evolutionary tools were used by the researchers when studying the growth of biofilms. These are bacterial lifestyle that is characterized by tight clusters of bacterial cells found on various surfaces.
According to Prof. Tomislav Domazet-Loso, who led the research, "Surprisingly, we found that the development of bacterial biofilms is comparable to animal embryogenesis. This means that bacteria are true multicellular organisms just like we are."
He continues, "Considering that the oldest known fossils are bacterial biofilms, it is quite likely that the first life was also multicellular, and not a single-celled creature as considered so far."
A day in the life of bacterial biofilms
Plants and animals can never be free from germs. These microorganisms and bacteria can always be found inside and outside of such macroscopic organisms. Surprisingly, these bacteria only form a small fraction of the total bacterial diversity that's present in all of our planet's biospheres. These even include large subterranean habitats deep within the Earth.
These environments are where bacterial cells are organized in clusters. Such structures are called biofilms. Domazet-Loso, who works for the Rudjer Boskovic Institute and the Catholic University of Croatia in Zagreb, further explains, "Evolutionary methods to study collective behavior of cells in animal development were at hand, but no one tried to transfer this technology from animal embryos to bacterial biofilms. Perhaps people were uncomfortable to challenge the special status of animal multicellularity, the idea that is culturally hardwired."
Modern technology as a gateway to the (distant) past
Domazet-Loso and his team were able to prove that evolution is mirrored in embryos. To further have a better look at the beginning of life, they developed genomic phylostratigraphy which is a computational approach. It enables the large-scale dating of genes and proteins.
Combining efforts and resources with University of Zagreb, Chalmers University, and Technical University of Denmark researchers, the tool was further refined for a more accurate examination of bacteria. "We generated the first phylostratigraphic maps of bacteria and this allowed us to link bacterial phenotypes in biofilms to evolutionary information," says Domazet-Loso.
He goes on to say, "Our results point that a biofilm should be viewed as a multicellular individual, and not as a pile of individual cells. Like in animal embryogenesis, every developmental phase has its own peculiarities."
He further concludes, "Critical transition stages in biofilm growth could now be targeted via their stage-specific genes that we detected. This could be a game changer in treating biofilm related diseases, and in preventing industrial losses."