Washington, July 18 : Yale University researchers believe that the earliest forms of life on Earth were single strands of nucleotides, which performed some of the complicated cellular functions proteins are known to carry out at present.
They say that their surmise is based on the finding that bacterial cells use ancient forms of RNA to swim, morph into new forms, and even become dangerously virulent-all without initial involvement of DNA.
Ronald Breaker, senior author of the study, reckons that such cellular functions would have been common on Earth some four billion years ago, well before DNA existed.
He says that proteins are not always necessary to spur such cellular changes in bacteria.
"How could RNA trigger changes in ancient cells without all the proteins present in modern cells? Well, in this case, no proteins, no problem," says Breaker, who is also a Howard Hughes Medical Institute investigator.
The researcher says that bacteria have a large RNA structure called 'riboswitch' that can independently "decide'' which genes in the cell to activate, an ability once thought to rest exclusively with proteins.
Breaker also highlights the fact that almost 20 classes of riboswitches have been found in nature in the last six years.
"We predicted that there would be an ancient 'RNA city' out there in the jungle, and we went out and found it,'' he says.
He and his colleagues believe that billions of years ago, single strands of nucleotides that comprise RNA were the first forms of life and carried out some of the complicated cellular functions now done by proteins.
The riboswitches are highly conserved in bacteria, illustrating their importance and ancient ancestry, he says.
According to him, understanding how these RNA mechanisms work may lead to medical treatments for bacterial infections like cholera.