US scientists said on Monday a microbe living inside sea squirts could be utilized to biosynthesize a chemical compound that may help fight cancer.

The photosynthetic microbe, Prochloron didemni, lives inside the sea squirt Lissoclinum patella. So far, scientists have not been able to culture the microbe anywhere else.

Ground-up extracts of that sea squirt have been shown to contain patellamides, small peptides that appear useful in treating some cancers. Until this study, scientists had suspected that Prochloron microbes produce patellamides.

The new study published on-line this week in the Proceedings of the National Academy of Sciences, demonstrates that Prochloron didemni produces two patellamide compounds (A and C) and pinpoints the gene pathways that are used in that chemical biosynthesis.

"Coral reefs and other ocean environments are like rainforests - - full of natural chemicals to potentially treat human disease," said Eric Schmidt, assistant professor from the University of Utah 's College of Pharmacy who led the study.

"It's difficult to supply pharmaceuticals from these delicate environments. We have solved this by finding specific genes for the synthesis of chemicals using laboratory bacteria."

Schmidt had isolated and prepared the DNA of the microbe samples collected from sea squirts in the seabed. The researchers then sequenced the Prochloron genome and found the chemical pathways in the microbe's gene sequence that are responsible for producing patellamide A and C.

By proving that the patellamide compounds are made by the microbes inside sea squirts, the study has shown it possible to produce sufficient quantities of patellamides through biosynthesis without having to destroy a large numbers of sea squirts in the process, the researchers said.

Since patellamides are small cyclic peptides consisting of eight amino acids, scientists had at first thought the biosynthetic mechanism involved a "non-ribosomal peptide synthetase," a large multimodular enzyme that incorporates amino acids residue into a peptide.

When scientists did not find such a chemical system related to patellamides in the microbe's draft genome sequence, they examined alternative biosynthetic mechanisms. Because it is a peptide, a ribosomal mechanism was an obvious possibility.

The researchers looked for every combination of eight amino acids constituting the cyclic patellamides in the draft genome. They found the sequence for Patellamide A, and after further examination, found the Patellamide C sequence adjacent to the patellamide A sequence in the same pre-peptides.

After the gene cluster was annotated, Schmidt used the genomic information to develop the likely mechanism for the biosynthesis of the patellamides and he demonstrated how the biosynthesis could be accomplished.

The Prochloron genome project is still under way, with scientists exploring more aspects of the microbe's DNA sequence, according to the researchers.

This study "demonstrates how genomics can assist natural products chemistry and work towards sustainable production of important marine drug candidates from microbes. This process can speed up the time it takes for a drug to go from lead compound to actual drugs, " they said.