The new research, published in the Proceedings of the National Academy of Sciences (PNAS), analysed the genomic data from a variety of bacteria to identify gene sequences that likely code for terpene synthases - enzymes that catalyse the production terpenes that could be used for a range of food applications including in flavours and as aroma compounds or top notes.
Led by Professor David Cane from Brown University, the team identified 262 gene sequences that likely code for the production of terpenes – of which were isolate 13 previously unidentified bacterial terpenes.
“Genes encoding such terpene synthases have been shown to be widely distributed in bacteria and represent a fertile source for discovery of new natural products,” said the authors.
Genetic sequencing
Since the discovery of terpenes more than 150 years ago, scientists have isolated some 50,000 different terpene compounds derived from plants and fungi. While bacteria and other microorganisms are known to make terpenes too, they've received much less study in the past, said the team.
The new research made use of the advanced search techniques that were developed from the results of previous searches to identify possible bacterial coding sequenced.
"Instead of using plant sequences or fungal sequences as your search query, we can now use bacterial sequences, which should yield a greater degree of similarity," said Cane. "So now we're fishing in the right waters with the right kind of bait, and you can find more matches."
Previous work had identified 140 probable sequences for terpene synthases, while the current work expanded that to 262.
Bacterial production
The next step was to verify that these sequences did indeed code for enzymes capable of making terpenes.
After selecting a few genetic sequences that they believed offered the best chance of finding terpene compounds that hadn't previously been identified, Cane and his colleagues made use of a genetically engineered Streptomyces bacterium as a bio-refinery to generate the terpene products.
By taking some of the gene sequences they found and splicing them into their test organism, the researchers could let the organisms generate the product using the instructions from the newly introduced gene.
Using this method, they were able to make 13 previously unknown terpenes, their structures verified by mass spectrometry and nuclear magnetic resonance spectroscopy.
"It's a big step forward in the area in that it provides a paradigm for how one could go about discovering many new substances," said Cane.
"It's a good example of how one can use sequence analysis to identify genes of interest and then apply molecular genetic and microbiological techniques to produce the chemical substances of interest."
The work also suggests that there may be many new terpene products as yet undiscovered hiding in the genomes of bacteria, said the team.
Source: PNAS
Published online ahead of print, doi: 10.1073/pnas.1422108112
“Terpene synthases are widely distributed in bacteria”
Authors: Yuuki Yamada, et al