Botryococcus braunii is a microorganism well known for its ability to produce biofuel-compatible hydrocarbons. For decades, it’s been a cornerstone of biofuel production. Now, groundbreaking genomic analysis has reclassified its chemical races as distinct species, paving the way for more precise biotechnological applications.
When the coronavirus pandemic struck in 2020, many of us were forced to change how we work. For Devon Boland, a researcher at Texas A&M, this meant leaving the lab and working from home. Faced with limitations on what he could work on, Boland started looking at Botryoccocus braunii.
This microorganism is technically a plant (a colonial green microalga) discovered in the mid-1800s and studied primarily due to its ability to produce hydrocarbons that can be converted into biofuels. Traditionally, B. braunii has been classified as a single species comprising three distinct chemical races — A, B, and L — each distinguished by the specific hydrocarbons they produce. But, as Boland found out, it’s not one species — but three.
“As a graduate student, you read papers that all say the same thing, that this is a single species with three chemical races, and you internalize it,” said Boland, first author of the study showing the genomic comparisons. “You start to think that must be right. No one has found otherwise, and all those scientists have had much longer careers than me — I’m just a kid.
“But I ended up getting to propose names for a species that were accepted for publication, which is something I never thought would happen.”
A change of focus
During lockdowns, Boland couldn’t work on his thesis, so he had to do something else. It was Tim Devarenne, associate head of undergraduate programs, who suggested he look at the genome of Botryoccocus braunii.
“Having the genome of your organism of interest mapped out is always ideal in research because it allows you to more easily find genes and work to determine their functions,” Devarenne said.
Daniel Browne, another researcher from the lab, had previously assembled the B race’s genome. Devarenne and Boland decided to do the same thing for the A and L races. As they discovered, even though the three seem identical under the microscope, they are genetically distinct.
It’s not easy to sample their DNA because of the thick, oily medium they live in. However, after some careful extraction and analysis, the team finally managed to isolate and feed the genetic data into a supercomputer. There, they ran comparison algorithms — and found key differences.
“It was like everywhere we looked, things were different,” he said.
Around 20% of the genomes of the three types were different. That’s comparable to the genetic differences between humans and dogs.
An important discovery
Given the substantial genomic differences, the researchers proposed reclassifying the three races into distinct species. They spent months deciding how to go about naming the species, and in the end, they came to a conclusion.
The B race, already the most studied, would retain the name Botryococcus braunii to preserve its historical identity, especially since it was the first to have its hydrocarbons — botryococcenes — identified. Lastly, the L race would be renamed Botryococcus lycopadienor, a nod to its production of the lycopadiene hydrocarbon. The A race would be renamed Botryococcus alkenealis, reflecting its unique production of alkadienes and alkatriens.
However, the significance of this finding extends beyond the realm of algae classification. The reclassification of B. braunii races into separate species has important implications for the fields of biofuels, evolutionary biology, and environmental science.
In the context of biofuels, the distinct species now identified within what was formerly known as B. braunii could lead to more targeted approaches in bioengineering. By understanding the specific genetic pathways responsible for hydrocarbon production in each species, scientists can potentially optimize these pathways for more efficient biofuel production. This could make B. alkenealis, B. braunii, and B. lycopadienor even more valuable as renewable energy resources.
From an evolutionary standpoint, the study provides a clear example of how both genetic and ecological factors can drive species divergence. The differences in hydrocarbon production, genome size, and repeat content among the three species suggest that they have adapted to different ecological niches or have undergone different selective pressures. This adds a new dimension to our understanding of speciation in microalgae, a group of organisms that play a crucial role in global carbon cycling and aquatic ecosystems.
Spreading knowledge of Botryococcus species
Unfortunately, it may take a while before other researchers acknowledge this change. For this reason, the team did their best to publish in an open-access journal that everyone can read. They also reached out and shared the team’s findings with more than 100 other researchers who study the organisms in their own labs.
“How we define separate species might not change much with how these organisms are used in research,” he said. “But it’s important for the scientific understanding, how we think about the ways these organisms are related to each other and to all other species.”
“It was important to us that the information was publicly available when it was ready to publish,” he said. “Science is community driven. The ultimate goal is always to further our collective knowledge, and I think that’s what we accomplished here.”
The study “Reclassification of Botryococcus braunii chemical races into separate species based on a comparative genomics analysis” was published in PLoS ONE.
