In a hot, steamy lava cave on the Kilauea Caldera in Hawai’i, microbiologists collecting samples from a dripping purple mat on the cave floor have found a new species that could reveal how bacteria that spit oxygen into the atmosphere millions of years ago evolved.
The purple mat was a type of biofilm, which is when microbes congregate together into one sticky mass. Another, more familiar type of biofilm is the plaque that gathers on the teeth.
This cave’s biofilm was different. The main species of this film was one not seen before that the researchers, including Jimmy Saw, Michael Schatz, and Stuart Donachie, decided to name Gloeobacter kilaueensis.
The paper regarding the new species was published on Oct. 23 in the online, open source journal PLoS ONE.
The genus Gloeobacter doesn’t have very many species, and in fact a new species for the genus hasn’t been named since 1974. However, the species Gloeobacter violaceus shares a close ancestor with the extraordinarily diverse and important cyanobacteria group.
When the first recognizable cyanobacteria diverged about 2.52 gya, they developed a critical ability: to emit gaseous oxygen during photosynthesis. Over time, cyanobacteria emerged that had specialized areas, or organelles, called thylakoid membranes and plant plastids to better carry out the photosynthetic reactions that produce oxygen.
Before cyanobacteria started churning out oxygen, the gas was only in very low levels in the atmosphere and was actually poisonous to most life (which at the time was entirely microbial). However, as oxygen levels from cyanobacteria photosynthesis increased, forms of life evolved that were able to tolerate and even use this oxygen, ultimately including animals.
In order to study cyanobacteria properly and how they figure into life’s history, scientists need to have a close relative to compare it to. G. violaceus and other Gloeobacter species, including the newly discovered G. kilaueensis are good candidates: G. violaceus are the first cyanobacteria capable of making oxygen during photosynthesis, but lack the specialized organelles in later cyanobacteria (and plants) that make the process more efficient.
The researchers hope to use the sequenced genome of the new species to help understand the evolutionary shift from anoxygenic to oxygenic photosynthesis. The genome of G. kilaueensis has over 4.7 million base pairs—the nucleotides in DNA that pair together to form DNA’s double helix structure.
Saw, Schatz, and the other researchers were able to find 4500 genes in the DNA that coded for proteins. Using the database BLAST, which gathers the functions of protein sequences across all the sequenced species, they were able to figure out the functions of 2800 of them. Future researchers can use these noted functions to determine how Gloeobacter, cyanobacteria, and their ancestors may have lived during Earth’s younger, hotter years.
Citation: Saw JHW, Schatz M, Brown MV, Kunkel DD, Foster JS, et al. (2013 Cultivation and Complete Genome Sequencing of Gloeobacter kilaueensis sp. nov., from a Lava Cave in Kilauea Caldera, Hawai’i. PLoS ONE 8(10): e76376. doi:10.1371/journal.pone.0076376