Culturable Bacterial Diversity
from the Basaltic Subsurface of the Young Volcanic Island of Surtsey, Iceland
Aerial Image of Surtsey (Baldursson, S. and Ingardóttir, Á, 2007)
Pauline Bergsten et al., discuss the unique laboratory provided by the volcanic island of Surtsey for discovering novel (new) microorganisms. This study is the first to report on the culturable microbial diversity from the basaltic subsurface of Surtsey. It isolated 195 strains of microorganisms representing 42 different genera most of which were aerobic and heterotrophic bacteria along with a few novel species, such as Rhodothermus bifroesti.
Figure 1. Taxonomical distribution at the phylum level (classes for Proteobacteria) of the bacterial isolates from Surtsey island by sampling sites. The percentages represent the relative cultivable bacterial abundance.
In 1979, borehole SE-01 was drilled to investigate the subsurface deposits of Surtsey. Thirty-eight years later three new cored boreholes (SE-02a, SE-02b, SE-03) were drilled specifically for microbiological and geological analysis. Since Surtsey serves as a unique opportunity for scientists to investigate very young rock-microbe interactions, the boreholes within the volcano can be thought of as “opened windows from the surface, allowing for the examination of subsurface microbial processes at high temperatures associated with oceanic crust”. The examination of samples from the boreholes during this study revealed diverse bacterial and archaeal taxa, many of which have been previously reported in surface and subsurface habitats in both terrestrial and marine settings. Along with these previously reported taxa, many clades were newly discovered, belonging to previously unknown lineages.
Figure 4. For each phylum, number of number of the number of Amplicon Sequence Variants (ASVs) obtained by high throughput sequencing (a) and cultured strains (b). (c) the fraction of the in situ diversity represented by cultured strains, and taxonomic classification (d). An ASV was considered to be represented by the cultured strains if the ASV had equal of higher than 98.65% sequence similarity with the 16S rRNA gene sequence of cultured strains. The taxonomic classification of the ASVs represented by the cultured strains at the genus level. Family given in parenthesis for Enterobacteriaceae, Intrasporangiaceae, Planococcaceae, and Rhodobacteraceae. NA. Not assigned genera
In total, 195 isolates of bacteria were obtained from fumarole samples, borehole fluids, and drill cores. 49.23% of isolates were found in borehole fluid samples, 26.15% of isolates were found in fumarole samples, and 24.62% were found in drill cores. The isolates were assigned to different families of bacterial phyla.
Remarkably, a few of the strains isolated in this study potentially represented novel species “according to the percentage value used as a boundary for species delineation of 98.65% 16S rRNA sequence similarity”. Sequences that were closest to these potentially new species have been previously detected in permafrost soils, seawater and deep-sea sediments, soils, or continental Antarctic lakes, and glacial sediments.
Overall, the work done in this study shows that several of the species in the very young Surtsey system that were isolated in this study are closely related to those previously found in marine, alkaline, and subsurface species with a few potential new species, such as Rhodothermus bifroesti.
Rhodothermus bifroesti
For further reading about Rhodothermus bifroesti:
Bergsten, P., Vannier, P., Mougeolle, A., Rigaud, L., Marteinsson, V. T., 2022, Rhodothermus bifroesti sp. nov., a thermophilic bacterium isolated from the basaltic subsurface of the volcanic island Surtsey: Int J Syst Evol Microbiol. 72(1). doi:10.1099/ijsem.0.005214. PMID: 35072600.
Citation
Bergsten, P., Vannier, P., Frion, J., Mougeolle, A., Marteinsson, V. T., 2022, Culturable Bacterial Diversity from the Basaltic Subsurface of the Young Volcanic Island of Surtsey, Iceland: Microorganisms, v. 10, p. 1177, doi:10.3390/microorganisms10061177.
