Microbial colonisation in different soils of Surtsey and diversity analysis of its subsurface microbiota
Although prokaryotes such as bacteria and blue-green algae were the first colonisers on Surtsey, most studies have been focusing on colonization of plants and animal and less on microbial succession. To explore surface colonization and the influence of nutrients on numbers of bacteria, we collected 45 samples from different soils around the island. Total viable bacterial counts were performed with plate count at 22°, 30° and 37°C for all soil samples. Selected samples were also tested for faecal and anaerobic bacteria at 30°C and colonisation of pathogenic bacteria i.e. Salmonella, Campylobacter and Listeria. The amount of organic matter and nitrogen was measured. To explore subsurface microbial colonisation we collected subsurface samples from a borehole. Diversity analysis of uncultivated biota was performed by 16S rRNA gene sequence analysis. Correlation was observed between the nutrient deficits and the number of microorganisms in soil samples. The lowest number of bacteria (1x104-1x105/g) was detected in pumice but the count was significant higher (1x106-1x109/g) in vegetated soil or pumice with bird drop. The number of faecal bacteria correlated to higher numbers of bacteria and soil. Bacteria belonging to Enterobacteriaceae were only detected in vegetated and sample containing bird drop. No pathogenic microbes were detected in any selected sample. Both bacteria and archaea were detected in the subsurface samples collected at 145m and 172m depth at 80°C and 54°C respectively. The microbiota sequences showed low affiliation to known 16S rRNA gene sequences.