The Open University ’ s repository of research publications and other research outputs Bacterial diversity of weathered terrestrial

1 The diversity of microbial communities inhabiting two terrestrial volcanic glasses of 2 contrasting mineralogy and age was characterised. Basaltic glass from a <0.8 Ma 3 hyaloclastite deposit (Valafell) harbored a more diverse Bacteria community than the 4 younger rhyolitic glass from ~150-300AD (Dόmadalshraun lava flow). Actinobacteria 5 dominated 16S rRNA gene clone libraries from both sites, however Proteobacteria, 6 Acidobacteria and Cyanobacteria were also numerically abundant in each. A 7 significant proportion (15-34%) of the sequenced clones displayed <85% sequence 8 similarities with current database sequences, thus suggesting the presence of novel 9 microbial diversity in each volcanic glass. The majority of clone sequences shared the 10 greatest similarity to uncultured organisms, mainly from soil environments, among 11 these clones from Antarctic environments and Hawaiian and Andean volcanic 12 deposits. Additionally, a large number of clones within the Cyanobacteria and 13 Proteobacteria were more similar to sequences from other lithic environments, 14 included among these Icelandic clones from crystalline basalt and rhyolite, however 15 no similarities to sequences reported from marine volcanic glasses were observed. 16 PhyloChip analysis detected substantially greater numbers of phylotypes at both sites 17 than the corresponding clone libraries, but nonetheless also identified the basaltic 18 glass community as the richer, containing approximately 29% unique phylotypes 19 compared to rhyolitic glass. 20