Mineralogy affects prokaryotic community composition in an acidic metal mine.

The microbial ecology of acidic mine and sulfide cave ecosystems is well characterised with respect to aquatic communities, typically revealing low taxonomic complexity and dominance by a relatively limited number of cosmopolitan acidophilic bacterial and archaeal taxa. Whilst pH, temperature, and geochemistry are recognised drivers of diversity in these ecosystems, the specific question of a possible influence of substratum mineralogy on microbial community composition remains unanswered. Here we address this void, using 81 subterranean mineral samples from a low temperature abandoned, acidic, sulfide ore mine system at Mynydd Parys (Parys Mountain in English), Wales, UK. Four primary and 15 secondary minerals were identified via x-ray diffraction, each sample containing a maximum of five and an average of two minerals. The mineralogy of primary (e.g. pyrite and quartz) and secondary (e.g. melanterite and pisanite) minerals was significantly correlated with prokaryotic community structure at multiple taxonomic levels, implying that the mineralosphere effect reported in less extreme terrestrial environments is also implicated in driving prokaryotic community composition in extremely acidic, base metal-bearing sulfide mineralisation at Mynydd Parys. Twenty phyla were identified, nine of which were abundant (mean relative abundance >1%). While taxa characteristic of acidic mines were detected, for example Leptospirillum (phylum Nitrospirae), Acidithiobacillus (phylum Proteobacteria), Sulfobacillus (phylum Firmicutes) and Ferroplasma (phylum Euryarchaeota), their abundance in individual samples was highly variable. Indeed, in the majority of the 81 samples investigated the abundance of these and other typical acidic mine taxa was low, with 25% of samples devoid of sequences from recognised acidic mine taxa. Most notable amongst the bacterial taxa not previously reported in such environments were the recently cultivated Muribaculaceae family (phylum Bacteroidetes), which often dominated Mynydd Parys samples regardless of their mineralogical content. Our results pose further questions regarding the mechanisms by which taxa not previously reported in such extreme environments appear to survive in Mynydd Parys, opening up research pathways for exploring the biodiversity drivers underlying microbial community composition and function in extremely acidic mine environments.

Priorities for research in soil ecology.

The ecological interactions that occur in and with soil are of consequence in many ecosystems on the planet. These interactions provide numerous essential ecosystem services, and the sustainable management of soils has attracted increasing scientific and public attention. Although soil ecology emerged as an independent field of research many decades ago, and we have gained important insights into the functioning of soils, there still are fundamental aspects that need to be better understood to ensure that the ecosystem services that soils provide are not lost and that soils can be used in a sustainable way. In this perspectives paper, we highlight some of the major knowledge gaps that should be prioritized in soil ecological research. These research priorities were compiled based on an online survey of 32 editors of Pedobiologia - Journal of Soil Ecology. These editors work at universities and research centers in Europe, North America, Asia, and Australia.The questions were categorized into four themes: (1) soil biodiversity and biogeography, (2) interactions and the functioning of ecosystems, (3) global change and soil management, and (4) new directions. The respondents identified priorities that may be achievable in the near future, as well as several that are currently achievable but remain open. While some of the identified barriers to progress were technological in nature, many respondents cited a need for substantial leadership and goodwill among members of the soil ecology research community, including the need for multi-institutional partnerships, and had substantial concerns regarding the loss of taxonomic expertise.

Pioneer microbial communities of the Fimmvörðuháls lava flow, Eyjafjallajökull, Iceland.

Little is understood regarding the phylogeny and metabolic capabilities of the earliest colonists of volcanic rocks, yet these data are essential for understanding how life becomes established in and interacts with the planetary crust, ultimately contributing to critical zone processes and soil formation. Here, we report the use of molecular and culture-dependent methods to determine the composition of pioneer microbial communities colonising the basaltic Fimmvörðuháls lava flow at Eyjafjallajökull, Iceland, formed in 2010. Our data show that 3 to 5 months post eruption, the lava was colonised by a low-diversity microbial community dominated by Betaproteobacteria, primarily taxa related to non-phototrophic diazotrophs such as Herbaspirillum spp. and chemolithotrophs such as Thiobacillus. Although successfully cultured following enrichment, phototrophs were not abundant members of the Fimmvörðuháls communities, as revealed by molecular analysis, and phototrophy is therefore not likely to be a dominant biogeochemical process in these early successional basalt communities. These results contrast with older Icelandic lava of comparable mineralogy, in which phototrophs comprised a significant fraction of microbial communities, and the non-phototrophic community fractions were dominated by Acidobacteria and Actinobacteria.

Land coverage influences the bacterial community composition in the critical zone of a sub-Arctic basaltic environment.

Silicate weathering improves soils by releasing bioessential nutrients from the bedrock to the soil ecosystem. However, whether bacteria are capable of inhabiting subsurface critical zones (zone of active rock weathering), and their role therein, are unknown. Next-generation sequencing and community fingerprinting permitted us to characterize communities from an Icelandic critical zone environment. Communities were compared with respect to physico-chemical properties of the environment to determine the factors influencing bacterial diversity. We showed that land coverage influenced critical zone communities. Analysis of tree-covered site (TCS) soils exhibited high cell densities (TCS = 2.25 × 10(7)  g(-1) ), whereas lichen- and moss-covered sites (LMS) had lower cell densities (LMS = 1.06 × 10(7)  cells g(-1) ), thought to be a result of the organic carbon produced by the trees. Differences in the bacterial community were observed from the abundance of 16S rRNA gene sequences affiliated with Acidobacteria and Proteobacteria, with TCS possessing higher abundances of Proteobacteria [no of sequences: LMS = 1526 (±497); TCS = 2214 (±531)], specifically Alpha- and Betaproteobacteria, and lower Acidobacteria numbers [no of sequences: LMS = 1244 (±338); TCS = 598 (±140)]. Diversity indices and 16S rRNA gene rarefaction showed that communities from TCS soils had lower α-diversity than sites without, indicative of specialized communities at sites with root-forming plants.

Factors affecting recruitment to an observational multicentre palliative care study.

OBJECTIVES: To identify those factors which adversely affected recruitment to a large multicentre palliative care study. METHODS: Patient accrual to a multicentre, observational, palliative care study was monitored at three critical junctures in the research process. (1) Eligibility-did the patient fulfil the study entry criteria? (2) Accessibility-was it possible to access the patient to be able to inform them about the study? (3) Consent-did the patient agree to participate in the study? The reasons why patients were ineligible, inaccessible or refused consent were recorded. RESULTS: 12 412 consecutive referrals to participating clinical services were screened for study inclusion of whom 5394 (43%) were deemed to be ineligible. Of the remaining patients 4617/7018 (66%) were inaccessible to the research team. The most common reasons being precipitous death, 'gatekeeping' by clinical staff or rapid discharge. Of the 2410 patients who were visited by the research team and asked to participate in the study 1378 (57%) declined. Overall 8.2% (1018/12 412) of patients screened participated in the study. There were significant differences in recruitment patterns between hospice inpatient units, hospital support and community palliative care teams. CONCLUSIONS: Systematic monitoring and analysis of patient flows through the clinical trial accrual process provided valuable insights about the reasons for failure to recruit patients to a clinical trial and may help to improve recruitment in future studies.

Following the kinetics: iron-oxidizing microbial mats in cold icelandic volcanic habitats and their rock-associated carbonaceous signature.

Icelandic streams with mean annual temperatures of less than 5 °C, which receive the cationic products of basaltic rock weathering, were found to host mats of iron-cycling microorganisms. We investigated two representative sites. Iron-oxidizing Gallionella and iron-reducing Geobacter species were present. The mats host a high bacterial diversity as determined by culture-independent methods. ß-Proteobacteria, Actinobacteria, α-Proteobacteria, and Bacteroidetes were abundant microbial taxa. The mat contained a high number of phototroph sequences. The carbon compounds in the mat displayed broad G and D bands with Raman spectroscopy. This signature becomes incorporated into the weathered oxidized surface layer of the basaltic rocks and was observed on rocks that no longer host mats. The presence of iron-oxidizing taxa in the stream microbial mats, and the lack of them in previously studied volcanic rocks in Iceland that have intermittently been exposed to surface water flows, can be explained by the kinetic limitations to the extraction of reduced iron from rocks. This type of ecosystem illustrates key factors that control the distribution of chemolithotrophs in cold volcanic environments. The data show that one promising sample type for which the hypothesis of the existence of past life on Mars can be tested is the surface of volcanic rocks that, previously, were situated within channels carved by flowing water. Our results also show that the carbonaceous signatures of life, if life had occurred, could be found in or on these rocks.

Bacterial diversity of terrestrial crystalline volcanic rocks, Iceland.

Bacteria inhabiting crystalline rocks from two terrestrial Icelandic volcanic lava flows of similar age and from the same geographical region, but differing in porosity and mineralogy, were characterised. Microarray (PhyloChip) and clone library analysis of 16S rRNA genes revealed the presence of a diverse assemblage of bacteria in each lava flow. Both methods suggested a more diverse community at the Dómadalshraun site (rhyolitic/andesitic lava flow) than that present at the Hnausahraun site (basaltic lava flow). Proteobacteria dominated the clone library at the Dómadalshraun site, while Acidobacteria was the most abundant phylum in the Hnausahraun site. Although analysis of similarities of denaturing gradient gel electrophoresis profiles suggested a strong correlation of community structure with mineralogy, rock porosity may also play an important role in shaping the bacterial community in crystalline volcanic rocks. Clone sequences were most similar to uncultured microorganisms, mainly from soil environments. Of these, Antarctic soils and temperate rhizosphere soils were prominent, as were clones retrieved from Hawaiian and Andean volcanic soils. The novel diversity of these Icelandic microbial communities was supported by the finding that up to 46% of clones displayed <85% sequence identities to sequences currently deposited in the RDP database.

Bacterial diversity of weathered terrestrial Icelandic volcanic glasses.

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