Metagenomic analyses of a microbial assemblage in a subglacial lake beneath the Vatnajökull ice cap, Iceland

Skaftárkatlar are two subglacial lakes located beneath the Vatnajökull ice cap in Iceland associated with geothermal and volcanic activity. Previous studies of these lakes with ribosomal gene (16S rDNA) tag sequencing revealed a limited diversity of bacteria adapted to cold, dark, and nutrient-poor waters. In this study, we present analyses of metagenomes from the lake which give new insights into its microbial ecology. Analyses of the 16S rDNA genes in the metagenomes confirmed the existence of a low-diversity core microbial assemblage in the lake and insights into the potential metabolisms of the dominant members. Seven taxonomic genera, Sulfuricurvum, Sulfurospirillum, Acetobacterium, Pelobacter/Geobacter, Saccharibacteria, Caldisericum, and an unclassified member of Prolixibacteraceae, comprised more than 98% of the rDNA reads in the library. Functional characterisation of the lake metagenomes revealed complete metabolic pathways for sulphur cycling, nitrogen metabolism, carbon fixation via the reverse Krebs cycle, and acetogenesis. These results show that chemolithoautotrophy constitutes the main metabolism in this subglacial ecosystem. This assemblage and its metabolisms are not reflected in enrichment cultures, demonstrating the importance of in situ investigations of this environment

SUSTAIN drilling at Surtsey volcano, Iceland, tracks hydrothermal and microbiological interactions in basalt 50 years after eruption

The 2017 Surtsey Underwater volcanic System for Thermophiles, Alteration processes and INnovative concretes (SUSTAIN) drilling project at Surtsey volcano, sponsored in part by the International Continental Scientific Drilling Program (ICDP), provides precise observations of the hydrothermal, geochemical, geomagnetic, and microbiological changes that have occurred in basaltic tephra and minor intrusions since explosive and effusive eruptions produced the oceanic island in 1963–1967. Two vertically cored boreholes, to 152 and 192 m below the surface, were drilled using filtered, UV-sterilized seawater circulating fluid to minimize microbial contamination. These cores parallel a 181 m core drilled in 1979. Introductory investigations indicate changes in material properties and whole-rock compositions over the past 38 years. A Surtsey subsurface observatory installed to 181 m in one vertical borehole holds incubation experiments that monitor in situ mineralogical and microbial alteration processes at 25–124 ∘C. A third cored borehole, inclined 55∘ in a 264∘ azimuthal direction to 354 m measured depth, provides further insights into eruption processes, including the presence of a diatreme that extends at least 100 m into the seafloor beneath the Surtur crater. The SUSTAIN project provides the first time-lapse drilling record into a very young oceanic basaltic volcano over a range of temperatures, 25–141 ∘C from 1979 to 2017, and subaerial and submarine hydrothermal fluid compositions. Rigorous procedures undertaken during the drilling operation protected the sensitive environment of the Surtsey Natural Preserve

Thermoactinoamide A, an Antibiotic Lipophilic Cyclopeptide from the Icelandic Thermophilic Bacterium Thermoactinomyces vulgaris

The thermophilic bacterium Thermoactinomyces vulgaris strain ISCAR 2354, isolated from a coastal hydrothermal vent in Iceland, was shown to contain thermoactinoamide A (1), a new cyclic hexapeptide composed of mixed d and l amino acids, along with five minor analogues (2-6). The structure of 1 was determined by one- and two-dimensional NMR spectroscopy, high-resolution tandem mass spectrometry, and advanced Marfey's analysis of 1 and of the products of its partial hydrolysis. Thermoactinoamide A inhibited the growth of Staphylococcus aureus ATCC 6538 with an MIC value of 35 μM. On the basis of literature data and this work, cyclic hexapeptides with mixed d/l configurations, one aromatic amino acid residue, and a prevalence of lipophilic residues can be seen as a starting point to define a new, easily accessible scaffold in the search for new antibiotic agents

Toward a sustainable maze cropping: X-omics support the understanding of the effects of some biotechnological practices

The adoption of more sustainable practices in maize cropping may be hampered by the challenges posed by climate change if the same do not also improve the resilience of the system to more stressing environment. The exploitation of beneficial microorganisms as bioinoculants appears as an environmental-friendly biotechnological tool in maize cropping as they can reduce requirements of inorganic fertilizers by positively influencing soil fertility. Biochar addition to soil is a promising strategy for climate change mitigation and soil fertility improvement. The objectives of this study were to unravel the synergistic effect of co-applied biochar and synthetic microbial consortia (SMC) or arbuscular mycorrhizal fungi on maize growth, soil microbiome and grain metabolome. Field experiments were carried out in two growing seasons in Italy. At different vegetative growth stages, both physiological parameters and soil chemical composition were evaluated. At harvest, yield performance was assessed, and maize kernels were collected to perform global metabolomic profiling. Rhizosphere microbial ecosystem was investigated by 16S metabarcoding sequencing and bioinformatic tools. SMC application did not significantly affect the microbial communities in terms of diversity and richness of species, with a low risk of a long-term impact on the ecology of the indigenous microbial population. However, biochar exerted a great impact on rhizosphere soil microbiome, suggesting that functionalization of biochar with SMC seems a promising approach for microbiome modulation and for enhancing plant growth also in limiting environments. Larger effects were found on the grain at metabolomic level on the presence of different fatty acids, aminoacids, and lipids

Thermoactinoamide A, an Antibiotic Lipophilic Cyclopeptide from the Icelandic Thermophilic Bacterium <i>Thermoactinomyces vulgaris</i>

The thermophilic bacterium <i>Thermoactinomyces vulgaris</i> strain ISCAR 2354, isolated from a coastal hydrothermal vent in Iceland, was shown to contain thermoactinoamide A (<b>1</b>), a new cyclic hexapeptide composed of mixed d and l amino acids, along with five minor analogues (<b>2</b>–<b>6</b>). The structure of <b>1</b> was determined by one- and two-dimensional NMR spectroscopy, high-resolution tandem mass spectrometry, and advanced Marfey’s analysis of <b>1</b> and of the products of its partial hydrolysis. Thermoactinoamide A inhibited the growth of <i>Staphylococcus aureus</i> ATCC 6538 with an MIC value of 35 μM. On the basis of literature data and this work, cyclic hexapeptides with mixed d/l configurations, one aromatic amino acid residue, and a prevalence of lipophilic residues can be seen as a starting point to define a new, easily accessible scaffold in the search for new antibiotic agents