Volatile organic compounds in the salt-lake sediments of the Tibet Plateau influence prokaryotic diversity and community assembly

Exploring eutrophic effects of marine sediments underneath fish cage farms: Insights from changes in eukaryotic and bacterial communities and volatile organic compounds

The roles of bacteria and eukaryotes in the sediments of fish farms have received considerable attention. High concentrations of volatile organic compounds (VOCs) in eutrophic sediments pose significant problems in the marine environment. However, the identification of VOCs and their association with bacteria and eukaryotes in marine sediments from fish farms remain unexplored. By using third-generation 18 s/16 s sequencing with bacterial absolute quantity and headspace solid-phase microextraction coupled with gas chromatography mass spectrometry (HS-SPME-GC-MS), we investigated benthic community structure and VOCs composition in the sediments from five large yellow croaker farms in China (DJ, DC, DT, NJ, and ND), as well as geological and chemical changes. The ND sediments, characterized as mud substrates with the highest moisture and nutrient levels, were dominated by ciliates and flagellates, whereas typical benthic organisms such as echinoderms, annelids, and cnidarians were absent in other farming areas. These sediments had higher bacterial density and increased proportions of Desulfuromonadia and Desulfobacterota but lower proportions of Campylobacterota compared to other areas. Additionally, ND sediments exhibited the highest VOC content, with 2-Octen-1-ol being the most abundant compound, characterized by mushroom-like, earthy, fishy, rancid, and metallic odors that may negatively influence the flavor of large yellow croaker. We identified 76 differential VOCs, most of which showed a positive correlation with bacteria, ciliates, and flagellates, while some VOCs showed a positive correlation with the annelid Aurospio foodbancsia and the cnidarian Diadumene cincta. Our study is the first to elucidate the complex interactions of benthic organisms and VOCs during the eutrophication process in sediments from cage fish farms, providing potential biomarkers for ecosystem monitoring.

Volatile organic compounds (VOCs) in terrestrial extreme environments: implications for life detection beyond Earth

Covering: 1961 to 2024Discovering and identifying unique natural products/biosignatures (signatures that can be used as evidence for past or present life) that are abundant, and complex enough that they indicate robust evidence of life is a multifaceted process. One distinct category of biosignatures being explored is organic compounds. A subdivision of these compounds not yet readily investigated are volatile organic compound (VOCs). When assessing these VOCs as a group (volatilome) a fingerprint of all VOCs within an environment allows the complex patterns in metabolic data to be unravelled. As a technique already successfully applied to many biological and ecological fields, this paper explores how analysis of volatilomes in terrestrial extreme environments could be used to enhance processes (such as metabolomics and metagenomics) already utilised in life detection beyond Earth. By overcoming some of the complexities of collecting VOCs in remote field sites, a variety of lab based analytical equipment and techniques can then be utilised. Researching volatilomics in astrobiology requires time to characterise the patterns of VOCs. They must then be differentiated from abiotic (non-living) signals within extreme environments similar to those found on other planetary bodies (analogue sites) or in lab-based simulated environments or microcosms. Such an effort is critical for understanding data returned from past or upcoming missions, but it requires a step change in approach which explores the volatilome as a vital additional tool to current 'Omics techniques.

SALINITY-Induced Changes in Diversity, Stability, and Functional Profiles of Microbial Communities in Different Saline Lakes in Arid Areas

Saline lakes, characterized by high salinity and limited nutrient availability, provide an ideal environment for studying extreme halophiles and their biogeochemical processes. The present study examined prokaryotic microbial communities and their ecological functions in lentic sediments (with the salinity gradient and time series) using 16S rRNA amplicon sequencing and a metagenomic approach. Our findings revealed a negative correlation between microbial diversity and salinity. The notable predominance of Archaea in high-salinity lakes signified a considerable alteration in the composition of the microbial community. The results indicate that elevated salinity promotes homogeneous selection pressures, causing substantial alterations in microbial diversity and community structure, and simultaneously hindering interactions among microorganisms. This results in a notable decrease in the complexity of microbial ecological networks, ultimately influencing the overall ecological functional responses of microbial communities such as carbon fixation, sulfur, and nitrogen metabolism. Overall, our findings reveal salinity drives a notable predominance of Archaea, selects for species adapted to extreme conditions, and decreases microbial community complexity within saline lake ecosystems.