Abstract
To obtain an accurate picture of microbial processes is essential for in-depth understanding of the dynamics of microbial communities and metabolic potentials. In this study, an apparatus for automatic multiple in situ nucleic acid collections (MISNAC) loaded and controlled by a lander was designed and applied for in situ microbial filtration, cell lysis and nucleic acid collection at different time points during three cruises in the South China Sea. The MISNAC apparatus completed 390 L in situ water filtration and collected a total of 1,176 ng DNA with six working units in four deployments at ~1,000 m depth. Microbial community structures in water samples obtained by the MISNAC and in situ microbial filtration and fixation (ISMIFF) apparatus, respectively, were compared by analyzing sequences of 16S rRNA amplicons. The result showed that these communities were largely consistent, regardless of the differences in the communities in the samples from different cruises and time points. In addition, the transcriptomes of the samples collected by the MISANC and a Niskin bottle dramatically differed in abundance and diversity of 16S rRNA gene reads, indicating that more in situ RNA molecules were preserved by the MISNAC, compared to the Niskin. The application of the MISNAC apparatus paved the way to time-series changes of deep-sea microorganisms and their response to various environmental factors.
Highlights
The oceans, as the habitats for a vast variety of organisms, are still mysterious for us
To examine the in situ nucleic acid collection abilities of the multiple in situ nucleic acid collections (MISNAC) apparatus in the deep-sea zone, three research cruises were conducted at ∼1,000 m depth in the South China Sea (SCS) in June–July, 2018 and September, 2019 (Supplementary Figure S1)
The MISNAC apparatus could complete the nucleic acid collection of nine water filtrations in one launch, only up to three of MISNAC units were used in this study in one launch due to time limitation in the cruises
Summary
The oceans, as the habitats for a vast variety of organisms, are still mysterious for us. It is remarkable that diverse biological communities playing vital roles in biogeochemical cycling were identified at the different layers of the oceans (Azam et al, 1983). Deep-sea planktonic microorganisms can survive in even tens of thousands of meters below the sea surface, with a striking feature of dark, high-pressure environment (Eloe et al, 2011; Nunoura et al, 2016). Sampling activities at the different depths and sites in the oceans have been conducted, but the collected samples still could not meet the requirement to capture the subtle changes of the deep-sea ecosystems. Because the majority of microorganisms in the deep-sea environment are not yet culturable, the ‘dark matter’ microbes in the deep waters were
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