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Drying-rewetting and freezing-thawing legacies on soil microbial communities

ABSTRACT: The sequences are from a laboratory experiment, where we tested how a legacy of freezing-thawing and drying-rewetting cycle affect the microbial community and its response to an additional fluctuation.

PROVIDER: PRJEB40946 | ENA |

REPOSITORIES: ENA

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			Action	DRS
	ERR4760660_1.fastq.gz	Fastqsanger.gz
	ERR4760660_2.fastq.gz	Fastqsanger.gz
	ERR4760670_1.fastq.gz	Fastqsanger.gz
	ERR4760670_2.fastq.gz	Fastqsanger.gz
	ERR4760680_1.fastq.gz	Fastqsanger.gz

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Project description:Purpose: The goal of this study was to determine the microRNA (miRNA) content of extracellular vesicles (EVs) derived from murine mesenchymal stem cells (mMSC), and evaluate reproducibility among distinct EV productions. We also aimed at assessing the effect of freeze-drying on EV miRNA content, by performing sequencing on freeze-dried EVs and calculating statistical difference between unmodified and freeze-dried EVs. Methods: mMSC-derived EVs were obtained from mMSC in culture in reduced serum medium Opti-MEM by differential centrifugation, with a final step at 100,000 g for 110 min at 4°C. EV pellets (freeze-dried (n=3) or not (n=2)) were resuspended in Qiazol lysis buffer and RNA was extracted following RNeasy Micro kit. cDNA libraries for sequencing were prepared using the TruSeq Small RNA Sample Preparation Kit. Amplified cDNA constructs were purified on 6 % PAGE gel and DNA molecules corresponding to 15–50 nucleotide transcripts were excised, eluted from gel, and concentrated. Image analyses and base calling were performed using the HiSeq Control Software and Real-Time Analysis component (Illumina). Before statistical analysis, genes with less than 15 reads (cumulating all the analysed samples) were filtered out. Differentially expressed miRNA were identified using three Bioconductor packages: edgeR, DESeq and DESeq2. Results: Considering miRNAs detected with at least 5 counts (in terms of normalised counts), 339 miRNAs were identified and miRNA content was highly conserved among the two batches tested, with 237 miRNAs out of the 339 present in both batches (70%). Statistical analysis did not evidence statistical difference between unmodified EVs (n=2) and freeze-dried EVs (n=3) (DESeq2, p<0.05). No statistical difference was found using other Bioconductor packages DESeq and edgeR. These results indicated conservation of miRNA content following freeze-drying. Conclusion: mMSC-EV miRNA content was comparable between the two EV productions analysed, indicating reproducibility. Some of the miRNAs identified were consistent with previously published results on MSC-derived EVs. Freeze-drying conserved miRNA content.

Project description:The viability of starter cultures is essential for an adequate contribution to the fermentation process and end-product. Therefore, robustness during processing and storage is an important characteristic of starter culture strains. For instance, during spray drying cells are exposed to heat and oxidative stress, generally resulting in loss of viability. In this study, we exposed the industrially relevant but stress-sensitive Lactococcus lactis strain SK11 to two cycles of heat stress, with intermediate recovery and cultivation at moderate temperatures. After these two cycles of heat exposure, the abundance of robust derivatives was increased as compared with the original culture, which enabled isolation of heat-resistant subpopulations displaying up to 1000-fold enhanced heat stress survival. Moreover, this heat-resistant subpopulation demonstrated an increased survival during spray drying. Derivatives from two independent lineages displayed different transcriptome changes as compared with the wild type strain, indicating that the increased robustness within these lineages was established by different adaptive strategies. Nevertheless, an overlap in differential gene expression in all five derivatives tested in both lineages included three genes in an operon involved in zinc transport. The link between zinc homeostasis and heat stress survival in L. lactis was experimentally established by culturing of the wild type strain SK11 in medium with various levels of zinc ions, which resulted in alterations in heat stress survival phenotypes. This study demonstrates that robust derivatives of a relatively sensitive L. lactis strain can be isolated by repeated exposure to heat stress. Moreover, this work demonstrates that transcriptome analysis of these robust derivatives can provide clues for improvement of the robustness of the original strain. This could boost the industrial application of strains with specific desirable traits but inadequate robustness characteristics.

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Drying-rewetting and freezing-thawing legacies on soil microbial communities

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