Project description:Anthropogenic activities have dramatically increased the inputs of reactive nitrogen (N) into terrestrial ecosystems, with potentially important effects on the soil microbial community and consequently soil C and N dynamics. Our analysis of microbial communities in soils subjected to 14 years of 7 g N m-2 year-1 Ca(NO3)2 amendment in a Californian grassland showed that the taxonomic composition of bacterial communities, examined by 16S rRNA gene amplicon sequencing, was significantly altered by nitrate amendment, supporting the hypothesis that N amendment- induced increased nutrient availability, yielded more fast-growing bacterial taxa while reduced slow-growing bacterial taxa. Nitrate amendment significantly increased genes associated with labile C degradation (e.g. amyA and xylA) but had no effect or decreased the relative abundances of genes associated with degradation of more recalcitrant C (e.g. mannanase and chitinase), as shown by data from GeoChip targeting a wide variety of functional genes. The abundances of most N cycling genes remained unchanged or decreased except for increases in both the nifH gene (associated with N fixation), and the amoA gene (associated with nitrification) concurrent with increases of ammonia-oxidizing bacteria. Based on those observations, we propose a conceptual model to illustrate how changes of functional microbial communities may correspond to soil C and N accumulation.
Project description:Chemical modifications to the tails of histone proteins act as gene regulators that play a pivotal role in adaptive responses to environmental stress. Determining the short and long term kinetics of histone marks is essential for understanding their functions in adaptation. We used Caenorhabditis elegans as a model organism to study the histone modification kinetics in response to environmental stress, taking advantage of their ability to live in both terrestrial and aquatic environments. We investigated the multigenerational genome-wide dynamics of five histone marks (H3K4me3, H3K27me3, H4K20me1, H3K36me1, and H3K9me3) by maintaining P0 animals on terrestrial (agar plates), F1 in aquatic cultures, and F2 back on terrestrial environments. We determined the distributions of histone marks in the gene promoter regions and found that H4K20me1, H3K36me1, and H3K9me3 showed up to eleven-fold differences in density, whereas H3K4me3 and H3K27me3 remained highly constant during adaptation from terrestrial to aquatic environments. Furthermore, we predicted that up to five combinations of histone marks can co-occupy single gene promoters and confirmed the colocalization of these histone marks by structured illumination microscopy. The co-occupancy increases with environment changes and different co-occupancy patterns contribute to variances in gene expressions and thereby presents a supporting evidence for the histone code hypothesis.
Project description:Study abstract: Axolotl salamanders (Ambystoma mexicanum) remain aquatic in their natural state, during which biomechanical forces on their diarthrodial limb joints are likely reduced relative to salamanders living on land. However, even as sexually mature adults, these amphibians can be induced to metamorphose into a weight-bearing terrestrial stage by environmental stress or the exogenous administration of thyroxine hormone. In some respects, this aquatic to terrestrial transition of axolotl salamanders through metamorphosis may model developmental and changing biomechanical skeletal forces in mammals during the prenatal to postnatal transition at birth and in the early postnatal period. To assess differences in the appendicular skeleton as a function of metamorphosis, anatomical and gene expression parameters were compared in skeletal tissues between aquatic and terrestrial axolotls that were the same age and genetically full siblings. The length of long bones and area of cuboidal bones in the appendicular skeleton, as well as the cellularity of cartilaginous and interzone tissues of femorotibial joints were generally higher in aquatic axolotls compared to their metamorphosed terrestrial siblings. A comparison of steady state mRNA transcripts encoding aggrecan core protein (ACAN), type II collagen (COL2A1), and growth and differentiation factor 5 (GDF5) in femorotibial cartilaginous and interzone tissues did not reveal any significant differences between aquatic and terrestrial axolotls. RNAseq samples: Total RNA was isolated from whole body tissue samples of Mexican axolotl salamanders (Ambystoma mexicanum) at the following developmental stages: Embryo at the tail bud stage, newly hatched larva, larva at the limb bud stage, juvenile at 8.5 centimeters, and adult using variations of guanidinium-based protocols. RNA quantity, purity, and integrity of both the individual samples and the resulting pool were determined with an Agilent 2100 Bioanalyzer using the Eukaryotic Total RNA nano series II analysis kit. The pooled RNA sample was poly-A selected and used for Illumina random priming directional library prep. Four lanes were sequenced only on one end providing single end reads and 4 lanes were sequenced at both ends giving paired-end reads. The library was sequenced on an Illumina HiSeq 2000 for 75bp reads producing 147,248,512 single end reads and 2 x 153,254,667 paired-end reads.
Project description:Analysis of aquatic microbial communities revealed that parts of its diversity consist of bacteria with cell sizes of ~0.1 μm. Such bacteria can show genomic reductions and metabolic dependencies with other bacteria. So far, no study investigated if such bacteria exist in terrestrial environments e.g. soil. Here, we show that such bacteria also exist in soil. The isolated bacteria was identified as Hylemonella gracilis.Co-culture assays with phylogenetically different soil bacteria revealed that H. gracilis grows better when co-cultured with other soil bacteria. Transcriptomics and metabolomics showed that H. gracilis was able to change gene expression, behavior, and biochemistry of the interacting bacteria without direct contact. Our study revealed that bacteria are present in soil that can pass through 0.1 µm filters. Such bacteria may have been overlooked in previous research on soil microbial communities and may contribute to the symbiosis of soil bacterial communities.
Project description:Enclosure experiments are frequently used to investigate the impact of changing environmental conditions on microbial assemblages. Yet, the question how individual members of bacterial communities respond to challenges posed by the incubation itself remained unanswered. We used metaproteomic profiling, 16S rRNA gene analysis and high nucleic acid content analysis to monitor bacterial communities during long-term incubations (55 days) under marine (M1), mesohaline (M2) and oligohaline (M3) conditions with and without the addition of terrestrial dissolved organic matter. Our results showed that early in the experiment (after one week, T2), bacterial communities were highly diverse and their composition differed significantly between marine, mesohaline and oligohaline conditions. Controls (BS) and tDOM-treated samples (FKB) showed notable differences at this stage. In contrast, in the late phase of the experiment (after 55 days, T6), bacterial communities in both, manipulated and untreated marine and mesohaline enclosures were quite similar to each other and were dominated by gammaproteobacterial Spongiibacter. In the oligohaline enclosure, the actinobacterial hgc-I clade was very abundant in this phase. Our findings suggest that individual capacities, e.g. grazing-resistance, antibiotics production, and the ability to access alternative carbon sources may enable Spongiibacter and hgc-I clade members to successfully prevail during long-term incubations. Bacterial community composition in enclosure experiments thus seems to be strongly influenced by the individual inherent bacterial strategies to cope with the incubation as such. Researchers intending to investigate the effects of manipulation on complex microbial communities may therefore want to use short incubation periods or sophisticated systems that avoid these unspecific effects of long-term experiments.
Project description:Background: While the luminal microbiome composition in the human cervicovaginal tract has been defined, the presence and impact of tissue-adherent ectocervical microbiota remain incompletely understood. Studies of luminal and tissue-associated bacteria in the gastrointestinal tract suggest that they may have distinct roles in health and disease. Here, we performed a multi-omics characterization of paired luminal and tissue samples collected from a clinically well-characterized cohort of Kenyan women. Results: We identified a tissue-adherent bacterial microbiome, with a higher alpha diversity than the luminal microbiome, in which dominant genera overall included Gardnerella and Lactobacillus, followed by Prevotella, Atopobium, and Sneathia. About half of the L. iners dominated luminal samples had a corresponding Gardnerella dominated tissue microbiome. Broadly, the tissue-adherent microbiome was associated with fewer differentially expressed host genes than the luminal microbiome. Gene set enrichment analysis revealed that L. crispatus-dominated tissue-adherent communities were associated with protein translation and antimicrobial activity, whereas a highly diverse microbiome was associated with epithelial remodeling and pro-inflammatory pathways. Communities dominated by L. iners and Gardnerella were associated with low host transcriptional activity. Tissue-adherent microbiomes dominated by Lactobacillus and Gardnerella correlated with host protein profiles associated with epithelial barrier stability, and with a more pro-inflammatory profile for the Gardnerella-dominated microbiome group. Tissue samples with a highly diverse composition had a protein profile representing cell proliferation and pro-inflammatory activity. Conclusion: We identified ectocervical tissue-adherent bacterial communities in all study participants. These communities were distinct from cervicovaginal luminal microbiota in a significant proportion of individuals. This difference could possibly explain that L. iners dominant luminal communities have a high probability of transitioning to high diverse bacterial communities including high abundance of Gardnerella. By performing integrative multi-omics analyses we further revealed that bacterial communities at both sites correlated with distinct host gene expression and protein levels. The tissue-adherent bacterial community is similar to vaginal biofilms that significantly impact women’s reproductive and sexual health.
2023-02-10 | GSE194276 | GEO
Project description:Bacterial communities of moss biocrusts and moss-removed soils
Project description:The diversity and environmental distribution of the nosZ gene, which encodes the enzyme responsible for the consumption of nitrous oxide, was investigated in marine and terrestrial environments using a functional gene microarray. The microbial communities represented by the nosZ gene probes showed strong biogeographical separation, with communities from surface ocean waters and agricultural soils significantly different from each other and from those in oceanic oxygen minimum zones. Atypical nosZ genes, usually associated with incomplete denitrification pathways, were detected in all the environments, including surface ocean waters. The abundance of nosZ genes, as estimated by quantitative PCR, was highest in the agricultural soils and lowest in surface ocean waters.