Project description:To explore the ecological basis for multiple bacteria species coexistence, we set up three bacteria (Ruegeria pomeroyi DSS-3, Vibrio hepatarius HF70, and Thalassospira sp. HF15), either in monoculture or in co-cultures (in all combinations) for a 8 day growth-dilution cycles. At ~15h of day 4 (P4) and day 8 (P8) of growth-dilution cycles, we examined transcriptomic responses of these bacteria. Differential gene expressions were used to generate hypothesis about ecological and physiological responses of one in the presence of another/other bacteria.
Project description:Effect of fertilization on the temporal dynamics of soil microbial community and multifunctionality along subtropical forest succession
Project description:We compared gene expression in the foregut tissues of two rodent species: Stephen's woodrat (Neotoma stephensi), which harbors a dense foregut microbial community, and the lab rat (Rattus norvegicus), which lacks such a community. We found that woodrats have higher abundances of transcripts associated with smooth muscle processes, specifically a higher expression of the smoothelin-like 1 gene, which may assist in contractile properties of this tissue to retain food material in the foregut chamber. The expression of genes associated with keratinization and cornification exhibited a complex pattern of differences between the two species, suggesting distinct molecular mechanisms for this process in each of the two species. Lab rats exhibited higher abundances of transcripts associated with immune function, likely to inhibit microbial growth in the foregut of this species. Some of our results were consistent with previous findings in ruminants (high expression of facilitative glucose transporters, lower expression of B4galnt2), suggestive of possible convergent evolution, while other results were unclear, and perhaps represent novel host-microbe interactions in rodents. Overall, our results suggest that harboring a foregut microbiota is associated with changes to the functions and host-microbe interactions of the foregut tissues.
Project description:Despite that most microorganisms live as part of community, we have modest knowledge about the interactions among microbial community members in nature, and the implications of those interactions for emergent community properties or ecosystem-relevant functions. To facilitate advances in understanding microbial interactions, we describe a straightforward synthetic community system for interrogating the extracellular interactions among microbial community members. The laboratory-scale system physically separates microbial populations within the community, but allows for chemical interactions via a shared media reservoir. Community goods, including small molecules, extracellular enzymes, and antibiotics, can be assayed using sensitive mass spectrometry, and community member outcomes can be assayed, for example, using flow cytometry, biomass measurements, and transcript analyses. The synthetic community design allows for determining the causes and consequences of community diversity and functional outcomes given manipulation of community membership or structure, abiotic stressors, or temporal dynamics. Because it is versatile to accommodate any artificial or environmental microbiome members, scalable to high-throughput capacity, flexible to an array of experimental designs, and accessible to a variety of laboratories because no specialized or costly components are required, this synthetic community system has the potential to practically advance knowledge of microbial interactions within both natural and artificial communities.
Project description:Coastal marine sediments, as locations of substantial fixed nitrogen loss, are very important to the nitrogen budget and to the primary productivity of the oceans. Coastal sediment systems are also highly dynamic and subject to periodic natural and anthropogenic organic substrate additions. The response to organic matter by the microbial community involved in nitrogen loss processes was evaluated using mesocosms of Chesapeake Bay sediments. Over the course of a 50-day incubation, rates of anammox and denitrification were measured weekly using 15N tracer incubations, and samples were collected for genetic analysis. Rates of both nitrogen loss processes and gene abundances associated with them corresponded loosely, probably because heterogeneities in sediments obscured a clear relationship. The rates of denitrification were stimulated more by the higher organic matter addition, and the fraction of nitrogen loss attributed to anammox slightly reduced. Furthermore, the large organic matter pulse drove a significant and rapid shift in the denitrifier community as determined using a nirS microarray, indicating the diversity of these organisms plays an essential role in responding to anthropogenic inputs. We also suggest that the proportion of nitrogen loss due to anammox in these coastal estuarine sediments may be underestimated due to temporal dynamics as well as from methodological artifacts related to conventional sediment slurry incubation approaches.
Project description:Coastal marine sediments, as locations of substantial fixed nitrogen loss, are very important to the nitrogen budget and to the primary productivity of the oceans. Coastal sediment systems are also highly dynamic and subject to periodic natural and anthropogenic organic substrate additions. The response to organic matter by the microbial community involved in nitrogen loss processes was evaluated using mesocosms of Chesapeake Bay sediments. Over the course of a 50-day incubation, rates of anammox and denitrification were measured weekly using 15N tracer incubations, and samples were collected for genetic analysis. Rates of both nitrogen loss processes and gene abundances associated with them corresponded loosely, probably because heterogeneities in sediments obscured a clear relationship. The rates of denitrification were stimulated more by the higher organic matter addition, and the fraction of nitrogen loss attributed to anammox slightly reduced. Furthermore, the large organic matter pulse drove a significant and rapid shift in the denitrifier community as determined using a nirS microarray, indicating the diversity of these organisms plays an essential role in responding to anthropogenic inputs. We also suggest that the proportion of nitrogen loss due to anammox in these coastal estuarine sediments may be underestimated due to temporal dynamics as well as from methodological artifacts related to conventional sediment slurry incubation approaches. Two color array (Cy3 and Cy5): the universal standard 20-mer oligo is printed to the slide with a 70-mer oligo (an archetype). Environmental DNA sequences (fluoresced with Cy3) within 15% of the 70-mer conjugated to a 20-mer oligo (fluoresced with Cy5) complementary to the universal standard will bind to the oligo probes on the array. Signal is the ratio of Cy3 to Cy5. Three replicate probes were printed for each archetype. Two replicate arrays were run on duplicate targets.
Project description:Here, we successfully used NO as the direct electron acceptor for the enrichment of a microbial community in a continuous bioreactor. The enrichment culture, mainly comprised of two new organisms from the Sterolibacteriaceae family, grew on NO reduction to N2 and formate oxidation, with virtually no accumulation of N2O. The microbial growth kinetics of the enrichment culture as well as its affinity for different N-oxides were determined. In parallel, using metagenomics, metatranscriptomics, and metaproteomics, the biochemical reactions underlying the growth of these microorganisms on NO were investigated. This study demonstrates that microorganisms thrive and can be enriched on NO, and presents new opportunities to study microbial growth on this highly energetic and climate-active molecule that may have been pivotal in the evolution of aerobic respiration.
Project description:The synthetic microbial community used in this study was composed of the major functional guilds (cellulolytic fermenter, sulfate reducer, hydrogenotrophic methanogen and acetoclastic methanogen) that mediate the anaerobic conversion of cellulosic biomass to CH4 and CO2 in wetland soils. The choice of a facultative sulfate-reducing bacterium (Desulfovibrio vulgaris Hildenborough) introduced metabolic versatility and enabled investigations into the community response to sulfate intrusion. The growth status of these multi-species cultures was measured over a week by daily analysis of substrate consumption and product accumulation. The quad-cultures were analyzed with metaproteomics at the end of experiment to characterize the community structure and metabolic activities.