Biology subjects

O'Flaherty, V.

Publications and source records attributed to O'Flaherty, V..

5 recordsLinked to original sources

bioRxiv2021

ASSEMBLY AND DYNAMICS OF MICROBIAL COMMUNITIES IN GRANULAR, FIXED-BIOFILM AND PLANKTONIC METHANOGENIC MICROBIOMES VALORIZING LONG CHAIN FATTY ACID (LCFA)-RICH WASTEWATER

Distinct microbial assemblages are engineered in anaerobic digestion (AD) reactors to drive sequential conversions of organics to methane. The spatio-temporal development of three such assemblages (granules, biofilms, planktonic) derived from the same inoculum was studied in replicated bioreactors treating long-chain fatty acids (LCFA)-rich wastewater at 20{degrees}C at hydraulic retention times (HRTs) of 12-72 h. We found granular, biofilm and planktonic assemblages differentiated by diversity, structure, and assembly mechanisms; demonstrating a spatial compartmentalisation of the microbiomes from the initial community reservoir. Our analysis linked abundant Methanosaeta and Syntrophaceae-affiliated taxa (Syntrophus and uncultured) to their putative, active roles in syntrophic LCFA bioconversion. LCFA loading rates (stearate, palmitate), and HRT, were significant drivers shaping microbial community dynamics and assembly. This study of the archaea and syntrophic bacteria actively valorising LCFAs at short HRTs and 20{degrees}C will help uncover the microbiology underpinning anaerobic bioconversions of fats, oil and grease. HighlightsO_LIGranular, biofilm and planktonic assemblages developed from the same seed reservoir C_LIO_LIThree assemblages forming metacommunity differed in diversity and composition C_LIO_LIMultiple null models applied to quantify deterministic and stochastic mechanisms C_LIO_LIDominant, active role of acetoclastic Methanosaeta confirmed in granules and biofilm C_LIO_LIDynamic, non-core-microbiome taxa correlated with environmental variables C_LI

microbiology↗

bioRxiv2021

Mining underutilized whole-genome sequencing projects to improve 16S rRNA databases

Current approaches to interpreting 16S rDNA amplicon data are hampered by several factors. Among these are database inaccuracy or incompleteness, sequencing error, and biased DNA/RNA extraction. Existing 16S rRNA databases source the majority of sequences from deposited amplicon sequences, draft genomes, and complete genomes. Most of the draft genomes available are assembled from short reads. However, repeated ribosomal regions are notoriously difficult to assemble well from short reads, and as a consequence the short-read-assembled 16S rDNA region may be an amalgamation of different loci within the genome. This complicates high-resolution community analysis, as a draft genomes 16S rDNA sequence may be a chimera of multiple loci; in such cases, the draft-derived sequences in a database may not represent a 16S rRNA sequence as it occurs in biology. We present Focus16, a pipeline for improving 16S rRNA databases by mining NCBIs Sequence Read Archive for whole-genome sequencing runs that could be reassembled to yield additional 16S rRNA sequences. Using riboSeed (a genome assembly tool for correcting rDNA misassembly), Focus16 provides a way to augment 16S rRNA databases with high-quality re-assembled sequences. In this study, we augmented the widely-used SILVA 16S rRNA database with the novel sequences disclosed by Focus16 and re-processed amplicon sequences from several benchmarking datasets with DADA2. Using this augmented SILVA database increased the number of amplicon sequence variants that could be assigned taxonomic annotations. Further, fine-scale classification was improved by revealing ambiguities. We observed, for example, that amplicon sequence variants (ASVs) may be assigned to a specific genus where Focus16-correction would indicate that the ASV is represented in two or more genera. Thus, we demonstrate that improvements can be made to taxonomic classification by incorporating these carefully re-assembled 16S rRNA sequences, and we invite the community to expand our work to augment existing 16S rRNA reference databases such as SILVA, GreenGenes, and RDP.

bioinformatics↗

bioRxiv2020

Circular Economy of Anaerobic Biofilm Microbiomes: A Meta-Analysis Framework for Re-exploration of Amplicon Sequencing Data

Use of high-throughput sequencing is widespread in efforts to understand the microbial communities in natural and engineered systems. Many built ecosystems, in particular those used for engineered wastewater treatment, have harnessed the metabolic capacity of complex microbial communities for the effective removal and recovery of organic pollutants. Recent efforts to better understand and precisely engineer such systems have increasingly used high-throughput sequencing to map the structure and function of wastewater treatment microbiomes. An enormous amount of data is readily available on online repositories such as the National Center for Biotechnology Information Short Read Archive (NCBI SRA). Here, we describe and provide an optimised meta-analysis workflow to utilise this resource to collate heterogenous studies together for anaerobic digestion research. We analysed 16S rRNA gene Illumina Miseq amplicon sequencing data from 31 anaerobic digestion studies (from high-rate digesters), including >1,300 samples. Additionally, we compare several methodological choices: extraction method, v-region, taxonomical database, and the classifier. We demonstrate that collation of data from multiple v-regions can be achieved by using only the taxa for which sequences are available in the reference databases, without losses in diversity trends. This is made possible by focusing on alternative strategies for taxonomic assignments, namely, bayesian lowest common ancestor (BLCA) algorithm which offers increased resolution to the traditional naive bayesian classifier (NBC). While we demonstrate this using an anaerobic digestion wastewater treatment dataset, this methodology can be translated to perform meta-analysis on amplicon sequences in any field. These findings not only provide a roadmap for meta-analysis in any field, but additionally provide an opportunity to reuse extensive data resources to ultimately advance knowledge of wastewater treatment systems. ImportanceIn this study, we have combined sequencing data from 31 individual studies with the purpose of identifying a meta-analysis workflow which can accurately collate data derived from sequencing different v-regions with minimal data loss and more accurate diversity patterns. While we have used Anaerobic Digestion (AD) communities for our proof-of-concept, our workflow (Fig 1) can be translated to any Illumina MiSeq meta-analysis study, in any field. Thereby, we provide the foundation for intensive data mining of existing amplicon sequencing resources. Such data-mining can provide a global perspective on complex microbial communities. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=110 SRC="FIGDIR/small/424166v1_fig1.gif" ALT="Figure 1"> View larger version (54K): org.highwire.dtl.DTLVardef@11fe518org.highwire.dtl.DTLVardef@f9a6eeorg.highwire.dtl.DTLVardef@3e5af0org.highwire.dtl.DTLVardef@1c45734_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOFigure 1.C_FLOATNO Overview of the meta-analysis workflow to assess the protocols used in the analysis of AD microbiomes. C_FIG Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=120 SRC="FIGDIR/small/424166v1_ufig1.gif" ALT="Figure 1"> View larger version (40K): org.highwire.dtl.DTLVardef@1392216org.highwire.dtl.DTLVardef@1ecd922org.highwire.dtl.DTLVardef@a35894org.highwire.dtl.DTLVardef@c7fc0_HPS_FORMAT_FIGEXP M_FIG C_FIG

microbiology↗

bioRxiv2019

Organic soil amendment with Spent Mushroom Substrate results in fungal colonisation, alters bacterial-fungal co-occurrence patterns and improves plant productivity.

In agricultural systems based on organic fertilisers, the activity of prokaryotes and fungi is essential for degradation of complex substrates and release of nutrients for plant uptake. Understanding the dynamics of microbial communities in these systems is, therefore, desirable for designing successful management strategies aiming to optimise nutrient availability and to improve plant productivity. Of particular interest is how the microbial inoculum provided by an organic substrate persists in the soil and interacts with soil and plant microbiomes, as these processes may affect the long-term benefits of organic amendments. We aimed to investigate how these dynamics occurred in soil treated with stabilised spent mushroom substrate (SMS), a soil amendment rich in nutrients and complex organic matter. We carried out a 14 weeks soil trial to assess the plant growth promoting properties of the SMS and to monitor the successional processes of the resulting SMS-soil communities compared to a mineral amended control. Bacterial and fungal communities were analysed by high-throughput sequencing at both DNA and RNA (cDNA) levels. Using a combination of computational tools, including SourceTracker and Network analysis, we assessed the persistence of SMS-derived taxa in soil, and the changes in co-occurrence patterns and microbial community structure over time. Prokaryotic and fungal communities presented remarkably distinct trajectories following SMS treatment. The soil prokaryotic communities displayed higher levels of resilience to the changes introduced by SMS treatment and rapidly tended toward a soil-like profile, with low persistence of SMS-derived prokaryotes. In contrast, the SMS fungal community had greater success in soil colonisation during the time monitored. SMS treatment promoted an increase in the participation of fungi in the highly connected fraction of the active community, including fungal taxa of SMS origin. We observed the presence of highly connected microbial guilds, composed by fungal and bacterial taxa with reported capabilities of complex organic matter degradation. Many of these taxa were also significantly correlated with the organic matter content and plant yield, suggesting that these highly connected taxa may play key roles not only in the community structure, but also in the plant-soil system under organic fertilisation.

microbiology↗

bioRxiv2019

The potential for polyphosphate metabolism in Archaea and anaerobic polyphosphate formation in Methanosarcina mazei.

Inorganic polyphosphate (polyP) is ubiquitous across all forms of life, but the study of its metabolism has been mainly confined to bacteria and yeasts. Few reports detail the presence and accumulation of polyP in Archaea, and little information is available on its functions and regulation. Here, we report that homologs of bacterial polyP metabolism proteins are present across the major taxa in the Archaea, suggesting that archaeal populations may have a greater contribution to global phosphorus cycling than has previously been recognised. We also demonstrate that polyP accumulation can be induced under strictly anaerobic conditions, in response to changes in phosphate (Pi) availability, i.e. Pi starvation, followed by incubation in Pi replete media (overplus), in cells of the methanogenic archaeon Methanosarcina mazei. Pi-starved M. mazei cells increased transcript abundance of the PHO-regulated alkaline phosphatase (phoA) gene and of the high-affinity phosphate transport (pstSCAB-phoU) operon: no increase in polyphosphate kinase 1 (ppk1) transcript abundance was observed. Subsequent incubation of Pi-starved M. mazei cells under Pi replete conditions, led to a 237% increase in intracellular polyphosphate content and a >5.7-fold increase in ppk1 gene transcripts. Ppk1 expression in M. mazei thus appears not to be under classical PHO regulon control.

microbiology↗