Nanotube-mediated cross-feeding couples the metabolism of interacting bacterial cells, bioRxiv, 2017-03-07
ABSTRACTBacteria frequently engage in cross-feeding interactions that involve an exchange of metabolites with other micro- or macroorganisms. The often obligate nature of these associations, however, hampers manipulative experiments, thus limiting our mechanistic understanding of the ecophysiological consequences that result for the organisms involved. Here we address this issue by taking advantage of a well-characterised experimental model system, in which auxotrophic genotypes of E. coli derive essential amino acid from prototrophic donor cells using intercellular nanotubes. Surprisingly, donor-recipient cocultures revealed that the mere presence of auxotrophic genotypes in coculture was sufficient to increase amino acid production levels in donor cells. Subsequent experiments unravelled that this effect was due to the depletion of amino acid concentrations in the cytoplasm of donor cells, which delayed feedback inhibition of the corresponding amino acid biosynthetic pathway. This finding indicates that in newly established mutualistic associations, an intercellular regulation of exchanged metabolites can simply emerge from the architecture of the underlying biosynthetic pathways, rather than through the evolution of new regulatory mechanisms. Taken together, our results show that a single loss-of-function mutation can physiologically couple the metabolism of two cross-feeding cells in a source-sink-like relationship.
biorxiv microbiology 100-200-users 2017Preprinting Microbiology, bioRxiv, 2017-02-24
AbstractThe field of microbiology has experienced significant growth due to transformative advances in technology and the influx of scientists driven by a curiosity to understand how microbes sustain myriad biochemical processes that maintain the Earth. With this explosion in scientific output, a significant bottleneck has been the ability to rapidly disseminate new knowledge to peers and the public. Preprints have emerged as a tool that a growing number of microbiologists are using to overcome this bottleneck. Posting preprints can help to transparently recruit a more diverse pool of reviewers prior to submitting to a journal for formal peer-review. Although use of preprints is still limited in the biological sciences, early indications are that preprints are a robust tool that can complement and enhance peer-reviewed publications. As publishing moves to embrace advances in internet technology, there are many opportunities for preprints and peer-reviewed journals to coexist in the same ecosystem.
biorxiv microbiology 0-100-users 2017Evaluation of Oxford Nanopore MinIONTM Sequencing for 16S rRNA Microbiome Characterization, bioRxiv, 2017-01-13
AbstractIn this manuscript we evaluate the potential for microbiome characterization by sequencing of near-full length 16S rRNA gene region fragments using the Oxford Nanopore MinION (hereafter ‘Nanopore’) sequencing platform. We analyzed pure-culture E. coli and P. fluorescens, as well as a low-diversity mixed community sample from hydraulic fracturing produced water. Both closed and open reference operational taxonomic unit (OTU) picking failed, necessitating the direct use of sequences without OTU picking. The Ribosomal Database Project classifier against the Green Genes database was found to be the optimal annotation approach, with average pure-culture annotation accuracies of 93.8% and 82.0% at the phyla and genus levels, respectively. Comparative analysis of an environmental sample using Nanopore and Illumina MiSeq sequencing identified high taxonomic similarity when using a weighted metric (Bray-Curtis), and significantly reduced similarity when using an unweighted metric (Jaccard). These results highlight the great potential of Nanopore sequencing to analyze broad microbial community trends, and the challenge of applying Nanopore sequencing to discern rare taxa in mixed microbial communities. Finally, we observed that between-run carryover following washes on the same flowcell accounted for >10% of sequence reads, necessitating future development to either prevent carryover or filter sequences of interest (e.g. barcoding).
biorxiv microbiology 0-100-users 2017In-field metagenome and 16S rRNA gene amplicon nanopore sequencing robustly characterize glacier microbiota, bioRxiv, 2016-09-08
ABSTRACTIn the field of observation, chance favours only the prepared mind (Pasteur). Impressive developments in genomics have led microbiology to its third “Golden Age”. However, conventional metagenomics strategies necessitate retrograde transfer of samples from extreme or remote environments for later analysis, rendering the powerful insights gained retrospective in nature, striking a contrast with Pasteur’s dictum. Here we implement highly portable USB-based nanopore DNA sequencing platforms coupled with field-adapted environmental DNA extraction, rapid sequence library generation and off-line analyses of shotgun metagenome and 16S ribosomal RNA gene amplicon profiles to characterize microbiota dwelling within cryoconite holes upon Svalbard glaciers, the Greenland Ice Sheet and the Austrian Alps. We show in-field nanopore sequencing of metagenomes captures taxonomic composition of supraglacial microbiota, while 16S rRNA Furthermore, comparison of nanopore data with prior 16S rRNA gene V1-V3 pyrosequencing from the same samples, demonstrates strong correlations between profiles obtained from nanopore sequencing and laboratory based sequencing approaches. gene amplicon sequencing resolves bacterial community responses to habitat changes. Finally, we demonstrate the fidelity and sensitivity of in-field sequencing by analysis of mock communities using field protocols. Ultimately, in-field sequencing potentiated by nanopore devices raises the prospect of enhanced agility in exploring Earth’s most remote microbiomes.
biorxiv microbiology 100-200-users 2016Transcriptome analysis in whole blood reveals increased microbial diversity in schizophrenia, bioRxiv, 2016-06-08
AbstractThe role of the human microbiome in health and disease is increasingly appreciated. We studied the composition of microbial communities present in blood across 192 individuals, including healthy controls and patients with three disorders affecting the brain schizophrenia, amyotrophic lateral sclerosis and bipolar disorder. By using high quality unmapped RNA sequencing reads as candidate microbial reads, we performed profiling of microbial transcripts detected in whole blood. We were able to detect a wide range of bacterial and archaeal phyla in blood. Interestingly, we observed an increased microbial diversity in schizophrenia patients compared to the three other groups. We replicated this finding in an independent schizophrenia case-control cohort. This increased diversity is inversely correlated with estimated cell abundance of a subpopulation of CD8+ memory T cells in healthy controls, supporting a link between microbial products found in blood, immunity and schizophrenia.
biorxiv microbiology 0-100-users 2016First detection of Zika virus in neotropical primates in Brazil a possible new reservoir, bioRxiv, 2016-04-21
Samples from sera and oral swabs from fifteen marmosets (Callithrix jacchus) and nine capuchin-monkeys (Sapajus libidinosus) captured in Ceara State in Brazil were tested for Zika virus. Samples were positive by Real time PCR and sequencing of the amplified product from a capuchin monkey showed 100% similarity to other ZIKV from South America. This is the first report on ZIKV detection among Neotropical primates.
biorxiv microbiology 100-200-users 2016