Metagenome-Assembled Genome Sequences Recovered from Epilithic River Biofilm in the Tama River, Japan

Draft genome sequences of putatively novel bacteria were assembled from the metagenome of epilithic biofilm samples collected from the Tama River (Tokyo, Japan). The metagenome contains 44,630,724 sequences, 44,792 contigs, and 48% G+C content. Binning resulted in 31 metagenome-assembled genomes (MAGs) with >50% completeness.

Gut microbiome-wide association study of depression

Depression is one of the most poorly understood diseases due to its elusive pathogenesis. There is an urgency to identify molecular and biological mechanisms underlying depression and the gut microbiome is a novel area of interest. In this study we investigated the relation of fecal microbiome diversity and composition with depression in 1,054 from the Rotterdam Study cohort and validated these findings in the Amsterdam HELIUS cohort in 1,539 subjects. Using supervised and unsupervised machine learning approaches, we identified and replicated the association of several microbial genera. We confirm the association of genus Eggerthella, Subdoligranulum, Coprococcus and family Ruminococcaceae and identify novel bacteria including Sellimonas, Lachnoclostridium, Hungatella, Ruminococcaceae (UCG002,UCG003 and UCG005), LachnospiraceaeUCG001, Eubacterium ventriosum and Ruminococcusgauvreauiigroup associated with depression. These bacteria are known to be involved in the synthesis of glutamate, butyrate, serotonin and gamma amino butyric acid (GABA), which are key neurotransmitters for depression. Our study suggests the gut microbiome composition may play a key role in depression.

Automated analysis of genomic sequences facilitates high-throughput and comprehensive description of bacteria

The study of microbial communities is hampered by the large fraction of still unknown bacteria. However, many of these species have been isolated, yet lack a validly published name or description. The validation of names for novel bacteria requires that the uniqueness of those taxa is demonstrated and their properties are described. The accepted format for this is the protologue, which can be time-consuming to create. Hence, many research fields in microbiology and biotechnology will greatly benefit from new approaches that reduce the workload and harmonise the generation of protologues.We have developed Protologger, a bioinformatic tool that automatically generates all the necessary readouts for writing a detailed protologue. By producing multiple taxonomic outputs, functional features and ecological analysis using the 16S rRNA gene and genome sequences from a single species, the time needed to gather the information for describing novel taxa is substantially reduced. The usefulness of Protologger was demonstrated by using three published isolate collections to describe 34 novel taxa, encompassing 17 novel species and 17 novel genera, including the automatic generation of ecologically and functionally relevant names. We also highlight the need to utilise multiple taxonomic delineation methods, as while inconsistencies between each method occur, a combined approach provides robust placement. Protologger is open source; all scripts and datasets are available, along with a webserver at www.protologger.de

Comparison of culture-based strategies for isolating bacteria from the porcine intestine

The isolation of bacteria that represent the diversity of autochthonous taxa in the gastrointestinal tract is necessary to fully ascertain function, but the majority of bacterial species inhabiting the intestines of mammals are fastidious, and thus challenging to isolate. The goal of the current study was to isolate a diverse assemblage of bacteria from the intestine of pigs as a model animal, and to comparatively examine various novel and traditional isolation strategies. Methods used included long-term enrichments, direct plating, a modified Ichip, as well as ethanol and Tyndallization treatment of samples to select for endospore-forming taxa. A total of 234 taxa (91 previously uncultured) comprising 80 genera and seven phyla were isolated from mucosal and luminal samples from the ileum, cecum, ascending colon, and spiral colon removed from animals under anesthesia. The diversity of bacteria isolated from the large intestine was less than detected by next-generation sequence analysis. Long-term enrichments yielded the greatest diversity of recovered bacteria (Shannon’s index [SI] = 4.7). Methods designed to isolate endospore-forming bacteria produced the lowest diversity (SI ≤ 2.7), with Tyndallization yielding a lower diversity than the ethanol method. However, the isolation frequency of previously uncultured bacteria was greatest for ethanol-treated samples (41.9%) and the Ichip method (32.5%). The goal of recovering a diverse collection of enteric bacteria was achieved. Importantly, study findings demonstrate that it is necessary to use a combination of methods in concert to isolate bacteria that are representative of the diversity within the intestines of mammals. IMPORTANCE This work determined that using a combination of isolation methods is necessary to increase the diversity of bacteria recovered from the intestines of monogastric mammals. Direct plating methods have traditionally been used to isolate enteric bacteria, and recent methods (e.g. diffusion methods [i.e. Ichip] or differential isolation of endospore-forming bacteria) have been suggested to be superior at increasing diversity, including the recovery of previously uncultured taxa. We showed that long-term enrichment of samples using a variety of media isolated the most diverse and novel bacteria. Application of the Ichip method delivered similar diversity of bacteria to enrichment and direct plating methods. Methods that selected for endospore-forming bacteria generated collections that differed in composition to other methods with reduced diversity. However, the ethanol treatment frequently isolated novel bacteria. By using a combination of methods in concert, a diverse collection of enteric bacteria was generated for ancillary experimentation.