Cobian-Guemes, A. G. | Search bioRxiv

bioRxiv2019

A Distinct Contractile Injection System Found in a Majority of Adult Human Microbiomes

An imbalance of normal bacterial groups such as Bacteroidales within the human gut is correlated with diseases like obesity. A current grand challenge in the microbiome field is to identify factors produced by normal microbiome bacteria that cause these observed health and disease correlations. While identifying factors like a bacterial injection system could provide a missing explanation for why Bacteroidales correlates with host health, no such factor has been identified to date. The lack of knowledge about these factors is a significant barrier to improving therapies like fecal transplants that promote a healthy microbiome. Here we show that a previously ill-defined Contractile Injection System is carried in the gut microbiome of 99% of individuals from the United States and Europe. This type of Contractile Injection System, we name here Bacteroidales Injection System (BIS), is related to the contractile tails of bacteriophage (viruses of bacteria) and have been described to mediate interactions between bacteria and diverse eukaryotes like amoeba, insects and tubeworms. Our findings that BIS are ubiquitous within adult human microbiomes suggest that they shape host health by mediating interactions between Bacteroidales bacteria and the human host or its microbiome.

microbiology↗

bioRxiv2019

Efficient whole genome sequencing of influenza A viruses

The constant threat of emergence for novel pathogenic influenza A viruses with pandemic potential, makes full-genome characterization of circulating influenza viral strains a high priority, allowing detection of novel and re-assorting variants. Sequencing the full-length genome of influenza A virus traditionally required multiple amplification rounds, followed by the subsequent sequencing of individual PCR products. The introduction of high-throughput sequencing technologies has made whole genome sequencing easier and faster. We present a simple protocol to obtain whole genome sequences of hypothetically any influenza A virus, even with low quantities of starting genetic material. The complete genomes of influenza A viruses of different subtypes and from distinct sources (clinical samples of pdmH1N1, tissue culture-adapted H3N2 viruses, or avian influenza viruses from cloacal swabs) were amplified with a single multisegment reverse transcription-PCR reaction and sequenced using Illumina sequencing platform. Samples with low quantity of genetic material after initial PCR amplification were re-amplified by an additional PCR using random primers. Whole genome sequencing was successful for 66% of the samples, whilst the most relevant genome segments for epidemiological surveillance (corresponding to the hemagglutinin and neuraminidase) were sequenced with at least 93% coverage (and a minimum 10x) for 98% of the samples. Low coverage for some samples is likely due to an initial low viral RNA concentration in the original sample. The proposed methodology is especially suitable for sequencing a large number of samples, when genetic data is urgently required for strains characterization, and may also be useful for variant analysis.

microbiology↗