Inflammation and bacteriophages affect DNA inversion states and functionality of the gut microbiota.

Reversible genomic DNA inversions control the expression of numerous gut bacterial molecules, but how this impacts disease remains uncertain. By analyzing metagenomic samples from inflammatory bowel disease (IBD) cohorts, we identified multiple invertible regions where a particular orientation correlated with disease. These include the promoter of polysaccharide A (PSA) of Bacteroides fragilis, which induces regulatory T cells (Tregs) and ameliorates experimental colitis. The PSA promoter was mostly oriented "OFF" in IBD patients, which correlated with increased B. fragilis-associated bacteriophages. Similarly, in mice colonized with a healthy human microbiota and B. fragilis, induction of colitis caused a decline of PSA in the "ON" orientation that reversed as inflammation resolved. Monocolonization of mice with B. fragilis revealed that bacteriophage infection increased the frequency of PSA in the "OFF" orientation, causing reduced PSA expression and decreased Treg cells. Altogether, we reveal dynamic bacterial phase variations driven by bacteriophages and host inflammation, signifying bacterial functional plasticity during disease.

Extracellular vesicles of the Gram-positive gut symbiont Bifidobacterium longum induce immune-modulatory, anti-inflammatory effects.

The gut microbiota is now well known to affect the host's immune system. One way of bacterial communication with host cells is via the secretion of vesicles, small membrane structures containing various cargo. Research on vesicles secreted by Gram-positive gut bacteria, their mechanisms of interaction with the host and their immune-modulatory effects are still relatively scarce. Here we characterized the size, protein content, and immune-modulatory effects of extracellular vesicles (EVs) secreted by a newly sequenced Gram-positive human gut symbiont strain - Bifidobacterium longum AO44. We found that B. longum EVs exert anti-inflammatory effects, inducing IL-10 secretion from both splenocytes and dendritic cells (DC)-CD4+ T cells co-cultures. Furthermore, the EVs protein content showed enrichment in ABC transporters, quorum sensing proteins, and extracellular solute-binding proteins, which were previously shown to have a prominent function in the anti-inflammatory effect of other strains of B. longum. This study underlines the importance of bacterial vesicles in facilitating the gut bacterial immune-modulatory effects on the host and sheds light on bacterial vesicles as future therapeutics.

Gut Bacteria-Not for the Faint of Heart.

The role of gut bacteria in complications of heart inflammation has previously not been fully understood. Gil-Cruz et al. (2019) demonstrate a commensal Bacteroides species that triggers a cross-immune response against a bacterial protein and heart epitope, causing cardiomyopathy. This study links commensal bacteria with heart inflammation mechanistically in mice and correlatively in patients.

A Protocol for Simple, Rapid, and Direct Detection of SARS-CoV-2 from clinical samples, using Reverse Transcribed Loop-Mediated Isothermal Amplification (RT-LAMP).

SARS-CoV-2 has quickly spread all around the globe causing illness and wide damages. Most countries were unprepared for such a rapid spread and crisis. This led to various strategies for effective control of the new pandemic. A key aspect in all countries was to effectively test the population for the virus. Most countries chose a lockdown strategy in which many workplaces and activities are completely closed, leading to substantial economy costs. Here, we present a protocol we recently developed that allows rapid and simple detection of SARS-CoV-2 for the large population, eliminating costs and involvement of professional teams and laboratories. This protocol is based on Reverse Transcribed Loop-Mediated Isothermal Amplification (RT-LAMP). We tested this protocol directly on patient samples, both nasal and throat clinical swabs as well as saliva. Notably, this protocol is simple, cheap and can be easily applied to other pathogens as well.

Direct on-the-spot detection of SARS-CoV-2 in patients.

IMPACT STATEMENT: Humanity is currently experiencing a global pandemic with devastating implications on human health and the economy. Most countries are gradually exiting their lockdown state. We are currently lacking rapid and simple viral detections, especially methods that can be performed in the household. Here, we applied RT-LAMP directly on human clinical swabs and self-collected saliva samples. We adjusted the method to allow simple and rapid viral detection, with no RNA purification steps. By testing our method on over 180 human samples, we determined its sensitivity, and by applying it to other viruses, we determined its specificity. We believe this method has a promising potential to be applied world-wide as a simple and cheap surveillance test for SARS-CoV-2.