Volume 5 Issue 4, April 2020

N⁶-methyladenosine (m⁶A) is a widespread modification on cellular RNA that is dynamically regulated involving m⁶A writers, erasers and readers, and can impact many cellular processes and pathways. A recent study demonstrates that viruses can use m⁶A to ensure their RNA avoids innate immune sensing.

Two studies now identify bradyzoite-formation deficient 1 and microrchidia as ‘master regulators’ of the transcriptional events that control developmental life cycle transitions in the protozoan parasite Toxoplasma gondii.

The combined selective pressures of residing in different protozoan hosts in the environment drives the evolution of virulence in the opportunistic pathogen Legionella pneumophila.

The present outbreak of a coronavirus-associated acute respiratory disease called coronavirus disease 19 (COVID-19) is the third documented spillover of an animal coronavirus to humans in only two decades that has resulted in a major epidemic. The Coronaviridae Study Group (CSG) of the International Committee on Taxonomy of Viruses, which is responsible for developing the classification of viruses and taxon nomenclature of the family Coronaviridae, has assessed the placement of the human pathogen, tentatively named 2019-nCoV, within the Coronaviridae. Based on phylogeny, taxonomy and established practice, the CSG recognizes this virus as forming a sister clade to the prototype human and bat severe acute respiratory syndrome coronaviruses (SARS-CoVs) of the species Severe acute respiratory syndrome-related coronavirus, and designates it as SARS-CoV-2. In order to facilitate communication, the CSG proposes to use the following naming convention for individual isolates: SARS-CoV-2/host/location/isolate/date. While the full spectrum of clinical manifestations associated with SARS-CoV-2 infections in humans remains to be determined, the independent zoonotic transmission of SARS-CoV and SARS-CoV-2 highlights the need for studying viruses at the species level to complement research focused on individual pathogenic viruses of immediate significance. This will improve our understanding of virus–host interactions in an ever-changing environment and enhance our preparedness for future outbreaks.

The discovery of the Factor that terminates transcription in Archaea (FttA) as a conserved archaeal protein that is able to disrupt transcription elongation complexes elucidates the mechanisms of transcription termination in these organisms.

A combination of cellular, molecular and structural biology approaches explains how the translating ribosome and the nascent peptide SpeFL interact to form a binding pocket that serves as an ornithine sensor to regulate polyamine biosynthesis in pathogenic bacteria.

This study describes the development of an approach to rapidly screen lineage B betacoronaviruses, such as SARS-CoV and the recently emerged SARS-CoV-2, for receptor usage and their ability to infect cell types from different species. Using it, they confirm human ACE2 as the receptor for SARs-CoV-2 and show that host protease processing during viral entry is a significant barrier for viral entry.

The microrchidia (MORC) protein from Toxoplasma gondii is a transcriptional repressor that regulates parasite development and sexual commitment, and its conditional depletion paves the way to develop improved in vitro systems to investigate parasite sexual development.

This study reports a novel function for the N⁶-methyladenosine RNA modification in allowing RIG-I to discriminate self from non-self RNA and shows that human metapneumovirus induces this modification of its RNA to evade recognition in vivo.

This study reports transposon sequencing analyses to identify genes required for Legionella pneumophila survival in amoeba hosts, showing that unique sets of genes are required for virulence in different amoebae. This enables the accumulation of virulence genes that collectively allow replication in macrophages and, in some cases, lead to redundancy in this host cell type.

A comparison of DNA methylation patterns between conventionally raised and germ-free mice shows that the presence of a commensal microbiota induces methylation changes at regulatory elements in a subset of genes that are important for intestinal homeostasis.

A search for genes encoding anti-CRISPR (Acr) proteins on plasmids and other conjugative elements identifies new Acrs that regulate plasmid dissemination and are broad-spectrum inhibitors of Cas9 in human cells.

Co-housing mice is shown to induce resistance against enterobacterial infection after antibiotic treatment through the ability to retain or share Klebsiella michiganensis, which is necessary and sufficient to prevent infection through competition for nutrients.

Gastrointestinal disturbances, such as non-antibiotic-induced diarrhoea, promote susceptibility to colonization by Clostridium difficile, providing additional insights into antibiotic-independent triggers for this infection.