Convergent evolution of viral-like Borg archaeal extrachromosomal elements and giant eukaryotic viruses.

Unlabelled: Borgs are huge extrachromosomal elements of anaerobic methane-oxidizing archaea. They exist in exceedingly complex microbiomes, lack cultivated hosts and have few protein functional annotations, precluding their classification as plasmids, viruses or other. Here, we used structure prediction methods to investigate potential roles for ∼10,000 Borg proteins.

Cleaning up our disinfectants: usage of antimicrobial biocides in direct-to-consumer products in Australia.

In supermarkets and chemists worldwide, consumers are faced with an array of antimicrobial domestic cleaning and personal hygiene products purporting to kill germs and keep people safe. Many of these proven active ingredients (biocides) encourage the development of antimicrobial resistance (AMR) in microbes and microbial populations, in turn increasing the likelihood of AMR infections. In order to understand and address the selective pressure towards AMR posed by the unrestricted use of biocides, it is necessary to understand which biocides are most frequently found in consumer products and the current regulatory framework that governs their use.

Dual recognition of multiple signals in bacterial outer membrane proteins enhances assembly and maintains membrane integrity.

Outer membrane proteins (OMPs) are essential components of the outer membrane of Gram-negative bacteria. In terms of protein targeting and assembly, the current dogma holds that a 'β-signal' imprinted in the final β-strand of the OMP engages the β-barrel assembly machinery (BAM) complex to initiate membrane insertion and assembly of the OMP into the outer membrane. Here, we revealed an additional rule that signals equivalent to the β-signal are repeated in other, internal β-strands within bacterial OMPs, by peptidomimetic and mutational analysis.

CasPEDIA Database: a functional classification system for class 2 CRISPR-Cas enzymes.

CRISPR-Cas enzymes enable RNA-guided bacterial immunity and are widely used for biotechnological applications including genome editing. In particular, the Class 2 CRISPR-associated enzymes (Cas9, Cas12 and Cas13 families), have been deployed for numerous research, clinical and agricultural applications. However, the immense genetic and biochemical diversity of these proteins in the public domain poses a barrier for researchers seeking to leverage their activities.

Identifying and Prioritising Behaviours to Slow Antimicrobial Resistance.

As a nation with relatively low levels of AMR, due to both community and agricultural stewardship, as well as geographical isolation, Australia is somewhat unique. As this advantage is being eroded, this project aimed to investigate the spectrum of human behaviours that could be modified in order to slow the spread of AMR, building upon the argument that doable actions are the best-targeted and least complex to change. We conducted a workshop with a panel of diverse interdisciplinary AMR experts (from sociology, microbiology, agriculture, veterinary medicine, health and government) and identified twelve behaviours that, if undertaken by the public, would slow the spread of AMR.

Epitopes in the capsular polysaccharide and the porin OmpK36 receptors are required for bacteriophage infection of Klebsiella pneumoniae.

To kill bacteria, bacteriophages (phages) must first bind to a receptor, triggering the release of the phage DNA into the bacterial cell. Many bacteria secrete polysaccharides that had been thought to shield bacterial cells from phage attack. We use a comprehensive genetic screen to distinguish that the capsule is not a shield but is instead a primary receptor enabling phage predation.

-derived outer membrane vesicles package β-lactamases to promote antibiotic resistance.

causes the sexually transmitted disease gonorrhoea. The treatment of gonorrhoea is becoming increasingly challenging, as has developed resistance to antimicrobial agents routinely used in the clinic. Resistance to penicillin is wide-spread partly due to the acquisition of β-lactamase genes.

Bacteriophages evolve enhanced persistence to a mucosal surface.

The majority of viruses within the gut are obligate bacterial viruses known as bacteriophages (phages). Their bacteriotropism underscores the study of phage ecology in the gut, where they modulate and coevolve with gut bacterial communities. Traditionally, these ecological and evolutionary questions were investigated empirically via in vitro experimental evolution and, more recently, in vivo models were adopted to account for physiologically relevant conditions of the gut.

A Structurally Characterized Evolutionary Escape Route from Treatment with the Antibiotic Linezolid.

Methicillin-resistant Staphylococcus aureus (MRSA) is a bacterial pathogen that presents great health concerns. Treatment requires the use of last-line antibiotics, such as members of the oxazolidinone family, of which linezolid is the first member to see regular use in the clinic. Here, we report a short time scale selection experiment in which strains of MRSA were subjected to linezolid treatment.

A noncanonical chaperone interacts with drug efflux pumps during their assembly into bacterial outer membranes.

Bacteria have membrane-spanning efflux pumps to secrete toxic compounds ranging from heavy metal ions to organic chemicals, including antibiotic drugs. The overall architecture of these efflux pumps is highly conserved: with an inner membrane energy-transducing subunit coupled via an adaptor protein to an outer membrane conduit subunit that enables toxic compounds to be expelled into the environment. Here, we map the distribution of efflux pumps across bacterial lineages to show these proteins are more widespread than previously recognised.

Mechanistic Insights into the Capsule-Targeting Depolymerase from a Klebsiella pneumoniae Bacteriophage.

The production of capsular polysaccharides by Klebsiella pneumoniae protects the bacterial cell from harmful environmental factors such as antimicrobial compounds and infection by bacteriophages (phages). To bypass this protective barrier, some phages encode polysaccharide-degrading enzymes referred to as depolymerases to provide access to cell surface receptors. Here, we characterized the phage RAD2, which infects K.

Component Parts of Bacteriophage Virions Accurately Defined by a Machine-Learning Approach Built on Evolutionary Features.

Antimicrobial resistance (AMR) continues to evolve as a major threat to human health, and new strategies are required for the treatment of AMR infections. Bacteriophages (phages) that kill bacterial pathogens are being identified for use in phage therapies, with the intention to apply these bactericidal viruses directly into the infection sites in bespoke phage cocktails. Despite the great unsampled phage diversity for this purpose, an issue hampering the roll out of phage therapy is the poor quality annotation of many of the phage genomes, particularly for those from infrequently sampled environmental sources.

Characterization of the Core Ribosomal Binding Region for the Oxazolidone Family of Antibiotics Using Cryo-EM.

Linezolid and tedizolid are oxazolidinones with established clinical utility for the treatment of Gram-positive pathogens. Over time it has become apparent that even modest structural changes to the core phenyl oxazolidinone leads to drastic changes in biological activity. Consequently, the structure-activity relationship around the core oxazolidinone is constantly evolving, often reflected with new structural motifs present in nascent oxazolidinones.

cryoEM-Guided Development of Antibiotics for Drug-Resistant Bacteria.

While the ribosome is a common target for antibiotics, challenges with crystallography can impede the development of new bioactives using structure-based drug design approaches. In this study we exploit common structural features present in linezolid-resistant forms of both methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococcus (VRE) to redesign the antibiotic. Enabled by rapid and facile cryoEM structures, this process has identified (S)-2,2-dichloro-N-((3-(3-fluoro-4-morpholinophenyl)-2-oxooxazolidin-5-yl)methyl)acetamide (LZD-5) and (S)-2-chloro-N-((3-(3-fluoro-4-morpholinophenyl)-2-oxooxazolidin-5-yl)methyl) acetamide (LZD-6), which inhibit the ribosomal function and growth of linezolid-resistant MRSA and VRE.

Structure and Membrane Topography of the Vibrio-Type Secretin Complex from the Type 2 Secretion System of Enteropathogenic Escherichia coli.

The β-barrel assembly machinery (BAM) complex is the core machinery for the assembly of β-barrel membrane proteins, and inhibition of BAM complex activity is lethal to bacteria. Discovery of integral membrane proteins that are key to pathogenesis and yet do not require assistance from the BAM complex raises the question of how these proteins assemble into bacterial outer membranes. Here, we address this question through a structural analysis of the type 2 secretion system (T2SS) secretin from enteropathogenic O127:H6 strain E2348/69.

Reductive evolution in outer membrane protein biogenesis has not compromised cell surface complexity in Helicobacter pylori.

Helicobacter pylori is a gram-negative bacterial pathogen that chronically inhabits the human stomach. To survive and maintain advantage, it has evolved unique host-pathogen interactions mediated by Helicobacter-specific proteins in the bacterial outer membrane. These outer membrane proteins (OMPs) are anchored to the cell surface via a C-terminal β-barrel domain, which requires their assembly by the β-barrel assembly machinery (BAM).

Structural basis for substrate selection by the translocation and assembly module of the β-barrel assembly machinery.

The assembly of proteins into bacterial outer membranes is a key cellular process that we are only beginning to understand, mediated by the β-barrel assembly machinery (BAM). Two crucial elements of that machinery are the core BAM complex and the translocation and assembly module (TAM), with each containing a member of the Omp85 superfamily of proteins: BamA in the BAM complex, TamA in the TAM. Here, we used the substrate protein FimD as a model to assess the selectivity of substrate interactions for the TAM relative to those of the BAM complex.

Structural Basis for Linezolid Binding Site Rearrangement in the Ribosome.

An unorthodox, surprising mechanism of resistance to the antibiotic linezolid was revealed by cryo-electron microscopy (cryo-EM) in the 70S ribosomes from a clinical isolate of This high-resolution structural information demonstrated that a single amino acid deletion in ribosomal protein uL3 confers linezolid resistance despite being located 24 Å away from the linezolid binding pocket in the peptidyl-transferase center. The mutation induces a cascade of allosteric structural rearrangements of the rRNA that ultimately results in the alteration of the antibiotic binding site. The growing burden on human health caused by various antibiotic resistance mutations now includes prevalent resistance to last-line antimicrobial drugs such as linezolid and daptomycin.

Structure and substrate fingerprint of aminopeptidase P from Plasmodium falciparum.

Malaria is one of the world's most prevalent parasitic diseases, with over 200 million cases annually. Alarmingly, the spread of drug-resistant parasites threatens the effectiveness of current antimalarials and has made the development of novel therapeutic strategies a global health priority. Malaria parasites have a complicated lifecycle, involving an asymptomatic 'liver stage' and a symptomatic 'blood stage'.

Potent dual inhibitors of Plasmodium falciparum M1 and M17 aminopeptidases through optimization of S1 pocket interactions.

Malaria remains a global health problem, and though international efforts for treatment and eradication have made some headway, the emergence of drug-resistant parasites threatens this progress. Antimalarial therapeutics acting via novel mechanisms are urgently required. Plasmodium falciparum M1 and M17 are neutral aminopeptidases which are essential for parasite growth and development.

Identification and Validation of a Potent Dual Inhibitor of the P. falciparum M1 and M17 Aminopeptidases Using Virtual Screening.

The Plasmodium falciparum PfA-M1 and PfA-M17 metalloaminopeptidases are validated drug targets for the discovery of antimalarial agents. In order to identify dual inhibitors of both proteins, we developed a hierarchical virtual screening approach, followed by in vitro evaluation of the highest scoring hits. Starting from the ZINC database of purchasable compounds, sequential 3D-pharmacophore and molecular docking steps were applied to filter the virtual 'hits'.

Conserved features in TamA enable interaction with TamB to drive the activity of the translocation and assembly module.

The biogenesis of membranes from constituent proteins and lipids is a fundamental aspect of cell biology. In the case of proteins assembled into bacterial outer membranes, an overarching question concerns how the energy required for protein insertion and folding is accessed at this remote location of the cell. The translocation and assembly module (TAM) is a nanomachine that functions in outer membrane biogenesis and virulence in diverse bacterial pathogens.

Screening the Medicines for Malaria Venture "Malaria Box" against the Plasmodium falciparum aminopeptidases, M1, M17 and M18.

Malaria is a parasitic disease that remains a global health burden. The ability of the parasite to rapidly develop resistance to therapeutics drives an urgent need for the delivery of new drugs. The Medicines for Malaria Venture have compounds known for their antimalarial activity, but not necessarily the molecular targets.