The unique and enigmatic spirochete symbiont of latrunculid sponges.

Bacterial symbionts are critical members of many marine sponge holobionts. Some sponge-associated bacterial lineages, such as Poribacteria, sponge-associated unclassified lineage (SAUL), and Tethybacterales, appear to have broad-host ranges and associate with a diversity of sponge species, while others are more species-specific, having adapted to the niche environment of their host. Host-associated spirochete symbionts that are numerically dominant have been documented in several invertebrates including termites, starfish, and corals.

Comparative Genomics Provides Insight into the Function of Broad-Host Range Sponge Symbionts.

The fossil record indicates that the earliest evidence of extant marine sponges (phylum Porifera) existed during the Cambrian explosion and that their symbiosis with microbes may have begun in their extinct ancestors during the Precambrian period. Many symbionts have adapted to their sponge host, where they perform specific, specialized functions. There are also widely distributed bacterial taxa such as , , and that are found in a broad range of invertebrate hosts.

Correction: Antiviral drug discovery: preparing for the next pandemic.

Correction for 'Antiviral drug discovery: preparing for the next pandemic' by Catherine S. Adamson et al., Chem.

Antiviral drug discovery: preparing for the next pandemic.

Clinically approved antiviral drugs are currently available for only 10 of the more than 220 viruses known to infect humans. The SARS-CoV-2 outbreak has exposed the critical need for compounds that can be rapidly mobilised for the treatment of re-emerging or emerging viral diseases, while vaccine development is underway. We review the current status of antiviral therapies focusing on RNA viruses, highlighting strategies for antiviral drug discovery and discuss the challenges, solutions and options to accelerate drug discovery efforts.

Conserved bacterial genomes from two geographically isolated peritidal stromatolite formations shed light on potential functional guilds.

Stromatolites are complex microbial mats that form lithified layers. Fossilized stromatolites are the oldest evidence of cellular life on Earth, dating back over 3.4 billion years.

Living phosphatic stromatolites in a low-phosphorus environment: Implications for the use of phosphorus as a proxy for phosphate levels in paleo-systems.

In the geological record, fossil phosphatic stromatolites date back to the Great Oxidation Event in the Paleoproterozoic, but living phosphatic stromatolites have not been described previously. Here, we report on cyanobacterial stromatolites in a supratidal freshwater environment at Cape Recife, South African southern coast, precipitating Ca carbonate alternating with episodes of Ca phosphate deposition. In their structure and composition, the living stromatolites from Cape Recife closely resemble their fossilized analogues, showing phosphatic zonation, microbial casts, tunnel structures and phosphatic crusts of biogenic origin.

Advances in Tetravirus Research: New Insight Into the Infectious Virus Lifecycle and an Expanding Host Range.

Tetraviruses are a group of relatively unknown small RNA viruses with particles that display a characteristic =4 capsid architecture. Tetraviruses are classified into three families, the , and , according to the divergent characteristics of their respective viral replicases. Tetraviruses generally infect the larvae of lepidopteran insect species, many of which are important agricultural pests and, until recently, were thought to have an unusually narrow host range and tissue tropism.

Providence virus: An animal virus that replicates in plants or a plant virus that infects and replicates in animal cells?

Introduction: Emerging viral diseases, most of which are zoonotic, pose a significant threat to global health. There is a critical need to identify potential new viral pathogens and the challenge is to identify the reservoirs from which these viruses might emerge. Deep sequencing of invertebrate transcriptomes has revealed a plethora of viruses, many of which represent novel lineages representing both plant and animal viruses and little is known about the potential threat that these viruses pose.

Molecular Networking Reveals Two Distinct Chemotypes in Pyrroloiminoquinone-Producing Tsitsikamma favus Sponges.

The temperate marine sponge, , produces pyrroloiminoquinone alkaloids with potential as anticancer drug leads. We profiled the secondary metabolite reservoir of sponges using HR-ESI-LC-MS/MS-based molecular networking analysis followed by preparative purification efforts to map the diversity of new and known pyrroloiminoquinones and related compounds in extracts of seven specimens. Molecular taxonomic identification confirmed all sponges as and five specimens (chemotype I) were found to produce mainly discorhabdins and tsitsikammamines.

A pivotal role for ocean eddies in the distribution of microbial communities across the Antarctic Circumpolar Current.

Mesoscale variability and associated eddy fluxes play crucial roles in ocean circulation dynamics and the ecology of the upper ocean. In doing so, these features are biologically important, providing a mechanism for the mixing and exchange of nutrients and biota within the ocean. Transient mesoscale eddies in the Southern Ocean are known to relocate zooplankton communities across the Antarctic Circumpolar Current (ACC) and are important foraging grounds for marine top predators.

A Place to Call Home: An Analysis of the Bacterial Communities in Two Tethya rubra Samaai and Gibbons 2005 Populations in Algoa Bay, South Africa.

Sponges are important sources of bioactive secondary metabolites. These compounds are frequently synthesized by bacterial symbionts, which may be recruited from the surrounding seawater or transferred to the sponge progeny by the parent. In this study, we investigated the bacterial communities associated with the sponge Samaai and Gibbons 2005.

Keeping it in the family: Coevolution of latrunculid sponges and their dominant bacterial symbionts.

The Latrunculiidae are a family of cold water sponges known for their production of bioactive pyrroloiminoquinone alkaloids. Previously it was shown that the bacterial community associated with a Tsitsikamma sponge species comprises unusual bacterial taxa and is dominated by a novel Betaproteobacterium. Here, we have characterized the bacterial communities associated with six latrunculid species representing three genera (Tsitsikamma, Cyclacanthia, and Latrunculia) as well as a Mycale species, collected from Algoa Bay on the South African southeast coast.

Binding and entry of a non-enveloped T=4 insect RNA virus is triggered by alkaline pH.

Tetraviruses are small, non-enveloped, RNA viruses that exclusively infect lepidopteran insects. Their particles comprise 240 copies of a single capsid protein precursor (CP), which undergoes autoproteolytic cleavage during maturation. The molecular mechanisms of capsid assembly and maturation are well understood, but little is known about the viral infectious lifecycle due to a lack of tissue culture cell lines that are susceptible to tetravirus infection.

Expanding the host range of small insect RNA viruses: Providence virus (Carmotetraviridae) infects and replicates in a human tissue culture cell line.

Tetraviruses are small, positive (+ve)-sense ssRNA viruses that infect the midgut cells of lepidopteran larvae. Providence virus (PrV) is the only member of the family Carmotetraviridae (previously Tetraviridae). PrV particles exhibit the characteristic tetraviral T=4 icosahedral symmetry, but PrV is distinct from other tetraviruses with respect to genome organization and viral non-structural proteins.

An encapsidated viral protein and its role in RNA packaging by a non-enveloped animal RNA virus.

Alphatetraviruses are small (+) ssRNA viruses with non-enveloped, icosahedral, T=4 particles that assemble from 240 copies of a single capsid protein precursor. This study is focused on the mechanisms underlying selection and packaging of genomic vRNAs by Helicoverpa armigera stunt virus. We demonstrate that the viral protein, p17, is packaged at low levels (between 4 and 8 copies per capsid) raising the possibility of icosahedral asymmetry in wild-type particles.

The African coelacanth genome provides insights into tetrapod evolution.

The discovery of a living coelacanth specimen in 1938 was remarkable, as this lineage of lobe-finned fish was thought to have become extinct 70 million years ago. The modern coelacanth looks remarkably similar to many of its ancient relatives, and its evolutionary proximity to our own fish ancestors provides a glimpse of the fish that first walked on land. Here we report the genome sequence of the African coelacanth, Latimeria chalumnae.

Complex pathways for regulation of pyrimidine metabolism by carbon catabolite repression and quorum sensing in Pseudomonas putida RU-KM3S.

Pseudomonads are metabolically versatile microbes that employ complex regulatory networks to control gene expression, particularly with respect to carbon and nitrogen metabolism. The aim of this study was to characterise the regulatory networks that control pyrimidine metabolism (hydantoin-hydrolysing activity) in Pseudomonas putida strain RU-KM3S, focussing on transcriptional activation of dihydropyrimidinase (Dhp) and β-ureidopropionase (Bup), encoding dhp and bup, respectively. The two genes are arranged divergently on the chromosome and are separated by ORF1, encoding a putative transporter, which lies upstream of and in the same orientation as bup.

Providence virus (family: Carmotetraviridae) replicates vRNA in association with the Golgi apparatus and secretory vesicles.

Providence virus (PrV) is the sole member of the family Carmotetraviridae (formerly Tetraviridae) sharing the characteristic T=4 capsid architecture with other tetravirus families. Despite significant structural similarities, PrV differs from other tetraviruses in terms of genome organization, non-structural protein sequence and regulation of gene expression. In addition, it is the only tetravirus that infects tissue culture cells.

Membrane targeting of an alpha-like tetravirus replicase is directed by a region within the RNA-dependent RNA polymerase domain.

The members of the family Tetraviridae are small positive-sense insect RNA viruses that exhibit stringent host specificity and a high degree of tissue tropism, suggesting that complex virus-host interactions are likely to occur during infection and viral replication. The alpha-like replicase of Helicoverpa armigera stunt virus (HaSV) (genus Omegatetravirus) has been proposed to associate with membranes of the endocytic pathway, which is similar to Semliki Forest virus, Sindbis virus and rubella virus. Here, we have used replicase-EGFP fusion proteins and recombinant baculovirus expression to demonstrate that the HaSV replicase associates strongly with cellular membranes, including detergent-resistant membranes, and that this association is maintained through a novel membrane targeting domain within the C-terminal region of the RNA-dependent RNA polymerase domain.

Diversity of bacterial communities associated with the Indian Ocean sponge Tsitsikamma favus that contains the bioactive pyrroloiminoquinones, tsitsikammamine A and B.

Tsitsikamma favus is a latrunculid sponge endemic to the coast of South Africa that produces unique pyrroloiminoquinones known as tsitsikammamines. Wakayin and makaluvamine A are structurally similar to the tsitsikammamines and are the only pyrroloiminoquinones isolated from a source other than Porifera (namely a Fijian ascidian Clavelina sp. and a laboratory culture of the myxomycete Didymium bahiense, respectively).

Enzymatic production of enantiopure amino acids from mono-substituted hydantoin substrates.

Biocatalytic conversion of 5-substituted hydantoin derivatives is an efficient method for the production of unnatural enantiomerically pure amino acids. The enzymes required to carry out this hydrolysis occur in a wide variety of eubacterial species each of which exhibit variations in substrate selectivity, enantiospecificity, and catalytic efficiency. Screening of the natural environment for bacterial strains capable of utilizing hydantoin as a nutrient source (as opposed to rational protein design of known enzymes) is a cost-effective and valuable approach for isolating microbial species with novel hydantoin-hydrolysing enzyme systems.