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THE VIRAL EXCEPTION. “The difficulties of metagenomic genome discovery are alleviated to a considerable extent when it comes to discovery of new virus genomes. Viral genomes are relatively small, for many important and abundant virus families, only several kilobases (kb) long, so that assembly of complete viral genome is often feasible.” https://lnkd.in/dyavu7e View in LinkedIn

CHALLENGES. “Sequences with high similarity to those from known organisms are readily assignable but those from truly novel genomes can be difficult to place. A further difficulty for metagenomic discovery is the correct assembly of long contigs.” https://lnkd.in/dyavu7e View in LinkedIn

THE ALARM has been called about the dangers of artificial intelligence (AI). Serious-minded people are seriously concerned. The most interesting aspect of this is the belief, by those qualified to give such an opinion, that a bucket of bolts could possibly think, learn, evolve, reproduce, and even compete with humans. This is the Grey Zone on steroids, a fascinating possibility. And a comment on our very biology. View in LinkedIn

SO ENDS this brief summary of the discovery of Polintons. These are very unusual creatures that are thought to transition between naked DNA transposons and viroids. It is worth remembering that we have so far only discovered less than 1% of the estimated number of virus species that exist. And these we both very numerous and very large. Also worth remembering is that only a small fraction of (known) viruses cause disease, and many have played key roles in the evolution of life on this planet. And, finally, there is an ongoing farcical discussion of whether viruses are even alive. View in LinkedIn

RECONSTRUCTED HISTORY. “Extensive comparative analysis of the genomes of dsDNA viruses infecting eukaryotes as well as dsDNA plasmids and transposons has led to an evolutionary scenario in which polintoviruses evolved directly from bacteriophages of the family Tectiviridae and played a central role in the origin and evolution of diverse selfish elements in eukaryotes including giant viruses of the proposed order “Megavirales”.” https://lnkd.in/dyavu7e View in LinkedIn

UNIQUE HYPOTHESIS. “Thus, we have hypothesized that Polintons lead a dual life style and, in addition to behaving like typical transposons, are capable of forming virions, hence the proposed name polintoviruses.” https://lnkd.in/dyavu7e View in LinkedIn

STRUCTURAL CLUES. “MCP and mCP respectively adopt intact double and single jelly-roll folds, strongly suggesting that Polintons are capable of forming virions.” https://lnkd.in/dyavu7e View in LinkedIn

STRUCTURAL PROTEINS. “Most of the Polintons encode putative major and minor capsid proteins (MCP and mCP, respectively).” https://lnkd.in/dyavu7e View in LinkedIn

TRANSITIONAL FORM. “Thus, Polintons have been often considered virus-like transposons although no structural proteins have been initially detected.” https://lnkd.in/dyavu7e View in LinkedIn

POLYMERASE INTEGRONS. “All Polintons encode a protein-primed DNA polymerase and a retrovirus-like integrase (hence the name of these elements: POLINTons). The majority of Polintons also encode a homolog of the DNA-packaging ATPase and maturation protease that are characteristic of diverse double-stranded (ds) DNA viruses.” https://lnkd.in/dyavu7e View in LinkedIn