A REPORT FROM THE AMERICAN ACADEMY OF MICROBIOLOGY VIRUSES THROUGHOUT LIFE & TIME FRIENDS, FOES, CHANGE AGENTS (original) (raw)
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What contemporary viruses tell us about evolution: a personal view
Archives of Virology, 2013
Recent advances in information about viruses have revealed novel and surprising properties such as viral sequences in the genomes of various organisms, unexpected amounts of viruses and phages in the biosphere, and the existence of giant viruses mimicking bacteria. Viruses helped in building genomes and are driving evolution. Viruses and bacteria belong to the human body and our environment as a well-balanced ecosystem. Only in unbalanced situations do viruses cause infectious diseases or cancer. In this article, I speculate about the role of viruses during evolution based on knowledge of contemporary viruses. Are viruses our oldest ancestors? RNA and viroids The beginning, when life started, was an RNA world, as this is widely accepted today [37, 41, 42, 44]. We do not really know how the first nucleotides, the building blocks
Viruses and Evolution – Viruses First? A Personal Perspective
Frontiers in Microbiology, 2019
The discovery of exoplanets within putative habitable zones revolutionized astrobiology in recent years. It stimulated interest in the question about the origin of life and its evolution. Here, we discuss what the roles of viruses might have been at the beginning of life and during evolution. Viruses are the most abundant biological entities on Earth. They are present everywhere, in our surrounding, the oceans, the soil and in every living being. Retroviruses contributed to about half of our genomic sequences and to the evolution of the mammalian placenta. Contemporary viruses reflect evolution ranging from the RNA world to the DNA-protein world. How far back can we trace their contribution? Earliest replicating and evolving entities are the ribozymes or viroids fulfilling several criteria of life. RNA can perform many aspects of life and influences our gene expression until today. The simplest structures with non-protein-coding information may represent models of life built on structural, not genetic information. Viruses today are obligatory parasites depending on host cells. Examples of how an independent lifestyle might have been lost include mitochondria, chloroplasts, Rickettsia and others, which used to be autonomous bacteria and became intracellular parasites or endosymbionts, thereby losing most of their genes. Even in vitro the loss of genes can be recapitulated all the way from coding to non-coding RNA. Furthermore, the giant viruses may indicate that there is no sharp border between living and non-living entities but an evolutionary continuum. Here, it is discussed how viruses can lose and gain genes, and that they are essential drivers of evolution. This discussion may stimulate the thinking about viruses as early possible forms of life. Apart from our view "viruses first", there are others such as "proteins first" and "metabolism first."
Counts and sequences, observations that continue to change our understanding of viruses in nature
Journal of Microbiology, 2015
Counts and sequences, observations that continue to change our understanding of viruses in nature § The discovery of abundant viruses in the oceans and on land has ushered in a quarter century of groundbreaking advancements in our understanding of viruses within ecosystems. Two types of observations from environmental samplesdirect counts of viral particles and viral metagenomic sequences -have been critical to these discoveries. Accurate direct counts have established ecosystem-scale trends in the impacts of viral infection on microbial host populations and have shown that viral communities within aquatic and soil environments respond to both short term and seasonal environmental change. Direct counts have been critical for estimating viral production rate, a measurement essential to quantifying the implications of viral infection for the biogeochemical cycling of nutrients within ecosystems. While direct counts have defined the magnitude of viral processes; shotgun sequences of environmental viral DNA -virome sequences -have enabled researchers to estimate the diversity and composition of natural viral communities. Virome-enabled studies have found the virioplankton to contain thousands of viral genotypes in communities where the most dominant viral population accounts for a small fraction of total abundance followed by a long tail of diverse populations. Detailed examination of long virome sequences has led to new understanding of genotype-to-phenotype connections within marine viruses and revealed that viruses carry metabolic genes that are important to maintaining cellular energy during viral replication. Increased access to long virome sequences will undoubtedly reveal more genetic secrets of viruses and enable us to build a genomics rulebook for predicting key biological and ecological features of unknown viruses.
This essay is designed to investigate the mystery of the virus: the smallest form of organic material that is able to replicate itself by following a parasitic approach that needs an external, living cell. As it is quite unable to metabolize nutrients, it is not considered to be alive. This essay will share some little known facts about viruses and help to dispel some dangerous myths that evolved about them and the vaccines used against them. Since 1892 when scientists started to investigate these objects, they have been confronted with the primary mystery: what are viruses? How do they survive on their endless quest from host to host? This essay will concentrate on the virulent viruses: those that cause a major threat to humanity; we will focus on the Big Three: smallpox, polio and influenza. The influenza story becomes central because it illustrates the false assumptions that have been made in the past with earlier false alarms, such as the Swine Flu panic of 1976 and the even larger false assumptions about the 'Great Spanish Flu Pandemic' of 1918-1920, where most deaths were due to deadly bacteria. The present covid panic seems to be a reflection of the 1976 Swine Flu panic. Several other viruses are examined (like Hepatitis B and the Herpes family: Herpes Simplex and Epstein-Barr) as they illustrate the successful vaccines used to defeat them; interestingly, this has NOT been used here in the current Covid Panic. This study of viruses has increased my respect for the variety of nature, no matter what its scale but a better understanding of how they function will help us react to their ongoing threats. Knowing their structure, is only the first step in understanding what is going on: processes are more significant than structure (relationships are key to knowledge; not just identifying-and naming-objects). Although written for an educated audience (but not virologists) there is much here of interest to non-scientists to show HOW real virology is done (slowly: one discovery at a time). I hope this great story will appeal to many.
What roles for viruses in origin of life scenarios
Important roles in origin of life (OL) scenarios have been and still are attributed to viruses. Yet the strict dependence of viruses on cells for their multiplication has been widely acknowledged since the first decades of the 20th century. How could viruses play critical roles in the OL if life relies on cellular organization and if viruses are defined as parasites of cells? In other words, how could viruses play a role in the emergence of cellular life if the existence of cells is a prerequisite for the existence of viruses? This paper investigates this issue and describes past and current OL scenarios conferring viruses with important roles, thereby completing the work of historian of science and physician Scott Podolsky who identified three major roles of viruses in past OL scenarios. Some objections raised by present OL scenarios conferring viruses with an important role are discussed. I argue that disagreements concerning the roles of viruses in OL scenarios stem from the different concepts of life and of virus scientists defend. Investigating the roles of viruses in OL scenarios not only helps identifying different ways to define life in the context of OL theorizing. It also offers the opportunity to better understand how viruses could be conceptualized. The relevance of the replication-first versus metabolism-first dichotomy in OL theorizing is briefly discussed.