Arquivo da tag: Oceanos

The aliens among us. How viruses shape the world (The Economist)

They don’t just cause pandemics

Leaders – Aug 22nd 2020 edition

HUMANS THINK of themselves as the world’s apex predators. Hence the silence of sabre-tooth tigers, the absence of moas from New Zealand and the long list of endangered megafauna. But SARSCoV-2 shows how people can also end up as prey. Viruses have caused a litany of modern pandemics, from covid-19, to HIV/AIDS to the influenza outbreak in 1918-20, which killed many more people than the first world war. Before that, the colonisation of the Americas by Europeans was abetted—and perhaps made possible—by epidemics of smallpox, measles and influenza brought unwittingly by the invaders, which annihilated many of the original inhabitants.

The influence of viruses on life on Earth, though, goes far beyond the past and present tragedies of a single species, however pressing they seem. Though the study of viruses began as an investigation into what appeared to be a strange subset of pathogens, recent research puts them at the heart of an explanation of the strategies of genes, both selfish and otherwise.

Viruses are unimaginably varied and ubiquitous. And it is becoming clear just how much they have shaped the evolution of all organisms since the very beginnings of life. In this, they demonstrate the blind, pitiless power of natural selection at its most dramatic. And—for one group of brainy bipedal mammals that viruses helped create—they also present a heady mix of threat and opportunity.

As our essay in this week’s issue explains, viruses are best thought of as packages of genetic material that exploit another organism’s metabolism in order to reproduce. They are parasites of the purest kind: they borrow everything from the host except the genetic code that makes them what they are. They strip down life itself to the bare essentials of information and its replication. If the abundance of viruses is anything to go by, that is a very successful strategy indeed.

The world is teeming with them. One analysis of seawater found 200,000 different viral species, and it was not setting out to be comprehensive. Other research suggests that a single litre of seawater may contain more than 100bn virus particles, and a kilo of dried soil ten times that number. Altogether, according to calculations on the back of a very big envelope, the world might contain 1031 of the things—that is one followed by 31 zeros, far outnumbering all other forms of life on the planet.

As far as anyone can tell, viruses—often of many different sorts—have adapted to attack every organism that exists. One reason they are powerhouses of evolution is that they oversee a relentless and prodigious slaughter, mutating as they do so. This is particularly clear in the oceans, where a fifth of single-celled plankton are killed by viruses every day. Ecologically, this promotes diversity by scything down abundant species, thus making room for rarer ones. The more common an organism, the more likely it is that a local plague of viruses specialised to attack it will develop, and so keep it in check.

This propensity to cause plagues is also a powerful evolutionary stimulus for prey to develop defences, and these defences sometimes have wider consequences. For example, one explanation for why a cell may deliberately destroy itself is if its sacrifice lowers the viral load on closely related cells nearby. That way, its genes, copied in neighbouring cells, are more likely to survive. It so happens that such altruistic suicide is a prerequisite for cells to come together and form complex organisms, such as pea plants, mushrooms and human beings.

The other reason viruses are engines of evolution is that they are transport mechanisms for genetic information. Some viral genomes end up integrated into the cells of their hosts, where they can be passed down to those organisms’ descendants. Between 8% and 25% of the human genome seems to have such viral origins. But the viruses themselves can in turn be hijacked, and their genes turned to new uses. For example, the ability of mammals to bear live young is a consequence of a viral gene being modified to permit the formation of placentas. And even human brains may owe their development in part to the movement within them of virus-like elements that create genetic differences between neurons within a single organism.

Evolution’s most enthralling insight is that breathtaking complexity can emerge from the sustained, implacable and nihilistic competition within and between organisms. The fact that the blind watchmaker has equipped you with the capacity to read and understand these words is in part a response to the actions of swarms of tiny, attacking replicators that have been going on, probably, since life first emerged on Earth around 4bn years ago. It is a startling example of that principle in action—and viruses have not finished yet.

Humanity’s unique, virus-chiselled consciousness opens up new avenues to deal with the viral threat and to exploit it. This starts with the miracle of vaccination, which defends against a pathogenic attack before it is launched. Thanks to vaccines, smallpox is no more, having taken some 300m lives in the 20th century. Polio will one day surely follow. New research prompted by the covid-19 pandemic will enhance the power to examine the viral realm and the best responses to it that bodies can muster—taking the defence against viruses to a new level.

Another avenue for progress lies in the tools for manipulating organisms that will come from an understanding of viruses and the defences against them. Early versions of genetic engineering relied on restriction enzymes—molecular scissors with which bacteria cut up viral genes and which biotechnologists employ to move genes around. The latest iteration of biotechnology, gene editing letter by letter, which is known as CRISPR, makes use of a more precise antiviral mechanism.

From the smallest beginnings

The natural world is not kind. A virus-free existence is an impossibility so deeply unachievable that its desirability is meaningless. In any case, the marvellous diversity of life rests on viruses which, as much as they are a source of death, are also a source of richness and of change. Marvellous, too, is the prospect of a world where viruses become a source of new understanding for humans—and kill fewer of them than ever before. ■

Correction: An earlier version of this article got its maths wrong. 1031 is one followed by 31 zeroes, not ten followed by 31 zeroes as we first wrote. Sorry.

Northern and southern hemisphere climates follow the beat of different drummers (Science Daily)

Date: March 30, 2014

Source: University of Bern

Summary: Over the last 1000 years, temperature differences between the Northern and Southern Hemispheres were larger than previously thought. Using new data from the Southern Hemisphere, researchers have shown that climate model simulations overestimate the links between the climate variations across the Earth with implications for regional predictions.

Field work in the Indian Ocean. The corals off the Broome coast, Western Australia, store information about past climate. Credit: Copyright Eric Matson, Australian Institute of Marine Science

Over the last 1000 years, temperature differences between the Northern and Southern Hemispheres were larger than previously thought. Using new data from the Southern Hemisphere, researchers have shown that climate model simulations overestimate the links between the climate variations across Earth with implications for regional predictions.

These findings are demonstrated in a new international study coordinated by Raphael Neukom from the Oeschger Centre of the University of Bern and the Swiss Federal Research Institute WSL and are published today in the journal Nature Climate Change.

The Southern Hemisphere is a challenging place for climate scientists. Its vast oceans, Antarctic ice, and deserts make it particularly difficult to collect information about present climate and, even more so, about past climate. However, multi-centennial reconstructions of past climate from so-called proxy archives such as tree-rings, lake sediments, corals, and ice-cores are required to understand the mechanisms of the climate system. Until now, these long-term estimates were almost entirely based on data from the Northern Hemisphere.

Over the past few years, an international research team has made a coordinated effort to develop and analyse new records that provide clues about climate variation across the Southern Hemisphere. Climate scientists from Australia, Antarctic-experts, as well as data specialists and climate modellers from South and North America and Europe participated in the project. They compiled climate data from over 300 different locations and applied a range of methods to estimate Southern Hemisphere temperatures over the past 1000 years. In 99.7 percent of the results, the warmest decade of the millennium occurs after 1970.

Surprisingly, only twice over the entire last millennium have both hemispheres simultaneously shown extreme temperatures. One of these occasions was a global cold period in the 17th century; the other one was the current warming phase, with uninterrupted global warm extremes since the 1970s. “The ‘Medieval Warm Period’, as identified in some European chronicles, was a regional phenomenon,” says Raphael Neukom. “At the same time, temperatures in the Southern Hemisphere were only average.” The researchers ascribe these large differences to so-called “internal variability.” This term describes the chaotic interplay of the ocean and atmosphere within the climate system that leads to temperatures changing in one or the other direction. Regional differences in these fluctuations appear to be larger than previously thought.

The scientists discovered that most climate models are unable to satisfactorily simulate the considerable differences between the hemispheres. The models appear to underestimate the influence of internal variability, in comparison with external forcings like solar irradiation, volcanic eruptions or human greenhouse gas emissions. “Regional differences in the climatic evolution of the next decades could therefore be larger than the current models predict,” says Neukom.

Journal Reference:

  1. Raphael Neukom, Joëlle Gergis, David J. Karoly, Heinz Wanner, Mark Curran, Julie Elbert, Fidel González-Rouco, Braddock K. Linsley, Andrew D. Moy, Ignacio Mundo, Christoph C. Raible, Eric J. Steig, Tas van Ommen, Tessa Vance, Ricardo Villalba, Jens Zinke, David Frank. Inter-hemispheric temperature variability over the past millenniumNature Climate Change, 2014; DOI:10.1038/NCLIMATE2174

Pesquisadores alertam sobre necessidade urgente de proteger os oceanos (Fapesp)

Artigo de brasileiro e uruguaio será publicado como editorial no periódico Marine Pollution Bulletin(Wikipedia)

02/10/2013

Por José Tadeu Arantes

Agência FAPESP – Estima-se que 41% dos mares e oceanos do planeta se encontrem fortemente impactados pela ação humana, segundo estudos. Trata-se de um problema grave que não tem recebido a merecida atenção. Um exemplo está no ritmo de implementação da diretriz relativa à proteção marinha definida pela Convenção sobre Diversidade Biológica (CDB), da Organização das Nações Unidas (ONU).

Aprovada por 193 países mais a União Europeia durante a 10ª Conferência das Partes da CDB, realizada em Nagoya, Japão, em outubro de 2010, essa diretriz estabeleceu que, até 2020, pelo menos 10% das áreas costeiras e marinhas, especialmente aquelas importantes por sua biodiversidade, deveriam estar protegidas.

Decorrido quase um terço do prazo, porém, as chamadas Áreas de Proteção Marinha (APMs) não cobrem mais do que 1,17% da superfície dos mares e oceanos do planeta. Dos 151 países com linha de costa, apenas 12 excederam os 10%. E a maior potência do mundo, os Estados Unidos, dotada de extensos litorais tanto no Atlântico como no Pacífico, não aderiu ao protocolo.

As informações, que configuram um alerta urgente, estão no artigo Politics should walk with Science towards protection of the oceans (“A política deve caminhar com a ciência na proteção dos oceanos”), assinado pelo brasileiro Antonio Carlos Marques, professor associado do Instituto de Biociências da Universidade de São Paulo, e pelo uruguaio Alvar Carranza, pesquisador do Museu Nacional de História Natural, do Uruguai. Enviado ao Marine Pollution Bulletin, o texto, que será publicado como editorial da versão impressa do periódico, está disponível on-line em www.sciencedirect.com/science/article/pii/S0025326X13004530.

O artigo também destaca que, com uma das mais extensas costas do mundo – de 9.200 quilômetros, se forem consideradas as saliências e reentrâncias –, o Brasil possui apenas 1,5% de seu litoral protegido por APMs. Além disso, 9% das áreas consideradas prioritárias para conservação já foram concedidas a companhias petroleiras para exploração. As costas altamente povoadas dos Estados de São Paulo e Rio de Janeiro concentram a maioria das reservas de petróleo do país.

Os dados publicados são derivados de dois projetos apoiados pela FAPESP e coordenados por Marques: um projeto de Auxílio à Pesquisa – Regular, que apoia a Rede Nacional de Pesquisa em Biodiversidade Marinha (Sisbiota Mar), e um Projeto Temático para pesquisar fatores que geram e regulam a evolução e diversidade marinhas.

“Como um expediente para cumprir a meta, alguns governos têm criado Áreas de Proteção Marinha gigantescas, mas em torno de ilhas ou arquipélagos praticamente desabitados, muito distantes do próprio país”, disse Marques à Agência FAPESP.

“A maior APM do mundo, situada no arquipélago de Chagos, tem mais de meio milhão de quilômetros quadrados. É uma área enorme, que cumpre, com sobra, a meta do Reino Unido”, disse. O arquipélago faz parte do Território Britânico do Oceano Índico.

“Porém a população dessa área se resume ao contingente rotativo de uma base britânica. A ninguém mais. Além disso, as características da área, situada no meio do Oceano Índico, em nada correspondem à biodiversidade do Reino Unido”, prosseguiu.

Embora reconheça o valor de uma APM como essa, Marques argumenta que sua criação não é necessariamente efetiva em termos de preservação ambiental. Segundo ele, cumpre-se o aspecto quantitativo, mas não o qualitativo, ou seja, não oferece proteção efetiva ao litoral do país onde está a maior parte de sua população. E o que é mais grave, segundo Marques, é que o mesmo expediente foi adotado em todas as outras grandes APMs criadas recentemente.

“Verificamos, e divulgamos em nosso artigo, que a população média das 10 maiores APMs do mundo, computada em raios de 10 quilômetros em torno das mesmas, é de apenas 5.038 pessoas”, informou Marques. E essa média é puxada para cima por apenas duas APMs, a Reserva Marinha de Galápagos (Equador) e o Parque Nacional da Grande Barreira de Corais (Austrália), ambas com pouco mais de 25 mil habitantes. A população total das demais APMs não chega a 4 mil indivíduos, sendo nula em três delas.

“Para os governos, é uma medida muito cômoda criar áreas de proteção ambiental em regiões como essas, porque o desgaste socioeconômico de tal implementação é baixíssimo. Exceto por uma ou outra indústria pesqueira, ninguém vai reclamar muito. É uma situação muito diferente da que ocorreria se as APMs fossem criadas nos litorais dos respectivos países”, disse Marques.

O pesquisador ressalta que essas áreas remotas são úteis, como nas APMs de Galápagos e da Barreira de Corais, pela especialidade dos ecossistemas protegidos. Mas as APMs não seriam representativas da gama de ambientes dos países.

Fracassos e sucessos

“Nossa principal intenção ao escrever o artigo foi destacar que existe uma necessidade de proteção, que pode ser parcialmente atendida pela meta de 10%, mas essa proteção tem que respeitar os ambientes reais dos países. Não basta alcançar o número sem que haja uma correspondência entre quantidade e qualidade”, disse Marques.

O pesquisador conta que, ao enviar o artigo para o Marine Pollution Bulletin, um de seus objetivos foi estabelecer uma interlocução com o editor do periódico, Charles Sheppard, da University of Warwick, no Reino Unido. Sheppard é considerado uma das maiores autoridades em conservação marinha do mundo e foi um dos mentores da APM britânica do arquipélago de Chagos.

“A resposta do professor Sheppard foi a mais positiva que eu poderia esperar, tanto que ele decidiu publicar nosso artigo como editorial do Marine Pollution Bulletin.

De acordo com Marques, os dados básicos e as análises gerados pelos cientistas são vitais para o melhor uso dos recursos, ao estabelecer áreas de preservação.

“É necessário entender se a área é a ideal para ser protegida do ponto de vista evolutivo, genético, biogeográfico, ecológico etc. Há exemplos de sucesso em que isso foi observado e exemplos de fracassos em que foi ignorado. O melhor cenário possível é aquele em que cientistas, técnicos e políticos participam francamente do processo”, disse.

A War Without End, With Earth’s Carbon Cycle Held in the Balance (Science Daily)

Feb. 13, 2013 — The greatest battle in Earth’s history has been going on for hundreds of millions of years — it isn’t over yet — and until now no one knew it existed, scientists reported Feb. 13 in the journalNature.

This SAR11 bacterium is infected with a Pelagiphage virus. (Credit: Image courtesy of Oregon State University)

In one corner is SAR11, a bacterium that’s the most abundant organism in the oceans, survives where most other cells would die and plays a major role in the planet’s carbon cycle. It had been theorized that SAR11 was so small and widespread that it must be invulnerable to attack.

In the other corner, and so strange-looking that scientists previously didn’t even recognize what they were, are “Pelagiphages,” viruses now known to infect SAR11 and routinely kill millions of these cells every second. And how this fight turns out is of more than casual interest, because SAR11 has a huge effect on the amount of carbon dioxide that enters the atmosphere, and the overall biology of the oceans.

“There’s a war going on in our oceans, a huge war, and we never even saw it,” said Stephen Giovannoni, a professor of microbiology at Oregon State University. “This is an important piece of the puzzle in how carbon is stored or released in the sea.”

Researchers from OSU, the University of Arizona and other institutions have just outlined the discovery of this ongoing conflict, and its implications for the biology and function of ocean processes. The findings disprove the theory that SAR11 cells are immune to viral predation, researchers said.

“In general, every living cell is vulnerable to viral infection,” said Giovannoni, who first discovered SAR11 in 1990. “What has been so puzzling about SAR11 was its sheer abundance; there was simply so much of it that some scientists believed it must not get attacked by viruses.”

What the new research shows, Giovannoni said, is that SAR11 is competitive, good at scavenging organic carbon, and effective at changing to avoid infection. Because of that, it thrives and persists in abundance even though it’s constantly being killed by the new viruses that have been discovered.

The discovery of the Pelagiphage viral families was made by Yanlin Zhao, Michael Schwalbach and Ben Temperton, OSU postdoctoral researchers working with Giovannoni. They used traditional research methods, growing cells and viruses from nature in a laboratory, instead of sequencing DNA from nature. The new viruses were so unique that computers could not recognize the virus DNA.

“The viruses themselves, of course, appear to be just as abundant as SAR11,” Giovannoni said. “Our colleagues at the University of Arizona demonstrated this with new technologies they developed for measuring viral diversity.”

SAR11 has several unique characteristics, including the smallest known genetic structure of any independent cell. Through sheer numbers, this microbe has a huge role in consuming organic carbon, which it uses to generate energy while producing carbon dioxide and water in the process. SAR11 recycles organic matter, providing the nutrients needed by algae to produce about half of the oxygen that enters Earth’s atmosphere every day.

This carbon cycle ultimately affects all plant and animal life on Earth.

Journal Reference:

  1. Yanlin Zhao, Ben Temperton, J. Cameron Thrash, Michael S. Schwalbach, Kevin L. Vergin, Zachary C. Landry, Mark Ellisman, Tom Deerinck, Matthew B. Sullivan, Stephen J. Giovannoni. Abundant SAR11 viruses in the ocean.Nature, 2013; DOI: 10.1038/nature11921