Viruses manipulate the marine environment.
ABSTRACT Marine viruses affect Bacteria, Archaea and eukaryotic organisms and are major components of the marine food web. Most studies have focused on their role as predators and parasites, but many of the interactions between marine viruses and their hosts are much more complicated. A series of recent studies has shown that viruses have the ability to manipulate the life histories and evolution of their hosts in remarkable ways, challenging our understanding of this almost invisible world.
SourceAvailable from: Beatriz Fernández-Gómez[Show abstract] [Hide abstract]
ABSTRACT: Prokaryotic microbes have the highest abundance and bio-mass of all organisms on our planet. The number of bacteria on earth by far exceeds the number of stars in the universe (Curtis and Sloan 2004; Pomeroy et al. 2007). The ocean alone contains an estimated 10 29 bacteria (Whitman et al. 1998); thus, billions of microbes are present in each liter of seawater. Consequently, it is not surprising that bacteria play a critical role in biogeochemical cycling in all ecosystems. Prokaryotic microbes fulfill an enormous diversity of functions (Harwood 2008), affecting a wide range of matter cycles, such as nitrogen fixation and phosphate storage (Davelaar 1993; Falkowski et al. 1998; Gruber and Galloway 2008). Bacteria function in degradation and transformation of organic matter, providing inorganic nutrients for phytoplankton, and bacteria serve as a food source for bacteriovores. In addition, marine bacteria, along with eukaryotic microbes, contribute to about half of all primary production on the planet (Arrigo 2005). Over the past four decades, research in microbial ecology has begun to reveal the diversity of microbes in the food web, and the breadth and complexity of their interactions and metabolic processes that drive biogeochemical cycles. These new discoveries changed the way we think about trophic interactions in the ocean, and drove the transformation of the classic linear food chain into a multidirectional food web that highlights the role of microbes in trophic dynamics and nutrient flux. This new food web also includes a remineralization and recycling pathway for dissolved organic material known as the microbial loop. In this chapter, we will outline the evolution of the microbial loop and discuss the bacterial groups and processes that Abstract Marine microbes have been studied for centuries. However, only in the past four decades have microbes been recognized as drivers of energy and nutrient cycles in the ocean. Several pivotal publications in the mid-to late-twentieth century affirmed the role of microbes in primary production and consumption of dissolved organic matter. These findings supported the hypothesis that microbes provide a link in the food web between phyto-plankton, dissolved nutrients, and zooplankton. This concept became known as the microbial loop. More recent discoveries have identified additional contributors to the loop, such as novel phototrophic bacteria, archaea and viruses, yet the role of many microbial specialists in nutrient cycling remains unclear. In this chapter, we summarize the history and development of the microbial loop concept, and discuss five bacterial groups whose contribution to the microbial loop has largely been overlooked in the literature. We propose a modified loop that integrates processes performed by nitrogen-fixing bacteria, particle-and organism-associated bacteria, bacterial symbionts, Flavobacteria, and predatory bacteria, and conclude that the microbial loop must continue to evolve as the ecology of additional microbial specialists is revealed.01/2014;
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ABSTRACT: In the evolutionary arms race between microbes, their parasites, and their neighbours, the capacity for rapid protein diversification is a potent weapon. Diversity-generating retroelements (DGRs) use mutagenic reverse transcription and retrohoming to generate myriad variants of a target gene. Originally discovered in pathogens, these retroelements have been identified in bacteria and their viruses, but never in archaea. Here we report the discovery of intact DGRs in two distinct intraterrestrial archaeal systems: a novel virus that appears to infect archaea in the marine subsurface, and, separately, two uncultivated nanoarchaea from the terrestrial subsurface. The viral DGR system targets putative tail fibre ligand-binding domains, potentially generating >1018 protein variants. The two single-cell nanoarchaeal genomes each possess ≥4 distinct DGRs. Against an expected background of low genome-wide mutation rates, these results demonstrate a previously unsuspected potential for rapid, targeted sequence diversification in intraterrestrial archaea and their viruses.Nature Communications 03/2015; 6. DOI:10.1038/ncomms7585 · 10.74 Impact Factor