An Ocean of Viruses | The Scientist Magazine®
The relationship between viral and microbial abundances is thus of great interest. It is often assumed that the abundance of virus-like particles. The majority of these viruses infect microbes, whether bacteria, archaea or the dynamic, ecological effects of virus infection of marine microbes. for specific functional relationships between viruses and microbial hosts. Viruses are a key component of marine ecosystems, but the assessment of their global role in regulating microbial communities and the flux of carbon . Because the relationship between viral and prokaryotic abundance was.
The subset of hosts that a virus typically infects is narrower than the range of microbes that are typically consumed by a grazer species e.Old & Odd: Archaea, Bacteria & Protists - CrashCourse Biology #35
However, there is evidence that viruses of microbes can infect hosts from different species or even different genera. For example, some cyanophages can infect different strains within the same cyanobacteria species, either Synechococcus or Prochlorococcus, as well as strains of different cyanobacterial genera [ 13 ]. The quantitative study of the host-range of viruses of microbes is in its infancy [ 22 - 26 ], an issue we return to later.
Successful viral infections can lead to lysis of hosts as well as the conversion of hosts into lysogens where the viral genome is integrated into that of the host, subsequently altering host physiology [ 22127 ].
Lytic viral infection of microbes and its effects are our primary concerns here.
Marine Viruses: Key Players in Marine Ecosystems
Viral lysis of microbes is thought to have direct effects on microbial community composition. Ostensibly, viral lysis should decrease the abundance of specific microbial lineages that are targeted by viral infection [ 28 ]. Estimates of bacterial-induced mortality suggest that viruses are, in some cases, as important as grazers in selectively killing microbes [ 2930 ], whereas, in other cases, they may be the dominant source of microbial mortality [ 3132 ].
The depletion of susceptible bacteria leads to the possibility of dynamic fluctuations in viral and microbial populations, a result predicted by simple population models [ 33 ]. Nonetheless, direct evidence for coupled oscillations between virus-microbe systems in the oceans is limited.
The reasons are complex, but likely due to the fact that the emergence of new or previously rare viral subtypes occurs frequently and rapidly [ 34 - 37 ]. The changing identities of strains and their populations can make it difficult to infer the consequences of virus-microbe interactions.
Hence, paradoxically, the seemingly most apparent consequences of viral-induced lysis of microbes may be hard to observe in practice. We anticipate that observations of virus and microbial abundances in situ via genomic and metagenomic methods, with improved time-scale resolution, will provide direct evidence for specific functional relationships between viruses and microbial hosts.
Viral infection and the availability of carbon and nutrients Virus-induced mortality of microbes has direct effects on ecosystem function.
Lysis of microbes involves the release of organic carbon and other nutrients back into the environment. For about 3 billion years, most organisms were microscopic, and bacteria and archaea were the dominant forms of life.
Here, eukaryotes resulted from the entering of ancient bacteria into endosymbiotic associations with the ancestors of eukaryotic cells, which were themselves possibly related to the Archaea. Later on, some eukaryotes that already contained mitochondria also engulfed cyanobacterial-like organisms. This led to the formation of chloroplasts in algae and plants. There are also some algae that originated from even later endosymbiotic events. Here, eukaryotes engulfed a eukaryotic algae that developed into a "second-generation" plastid.
The marine Thiomargarita namibiensislargest known bacterium Cyanobacteria blooms can contain lethal cyanotoxins Chloroplastssuch as the chloroplasts of this glaucophytemay have originated from cyanobacteria. This Pompeii worman extremophile found only at hydrothermal ventshas a protective cover of bacteria.
The largest known bacterium, the marine Thiomargarita namibiensiscan be visible to the naked eye and sometimes attains 0. These microbes are prokaryotesmeaning they have no cell nucleus or any other membrane-bound organelles in their cells. Archaea were initially classified as bacteriabut this classification is outdated.
The Archaea are further divided into multiple recognized phyla. Classification is difficult because the majority have not been isolated in the laboratory and have only been detected by analysis of their nucleic acids in samples from their environment. Archaea and bacteria are generally similar in size and shape, although a few archaea have very strange shapes, such as the flat and square-shaped cells of Haloquadratum walsbyi.
Ocean viruses and their effects on microbial communities and biogeochemical cycles
Other aspects of archaeal biochemistry are unique, such as their reliance on ether lipids in their cell membranessuch as archaeols. Archaea use more energy sources than eukaryotes: Salt-tolerant archaea the Haloarchaea use sunlight as an energy source, and other species of archaea fix carbon ; however, unlike plants and cyanobacteriano known species of archaea does both. Archaea reproduce asexually by binary fissionfragmentationor budding ; unlike bacteria and eukaryotes, no known species forms spores.
Unlike viruses and bacteria, no known archaea is a pathogen. Archaea are particularly numerous in the oceans, and the archaea in plankton may be one of the most abundant groups of organisms on the planet. Archaea are a major part of Earth's life and may play roles in both the carbon cycle and the nitrogen cycle. Halobacteriafound in water saturated or nearly saturated with salt, are now recognized as being archaea. The flat and square-shaped cells of the archaea Haloquadratum walsbyi.