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The viral eukaryogenesis hypothesis posits that eukaryotes are composed of three ancestral elements: a viral component that became the modern nucleus; a prokaryotic cell (an archaeon according to the eocyte hypothesis) which donated the cytoplasm and cell membrane of modern cells; and another prokaryotic cell (here bacterium) that, by endocytosis, became the modern mitochondrion or chloroplast.
Most bacteria and viruses undergo passive uptake, where they rely on the host cell for uptake. However, apicomplexans engage in active entry. [8] One obligate wasp parasite, Polistes atrimandibularis, infiltrates its hosts' colony by modifying its chemical signature to match that of the hosts. [9]
An archaeal virus is a virus that infects and replicates in archaea, a domain of unicellular, prokaryotic organisms.Archaeal viruses, like their hosts, are found worldwide, including in extreme environments inhospitable to most life such as acidic hot springs, highly saline bodies of water, and at the bottom of the ocean.
Non-cellular life, also known as acellular life, is life that exists without a cellular structure for at least part of its life cycle. [1] Historically, most definitions of life postulated that an organism must be composed of one or more cells, [2] but, for some, this is no longer considered necessary, and modern criteria allow for forms of life based on other structural arrangements.
A virus is a submicroscopic infectious agent that replicates only inside the living cells of an organism. [1] Viruses infect all life forms, from animals and plants to microorganisms, including bacteria and archaea. [2] [3] Viruses are found in almost every ecosystem on Earth and are the most numerous type of biological entity.
The lytic cycle (/ ˈ l ɪ t ɪ k / LIT-ik) is one of the two cycles of viral reproduction (referring to bacterial viruses or bacteriophages), the other being the lysogenic cycle. The lytic cycle results in the destruction of the infected cell and its membrane.
They infect and destroy the bacteria in aquatic microbial communities and this is the most important mechanism of recycling carbon in the marine environment. The organic molecules released from the bacterial cells by the viruses stimulate fresh bacterial and algal growth. [99] Microorganisms constitute more than 90% of the biomass in the sea.
Structural model at atomic resolution of bacteriophage T4 [1] The structure of a typical myovirus bacteriophage Anatomy and infection cycle of bacteriophage T4. A bacteriophage (/ b æ k ˈ t ɪər i oʊ f eɪ dʒ /), also known informally as a phage (/ ˈ f eɪ dʒ /), is a virus that infects and replicates within bacteria and archaea.