8/25/2023 0 Comments 11. What specialized cells line the inner cavity and move fluids through filter feeding sponges?Together with sponges and cnidarians this group of colonial invertebrates is among the dominating foulers in many bottom communities from the intertidal zone to a depth of 8 km 51, 52, 53, 54. The phylum Bryozoa is comprised of active filterers that feed mainly on microscopic algae, gathering them out of seawater 46, 47, 48, 49, 50. Recently a bacteriophage was found to enhance the biofilm formation in the gut of an ascidian by interacting with its bacterial hosts 45. Similarly, filter-feeders such as bivalve mollusks and tunicates and bacteria living in them also acquire viruses (reviewed in 41, 42, 43, 44). Corals, together with their eukaryotic and prokaryotic symbionts, harbor a variety of viruses too (e.g. Indeed, by filtering enormous volumes of water, sea sponges acquire viruses that infect their cells 30, 31, 32 as well as their bacterial symbionts 33. Being present in large numbers in the seawater 27, 28, viruses, among others, enter suspension-feeders (e.g. In the marine realm, the large variety of viruses are found across diverse taxa, including protists and various invertebrates such as sponges, cnidarians, flatworms, polychaetes, mollusks, crustaceans and echinoderms (reviewed in 15, 16, 17, 18, 19) see also 20, 21, 22, 23, 24, 25, 26 and references therein). This phage also encodes proteins important for bacterium interactions with the host 14. In turn, the bacteriophage WO influences the bacterial titer in the host tissues 13. The symbiotic bacteria Wolbachia exert a major influence on their arthropod hosts by manipulating their reproduction and providing increased resistance to infections 12. The best-known example is Wolbachia bacteriophage WO. Although such symbionts are either intracellular or live in the host tissues (sometimes in special organs), they can also harbor bacteriophages. In addition to the complex microbiomes associated with invertebrate digestive systems or body surfaces, some species harbor specific bacterial symbionts that may be vertically transmitted. ![]() These studies showed that such communities are species-specific and may be significant for homeostasis of the animal hosts. For example, the viral communities associated with the cnidarian Hydra 8, 9 and certain scleractinian corals 10, 11 have been recently characterized using metagenomic methods. Although the bacteriophage communities (viromes) of vertebrates are much better studied (reviewed in refs 5, 6, 7), some data are also available for invertebrates. Most of these viruses are bacteriophages. In addition to harboring the viruses replicating in eukaryotic cells, all known animals (as well as other multicellular organisms) are associated with specific microbial communities that include viruses infecting their symbiotic microorganisms. Viruses are found in all kingdoms of living organisms and are best studied in those that have an applied or medical value ( 1, 2, 3, 4, ). sinuosa with so-called metamorphosis associated contractile structures (MACs) formed in the cells of the marine bacterium Pseudoalteromonas luteoviolacea which are known to trigger larval metamorphosis in a polychaete worm. Finally, we compare unusual ‘sea-urchin’-like structures found in the collapsed bacteria in P. ![]() We develop two hypotheses explaining exo- and endogenous circulation of the viruses during the life-cycle of B. We speculate that viruses destroying bacteria regulate symbiont numbers in the bryozoan hosts, a phenomenon known in some insects. We also documented the effect of VLPs on bacterial hosts: we explain different bacterial ‘ultrastructural types’ detected in bryozoan tissues as stages in the gradual destruction of prokaryotic cells caused by viral multiplication during the lytic cycle. Our ultrastructural study showed for the first time a variety of virus-like particles (VLPs) and supposed virus-related structures inside symbiotic bacteria in two marine species from the phylum Bryozoa, the cheilostomes Bugula neritina and Paralicornia sinuosa. ![]() In fact, they have never been reported for most animal phyla. Bacteriophage communities associated with humans and vertebrate animals have been extensively studied, but the data on phages living in invertebrates remain scarce.
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