Acidocalcisomes - Conserved from bacteria to man

Department of Cellular Biology and Center for Tropical and Global Emerging Diseases, University of Georgia, Athens, Georgia 30602, USA.
Nature Reviews Microbiology (Impact Factor: 23.57). 04/2005; 3(3):251-61. DOI: 10.1038/nrmicro1097
Source: PubMed


Recent work has shown that acidocalcisomes, which are electron-dense acidic organelles rich in calcium and polyphosphate, are the only organelles that have been conserved during evolution from prokaryotes to eukaryotes. Acidocalcisomes were first described in trypanosomatids and have been characterized in most detail in these species. Acidocalcisomes have been linked with several functions, including storage of cations and phosphorus, polyphosphate metabolism, calcium homeostasis, maintenance of intracellular pH homeostasis and osmoregulation. Here, we review acidocalcisome ultrastructure, composition and function in different trypanosomatids and other organisms.

    • "Bacterial PPBs were first described in Agrobacterium tumefaciens (Seufferheld et al., 2003), the same bacterium examined in this work. PPBs may be the only cellular organelle that has been conserved between prokaryotic and eukaryotic organisms (Docampo et al., 2005). Other types of bacterial storage granules include carboxysomes, involved in respiration and recognizable by their characteristic polygonal shape (Yeates et al., 2008; Iancu et al., 2010; Cameron et al., 2013), and polyhydroxybutyrate granules for storing carbon (Beeby et al., 2012). "
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    ABSTRACT: Bacterial cells often contain dense granules. Among these, polyphosphate bodies (PPBs) store inorganic phosphate for a variety of essential functions. Identification of PPBs has until now been accomplished by analytical methods that required drying or chemically fixing the cells. These methods entail large electron doses that are incompatible with low-dose imaging of cryogenic specimens. We show here that Scanning Transmission Electron Microscopy (STEM) of fully hydrated, intact, vitrified bacteria provides a simple means for mapping of phosphorus-containing dense granules based on quantitative sensitivity of the electron scattering to atomic number. A coarse resolution of the scattering angles distinguishes phosphorus from the abundant lighter atoms: carbon, nitrogen and oxygen. The theoretical basis is similar to Z contrast of materials science. EDX provides a positive identification of phosphorus, but importantly, the method need not involve a more severe electron dose than that required for imaging. The approach should prove useful in general for mapping of heavy elements in cryopreserved specimens when the element identity is known from the biological context. © 2015 The Authors Journal of Microscopy © 2015 Royal Microscopical Society.
    No preview · Article · Jul 2015 · Journal of Microscopy
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    • "Unfortunately through the years many studies have not been and polyphosphate (poly P) [55]. In eukaryotic microbes, acidocalcisomes function in P metabolism, Ca 2+ homeostasis, maintenance of intracellular pH, and osmoregulation [55] [56]. Prokaryotic acidocalcisomes are very similar to their eukaryotic counterparts containing the transporters H + -ATPase and the vacuolar proton translocating pyrophosphatase responsible for their acidification [53]. "
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    ABSTRACT: With the continued increase of genomic information and computational analyses during the recent years, the number of newly discovered calcium binding proteins (CaBPs) in prokaryotic organisms has increased dramatically. These proteins contain sequences that closely resemble a variety of eukaryotic calcium (Ca2+) binding motifs including the canonical and pseudo EF-hand motifs, Ca2+-binding ß-roll, Greek key motif and a novel putative Ca2+-binding domain, called the Big domain. Prokaryotic CaBPs have been implicated in diverse cellular activities such as division, development, motility, homeostasis, stress response, secretion, transport, signaling, and host-pathogen interactions. However, the majority of these proteins are hypothetical, and only few of them have been studied functionally. The finding of many diverse CaBPs in prokaryotic genomes opens an exciting area of research to explore and define the role of Ca2+ in organisms other than eukaryotes. This review presents the most recent developments in the field of CaBPs and novel advancements in the role of Ca2+ in prokaryotes.
    Full-text · Article · Dec 2014 · Cell Calcium
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    • "Organisms utilize polyphosphate to regenerate nucleotide triphosphates (Kuroda et al. 1997); therefore, polyphosphate storage granules are regarded as energy storage granules. In eukaryotes, polyphosphate storage granules are found in membrane bound organelles and a similar architecture has been suggested in bacteria (Docampo et al. 2005). Other types of membrane-encapsulated particles have been clearly visualized by ECT (Komeili 2006); however, in C. jejuni the polyphosphate storage granules are not enclosed by membranes . "
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    ABSTRACT: Campylobacter jejuni is one of the most successful food-borne human pathogens. Here we use electron cryotomography to explore the ultrastructure of C. jejuni cells in logarithmically growing cultures. This provides the first look at this pathogen in a near-native state at macromolecular resolution (~5 nm). We find a surprisingly complex polar architecture that includes ribosome exclusion zones, polyphosphate storage granules, extensive collar-shaped chemoreceptor arrays, and elaborate flagellar motors.
    Full-text · Article · Oct 2014 · MicrobiologyOpen
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