Hydrogenosome‐Methanogen Assemblages in the Echinoid Endocommensal Plagiopylid Ciliates, Lechriopyla mystax Lynch, 1930 and Plagiopyla minuta Powers, 19331
TL;DR: Both Lechriopyla mystax Lynch and Plagiopyla minula Powers, 1933 contain hydrogenosome-methanogen assemblages similar to those reported for other plagiopylid ciliates, which probably plays a significant role in exploitation of the methanogens by the host ciliate.
Abstract: . Lechriopyla mystax Lynch, 1930 and Plagiopyla minula Powers, 1933 contain hydrogenosome-methanogen assemblages similar to those reported for other plagiopylid ciliates. These assemblages are stacks of elongate ovoid hydrogenosomes alternating with methanogens; these stacks are surrounded by cisternae of the rough endoplasmic reticulum that are often accompanied by Golgi complexes. The individual methanogens in the larger ciliate, L. mystax, are about four times the volume of those in the smaller ciliate, P. minuta, but both ciliates appear to contain Gram-negative methanococcoid bacteria, possibly Methanoplanus sp. The endoplasmic reticulum-Golgi complex probably plays a significant role in exploitation of the methanogens by the host ciliate.
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TL;DR: In the ongoing challenge to detect anaerobic or anoxic-tolerant lineages of eukaryotes, DNA is directly extracted from the anoxic sediment of a saline meromictic lake, genetic libraries of PCR-amplified SSU rDNA are constructed, and phylogenetic analyses with the cloned SSu rDNA sequences are performed.
98 citations
TL;DR: The Archezoa are living ‘relics’ of the earliest phase of anaerobic eukaryotic evolution which occurred when free oxygen was scarce in the atmosphere.
Abstract: Anaerobic environments are widespread and common : they include marine and freshwater sediments, waterlogged soils, sewage and the gastro-intestinal tracts of animals. The interior of organic aggregates with diameters greater than about 1 mm may also be anaerobic if diffusion is the only means by which 0, can penetrate (Fenchel & Finlay, 1991 a). Anaerobic environments often contain large numbers of prokaryotes and these in turn support a variety of anaerobic protozoa which feed on them (Fenchel & Finlay, 1990). Protozoa w h c h live exclusively in anaerobic environments and which lack the enzymes necessary for oxidative phosphorylation can be divided into two groups. The first includes protozoa which are probably ‘ primitively ’ anaerobic, principally the trichomonads, diplomonads and microsporidia; these taxa form the core of the phylum Archezoa (Cavalier-Smith, 1987). On the basis of their small subunit (SSU) ribosomal (r)RNA sequences, the few Archezoa sequenced so far form the basal lineages in the eukaryotic tree (Vossbrinck e t al., 1987; Sogin e t al., 1989; Chakrabarti e t ul., 1992; Van Keulen e t al., 1993; Leipe e t al., 1993). All Archezoa lack mitochondria and Variomorpha laecatrzx has prokaryote-sized (70s) ribosomes (Vossbrinck e t al., 1987). The Archezoa are living ‘relics’ of the earliest phase of anaerobic eukaryotic evolution (Cavalier-Smith, 1987) which occurred when free oxygen was scarce in the atmosphere.
93 citations
01 Jan 2007
TL;DR: The chapter introduces model organisms and systems that have been used to study fundamental properties and principles of archaeal biology, in addition to those that have served as models for understanding the biology of more complex eucaryal cells.
Abstract: This chapter provides an overview of the Archaea and some of their morphological, physiological, biochemical, and molecular properties. It introduces model organisms and systems that have been used to study fundamental properties and principles of archaeal biology, in addition to those that have served as models for understanding the biology of more complex eucaryal cells. The chapter describes phylogeny of Archaea and the origin of life, and gives an overview of the characteristic properties of archaeal cells. Rather than one model organism, a broad range of archaea have proven useful for studying morphology, physiology, molecular mechanisms of adaptation, and so forth. These include Methanothermobacter thermautotrophicus, M. marburgensis, and Methanosarcina spp. for methanogenesis; Thermoplasma for proteolysis; Halobacterium for light-driven proton translocation, gene regulation, chemotaxis, and gas vesicles synthesis; Archaeoglobus for sulfate reduction; Pyrococcus and Acidianus ambivalens for inorganic sulfur metabolism; Sulfolobus, A. ambivalens, Pyrococcus, and the methanogens for electron transport chains; Sulfolobus and Pyrococcus for DNA replication and transcription; Halobacterium, Haloarcula, and Sulfolobus for translation. The chapter also describes the properties of major archaeal taxa according to their ecology and molecular similarity. Important characteristics of some of the key organisms are also included in this chapter. Methanosarcina barkeri, M. mazei, and M. acetivorans are the most well studied methanogens and are important model organisms for studies on acetoclastic methanogenesis, transcription, and chaperonins.
54 citations
TL;DR: Various echinoderms are colonized by species from several classes of the Phylum Ciliophora, indicating that the echinoderm “habitat” has been invaded independently on numerous occasions throughout evolutionary history.
Abstract: Various echinoderms are colonized by species from several classes of the Phylum Ciliophora, indicating that the echinoderm "habitat" has been invaded independently on numerous occasions throughout evolutionary history. Two "echinoderm" ciliates whose phylogenetic positions have been problematic are Licnophora macfarlandi Stevens, 1901 and Schizocaryum dogieli Poljansky and Golikova, 1957. Licnophora macfarlandi is an endosymbiont of the respiratory trees of holothuroids, and S. dogieli is found in the esophagus of echinoids. A third species, Lechriopyla mystax Lynch, 1930, is a plagiopylid ciliate found in the intestine of echinoids. Host echinoderms were collected near the Friday Harbor Laboratories, San Juan Island, WA. Specimens of S. dogieli and L. mystax were obtained from the esophagus and intestine, respectively, of the sea urchin Strongylocentrotus pallidus. Specimens of L. macfarlandi were collected from the fluid obtained from the respiratory trees of Parastichopus californicus. Using small subunit ribosomal RNA (SSrRNA) sequences of these three ciliates and a global alignment of SSrRNA sequences of other ciliates, we established the following. 1) Licnophora is a spirotrich ciliate, clearly related to the hypotrichs and stichotrichs; this is corroborated by its possession of macronuclear replication bands. 2) Lechriopyla is the sister genus to Plagiopyla and is a member of the Class Plagiopylea, which was predicted based on its cytology. 3) Schizocaryum clusters in the Class Oligohymenophorea and is most closely related to the scuticociliates; there are currently no morphological features known to relate Schizocaryum to the scuticociliates.
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TL;DR: The phytochemical properties of pyruvate, particularly the polymethine-like properties of butyrate, have been found to be attractive to the purposes of cosmetics and anti-freezing agents.
Abstract: INTRODUCTION .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . ..... ..... . . . . . . . . . . GENERAL CONSIDERATIONS . GLyCOLySIS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . METABOLISM OF PYRUVATE BY DECARBOXYLATION . Oxidation of Pyruvate to Acetyl Coenzyme A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Acetate ai1d Butyrate Formation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ethanol Formation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ELECTRON TRANSFER . General Comments and Electron Carriers . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . Transfer of Electrons to Organic Acceptors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . �::����,:���������. :::::: : : : : : ::::: : : : : : : : : :: ::::: : : : : : : : : : : : ::::::::::: : : : : : : : : : : : : :::: : : : : : : : Reduction of Nitro-Derivatives Active Against Anaerobic Microorganisms . . . . . . . . . . . HYDROGENOSOMES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ... . . . ... ..... .. . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . ... . EVOLUTIONARY CONSIDERATIONS . CONCLUSIONS .
303 citations
TL;DR: It is concluded that the evolution of anaerobic forms has taken place independently within different taxonomic groups and that hydrogenosomes are modified mitochondria.
149 citations
TL;DR: The physiological background of this endosymbiosis and its functioning in degradation processes in the anoxic environment are discussed.
Abstract: Fluorescent bacteria were demonstrated to be abundantly spread as single cells throughout the cytoplasm of the giant amoeba Pelomyxa palustris, the sapropelic ciliate Metopus striatus and six other anaerobic protozoa examined. The endosymbionts of P. palustris and M. striatus were identified as methanogenic bacteria on the basis of the presence of the deazaflavin coenzyme F420 and the pterin compound F342. Moreover individuals of P. palustris produced methane over a long period of incubation. The number of methanogenic bacteria was above 1010 cells/ml protozoal cytoplasm. Two types of methanogenic bacteria together with unidentified thick bacteria were found in P. palustris. The physiological background of this endosymbiosis and its functioning in degradation processes in the anoxic environment are discussed.
132 citations
TL;DR: It is believed that the microbodies found in six anaerobic ciliated protozoa are hydrogenosomes, that they are derived from mitochondria, and that their biochemical modification has incurred little change in the original mitochondrial ultrastructure.
Abstract: Microbodies in six anaerobic ciliated protozoa (Metopus, Brachonella, Plagiopyla, Parablepharisma, Sonderia, Saprodinium) were found to be enclosed by two membranes. The inner membrane showed extensive infolding, division stages were observed, and in all genera apart from Sonderia and Parablepharisma, the microbodies contained an hydrogenase and were attached to methanogenic bacteria. Some of these ciliates are related to aerobic species with mitochondria. We believe that the microbodies are hydrogenosomes, that they are derived from mitochondria, and that their biochemical modification has incurred little change in the original mitochondrial ultrastructure. These observations weaken the case for the independent origin of hydrogenosomes from anaerobic prokaryotes.
131 citations
TL;DR: Most of the anaerobic ciliates harbor a flora of ecto- and endosymbiotic bacteria as demonstrated by transmission and scanning electron micrographs and it is speculated that the bacteria may utilize the metabolic end products of the protozoa for growth and energy yielding processes.
Abstract: SYNOPSIS. Marine, sediment-dwelling ciliates were examined for cytochrome oxidase activity by a cytochemical method and for fine structural details. Species of Plagiopylidae (Trichostomatida), i.e. Plagiopyla frontata, Sonderia vorax and Sonderia sp., and of Heterotrichida, i.e., Parablepharisma pellitum, Parablepharisma sp., Metopus contortus, Metopus vestitus and Caenomorpha capucina; previously considered to be obligate anaerobes because of their sulfide-containing habitat, do not have cytochrome oxidase activity or mitochondria with cristae or tubuli. The evolutionary origin and significance of anaerobic ciliates is discussed. Most of the anaerobic ciliates harbor a flora of ecto- and endosymbiotic bacteria as demonstrated by transmission and scanning electron micrographs. It is speculated that the bacteria may utilize the metabolic end products of the protozoa for growth and energy yielding processes. These associations are also compared with other, previously described cases of symbiosis involving prokaryotes and protozoa.
130 citations