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  • Coevolution  (1)
  • d-Alanine  (1)
  • ecology  (1)
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  • 1
    Electronic Resource
    Electronic Resource
    Evidence for phylogenetic congruence among sulfur-oxidizing chemoautotrophic bacterial endosymbionts and their bivalve hosts (1994)
    Springer
    Journal of molecular evolution 38 (1994), S. 533-542 
    Details
    ISSN: 1432-1432
    Keywords: Coevolution ; Phylogeny ; 16S rRNA ; Hydrothermal vent ; Chemoautotrophic symbionts
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Sulfur-oxidizing chemoautotrophic (thioautotrophic) bacteria are now known to occur as endosymbionts in phylogenetically diverse bivalve hosts found in a wide variety of marine environments. The evolutionary origins of these symbioses, however, have remained obscure. Comparative 16S rRNA sequence analysis was used to investigate whether thioautotrophic endosymbionts are monophyletic or polyphyletic in origin and to assess whether phylogenetic relationships inferred among these symbionts reflect those inferred among their hosts. 16S rRNA gene sequences determined for endosymbionts from nine newly examined bivalve species from three families (Vesicomyidae, Lucinidae, and Solemyidae) were compared with previously published 16S rRNA sequences of thioautotrophic symbionts and free-living bacteria. Distance and parsimony methods were used to infer phylogenetic relationships among these bacteria. All newly examined symbionts fall within the gamma subdivision of the Proteobacteria, in clusters containing previously examined symbiotic thioautotrophs. The closest free-living relatives of these symbionts are bacteria of the genus Thiomicrospira. Symbionts of the bivalve superfamily Lucinacea and the family Vesicomyidae each form distinct monophyletic lineages which are strongly supported by bootstrap analysis, demonstrating that host phylogenies inferred from morphological and fossil evidence are congruent with phylogenies inferred for their respective symbionts by molecular sequence analysis. The observed congruence between host and symbiont phylogenies indicates shared evolutionary history of hosts and symbiont lineages and suggests an ancient origin for these symbioses.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00178852
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  • 2
    Electronic Resource
    Electronic Resource
    The gutless oligochaete Phallodrilus leukodermatus Giere, a tubificid of structural, ecological and physiological relevance (1984)
    Springer
    Hydrobiologia 115 (1984), S. 83-89 
    Details
    ISSN: 1573-5117
    Keywords: aquatic Oligochaeta ; gutless oligochaetes ; structure ; ecology ; physiology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Phallodrilus leukodermatus is not only characterized by the complete absence of mouth, gut, anus and nephridia, but also by an exceptional dermal ultrastructure which is associated with gram-negative bacteria. The vertical distribution of the worms from Bermudian carbonate sands is also unusual in attaining population maximum at oligoxic or anoxic depths around the redox discontinuity (RPD) layer, where extremely high concentrations of amino acids and sugars are to be recorded. Based on results from current ecophysiological and ultrastructural studies, an interpretation of the unique biology of the worms is attempted.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00027897
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  • 3
    Electronic Resource
    Electronic Resource
    d-Alanine metabolism in the lucinid clam Lucinoma aequizonata (1995)
    Springer
    Journal of comparative physiology 164 (1995), S. 561-569 
    Details
    ISSN: 1432-136X
    Keywords: d-Alanine ; Chemoautotrophic symbiosis ; Lucinidae ; Clam, Lucinoma
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The chemoautotrophic symbiont-bearing clam Lucinoma aequizonata contains very high levels of free d-alanine in all tissues. The possible sources for this amino acid and its involvement in the clams' metabolism were investigated. Very low levels of d-alanine (generally below 1 μmol·l-1) were measured in the sediment porewaters from the habitat of the clams. Experiments with 14C-labeled tracers demonstrate an active metabolism of d-alanine in the clams rather than a role as inert waste product. d-alanine is metabolized at about 0.12 μmol·g fw-1·h-1. Label from aspartate, but not glucose and CO2, is incorporated into d-alanine. Incubation with labeled d-alanine did not result in formation of radioactive l-alanine. Tests for alanine racemase (EC 5.1.1.1) and d-amino acid oxidase (EC 1.4.3.3.) did not show activity in either gill, i.e. symbiont and host, or foot tissue. d-Alanine amino transferase (EC 2.6.1.b.) was demonstrated in gill and foot tissues. Two sources for d-alanine are proposed: a degradation of cell walls of symbiotic bacteria and production by the host using a d-specific alanine transaminase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00261397
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