Molecular phylogenetics of Stenodermatini bat genera: congruence of data from nuclear and mitochondrial DNA

Within the tribe Stenodermatini the systematics of the complex of species allied with the genus Artibeus has generated several alternative phylogenetic hypotheses. The most recent treatment recognized four genera (Artibeus, Dermanura, Enchisthenes, and Koopmania) and suggested that the most recent common ancestor of these four genera would include the common ancestor of all other currently recognized Stenodermatini genera except Sturnira. To test this hypothesis, we examined an EcoRI-defined nuclear satellite DNA repeat and 402 bp of DNA sequence variation from the mitochondrial cytochrome b gene. Phylogenetic conclusions based on Southern blot analyses, in situ hybridization, and mitochondrial DNA sequence data indicate that Enchisthenes is not closely related to Dermanura, Artibeus, or Koopmania and that Dermanura, Artibeus, and Koopmania shared a common ancestor after diverging from the remainder of the Stenodermatini. If our conclusions are correct, then justification for recognizing Dermanura and Koopmania as generically distinct from Artibeus must be based on the magnitude of difference that distinguishes each rather than on the conclusion that to place them as congeneric with Artibeus creates a paraphyletic taxon.      

Association between chloroplast and mitochondrial lineages in oaks

Patterns of chloroplast DNA (cpDNA) and mitochondrial DNA (mtDNA) variation were studied in 378 populations of oak trees sampled throughout the southern half of France. Six cpDNA haplotypes detected in a previous European survey and three new cpDNA haplotypes were found in this region. Two mitochondrial polymorphisms detected earlier by restriction analysis of PCR-amplified fragments alone, or in combination with single-strand conformation polymorphism (SSCP), were compared with the cpDNA data. Sequencing revealed the nature of the two mitochondrial mutations: a single-base substitution and a 4-bp inversion associated with a 22-bp hairpin secondary structure. The single-base substitution was then analyzed by allele-specific amplification. Results for the two cytoplasmic genomes were combined, which allowed the identification of 12 cpDNA-mtDNA haplotypes. The 4-bp mtDNA inversion has appeared independently in different cpDNA lineages. Given the peculiar nature of this mtDNA mutation, we suggest that intramolecular recombination leading to repeated inversions of the 4-bp sequence (rather than paternal leakage of one of the two genomes) is responsible for this pattern. Furthermore, the geographic locations of the unusual cpDNA-mtDNA associations (due to the inversion) usually do not match the zones of contact between divergent haplotypes. In addition, in southern France, the groupings of populations based on the mtDNA substitution were strictly congruent with those based on cpDNA. Because many populations that are polymorphic for both cpDNA and mtDNA have remained in contact since postglacial recolonization in this area without producing any new combination of cytoplasms involving the mitochondrial substitution, we conclude that paternal leakage is not a significant factor at this timescale. Such results confirm and expand our earlier conclusions based on controlled crosses.      

Cytosolic isocitrate dehydrogenase in humans, mice, and voles and phylogenetic analysis of the enzyme family

In this study, we report cDNA sequences of the cytosolic NADP-dependent isocitrate dehydrogenase for humans, mice, and two species of voles (Microtus mexicanus and Microtus ochrogaster). Inferred amino acid sequences from these taxa display a high level of amino acid sequence conservation, comparable to that of myosin beta heavy chain, and share known structural features. A Caenorhabditis elegans enzyme that was previously identified as a protein similar to isocitrate dehydrogenase is most likely the NADP-dependent cytosolic isocitrate dehydrogenase enzyme equivalent, based on amino acid similarity to mammalian enzymes and phylogenetic analysis. We also suggest that NADP-dependent isocitrate dehydrogenases characterized from alfalfa, soybean, and eucalyptus are most likely cytosolic enzymes. The phylogenetic tree of various isocitrate dehydrogenases from eukaryotic sources revealed that independent gene duplications may have given rise to the cytosolic and mitochondrial forms of NADP-dependent isocitrate dehydrogenase in animals and fungi. There appears to be no statistical support for a hypothesis that the mitochondrial and cytosolic forms of the enzyme are orthologous in these groups. A possible scenario of the evolution of NADP-dependent isocitrate dehydrogenases is proposed.      

Immunological similarities between specific chloroplast ribosomal proteins from Chlamydomonas reinhardtii and ribosomal proteins from Escherichia coli

Polyclonal antibodies were elicited against seven of the 33 different proteins of the large subunit of the chloroplast ribosome from Chlamydomonas reinhardtii. Three of these proteins are synthesized in the chloroplast and four are made in the cytoplasm and imported. In western blots, six of the seven antisera are monospecific for their respective large subunit ribosomal proteins, and none of these antisera cross-reacted with any chloroplast small subunit proteins from C. reinhardtii. Antisera to the three chloroplast-synthesized ribosomal proteins cross-reacted with specific Escherichia coli large subunit proteins of comparable charge and molecular weight. Only one of the four antisera to the chloroplast ribosomal proteins synthesized in the cytoplasm cross-reacted with an E. coli large subunit protein. None of the antisera cross-reacted with any E. coli small subunit proteins. On the assumption of a procaryotic, endosymbiotic origin for the chloroplast, those chloroplast ribosomal proteins still synthesized within the organelle appear to have retained more antigenic sites in common with E. coli ribosomal proteins than have those which are now the products of cytoplasmic protein synthesis. Antisera to this cytoplasmically synthesized group of chloroplast ribosomal proteins did not recognize any antigenic sites among C. reinhardtii cytoplasmic ribosomal proteins, suggesting that the genes for the cytoplasmically synthesized chloroplast ribosomal proteins either are not derived from the cytoplasmic ribosomal protein genes or have evolved to a point where no antigenic similarities remain.      

Scale-up issues for in situ anaerobic tetrachloroethene bioremediation

For the full scale implementation of in situ anaerobic bioremediation of tetrachloroethene (PCE) in groundwater, the following issues must be addressed: which organic substrates at which concentration would be most effective in promoting dechlorination and are economical; how far the substrate, electron acceptor, and nutrients can be transported in the aquifer; and the placement of delivery and recovery wells for distributing these amendments. In a microcosm study, almost all of the tested inexpensive substrates supported reductive dechlorination of PCE through vinyl chloride (VC) under methanogenic conditions. A minimum of about 60 mg L⁻¹ of organic carbon was needed to dechlorinate 23 μM PCE with a single feeding. In a second microcosm study dechlorination stopped at 1,2-dichloroethene (DCE) in microcosms fed higher concentrations of several substrates. At the highest concentrations the substrates inhibited DCE production. Three field tracer tests were conducted to evaluate methods to distribute the amendments across the aquifer. The natural groundwater gradient is not sufficient to distribute substrate evenly. Groundwater injection at 60 times the natural flux rate increased the distribution of substrate. A mixing strategy of cross-gradient injection further increased the distribution of the substrate. Ammonia-nitrogen, sulfate, and phosphate were retarded relative to the substrate and inorganic tracer. Received 30 October 1995/ Accepted in revised form 07 June 1996