Genetics of naphthalene and phenanthrene degradation by Comamonas testosteroni

Naphthalene and phenanthrene have long been used as model compounds to investigate the ability of bacteria to degrade polycyclic aromatic hydrocarbons. The catabolic pathways have been determined, several of the enzymes have been purified to homogeneity, and genes have been cloned and sequenced. However, the majority of this work has been performed with fast growing Pseudomonas strains related to the archetypal naphthalene-degrading P. putida strains G7 and NCIB 9816-4. Recently Comamonas testosteroni strains able to degrade naphthalene and phenanthrene have been isolated and shown to possess genes for polycyclic aromatic hydrocarbon degradation that are different from the canonical genes found in Pseudomonas species. For instance, C. testosteroni GZ39 has genes for naphthalene and phenanthrene degradation which are not only different from those found in Pseudomonas species but are also arranged in a different configuration. C. testosteroni GZ42, on the other hand, has genes for naphthalene and phenanthrene degradation which are arranged almost the same as those found in Pseudomonas species but show significant divergence in their sequences. Received 10 August 1997/ Accepted in revised form 15 August 1997     

Studies in Montia L. and Claytonia L. and Allied Genera

The pollen morphology of several genera in Portulacaceae is described. Particular attention has been paid to the genera of the subfamily Montioideae, as a stage of continued monographical studies. Among genera especially dealt with are Claytonia, Montia, Crunocallis, Naiocrene, Neopaxia, Mona, Maxia, Limnalsine, and Montiastrum. In the taxonomical treatment of these genera the pollen morphology has proved to afford many important additional characters.

The pollen grains of Claytonia are distinguished from those of the remainder in being 3-colpate. The grains of the Claytonia-type have many similarities with those of Lewisia, a genus of the subfamily Portulacoideae. The other genera of Montioideae have pantocolpate pollen grains. Among these genera several different pollen types are distinguished, chiefly with regard to the sexine structures and the aperture membranes. The Montiastrum-type is especially interesting, with tholate grains, a particular pollen type not met with in any other genus in the family. The pollen morphology of some genera in the Portulacoideae is also treated. In some species in Calandrina and Talinum pantotreme pollen grains are observed with apertures transitional between pori and colpi. The apertures of the pantotreme grains are arranged in characteristic patterns.

Particular attention has been given to the variation of the pollen morphological characters. This variation has been examined with regard to the differences between different populations of the same species as well as between different species. The greatest variation has been observed in the shape and size of the grains. The structure and sculpture and thickness of the sexine and the aperture membranes are less variable. Some polyploid taxa are connected with the occurrence of pollen grains with divergent and varying aperture numbers.

In a survey of the genera the taxonomical results of the investigation are presented with particular regard to the pollen morphology. The new genus, Maxia Ö. Nilss., is described. One new species, Montia clara Ö. Nilss., is described and some new combinations are made.

Pollen morphological diagnoses are given for 46 different taxa. The aperture conditions for 96 different species are presented.     

Die Zweiteiligkeit der Chromatophoren bei Cryptomonaden

In theChrysophyceae as well as in different species ofCryptomonas bilobed chromatophores are present. These chromatophores consist of two large parietal lobes closed to the lateral sides of the cell and joined by a narrow bridge on its dorsal part. A survey of all species with a single bilobed chromatophore is given. Besides, also species with two separate chromatophores have been found. The presence of several chromatophores inCryptomonas cells is doubtful. The morphology of the chromatophores has to be taken into consideration in the taxonomy ofCryptomonas.

     

Evolutionary trend in feeding habits of <Emphasis Type="Italic">Girella</Emphasis> (Perciformes: Girellidae)

Although some Girella species are herbivorous, having basically tricuspid teeth, some are omnivorous. To determine the evolutionary trends in feeding habits of Girella, the phylogenetic relationships of several species of Girella were estimated by partially sequencing the mitochondrially encoded NADH dehydrogenase subunit 2 gene, and the dentition and adductor mandibulae complex of each species were examined. The cladogram determined from the mitochondrial DNA analysis indicated that multiple tooth-rows containing incisor-like teeth existed in adults of the ancestral species of Girella, species with a single tooth-row of tricuspid teeth in the adult stage having diverged subsequently on several occasions. The tendinous connections between each section of the adductor mandibulae complex are believed to have been simple in the ancestral species, more complicated connections also having diverged later on several occasions. Multiple tooth-rows containing incisor-like teeth and the simple adductor mandibulae complex are deduced as adaptations to herbivory; on the other hand, a single tooth-row of tricuspid teeth and the complicated adductor mandibulae complex are deduced as adaptations to omnivory. Therefore, the ancestral species of Girella is suggested as having been adapted to herbivory, with species adapted to omnivory having diverged on several subsequent occasions.     

Morphology and Molecular Phylogeny of Staurojoenina mulleri sp. nov. (Trichonymphida,Parabasalia) from the Hindgut of the Kalotermitid Neotermes jouteli

Staurojoenina is a large and structurally complex genus of hypermastigont parabasalians found in the hindgut of lower termites. Although several species of Staurojoenina have been described worldwide, all Staurojoenina observed to date in different species of North American termites have been treated as the same species, S. assimilis. Here, we characterize Staurojoenina from the North American termite Neotermes jouteli using light microscopy, scanning electron microscopy, and phylogenetic analysis of small subunit ribosomal RNA, and compare it with S. assimilis from its type host, Incisitermes minor. The basic morphological characteristics of the N. jouteli symbiont, including its abundant bacterial epibionts, are similar as far as they may be compared with existing data from S. assimilis, although not consistently identical. In contrast, we find that they are extremely distantly related at the molecular level, sharing a pairwise similarity of SSU rRNA genes comparable to that seen between different genera or even families of other parabasalians. Based on their evolutionary distance and habitat in different termite genera, we consider the N. jouteli Staurojoenina to be distinct from S. assimilis, and describe a new species, Staurojoenina mulleri, in honor of the pioneering parabasalian researcher, Miklos Muller.     

Organization of a dispersed repeated DNA element in the Zamia genome

Occurrence and genomic organization of dispersed elements containing ZpS1 satellite repeats have been investigated in a wide representation of species of the old plant genus Zamia (Zamiaceae, Cycadales). In Z. paucijuga, the ZpS1 repeat is organized as long satellite DNA arrays and as short arrays inserted into AT-rich dispersed elements. A comparative study by Southern analysis shows that these unusual dispersed elements containing the ZpS1 repeat are present with different organizations in all investigated Zamia species. In some species these elements are present with a low copy number, while in other species secondary amplification events, involving specific sequence clusters, appear to have generated characteristic dispersed elements in a high copy number. Among Zamia species, several groups share similar restriction patterns, as the Zamia loddigesii complex and the Caribbean species suggesting a general correlation between organization and genomic representation of the dispersed repeated sequence and the pattern of phyletic relationships in the genus. However, the finding of different patterns also among closely related species suggests a complex history of amplifications and losses of these dispersed repetitive elements that cannot be always easily traced through the phylogenetic reconstruction of this ancient plant group.     

The cytology of the genus Briza L. (Gramineae)

Chromosome numbers have been determined and karyotypes studied in several species of the genus Briza L. Nuclear DNA amounts have also been determined for some of the species and show a considerable variation between the species. The evolution of the karyotypes, particularly that of B. minor, is discussed and an attempt made to relate nuclear DNA content to karyotypes, breeding systems and habit in the different species.     

Immature stages of three species of Blissidae from Mexico (Heteroptera: Lygaeoideae)

Chinch bugs are associated with several species of monocots, and species of Gramineae are the principal plants utilized. In Mexico, 24 species of Blissidae have been recorded. The immature stages of Ischnodemus sallei (Signoret), Toonglasa munda (Slater & Wilcox), and T. tumorosis (Slater & Wilcox) are described and illustrated. These species have been recorded from several species of bamboo. Distributional records in Mexico and the host plants of these chinch bugs are also included.     

Characterization of two endoglucanases for the classification of the earthworm,Eisenia fetida Waki

Eisenia fetida and Eisenia andrei are vermicomposting species that are used as model animals for testing chemical material toxicology. Eisenia spp. are grown commercially in various fields in Japan. However, these two species have not been classified because it is difficult to distinguish them morphologically; thus, all bred earthworms are called E. fetida. However, it has been proposed that these two species have different expression regulation mechanisms. Here, we classified a sample of earthworms purchased from several farms, confirming that both E. fetida and E. andrei are present in Japanese earthworm breeding programs. We also characterized two highly active endoglucanases (EfEG1 and EfEG2) from the E. fetida Waki strain, which contained strong fibrinolytic enzymes for improving human health. We confirmed that EfEG1 is 1371 bp long and belongs to GHF9. Thus, E. fetida Waki may have commercial application for biomass utilization and as a dietary health supplement.     

Action mechanisms of probiotics on Candida spp. and candidiasis prevention: an update

Due to the high incidence of fungal infections caused by Candida species and their increasing resistance to antimicrobial treatments, alternative therapies such as probiotics have been studied. It has been show that several species of the genus Lactobacillus have anti-Candida activity, probably by direct inhibition, through competition for adhesion sites or production of secondary metabolites, and by indirect inhibition, through stimulation of the immune system of their host. However, the mechanisms of inhibition of these probiotics on Candida species have not yet been fully elucidated since this effect is related to more than one inhibition pathway. In the literature, several in vitro and in vivo studies have been developed seeking to elucidate the probiotics mechanisms of action. These studies have been focused on C. albicans inhibition assays, including analysis of antimicrobial activity, adherence capacity, biofilms formation, filamentation and interference on virulence genes, as well as assays of experimental candidiasis in invertebrate and vertebrate models. In this context, the purpose of this review was to gather different studies focused on the action mechanism of probiotic strains on Candida sp. and to discuss their impact on the candidiasis prevention.     

Morphological variability of the diatom Cyclotella atomus Hustedt var. atomus and C. atomus var. gracilis var. nov.

Cyclotella atomus collected from different rivers, reservoirs and lakes shows considerable morphological variability. On the basis of electronmicroscopic (EM) study, we propose Cyclotella atomus var. gracilis Genkal et Kiss as a new variety of this species. Cyclotella atomus var. atomus has short and long radial striae, which are irregularly arranged on the same valve, and the alveolar chambers are not clearly divided from the central, hyaline part of the valve face. In addition to the described basic form, several specimens with other features have also been found and are thought to belong to an undescribed variety. The striae of the new variety are equal in length, and the alveolar chambers are clearly divided from the hyaline central area of the valve face by a curved structure.There are EM micrographs on Cyclotella atomus var. gracilis under different names in different papers. The new variety has several characteristics also found in other species, e.g. Cyclotella caspia Grun., or C. meneghiniana Kütz.     

Chromosome painting supports lack of homology among sex chromosomes in Oncorhynchus, Salmo, and Salvelinus (Salmonidae)

The sex chromosome pair has been identified previously as the largest submetacentric pair in the genome in several species of the genus Salvelinus (eastern trouts and chars) including S. namaycush (lake trout) and as a large subtelocentric/acrocentric pair in several species of the genus Oncorhynchus (Pacific trouts and salmon). Sex chromosomes have not been identified in Salmo (Atlantic salmon and brown trout). Two paint probes, one specific for the short arm (Yp) and the other for the long arm (Yq) of the sex chromosome pair in Salvelinus namaycush were hybridized to chromosomes of Oncorhynchus mykiss (rainbow trout) and O. tshawytscha (chinook salmon) and Salmo salar (Atlantic salmon) and S. trutta (brown trout). The two probes hybridized to two different autosomal pairs in each of the Oncorhynchus species, supporting lack of homology between the sex chromosomes in the two genera. The Yp probe hybridized to interstitial regions on two different chromosome pairs in S. salar and one pair in S. trutta. The Yq probe hybridized to a different pair in both species.     

Species delimitation methods reveal cryptic diversity in the Hypnea cornuta complex (Cystocloniaceae,Rhodophyta)

The simple and convergent morphologies of many red algae make these species difficult to identify using traditional morphological characters. Many cryptic species have been described in recent years based on molecular datasets, and this has led to the application of an integrative taxonomy approach in species delimitation. Here, we performed several species delimitation methods (mBGD, ABGD, SPN, PTP, GMYCs and GMYCm) based on two different loci (COI-5P and rbcL) in species of the Hypnea cornuta complex. These methods were combined with morphological and phylogenetic data, extensive sampling, analysis of topotype material, and historically relevant herbarium samples. Our findings demonstrate that the groups morphologically assigned to H. cornuta and H. stellulifera consist of five different cryptic species. H. cornuta is a polyphyletic taxon composed of three well-separated lineages, thus requiring sequencing of type or topotype specimens to determine which one is Hypnea cornuta sensu stricto. We have revealed that the distribution of H. stellulifera is limited to Asia, while the Brazilian specimens initially assigned to this species were clarified as a new endemic species: Hypnea cryptica sp. nov. Our results indicated that only an integrative approach combining several lines of evidence, including morphology, nomenclature history, molecular data, biogeography and ecology can correctly solve the taxonomic status of widely distributed cryptic species.     

Preservation of organic-walled dinoflagellate cysts in different oxygen regimes: a 10,000 year natural experiment

The occurrence of organic-walled dinoflagellate cysts in (fossil) sediments depends on several factors, including as the ecological preferences of the cyst-forming dinoflagellates, cyst production, transport and preservation. Although laboratory experiments have shown that several cyst species are sensitive to chemical treatment, no information about the selective preservation of dinoflagellate cyst species in natural environments has previously been presented. Here, we present data on the effects of oxygen availability in bottom sediments on a cyst assemblage from the ungraded Madeira Abyssal Plain f-turbidite of which only the upper layer has been oxidized. Based on differences in species composition between the oxidized and underlying, unoxidized layers of this turbidite, the influence of oxygen availability on the preservation of individual species has been estimated. Cyst species have been classified in ascending order of resistance to oxygen availability in sediments as: (1) highly sensitive (cysts formed by Protoperidinium species), (2) moderately sensitive (e.g. Spiniferites species), (3) moderately resistant (e.g. Impagidinium paradoxum and Nematosphaeropsis labyrinthus) and (4) resistant (e.g. Impagidinium aculeatum).     

The plasmids of the morels: characterization and prerequisites for vector development

Summary In several Morchella species linear dsDNA plasmids have been discovered and analyzed. Two linear plasmids of the strain Morchella conica 3 analyzed in detail are associated with the mitochondria but not as an integrative part of the high molecular weight mt DNA. In addition, homologies between different plasmids from different species could be detected. These homologies extend to all parts of the plasmids. Differences in size are due to different lengths of nonhomologous inner parts rather than to differences at the termini. Fragments comprising the entire plasmids were cloned into bacterial vectors and a selectable marker gene for eukaryotes was added to the resulting hybrid plasmids. Transformation of yeast led to the identification of autonomously replicating sequences, this being a prerequisite for the development of autonomously replicating vectors for Morchella.Dedicated to Prof. Dr. H.-J. Rehm on the occasion of his 60th birthday     

Root-knot nematode (Meloidogyne spp.) Me resistance genes in pepper (Capsicum annuum L.) are clustered on the P9 chromosome

The root-knot nematode (Meloidogyne spp.) is a major plant pathogen, affecting several solanaceous crops worldwide. In Capsicum annuum, resistance to this pathogen is controlled by several independent dominant genes—the Me genes. Six Me genes have previously been shown to be stable at high temperature in three highly resistant and genetically distant accessions: PI 322719, PI 201234, and CM334 (Criollo de Morelos 334). Some genes (Me4, Mech1, and Mech2) are specific to certain Meloidogyne species or populations, whereas others (Me1, Me3, and Me7) are effective against a wide range of Meloidogyne species, including M. arenaria, M. javanica, and M. incognita, the most common species in Mediterranean and tropical areas. These genes direct different response patterns in root cells depending on the pepper line and nematode species. Allelism tests and fine mapping using the BSA-AFLP approach showed these genes to be different but linked, with a recombination frequency of 0.02–0.18. Three of the PCR-based markers identified in several genetic backgrounds were common to the six Me genes. Comparative mapping with CarthaGene software indicated that these six genes clustered in a single genomic region within a 28 cM interval. Four markers were used to anchor this cluster on the P9 chromosome on an intraspecific reference map for peppers. Other disease resistance factors have earlier been mapped in the vicinity of this cluster. This genomic area is colinear to chromosome T12 of tomato and chromosome XII of potato. Four other nematode resistance genes have earlier been identified in this area, suggesting that these nematode resistance genes are located in orthologous genomic regions in Solanaceae.     

The decline of the native fishes of lakes Victoria and Kyoga (East Africa) and the impact of introduced species,especially the Nile perch,Lates niloticus,and the Nile tilapia,Oreochromis niloticus

Synopsis There has been a decline, and in some cases an almost total disappearance, of many of the native fish species of lakes Victoria and Kyoga in East Africa since the development of the fisheries of these lakes was initiated at the beginning of this century. The Nile perch, Lates niloticus, a large, voracious predator which was introduced into these lakes about the middle of the century along with several tilapiine species, is thought to have caused the reduction in the stocks of several species. But overfishing and competition between different species also appear to have contributed to this decline. By the time the Nile perch had become well established, stocks of the native tilapiine species had already been reduced by overfishing. The Labeo victorianus fishery had also deteriorated following intensive gillnetting of gravid individuals on breeding migrations. L. niloticus is, however, capable of preying on the species which haven been overfished and could have prevented their stocks from recovering from overfishing. L. niloticus is also directly responsible for the decline in populations of haplochromine cichlids which were abundant in these lakes before the Nile perch became established. Even without predation by Nile perch, it has been shown that the haplochromine cichlids could not have withstood heavy commercial exploitation if a trawl fishery had been established throughout Lake Victoria. Their utilisation for human food has also posed some problems. The abundance of the native tilapiine species may also have been reduced through competition with introduced species which have similar ecological requirements. At present, the Nile perch and one of the introduced tilapiine species, Oreochromis niloticus, form the basis of the fisheries of lakes Victoria and Kyoga.Invited editorial     

ABA signaling in stomatal guard cells: lessons from <Emphasis Type="Italic">Commelina</Emphasis> and <Emphasis Type="Italic">Vicia</Emphasis>

Abscisic acid (ABA) signaling mechanisms have been studied in a broad variety of plant species using complementary analyses, taking advantage of different methodologies suitable for each plant species. Early studies on ABA biosynthesis using Solanum lycopersicum mutants suggested an importance of ABA synthesis in stomatal closure. To understand ABA signaling in guard cells, cellular, biochemical and electrophysiological studies in Vicia faba and Commelina communis have been conducted, providing fundamental knowledge that was further reconfirmed by molecular genetic studies of Arabidopsis. In this article, examples of stomatal studies in several plants and prospects in ABA research are discussed.     

THE CHROMOSOMES OF PACHYPHYTUM (CRASSULACEAE)

Eleven of the 12 species of Pachyphytum, all that are available, have n = 31–33 standard chromosomes, or a multiple. Accessory chromosomes were found in some or all collections of four species; some cells of one plant have more than 50 of them. Accessory chromosomes often occur in groups at metaphase I, corresponding to their origin from one to several chromocenters of prophase I. Intraspecific polyploidy occurs within five species, with diploids to 12-ploids (n = ca. 186) in P. compactum and diploids to decaploids (n = ca. 160) in P. hookeri. Although the basic chromosome number is high, evidence from meiosis in certain hybrids shows that the basic 31–33 chromosomes are probably all different: they do not pair with each other and they do not duplicate each other. Polyploids, with 62 or more chromosomes, are probably autopolyploids: they form multivalents, and the chromosomes they contribute to hybrids pair with each other. Three different probable hybrids have been found in the wild, and more than 300 hybrids have been produced in cultivation.