Speedy speciation in a bacterial microcosm: new species can arise as frequently as adaptations within a species

Microbiologists are challenged to explain the origins of enormous numbers of bacterial species worldwide. Contributing to this extreme diversity may be a simpler process of speciation in bacteria than in animals and plants, requiring neither sexual nor geographical isolation between nascent species. Here, we propose and test a novel hypothesis for the extreme diversity of bacterial species—that splitting of one population into multiple ecologically distinct populations (cladogenesis) may be as frequent as adaptive improvements within a single population''s lineage (anagenesis). We employed a set of experimental microcosms to address the relative rates of adaptive cladogenesis and anagenesis among the descendants of a Bacillus subtilis clone, in the absence of competing species. Analysis of the evolutionary trajectories of genetic markers indicated that in at least 7 of 10 replicate microcosm communities, the original population founded one or more new, ecologically distinct populations (ecotypes) before a single anagenetic event occurred within the original population. We were able to support this inference by identifying putative ecotypes formed in these communities through differences in genetic marker association, colony morphology and microhabitat association; we then confirmed the ecological distinctness of these putative ecotypes in competition experiments. Adaptive mutations leading to new ecotypes appeared to be about as common as those improving fitness within an existing ecotype. These results suggest near parity of anagenesis and cladogenesis rates in natural populations that are depauperate of bacterial diversity.     

Vaucheria lii Rieth,a new alga for the Netherlands

Summary In April 1976,Vaucheria lii Rieth was found within a cultivated algal sample which was collected from a lowland brook near the village of Milsbeek, Prov. Limburg (The Netherlands) on February 10th of the same year.V. lii occurred, intermingled in aVaucheria-mat withV. aversa Hass.,V. prona Christ.,V. geminata (Vauch.) DC andV. racemosa (Vauch.) DC.     

Alnion forests in Lower Saxony (FRG), their ecological requirements,classification and position within Carici elongatae-Alnetum of Northern Central Europe

In the diluvial plain of Lower Saxony ( = Niedersachsen) two types of alder fen woods are found: alder swamp woods (alder carrs) with a more changing water table and inundations in winter, and alder spring woods without hibernal inundation and a more or less constant water table. While all alder swamp woods are Alnion forests, the alder spring woods can be devided into Alnion and Alno-Ulmion forests.All Alnion forests in the diluvial plain of Lower Saxony belong to the association Carici elongatae-Alnetum Schwick. 1933. This association can be devided into three subassociations, C. el.-Al. betuletosum Bodeux 1955, C. el.-Al. typicum Meijer Drees 1936 and C. el.-Al. cardaminetosum Meijer Drees 1936.Low pH-values and high C/N-ratios of the soil are good indicators to distinguish the Carici elongatae-Alnetum betuletosum from the other two subassociations. Humus contents has a tendency to decrease in the sequence C. el.-Al. betuletosum > C. el.-Al. typicum > C. el.-Al cardaminetosum, but is no reliable factor for classification of a single plot. Differences in annual groundwater level variations cause a floristical differentiation only within alderwoods of meso- to eutrophic sites. Here a nearly constant water table or at least no hibernal inundation leads to a Carici elongatae-Alnetum cardaminetosum, while sites which are inundated in winter carry the Carici elongatae-Alnetum typicum. On oligotrophic sites both, swamp and spring woods belong to the Carici elongatae-Alnetum betuletosum.The subdivision of the Carici elongatae-Alnetum for the whole lowlands of northern Central Europe is generally the same as for Lower Saxony. Source reference: This paper was presented as a poster with the title Alnion Forests in Lower Saxony (FRG)-Syntaxonomical position and ecological requirements on the IAVS-Symposium Forests of the World, Upsala 20.–27.8.1989.     

Physician assisted suicide: new developments in the Netherlands

Until recently, physician assisted suicide was dealt with on the same basis as active voluntary euthanasia in the Netherlands. Over the last years, several cases relating to assistance in suicide of mental patients did raise specific issues, not addressed so far in the debate on euthanasia. One of these cases resulted in a Supreme Court decision. The paper summarizes this decision and comments on it from a legal point of view.     

Hepatitis E virus as a Cause of Acute Hepatitis in The Netherlands

Background

Recent studies indicate that 27% of Dutch blood donors have evidence of past infection with HEV. However, the low number of diagnosed HEV infections indicates either an asymptomatic course or under diagnosis.

Objectives

We investigated whether HEV is a cause of acute hepatitis in Dutch patients and which diagnostic modality (serology or PCR) should be used for optimal detection.

Study design

Serum samples were retrospectively selected from non-severely immuno-compromised patients from a university hospital population, suspected of having an infectious hepatitis. Criteria were: elevated alanine aminotransferase (ALT> 34 U/l) and request for antibody testing for CMV, EBV or Hepatitis A (HAV).

Results

All samples were tested for HEV using ELISA and PCR. Ninety patients/sera were tested, of which 22% were HEV IgG positive. Only one serum was IgM positive. HEV PCR was positive in two patients: one patient was both HEV IgM and IgG positive, the other patient was only IgG positive. Both HEV RNA positive samples belonged to genotype 3. Evidence of recent infection with CMV, EBV and HAV was found in 13%, 10% and 3% respectively.

Conclusions

Although our study is limited by small numbers, we conclude that HEV is a cause of acute hepatitis in hospital associated patients in The Netherlands. Moreover, in our study population the prevalence of acute HAV (3%) was almost similar to acute HEV (2%). We propose to incorporate HEV testing in panels for acute infectious hepatitis. Negative results obtained for HEV IgM in a HEV PCR positive patient, indicates that antibody testing alone may not be sufficient and argues for PCR as a primary diagnostic tool in hospital associated patients. The high percentage of HEV IgG seropositivity confirms earlier epidemiological studies.     

Syntaxonomy and ecology of plant communities of the Carici rupestris-Kobresietea bellardii in the western carpathians

We present a syntaxonomic account of the communities of the alliances of Oxytropido-Elynion Br.-Bl. 1949 and Festucion versicoloris Krajina 1933 from Western Carpathians. Both alliances comprise naked-rush, cushion form and dwarf-shrub heath communities typical of wind-exposed habitats occurring at the highest altitudes of the Tatra Mts. They represent a relic vegetation of the cold stages of the Pleistocene (probably Late Glacial Maximum) and they can be classified within the class of Carici rupestris-Kobresietea bellardii Ohba 1974. A set of relevés was subject to numerical-classification analysis. Floristics and ecology of the communities were characterised and the relationships to similar syntaxa were discussed. The Oxytropido-Elynion is restricted to the extreme ridge positions in the highest altitudes of the Belianske Tatry Mts. Five associations were distinguished, such as the Pyrolo carpaticae-Salicetum reticulatae, the Festuco versicoloris-Oreochloetum distichae, the Festucetum versicoloris, the Oxytropido carpaticae-Elynetum myosuroides and the Drabo siliquosae-Festucetum versicoloris. The Festucion versicoloris is limited to the mylonite zone of the alpine and subnival belt of the Vysoké Tatry and Západné Tatry Mts (and found as rare in the Nízke Tatry Mts). The stands of these communities prefer terraces of steep rocky faces and cliffs and stabilised small-grained screes below the cliffs. Within this alliance, three associations were described, including the Agrostio alpinae-Festucetum versicoloris, the Silenetum acaulis and the Salicetum kitaibelianae.     

Archiascomycetes: detection of a major new lineage within the Ascomycota

For phylogenetic analysis of the higher fungi, we sequenced the nuclear small subunit rRNA (18S rRNA) gene fromTaphrina populina, the type species of the genusTaphrina, andProtomyces lactucae-debilis. The molecular phylogeny inferred from these 2 sequences and 75 sequences from the DNA data bank divided the Ascomycota into three major lineages: the hemiascomycetes, the euascomycetes, and the archiascomycetes, newly described herein. The former two lineages are monophyletic, whereas the archiascomycetes, which originated first and are comprised ofTaphrina, Protomyces, Saitoella, Schizosaccharomyces, andPneumocystis, may not be monophyletic. Among the archiascomycetes, theTaphrina/Protomyces branch is monophyletic. Confirmation of the archiascomycetes as a monophyletic taxonomic class will require comparison of additional genetically defined characters.This work was supported in part by grants 05454030 from the Ministry of Education, Science, and Culture of Japan (to J. S.) and 4369 from the Japan Society for the Promotion of Science Fellowship Programs (to H. N.).     

Progesterone as a neurosteroid: Actions within the nervous system

Summary 1. Some progesterone is synthesized within both the central and the peripheral nervous systems, where it regulates neurotransmission and important glial functions, such as the formation of myelin. Progesterone can thus be designated a neurosteroid.2. Steroids act not only on the brain, but also on peripheral nerves, which offer many advantages to study the biological significance of locally produced neurosteroids: their remarkable plasticity and regenerative capacity and their relatively simple structure.3. By using the regenerating mouse sciatic nerve as a model, we have shown that progesterone synthesized by rat Schwann cells promotes the formation of new myelin sheaths. Progesterone also increases the number of myelinated axons when added at a low concentration to cocultures of Schwann cells and sensory neurons.4. These findings show a function on myelination for locally produced progesterone and suggest a new pharmacological approach of myelin repair.     

Localization of a new fiber-forming protein within Tetrahymena pyriformis

As a step to study the biological function of a new protein, fiber-forming protein-38,000 (FFP-38), which was previously isolated from Tetrahymena pyriformis, its intracellular localization was investigated by using antiserum specific for FFP-38. Double immunodiffusion tests revealed that the anti-FFP-38 serum reacted with the protein(s) in isolated organelles such as oral apparatus, pellicles and mitochondria, to give rise to a precipitin line confluent with the line formed between the antiserum and the FFP-38. Furthermore, indirect fluorescent antibody staining showed that fluorescence was intensely localized in the oral apparatus and faintly distributed throughout the cytoplasm. In particular, distinct fluorescence was found along the division furrow of dividing Tetrahymena.     

Muskrats as carriers of pathogenic leptospires in The Netherlands

Leptospires were isolated from 24 of 327 (7%) muskrats (Ondatra zibethicus) caught in The Netherlands. All isolates were identified asLeptospira interrogans. One isolate was typed as serovarcopenhageni in the Icterohaemorrhagiae serogroup, one as serovarlora in the Australis serogroup. Twenty-one isolates showed a close relationship with serovarsgrippotyphosa, valbuzzi, muelleri andratnapura from the Grippotyphosa serogroup. One isolate was lost. Sera from 196 muskrats were examined by the microscopic agglutination test. Forty-five (23%) sera reacted positively (titers1: 160), 42 (21%) of these 45 sera to Grippotyphosa and 3 (2%) to Sejroe serogroup antigens. This is the first report of serological and cultural evidence of leptospira infection in muskrats in The Netherlands.Abbreviations CAAT cross agglutination absorption test - 5-FU 5-fluorouracil - MAT microscopic agglutination test - MCA monoclonal antibodies - PBS phosphate buffered saline - REA restriction endonuclease analysis - SDS sodium dodecyl sulphate     

Pythium cryptoirregulare, a new species within the P. irregulare complex

Pythium identification is based on several characteristics with considerable variation, particularly in Pythium irregulare Buis. as currently recognized. Thirty-one isolates of Pythium irregulare Buis. from various hosts and geographic regions were compared by genetic analysis of multiloci DNA fingerprints, sequence analysis of nuclear and mitochondrial genes and morphological and growth rate studies. Previous research indicated two distinct groupings within the species, P. irregulare sensu stricto and a clade referred to here as Pythium sp. Parsimony analyses of 338 AFLP markers divided P. irregulare s.l. into two clades. Comparison of the allele frequencies of 236 polymorphic AFLP loci revealed significant differences between them. The two clades differed in the frequencies of 182 (77%) alleles. P. irregulare s.s. had 122 (52%) polymorphic loci while Pythium sp. had 205 (87%). Pythium sp. had one fixed allele and 79 polymorphic loci absent in P. irregulare s.s. P. irregulare s.s. displayed 16 polymorphic loci absent in Pythium sp. Parsimony and distance analyses of the ribosomal intergenic transcribed spacers (ITS) and the cox II gene sequences support the separation of P. irregulare s.s. and Pythium sp. Amplicon length in P. irregulare s.s. ITS sequences were 936-938 bp and 936-949 bp in Pythium sp. The two clades were separated by two fixed insertion/deletion mutations, nine fixed nucleotide substitutions in the ITS region and three fixed single nucleotide substitutions in the cox II sequences. Average growth rates of the groups differed at 10, 30 and 36 C but not at 15, 21 or 25 C. Statistically significant differences were found in oogonium, oospore and ooplast diameters, antheridial cell length and in ooplast index. We propose that a new species, Pythium cryptoirregulare, be delineated from Pythium irregulare sensu stricto.     

Phytophthora gemini sp. nov., a new species isolated from the halophilic plant Zostera marina in the Netherlands

Eight strains belonging to the Oomycete genus Phytophthora were isolated from Zostera marina (seagrass) in The Netherlands over the past 25 y. Based on morphology, isozymes, temperature-growth relationships and ITS sequences, these strains were found to belong to two different Phytophthora species. Five strains, four of them isolated from rotting seeds and one isolated from decaying plants, could not be assigned to a known species and hence belong to a new species for which we propose the name Phytophthora gemini sp. nov. Three strains were isolated from decaying plants and were identified as Phytophthora inundata, thereby expanding the known habitat range of this species from fresh to brackish-saline areas. The possible role of both Phytophthora species in the decline of Z. marina in The Netherlands and the evolutionary significance of the presence of Phytophthora species in marine environments are discussed.     

Mousepox in the Netherlands

Two independent outbreaks of ectromelia in mice occurred in The Netherlands. In both cases, the causative virus was isolated and identified as ectromelia virus on the basis of serology, demonstration of antigen by indirect immunofluorescence, negative contrast electron microscopy, morphology of lesions on chorioallantoic membranes of embryonated chicken eggs, and cytopathogenicity for mouse cells. Inoculation of the virus into the dermis of rabbits demonstrated a low virulence for this species.     

A malaria protein exported into a new compartment within the host erythrocyte.

A Plasmodium falciparum protein which is exported into a new compartment in the host erythrocyte has been located. This protein, exp-1, has a variable region recognized by a monoclonal antibody. Naturally occurring mutants of this region have been characterized. All mutants studied so far have the same A----G transition abolishing the target for the antibody. The exp-1 gene has a complex structure containing two introns. It is highly conserved in five independent, genetically defined parasite lines, suggesting that exp-1 has an important function. We discuss the possible role of exp-1 in P. falciparum infections.