Infection of the diatom Asterionella by a chytrid. II. Effects of light on survival and epidemic development of the parasite

A model is formulated to investigate the ability of chytridparasites to survive or become epidemic within populations oftheir algal hosts The model is used for an analysis of the effectsof light on the occurrence of Rhizophydium planktonicum Canteremend., a chytrid parasite of the freshwater diatom Asterionellaformosa Hass., using the information on the growth parametersof host and parasite presented in the first part of this article(J. Plankton Res ., 13, 103–117). According to the model,conditions for survival of the parasite are optimal when thehost grows at saturating light conditions. Under limiting lightconditions, Rhizophydium needs higher host densities in orderto maintain itself. The parasite is not able to survive prolongedperiods of severe light limitation of the host Epidemic development,however, turned out to be facilitated by a moderate light limitationof the host. Both light saturation and severe light limitationhamper epidemic development, but in the first case, epidemicdevelopment is still possible at sufficiently high host densities.     

The relationship between plankton-feeding Bonaparte's and Mew Gulls and tidal upwelling at Active Pass, British Columbia

The food habits of Bonaparte's (Larus Philadelphia) and MewGulls (L. canus) were studied at Active Pass, British Columbia,in relation to upwelling of zooplankton. Bonaparte's Gulls fedmostly on planktonic crustaceans during September-November andagain during April-May, while Mew Gulls foraged there chieflyin February and March. Both species ate predominantly the euphausiid,Thysanoessa raschii, in spring, while Bonaparte's Gulls fedmainly on the amphipods, Parathemisto pacifica and Calliopiuslaeviusculus, in fall. Year-round sampling of zooplankton andcollection of temperature and salinity data showed gull numbersto correlate with times of maximum upwelling and abundance ofzooplankton prey in surface waters. Outside the upwelling zonein Active Pass, Bonaparte's and Mew Gulls fed mostly on fishesand intertidal organisms, but also on zooplankton along tidelines.     

Cooning of the genes encoding the two different glucose dehydrogenases fromAcinetobacter calcoaceticus

Glucose dehydrogenase (GDH) is a PQQ dependent bacterial enzyme which converts aldoses to their corresponding acids.A. calcoaceticus contains two different PQQ dependent glucose dehydrogenases designated GDH-A which is activein vivo and GDH-B of which onlyin vitro activity can be shown. We cloned the genes coding for the two GDH enzymes. The DNA sequences of bothgdh genes were determined. There is no obvious homology betweengdhA andgdhB. Both GDH enzymes oxidize D-glucosein vitro but disaccharides are specific GDH-B substrates and 2-deoxyglucose is specifically oxidized by GDH-A.     

Netherlands twin family study of anxious depression (NETSAD).

In a longitudinal study of Dutch adolescent and young adult twins, their parents and their siblings, questionnaire data were collected on depression, anxiety and correlated personality traits, such as neuroticism. Data were collected by mailed surveys in 1991, 1993, 1995 and 1997. A total of 13,717 individuals from 3344 families were included in the study. To localise quantitative trait loci (QTLs) involved in anxiety and depression, the survey data were used to select the most informative families for a genome-wide search. For each individual a genetic factor score was computed, based on a genetic multivariate analysis of anxiety, depression, neuroticism and somatic anxiety. A family was selected if at least two siblings (or DZ twins) had extreme factor scores. Both discordant (high-low) and concordant (high-high and low-low) pairs were included in the selected sample. Once an extreme sibling pair was selected, all family members (parents and additional siblings of the selected pair) who had at least once returned a questionnaire booklet were asked to provide a DNA sample. In total, 2724 individuals from 563 families (1007 parents and 1717 offspring) were approached and 1975 individuals from 479 families (643 patients and 1332 offspring) complied by returning a buccal swab for DNA isolation. All offspring from selected families were asked to participate in a psychiatric interview and in a 24-hour ambulatory assessment of cardiovascular parameters and cortisol. The interview consisted of the WHO-Composite International Diagnostic Interview and was administered to 1253 offspring. In this paper we describe the genetic-epidemiological analyses of the survey data on anxiety, somatic anxiety, neuroticism and depression. We detail how these data were used to select families for the QTL study and discuss strategies that may help elucidate the molecular pathways leading from genes to anxious depression.     

Possible role of adenylates in the engagement of the cyanideresistant pathway in nutrient-starved Catharanthus roseus Cells

In Cathuranthus roseus (L.) G. Don cells the cyanide-resistant pathway is engaged after phosphate or nitrogen starvation. Re-addition of these nutrients disengaged it again. Re-addition of phosphate leads to a transient disengagement which becomes only permanent after a second addition of phosphate. Disengagement after re-addition of nitrogen is slow: it takes 9 days before the activity has disappeared. In this system the mechanism of engagement of the cyanide-resistant pathway was studied. Addition of phosphate to phosphate-starved cells induced cell division within 24 h. The disengagement of the cyanide-resistant pathway was probably only an indirect effect of phosphate because the cellular P, content, which increased rapidly after addition, was low again before the cyanide-resistant pathway was disengaged. A better correlation was observed between high ADP and adenylate content of the cells and disengagement of the cyanide-resistant pathway. In addition it appeared that the engagement of the cyanide-resistant pathway was not the result of a limited carrier capacity of the cytochrome pathway. It is tentatively concluded that the engagement of the cyanide-resistant pathway in phosphate-starved cells was the result of a limited adenylate content. After nitrogen addition to N-starved cells, it took 5 days until the first growth occurred. Before the cyanide-resistant pathway was disengaged, its activity increased with the increased respiration rate which preceded growth. Within 72 h a higher ADP content was observed, which was still high after 10 days. The stimulation of the cytochrome pathway by uncoupler was small and more or less the same with and without added nitrogen, as long as the cyanide-resistant pathway was engaged. After disengagement the stimulation by uncoupler was significantly larger. It is suggested that the engagement during N-starvation was the result of a limited carrier capacity of the cytochrome pathway. Stimulation of the metabolism by re-addition of phosphate, nitrogen or sucrose resulted in a rapid increase in the levels of uracil nucleotides and uridine diphosphoglucose (UDPG) which are involved in sucrose metabolism.     

Synthesis of the functionalizable methionine surrogate azidohomoalanine using Boc-homoserine as precursor

This protocol describes a synthetic route to the non-canonical amino acid azidohomoalanine (AHA) using protected homoserine as a starting material. An alternative route to AHA is presented in a companion paper. This synthesis can be completed in 5 days.     

Isolation and characterisation of Isaria farinosa and Purpureocillium lilacinum associated with emerald ash borer,Agrilus planipennis in Canada

Entomopathogenic fungi of the genera Isaria and Purpureocillium were recovered from infestation sites of emerald ash borer (EAB) in Southern Ontario, Canada. Isolates were identified using morphological characters and by sequencing the ITS1-5.8S-ITS2 ribosomal DNA gene and partial β-tubulin gene. Phylogenetic analysis and constructed trees based on the ITS and β-tubulin gene explicitly confirm isolates L66B, SY17-a and LHY46-a as Isaria farinosa and B3A, B59A and SY45B-a as Purpureocillium lilacinum. Pathogenicity was tested in the laboratory against adult EAB using a single concentration (2.0×10⁷ conidia/ml) applied topically to adults. Controls included three commercial isolates: Isaria fumosorosea LRC176, Metarhizium brunneum LRC187 and Beauveria bassiana strain GHA. The native isolates I. farinosa L66B and P. lilacinum SY45B-a killed 75 and 50% of the beetles 14 days post-inoculation. Although these indigenous entomogenous fungi were less virulent compared with the commercial isolates, yearly isolation from EAB populations suggests they are one of the natural mortality factors of EAB in Canada.     

Characterization of Bordetella holmesii isolates from patients with pertussis-like illness in The Netherlands

Bordetella holmesii is a recently described human pathogen mainly isolated from blood. However, in the US and Canada, B. holmesii has also been cultured from the nasopharynx of patients with pertussis-like symptoms. To the best of our knowledge, respiratory isolates from Europe have not been characterized. Here, we report the isolation and characterization of B. holmesii from Dutch patients with pertussis-like illness. Species determination was confirmed by 16S rRNA gene sequencing and detection by PCR of IS481 and bhoE, a gene not found in Bordetella pertussis but present in B. holmesii. Comparative genomic hybridization (CGH) with microarrays revealed that the Dutch isolates formed a cluster distinct from isolates from the US and UK suggesting a distinct population or an epidemiological relationship between the Dutch isolates. All isolates contained a locus involved in iron uptake, previously suggested to originate from B. pertussis. The causes for the apparent increase in the isolation of B. holmesii are discussed.     

Integrin cytoplasmic domain-associated protein-1 (ICAP-1) interacts with the ROCK-I kinase at the plasma membrane

The integrin cytoplasmic domain-associated protein-1 (ICAP-1) binds via its C-terminal PTB (phosphotyrosine-binding) domain to the cytoplasmic tails of beta1 but not other integrins. Using the yeast two-hybrid assay, we found that ICAP-1 binds the ROCK-I kinase, an effector of the RhoA GTPase. By coimmunoprecipitation we show that ICAP-1 and ROCK form complexes in cells and that ICAP-1 contains two binding sites for ROCK. In cells transfected with both ICAP-1 and ROCK, the proteins colocalized at the cell membrane predominantly in lamellipodia and membrane ruffles, but also in retraction fibers. ROCK was not found at these sites when ICAP-1 was not co-transfected, indicating that ICAP-1 translocated ROCK. In lamellipodia ICAP-1 and ROCK colocalized with endogenous beta1 integrins and this colocalization was also observed with the isolated ICAP-1 PTB domain. The plasma membrane localization of ROCK did not depend on beta1 integrin ligation or ROCK kinase activity, and in truncated ROCK proteins it required the presence of the ICAP-1-binding domain. To show that the interaction was direct, we measured fluorescence resonance energy transfer (FRET) between cyan fluorescent protein (CFP) fused to ICAP-1 and yellow fluorescent protein (YFP) fused to ROCK. FRET was observed in lamellipodia in cells that were induced to spread. These results indicate that ICAP-1-mediated binding of ROCK to beta1 integrin serves to localize the ROCK-I kinase to both the leading edge and the trailing edge where ROCK affects cell migration.