23 research outputs found
The arrangement of actin bundles and chloroplasts in the nodal regions of Characean internodal cells
Disturbance history of a European oldâgrowth mixedâspecies forestâA spatial dendroâecological analysis
Metadata-driven comparative analysis tool for sequences (meta-CATS): An automated process for identifying significant sequence variations that correlate with virus attributes
The major outer membrane protein of Chlamydia trachomatis: critical binding site and conformation determine the specificity of antibody binding to viable chlamydiae
Evolution of the diatoms: insights from fossil, biological and molecular data
Molecular sequence analyses have yielded many important insights into diatom evolution, but there have been few attempts to relate these to the extensive fossil record of diatoms, probably because of unfamiliarity with the data available, which are scattered widely through the geological literature. We review the main features of molecular phylogenies and concentrate on the correspondence between these and the fossil record; we also review the evolution of major morphological, cytological and life cycle characteristics, and possible diatom origins. The first physical remains of diatoms are from the Jurassic, and well-preserved, diverse floras are available from the Lower Cretaceous. Though these are unequivocally identifiable as centric diatoms, none except a possible Stephanopyxis can be unequivocally linked to lineages of extant diatoms, although it is almost certain that members of the Coscinodiscophyceae (radial centrics) and Mediophyceae (polar centrics) were present; some display curious morphological features that hint at an unorthodox cell division mechanism and life cycle. It seems most likely that the earliest diatoms were marine, but recently discovered fossil deposits hint that episodes of terrestrial colonization may have occurred in the Mesozoic, though the main invasion of freshwaters appears to have been delayed until the Cenozoic. By the Upper Cretaceous, many lineages are present that can be convincingly related to extant diatom taxa. Pennate diatoms appear in the late Cretaceous and raphid diatoms in the Palaeocene, though molecular phylogenies imply that raphid diatoms did in fact evolve considerably earlier. Recent evidence shows that diatoms are substantially underclassified at the species level, with many semicryptic or cryptic species to be recognized; however, there is little prospect of being able to discriminate between such taxa in fossil material
Managerial competency requirements that enhance organisational competences: a study of a Sri Lankan telecom organisation
High-level expression and epitope localization of the major outer membrane protein of Chlamydia trachomatis serovar L1
Fragments of the gene encoding the major outer membrane porin protein (MOMP) of Chlamydia trachomatis serovar L1 were ligated into the pUC plasmid vectors to give a series of overlapping recombinants expressing MOMP from the lac promoter. Induction of this promoter with IPTG leads to high-level expression of the recombinant porin protein. Electron microscopy shows the presence of insoluble inclusions within the Escherichia coli host cells. Probing the expressed MOMP fragments with a set of monoclonal antibodies permitted localization of the four binding sites (epitopes) of primary-sequence-dependent monoclonal antibodies that exhibit genus-, species-, subspecies- and type (serovar)-specific reactivities