The plastid organelle of plants, eukaryotic algae and apicomplexan protists contains its own DNA genome (the ‘plastome’). In higher plants, at least two RNA polymerases have been shown to participate in the transcription of plastid genes. The multisubunit ‘plastid-encoded plastid RNA polymerase’ (PEP) is derived from the cyanobacterial ancestor of the organelle and is structurally similar to eubacterial RNA polymerases. The core subunits of PEP are encoded by genes on the plastome, whilst sigma-like transcription factors and other regulatory factors are encoded in the nucleus. In contrast, the ‘nuclear-encoded plastid RNA polymerase’ (NEP) is a single-subunit enzyme related to the T3/T7 bacteriophage and mitochondrial RNA polymerases that is believed to have arisen by duplication of the nuclear gene for the mitochondrial enzyme. The situation in algal plastids is less well understood. All algal groups, apart from possibly the dinoflagellates, possess a PEP but it is far from clear whether any possess additional plastid RNA polymerases. In this article we review what is known about the transcription apparatus of algal plastids, and examine the evidence for and against the presence of NEPs.

The utility of absorbance and fluorescence-emission spectra for discriminating among microalgal phylogenetic groups, selected species, and phycobilin- and non-phycobilin-containing algae was examined using laboratory cultures. A similarity index algorithm, in conjunction with fourth-derivative transformation of absorbance spectra, provided discrimination among the chlorophyll [Chl] a/phycobilin (cyanobacteria), Chl a/Chl c/phycobilin (cryptophytes), Chl a/Chl b (chlorophytes, euglenophytes, prasinophytes), Chl a/Chl c/fucoxanthin (diatoms, chrysophytes, raphidophytes) and Chl a/Chl c/peridinin (dinoflagellates) spectral classes, and often between/among closely related phylogenetic groups within a class. Spectra for phylogenetic groups within the Chl a/Chl c/fucoxanthin, Chl a/Chl c/peridinin, Chl a/phycobilins and Chl a/Chl c/phycobilin classes were most distinguishable from spectra for groups within the Chl a/Chl b spectral class. Chrysophytes/diatoms/raphidophytes and dinoflagellates (groups within the comparable spectral classes, Chl a/Chl c/fucoxanthin and Chl a/Chl c/peridinin, respectively) displayed the greatest similarity between/among groups. Spectra for phylogenetic groups within the Chl a/Chl c classes displayed limited similarity with spectra for groups within the Chl/phycobilin classes. Among the cyanobacteria and chlorophytes surveyed, absorbance spectra of species possessing dissimilar cell morphologies were discriminated, with the greatest range of differentiation occurring among cyanobacteria. Among the cyanobacteria, spectra for selected problematic species were easily discriminated from spectra from each other and from other cyanobacteria. Fluorescence-emission spectra were distinct among spectral classes and the similarity comparisons involving fourth-derivative transformation of spectra discriminated the increasing contribution of distinct cyanobacterial species and between phycobilin- and non-phycobilin-containing species within a hypothetical mixed assemblage. These results were used to elucidate the application for in situ moored instrumentation incorporating such approaches in water quality monitoring programmes, particularly those targeting problematic cyanobacterial blooms.

The reproductive stages of Dermocarpella gardneri and D. stellata, which have been reported only once, are described. Formation of baeocytes occurs by cellular divisions that are parallel to the substratum, followed by a series of anticlinal radial divisions. In some cases in D. gardneri, the superior cell, resulting from the first division parallel to the substratum, is liberated prior to radial divisions, and these probably represent the ‘macrogonidia’ originally described by Lemmermann for D. hemisphaerica. The baeocytes are released through a circular apical pore, which develops after the formation of a papilla that eventually dissolves to form a pore.

The apex of the tetrasporangial branches of Osmundea spectabilis var. spectabilis (= Laurencia spectabilis var. spectabilis) exhibits cavities in which tufts of multicellular trichoblasts occur. Trichoblast development in Osmundea spectabilis var. spectabilis begins with the differentiation of an epidermal cell within the crypt. This cell differentiates into a trichoblast mother cell (TMC). The TMC divides to form a two-celled incipient trichoblast. Successive periclinal divisions of the apical cell of the young trichoblast result in the formation of a multicellular developing trichoblast. With the exception of the apical cell all trichoblast cells are at the same developmental stage. They possess a large nucleus, abundant plastids with peripheral and some internal thylakoids and dictyosomes. Daughter chloroplasts result from one constriction or multiple fission of a single chloroplast. Dictyosomal cisternae and mucilage sacs contribute material to wall formation. Each differentiating trichoblast cell is surrounded by a bi-layered wall. The outer wall layer represents the trichoblast mother cell wall and the inner wall layer is the trichoblast cell wall. Mature trichoblast cells have thin walls, probably as a consequence of mucilage extrusion, the most likely function of trichoblasts in Osmundea.

Field emission scanning electron microscopy (FESEM) preparation techniques have been successfully adapted for visualization of the internal and external ultrastructure of Mougeotia filaments and protoplasts. FESEM of the innermost layer of cell wall in Mougeotia filaments revealed that microfibrils are deposited parallel to each other in an interconnected mesh and are oriented perpendicular to the direction of elongation. For the first time, the surface of protoplasts at different stages of regeneration has been observed using FESEM. Nascent microfibril deposition occurs between 1 and 2 h after isolation and arrangement of these microfibrils is random for at least 8 h. Observation of the inner surface of the plasma membrane in burst protoplasts showed that microtubules are not strongly attached for at least 3 h after protoplast isolation.

Grateloupia doryphora (Montagne) Howe, originally described from Peru, has repeatedly been reported as an invasive species in Atlantic and Mediterranean waters. Various attempts to explain this species’ route of introduction have been unsatisfactory. New evidence from comparative rbcL sequence analysis and morphology suggests that this adventive species in the NE and NW Atlantic corresponds with G. turuturu Yamada, originally described from Japan. This provenance follows a well-recognized trend of invasive marine organisms that have colonized the Atlantic Ocean and Mediterranean Sea from Pacific NE Asia.

In the course of the cell cycles of synchronous cultures of the chlorococcal alga Scenedesmus quadricauda, the following were monitored: total protein and RNA accumulation as a measure of growth processes, the timing of the commitment points at which the cells trigger the sequence of reproductive processes (DNA replication, nuclear and cellular division) and the course of the reproductive processes. The synchronous cultures were grown either under various lighting regimes, or in the temporary presence of specific inhibitors of either proteosynthesis (cycloheximide) or DNA replication (5-fluorodeoxyuridine). By adjusting the length of the light period, the cell cycle could be manipulated. Cell cycle patterns could be altered to give different numbers of sequences of reproductive processes. The extent of their mutual overlap could be influenced and the number of daughter cells produced could be altered. Schematic illustrations of various cell cycle patterns and comparisons with those of higher plants and other algal species are presented.

Phylogenetic analyses, based upon nuclear small-subunit ribosomal RNA gene sequences, of four ‘chlorosarcinoid’ species referred to Planophila Gerneck show that the genus is polyphyletic. The type species, P. laetevirens Gerneck, is closely related to species in the Ulotrichales, Ulvophyceae. The monotypic sarcinoid genus Pseudendocloniopsis is the closest relative of Planophila; the two genera represent the addition of a new morphological type to the Ulotrichales. Planophila microcystis (Dangeard) Kornmann & Sahling forms a clade at the base of the Ulvophyceae with Oltmannsiellopsis, and thus belongs to the Oltmannsiellopsidales. This result is also supported by the Oltmannsiellopsis-like ultrastructure of P. microcystis zoospores. Planophila sp. B from Antarctica, which has Trebouxia-like pyrenoid structure, is a trebouxiophyte closely related to Chlorella-like unicellular coccoids, Stichococcus bacillaris and Prasiola species. This is the first robustly supported molecular phylogenetic analysis that places Prasiola in the Trebouxiophyceae. As shown previously, P. terrestris Groover & Hofstetter belongs to the Chaetopeltidales, Chlorophyceae. Dangemannia gen. nov. (type species: D. microcystis (Dangeard) comb. nov.), Floydiella gen. nov. (type species: F. terrestris (Groover & Hofstetter) comb. nov.) and Pabia gen. nov. (type: P. signiensis sp. nov.) are proposed.

Phylogenetic relationships within the Sphacelariales sensu stricto were investigated using both a molecular and a morphological approach. Twenty species were included, representing all three families (i.e. Cladostephaceae, Sphacelariaceae and Stypocaulaceae) and six of the eight genera. The outgroup consisted of six species representing the Syringodermatales, Dictyotales, Choristocarpaceae and Onslowiaceae. DNA sequences of partial rbcL [1255–1375 nucleotides (nt)] and the adjacent RUBISCO spacer (40–842 nt) were determined in order to assess the molecular phylogeny. Only the 3′-end of the spacer (112 nt positions) was alignable for the ingroup taxa. Partition homogeneity testing showed that rbcL and RUBISCO spacer sequences could be combined. However, analysis of rbcL alone or in combination with the RUBISCO spacer gave the same results with only slight differences in support (bootstrap, jackknife, decay). Support was low at the base of the ingroup. Four basal clades could be discerned: (1) Stypocaulaceae, (2) Sphacelaria radicans, (3) Sphacelaria caespitula and (4) all other included taxa: (Sphacella subtilissima+the Sphacelaria subgenus Propagulifera) and (Cladostephus spongiosus+Sphacelaria nana+the Sphacelaria subgenera Battersia+Pseudochaetopteris). The independent morphological analysis (using 23 unordered morphological characters) revealed high homoplasy and an almost completely unresolved tree in which only the subgenus Propagulifera was supported. The morphological characters were subsequently mapped onto the rbcL tree in order to identify diagnostic or phylogenetically informative characters. Blackening in response to bleach and the presence of secondary segments were found to be basal synapomorphies for the Sphacelariales; presence of propagules with a lenticular central apical cell defines the Propagulifera; and strict acroblastic branching mode and axillary zoidangia define the Stypocaulaceae. The remaining characters have been gained or lost multiple times. This study highlights the problem of extreme morphological convergence and/or plasticity. Four options for a new circumscription including nomenclatural changes are discussed. It is concluded that none of the options will lead to greater clarity with respect to either identification or classification.

Molecular and breeding studies on two pan-tropical marine red algae reveal vastly different levels of genetic variation and reproductive isolation. Sequenced DNA regions from the nuclear, mitochondrial and plastid genomes (partial LSU rRNA, cox2-3 spacer, RuBisCo spacer, respectively) revealed high genetic variation among individuals of Spyridia filamentosa. An rbcL analysis shows that Spyridia is a monophyletic genus distinct from other Ceramiaceae sampled, suggesting that the Ceramiaceae could be paraphyletic. There is complete congruence between all data sets of S. filamentosa, showing a well-supported phylogeographic pattern with samples from the Pacific distinct from Atlantic and Indian Ocean samples. One western Mediterranean sample is associated with Atlantic specimens, while an eastern Mediterranean sample has closer affinities to Pacific samples, possibly indicating a recent cryptic introduction into the eastern Mediterranean. Limited breeding studies imply that these samples are mostly reproductively isolated, whereas a successful cross demonstrated maternal inheritance of organellar DNA. These data indicate that S. filamentosa exists as several cryptic species. Murrayella periclados exhibits low levels of genetic variation and no phylogeographic structure, and almost complete reproductive compatibility between isolates. This suggests that all M. periclados samples share a recent common ancestor that may have dispersed relatively rapidly, or that rates of base pair substitution between these two species vary greatly. Rapid long-distance dispersal of M. periclados is not indicated by what is known of the biology of M. periclados, especially in comparison with S. filamentosa, which appears to be a much better candidate for long-distance dispersal. These data demonstrate that red algal morphospecies are not equivalent units of diversity, with implications for our view of red algal biodiversity and evolution.

Glutamate-l-semialdehyde (GSA) aminotransferase catalyses the final step in the C5 pathway converting glutamate to the tetrapyrrole precursor δ-aminolaevulinic acid. This enzyme is sensitive to gabaculine (2,3-dihydro-3-amino benzoic acid) and to 4-amino-5-fluoropentanoic acid (AFPA), which are irreversible, mechanism-based inhibitors of pyridoxal phosphate-dependent enzymes. Spontaneous mutants of Synechococcus PCC6301 resistant to these inhibitors contain altered enzyme that displays corresponding resistance to high concentrations of the inhibitor. The enzyme from strain GR6, resistant to both inhibitors, contains a three-amino-acid deletion at positions 5–7 and a Met248→Ile substitution. The enzyme from strain K40 resistant to AFPA but not to gabaculine, contains a Ser163→Thr substitution. GSA aminotransferases containing either the deletion or the substitution that are characteristic of the GR6 mutant were produced in Escherichia coli using the expression vector pMalc2. These engineered mutant enzymes were characterized in terms of their catalytic parameters and sensitivities to gabaculine and AFPA. Furthermore, maltose binding protein/aminotransferase fusion proteins were characterized spectrophotometrically to monitor the interaction of bound cofactor with diamino- and dioxo-compounds related to the substrate and both inhibitors. Results were compared with those for similarly produced recombinant wild-type, K40 and GR6 GSA aminotransferases. The engineered products with either the N-terminal deletion or the Met248→Ile substitution displayed catalytic efficiencies that were intermediate between the wild-type and GR6 or K40 enzymes. However, with respect to their absorption spectra, sensitivity to inhibitors and the reactivity of bound cofactor, they were essentially wild-type. These in vitro studies demonstrate that both changes in enzyme structure are necessary to obtain the distinctive properties of the GR6 aminotransferase, including resistance to high concentrations of gabaculine and AFPA.

Amphora angusta Gregory, Amphora ventricosa Gregory and Amphora macilenta Gregory have been misunderstood for the last 140 years. Gregory described these species from sublittoral sediments off the west coast of Scotland. Although the illustrations were excellent for their time (1857), it is impossible to be confident of identification using Gregory's paper, and subsequent authors have created such confusion that records of these taxa must be regarded as untrustworthy unless backed by photographic evidence. In this paper, the first to describe in detail the recently established genus Seminavis, we show that A. angusta is in fact a species of Amphora Ehrenberg, whereas A. ventricosa sensu Gregory represents two independent species of the genus Seminavis D. G. Mann, namely Seminavis ventricosa (Gregory) Garcia-Baptista (non S. ventricosa sensu Garcia-Baptista 1993) and Seminavis arranensis Danielidis & D. G. Mann, sp. nov. The form usually known as A. ventricosa is neither of these and requires a new name, Seminavis robusta Danielidis & D. G. Mann, sp. nov. The long forgotten and misclassified species A. macilenta Gregory is shown to be yet another Seminavis species, requiring a new combination as S. macilenta (Gregory) Danielidis & D. G. Mann, comb. nov.; contrary to previous claims, it is separate from A. ergadensis Gregory, which is a true Amphora. Valve and girdle ultrastructure, plastid arrangement and auxosporulation are described for Seminavis and resemble those in the Naviculaceae sensu stricto.

How are microphytobenthic biofilms adapted to the high incident irradiances and temperatures, low inorganic nutrient concentrations and high desiccation stresses on intertidal flats present in tropical environments? This study investigated biofilms subject to different environmental conditions in a range of tropical sites in Suva lagoon, Fiji. PAM fluorescence was used to measure photophysiological responses to the light climate. Biofilm colloidal carbohydrate, extracellular polymeric substances (EPS) and low molecular weight (MW) carbohydrate concentrations and diel carbohydrate production patterns were measured. Average biomass (Chl a) ranged from 15 to 36 mg m−2, and was highest in seagrass bed sediments, but biomass was not correlated with water column or sediment porewater nutrient concentrations. Biofilm photophysiology differed significantly along a combined gradient of light and nutrient availability, with Fv/Fm, relative ETRmax and Ek of biofilms highest in mangrove and intertidal main island sites and lowest in subtidal coral reef flats. Subtidal biofilms showed photoinhibition at irradiances >1000 μmol m−2 s−1. Significant correlations between Chl a and colloidal carbohydrate concentrations were present (except on intertidal sandflats), and tropical biofilms had higher ratios of colloidal carbohydrate and EPS to Chl a than temperate estuarine biofilms, probably due to a combination of high irradiance and low nutrient availability leading to the production of excess photoassimilates. The percentage of EPS present in the colloidal fraction was highest in coral sand biofilms (42%), which had the lowest nutrient concentrations, compared with other sites (25–32%). Intertidal biofilms predominantly consisted of large motile taxa and showed strong rhythms of vertical migration. During tidal emersion, high sediment temperatures (41 °C), irradiance (>2300 μmol m−2 s−1) and salinity (49‰) stimulated downward migration. In silty sediments, migration resulted in a reduction in photosynthetic activity during the midday period but, in sands with high light penetration (to a depth of >1700 μm), high production rates of EPS (18.2 μg carbo. μg Chl a−1 h−1) and low MW carbohydrate exudates (40.2 μg carbo. μg Chl a−1 h−1) occurred. Vertical migration, high Ek and high rates of photoassimilate dumping are all adaptations to living in the tropical intertidal zone. Seagrass and reef flat biofilms consisted of a diverse non-migratory flora of motile and non-motile taxa that were not subject to such extreme temperature and irradiance conditions. Low values of photosynthetic parameters and high colloidal and EPS content indicated that these biofilms were nutrient-limited.

Systematics of the red algal order Acrochaetiales and related taxa was investigated using combined small- and large-subunit nuclear ribosomal DNA (SSU and LSU rDNA, respectively) sequence data. These data were subjected to distance, parsimony and maximum likelihood analyses. The resulting phylogenies were congruent with previously published SSU results in that all included orders (Balbianiales, Batrachospermales, Nemaliales, Palmariales and Thoreales) were resolved as monophyletic except the Acrochaetiales, which consisted of two lineages (Acrochaetiales I and II). The Batrachospermales and Thoreales occupied equivocal positions as early diverging lineages, while the Balbianiales generally resolved as sister to an Acrochaetiales–Nemaliales–Palmariales (ANP) complex. Relationships among the four lineages of the ANP complex were not completely resolved, but detailed analyses weakly positioned Acrochaetiales II as sister to the Nemaliales, whereas Acrochaetiales I displayed a moderate to strong affiliation with the Palmariales. Acrochaetiales I included representatives of the genera Acrochaetium,Audouinella and Rhodochorton, whereas Acrochaetiales II had a number of acrochaetioid species including a representative of the genus Colaconema. Compared with published SSU phylogenies, bootstrap values within the two Acrochaetiales lineages increased substantially in combined SSU/LSU analyses. Based on these results, emended generic descriptions are provided for Acrochaetium, Audouinella, Colaconema and Rhodochorton, and a new family of acrochaetioid algae is described, the Colaconemataceae J. T. Harper et G. W. Saunders. The Acrochaetiaceae now includes the genera Acrochaetium, Audouinella and Rhodochorton, while the Colaconemataceae is considered monogeneric at this time. It is quite likely that additional genera will be recognized within the Colaconemataceae pending further investigation. Acrochaetiaceae is retained as the sole family of the Acrochaetiales, although the tenuous recognition of the Palmariales as distinct from this order is discussed, whereas Colaconemataceae is transferred to the new order Colaconematales J. T. Harper et G. W. Saunders.

Volcanic areas with highly acidic solfatara soils and temperatures of up to 56 °C are inhabited by the red algal genus Galdieria. We examined three highly acidic but non-volcanic habitats in the western part of the Czech Republic for the occurrence of this red alga. In soil samples from the National Nature Reserve of Soos we found, together with Euglena mutabilis, Pseudococcomyxa simplex and species of Chlorella, a new strain of Galdieria. In contrast to all other Galdieria strains described so far, the strain from Soos exhibited a low temperature optimum for growth of about 30 °C. Other properties, such as the substrate spectrum for heterotrophic growth, ultrastructure, fatty acid composition, thermostability of enzymes and the nitrogen source, showed no obvious differences from other strains of Galdieria. Within a phylogenetic tree based on 18S rRNA sequence data, the strain from Soos occupied a position at the base of the ‘Galdieria’-branch. Our findings indicate that the genus Galdieria is not restricted to volcanic and mining areas and that strains of Galdieria are able to compete successfully with green algae in habitats like Soos.

The Third European Phycological Congress (EPC3) will be held in Belfast from 21–26 July 2003. The following is an outline of the plenary lectures and symposia. Further details can be obtained from our website www.epc3.org (email: [email protected]). A full social programme will also be provided, and there will be mid-congress visits to attractions such as the Giant's Causeway and the Mountains of Mourne.