Binding and Functional Properties of Five Extrinsic Proteins in Oxygen-evolving Photosystem II from a Marine Centric Diatom,Chaetoceros gracilis

Oxygen-evolving photosystem II (PSII) isolated from a marine centric diatom, Chaetoceros gracilis, contains a novel extrinsic protein (Psb31) in addition to four red algal type extrinsic proteins of PsbO, PsbQ′, PsbV, and PsbU. In this study, the five extrinsic proteins were purified from alkaline Tris extracts of the diatom PSII by anion and cation exchange chromatographic columns at different pH values. Reconstitution experiments in various combinations with the purified extrinsic proteins showed that PsbO, PsbQ′, and Psb31 rebound directly to PSII in the absence of other extrinsic proteins, indicating that these extrinsic proteins have their own binding sites in PSII intrinsic proteins. On the other hand, PsbV and PsbU scarcely rebound to PSII alone, and their effective bindings required the presence of all of the other extrinsic proteins. Interestingly, PSII reconstituted with Psb31 alone considerably restored the oxygen evolving activity in the absence of PsbO, indicating that Psb31 serves as a substitute in part for PsbO in supporting oxygen evolution. A significant difference found between PSIIs reconstituted with Psb31 and with PsbO is that the oxygen evolving activity of the former is scarcely stimulated by Cl⁻ and Ca²⁺ ions but that of the latter is largely stimulated by these ions, although rebinding of PsbV and PsbU activated oxygen evolution in the absence of Cl⁻ and Ca²⁺ ions in both the former and latter PSIIs. Based on these results, we proposed a model for the association of the five extrinsic proteins with intrinsic proteins in diatom PSII and compared it with those in PSIIs from the other organisms.     

Increase in Si:N drawdown ratio due to resting spore formation by spring bloom-forming diatoms under Fe- and N-limited conditions in the Oyashio region

Resting spore formation and Si:N drawdown ratios were investigated under iron (Fe)- and nitrogen (N)-limited conditions using a unialgal culture of Thalassiosira nordenskioeldii and natural phytoplankton assemblages during the spring bloom in the Oyashio region. In the unialgal culture of T. nordenskioeldii, 20% and 100% of the cells formed resting spores under Fe- and N-limited conditions, respectively. The Si:N drawdown ratios were 2- and 14-fold higher in Fe- and N-limited conditions, respectively, compared to Fe- and N-sufficient conditions. At the start of the natural phytoplankton incubation, 18 among 47 identified diatom species were known resting spore-forming species. Approximately 15 common diatom species formed resting spores under Fe- and N-limited conditions. During the natural phytoplankton incubation, the percentage of the resting spores increased with time under both Fe- and N-limited conditions, reaching 25% and 40% of total diatom abundance, respectively. The Si:N drawdown ratios significantly increased with an increase in the contribution of resting spores in both the unialgal culture and natural phytoplankton incubations. These results suggest that if the bloom dominated by neritic, resting spore-forming diatom species decline by either Fe- or N-depletion, Si may be utilized preferentially to N in the upper mixed layer due to the formation of heavily silicified resting spores.     

Purification of the blue-green pigment “marennine” from the marine tychopelagic diatom Haslea ostrearia (Gaillon/Bory) Simonsen

The diatom Haslea ostrearia that lives in oyster ponds has the distinctive feature of synthesizing “marennine”, a blue-green pigment of which the chemical nature still remains unknown. This pigment is responsible for the greening of oyster gills. Here, we report a new method for extraction and purification of intracellular (accumulated in the apex of the cell) and extracellular (released into the external medium) forms of the pigment. Intracellular marennine is obtained by extraction from blue algal pellets with a carbonate buffer. The extract is then centrifuged and filtered. Extracellular marennine is obtained by clarification of blue-coloured culture medium. Both extracts are then purified by a semi-preparative process, using ultrafiltration through membranes and anion-exchange chromatography. This procedure allows us to produce native pigment displaying the degree of purity required to enter upon the molecular characterisation of marennine. By this process, about 35% of the initial amount of pigment can be recovered. If necessary, this method could be easily scaled up to a larger production system to accommodate potential industrial applications.     

The Impact of the Weed Chrysanthemoides monilifera ssp. rotundata on Coastal Leaf Litter Invertebrates

In coastal areas of Australia, there are extensive infestations of the environmental weed Chrysanthemoides monilifera ssp. rotundata (bitou bush). This study looked at the impact of long-term infestations on the abundance and assemblage composition of leaf litter invertebrates. Assemblages were compared in weed infested and native shrublands along the New South Wales coastline over 12 months. The total abundance was not significantly reduced in the weedy habitat but the abundance of mites, thrips, spiders, ants, and centipedes was reduced at many sites. The invertebrate assemblages also differed between habitats, with the C. monilifera supporting a lower diversity of beetles. However, the millipedes, amphipods, earthworms, pseudoscorpions and isopods appeared to respond positively to the invasion, occurring in higher abundance and detected more frequently in the weedy areas. This has been partially attributed to a change in microclimate within the C. monilifera infestations. It is generally moister and darker, which these invertebrates tend to prefer. Secondly, C. monilifera produces less leaf litter of higher quality, and possibly higher palatability than the native sclerophyllous vegetation, which may encourage species that consume litter.     

New palaeontological assemblage, sedimentological and chronological data from the Pleistocene Ma U'Oi cave (northern Vietnam)

This paper describes recent material gathered during the second fieldwork at Ma U'Oi in November 2002 by a Vietnamese–French–Japanese team. The Ma U'Oi cave, located in the province of Hoà Binh (60 km SW from Hanoi), northern Vietnam, belongs to a karstic network developed in Triassic dark-grey limestones.

The cave is filled with coarse-grained breccias containing numerous fossil remains, partially preserved at several loci inside the cave (wall, vault and ground). We describe new teeth which confirm the occurrence of mammal taxa already mentioned at Ma U'Oi (Bacon et al., 2004)[Bacon, A-M., Demeter, F., Schuster, M., Long, V.T., Thuy, N.K., Antoine, P-O., Sen, S., Nga, H.H., Huong, N.T.M., 2004. The Pleistocene Ma U'Oi cave, northern Vietnam: palaeontology, sedimentology and palaeoenvironments. Geobios 37, 305–314], while others, mainly microvertebrates, emphasize the occurrence of new species for the Pleistocene of Vietnam. We report here, for the first time, the occurrence of these microvertebrates of different groups (primates, rodents, insectivores, small reptiles and amphibians) in the faunal assemblage. Among mammal taxa, the presence of one more hominid affiliated to archaic Homo is also attested by our findings. U/Th dating carried out on 2 samples extracted from breccia speleothems confirms the biochronological estimate, with fossiliferous fillings ranging from late Middle Pleistocene to Late Pleistocene.     

Macroinvertebrate communities in Phragmites australis (Cav.) Trin. ex Steud. reed beds and open bank habitats in central victorian streams in Australia

Reed invasion is a common phenomenon of open streams with disturbed riparian vegetation in river catchments. Knowledge of the effects of such vegetation change on aquatic communities is fundamental to river management. Macroinvertebrate fauna in Phragmites australis (Cav.) Trin. ex Steud. and open bank habitats were examined in three rivers in central Victoria in order to understand the effect of such littoral habitat on macroinvertebrates. Data were analysed using Partially Nested Factorial ANOVA with season, river and habitats as main effects. Habitat structure had a significant effect (p<0.05) on macroinvertebrate species richness, however this was not seasonally consistent across the three rivers. There was a significant increase (p<0.05) in macroinvertebrate taxa richness in Phragmites habitats during winter and spring seasons. Total abundance of taxa showed no consistent significant differences in the two habitats. Results of Canonical Analysis of Principle Coordinates indicated significant differences (p<0.05) in macroinvertebrate assemblages between Phragmites and bare bank habitats in all seasons. Habitat selection by taxa could be related to the microphysical environment of the habitats. This study suggests that reed beds create important littoral habitat structures which support diverse macroinvertebrate assemblages.     

A branched beta-D-(1-->3,1-->6)-glucan from the marine diatom Chaetoceros debilis (Bacillariophyceae) characterized by NMR

The chrysolaminaran from the marine diatom Chaetoceros debilis was isolated and characterized by NMR spectroscopy. Cells were harvested in the stationary phase of growth after the medium had been depleted of nitrate when the chrysolaminaran content was expected to be at its highest. The chrysolaminaran was isolated with an yield of 17.5 mg/L, which corresponds to 15.8 pg/cell. 1H NMR indicated that the structure was similar to that of a beta-(1-->3) main chain with beta-(1-->6)-linked side chains. The degree of polymerization was found to be 30, corresponding to a molecular weight of approximately 4900. Thirty-three percent of the residues were found to be beta-(1-->6)-linked branches. The characteristics of the beta-(1-->6) branching were examined by NOESY NMR, which suggested pustulan-like branches, being beta-(1-->6) linked chains connected to the main chain with few branch points. Confirmation of the 1H NMR data was done by 13C-DEPT, TOCSY, COSY and HMQC NMR spectroscopy. The assignment of the resonances of the main beta-(1-->3) and beta-(1-->6) chains is presented. The structure proposed from our analyses is compared against other chrysolaminaran structures.     

Sampling termites in forest habitats: A reply to Roisin and Leponce

Abstract To characterize the structure and species density of termite assemblages in tropical forests, we developed a sampling protocol based on a single large quadrat (belt transect) that standardises sampling effort and area. Emphasizing the estimation of species richness, Roisin and Leponce (2004, Austral Ecology, 29 : 637–46) recommend sampling numerous small quadrats, and varying the number of quadrats depending on local species density. However, their method would result in the loss of standardisation and speed, taking up to four times longer to collect and process the samples. We show that even for a subtropical forest with low species density, our protocol produces robust results.     

Do miners (Manorina spp.) affect bird assemblages in continuous savanna woodlands in north‐eastern Australia?

Overabundant native species can have a significant cascading effect on other components of wildlife, and those that deplete other species, often promoted by anthropogenic change to vegetation cover and habitat, are called reverse keystone species. Birds in the genus Manorina are widely reported as being such species, and in highly disturbed or fragmented environments, and some intact environments, noisy miners Manorina melanocephala can have a strong negative effect on small passerine species via hyper‐aggressive mobbing. The tropical savannas of northern Australia consist of largely unmodified woodlands, and two species of Manorina occur naturally in this region: the noisy miner and the yellow‐throated miner Manorina flavigula. Therefore, what effect do these species have on bird assemblage in predominantly continuous habitats, relative to other typical determinants of avifauna assemblage such as vegetation structure? We used data collected from bird surveys at 511 sites across northern Queensland (179 noisy miner M. melanocephala sites, 332 yellow‐throated miner M. flavigula sites) between 1998 and 2010. We examined the variation in bird composition at each site due to increasing abundance of Manorina spp. using uni‐ and multivariate techniques. We found total bird richness was significantly lower in sites where noisy and yellow‐throated miner abundances were highest, and passerine species seemed most affected. For species, 45 species varied significantly in abundance with increasing miner numbers, and the overall effect of yellow‐throated miners on other birds seemed more pronounced. However, vegetation structure was generally an equal or more important predictor of avifauna richness and abundance. We conclude that despite the superficially intact nature of northern Australian woodlands, pastoral intensification or poor land management might create disturbances that facilitate increases in the abundance of Manorina, causing localized overabundance and a compounding negative effect on other native bird species.     

西秦岭地区志留/泥盆系过渡带中的鱼类微体化石及其组合序列

西秦岭是开展华南板块志留/泥盆系界线层序研究的一个重要地区.该区普通沟剖面中的志留/泥盆系过渡带包括羊路沟组上部和下普通沟组下部,产丰富的鱼类微体化石,包括花鳞鱼类、棘鱼类、软骨鱼类及盾皮鱼类.这些化石构成两个完全不同的鱼类微体化石组合:羊路沟组合和下普通沟组合.通过与波罗的海等地区鱼类微体化石带的对比,羊路沟和下普通沟组合的地质时代分别为志留纪普里道利世晚期和早泥盆世洛霍考夫期早期.西秦岭地区志留/泥盆系过渡带中的鱼类微体化石及其组合序列的研究,为该区志留/泥盆系界线的精确确定提供了重要的古鱼类学证据.