Bamboo dominance reduces tree regeneration in a disturbed tropical forest

Human disturbance may change dominance hierarchies of plant communities, and may cause substantial changes in biotic environmental conditions if the new dominant species have properties that differ from the previous dominant species. We examined the effects of bamboos (Bambusa tulda and Cephalostachyum pergracile) and their litter on the overall woody seedling abundance, species richness and diversity in a mixed deciduous forest in northeastern Thailand. These bamboo species are gaining dominance after human disturbance. Our results show that seedling abundance and species richness were reduced by bamboo canopies. Seedling abundance and species diversity under bamboo canopies were affected by bamboo litter, whereas seedling abundance and species diversity outside bamboo canopies did not respond to the mixed-tree litter manipulation. Removal of bamboo litter increased seedling abundance and species diversity. However, bamboo litter addition did not affect seedling abundance or species diversity compared to either control or litter removal. This may indicate that the effect of natural amount of bamboo litter is as high as for litter addition in preventing seedling establishment by woody species and hence in minimizing resource competition. We conclude that undergrowth bamboos and their litter affect tree seedling regeneration differently from mixed-tree litter, causing changes in plant community composition and species diversity. Increased human disturbance, causing a shift in dominance structure of these forests, may result in a concomitant reduction in their overall woody species abundance, richness and diversity. Thus, management of bamboos by controlling their distribution in areas of high bamboo density can be an important forest restoration method.     

Fossil water‐penny beetles (Coleoptera: Psephenidae: Eubrianacinae) from the Eocene of Europe,with remarks on their phylogenetic position and biogeography

Abstract: A species of water‐penny beetles is recorded from larval instars from the Middle Eocene Messel pit fossil site in Germany. This species clearly belongs to the psephenid subfamily Eubrianacinae, but its precise systematic affinities remain unclear. It is the second fossil species of this taxon recorded from Europe. The holotype of the first fossil species, Eubrianax vandeli Bertrand and Laurentiaux, 1963, is lost. The high number of fossil specimens from Messel allowed discussion of stratigraphic and spatial occurrence of the eubrianacine species in the Messel pit, but its larval ontogeny could not be unravelled. Because of the high number of fossils and their wide occurrence, it is inferred that the species from Messel gen. sp. 1 was an autochthonous faunal element of the Eocene Lake Messel, which might indicate that some parts of the former Lake Messel had a shore area with stones. The analysis of the phylogenetic position of both Eocene eubrianacine species showed that their phylogenetic placement cannot be resolved because preservational influences limit the evaluation of characters. The historical biogeography of Psephenidae and Eubrianacinae is analysed and discussed. The fossil record shows that psephenid beetles have fossil members occurring outside their current distribution range, so interpretations of their biogeography based only on extant members can be misleading.     

Effects of river ice on riparian vegetation

1. Many rivers and streams experience pronounced ice dynamics caused by the formation of anchor and frazil ice, leading to flooding and disturbance of riparian and aquatic communities. However, the effects of dynamic ice conditions on riverine biota are little known. 2. We studied the formation of anchor ice in natural streams over 2 years and assessed the effects of anchor ice on riparian vegetation by comparing sites with frequent or abundant and little or no anchor ice formation. We also studied the direct impact of ice on riparian plants by experimentally creating ice in the riparian zone over three winters and by exposing plants of different life forms to ?18 °C cold ice in the laboratory. 3. Riparian species richness per 1‐m² plot was higher at sites affected by anchor ice than at sites where anchor ice was absent or rare, whereas dominance was lower, suggesting that disturbance by ice enhances species richness. Species composition was more homogenous among plots at anchor ice sites. By experimentally creating riparian ice, we corroborated the comparative results, with species richness increasing in ice‐treated plots compared to controls, irrespective of whether the sites showed natural anchor ice. 4. Because of human alterations of running waters, the natural effects of river ice on stream hydrology, geomorphology and ecology are little known. Global warming in northern streams is expected to lead to more dynamic ice conditions, offering new challenges for aquatic organisms and river management. Our results should stimulate new research, contributing to a better understanding of ecosystem function during winter.     

Culturing of stoneworts and submersed angiosperms with phosphate uptake exclusively from an artificial sediment

1. We aimed to demonstrate reproducible nutrition and growth of macrophytes in non‐axenic laboratory cultures preventing growth of phytoplankton and epiphytes. 2. Macrophyte shoot segments were planted in a mixture of commercial acid‐washed silica sand with crystalline tricalcium phosphate, and this artificial sediment was covered with a layer of pure silica sand. The liquid mineral media used did not contain phosphorus but were rich in all other nutrient elements. A CO₂ reservoir provided sustainable CO₂ supply to macrophyte cultures by gas diffusion through a polyethylene membrane. 3. Chara hispida, Chara tomentosa, Chara baltica, Elodea canadensis, Potamogeton pectinatus and Zanichellia palustris could be cultivated for long term without medium exchange and aeration. Microalgae growth was prevented by the absence of phosphate in the water column. Mobilisation of tricalcium phosphate and phosphate uptake by the rhizoids of C. hispida enabled sustainable rapid shoot growth and increased the concentration of inorganic phosphate in the shoot dry weight by five to six times in comparison with plants cultivated on pure silica sand. A significant growth support from tricalcium phosphate was also observed for E. canadensis, but the rate of phosphate uptake by the roots was not sufficient to maintain a storage pool of inorganic phosphate (P_i) in the growing shoots of this plant. 4. Membrane‐controlled CO₂ supply from a reservoir and artificial sediments like the one described provide attractive options for the laboratory culture of macrophytes.     

Conformational variability of different sulfonamide inhibitors with thienyl-acetamido moieties attributes to differential binding in the active site of cytosolic human carbonic anhydrase isoforms

The X-ray crystal structures of the adducts of human carbonic anhydrase (hCA, EC 4.2.1.1) II complexed with two aromatic sulfonamides incorporating 2-thienylacetamido moieties are reported here. Although, the two inhibitors only differ by the presence of an additional 3-fluoro substituent on the 4-amino-benzenesulfonamide scaffold, their inhibition profiles against the cytosolic isoforms hCA I, II, III, VII and XIII are quite different. These differences were rationalized based on the obtained X-ray crystal structures, and their comparison with other sulfonamide CA inhibitors with clinical applications, such as acetazolamide, methazolamide and dichlorophenamide. The conformations of the 2-thienylacetamido tails in the hCA II adducts of the two sulfonamides were highly different, although the benzenesulfonamide parts were superimposable. Specific interactions between structurally different inhibitors and amino acid residues present only in some considered isoforms have thus been evidenced. These findings can explain the high affinity of the 2-thienylacetamido benzenesulfonamides for some pharmacologically relevant CAs (i.e., isoforms II and VII) being also useful to design high affinity, more selective sulfonamide inhibitors of various CAs.     

IRF6 is a mediator of Notch pro-differentiation and tumour suppressive function in keratinocytes

While the pro-differentiation and tumour suppressive functions of Notch signalling in keratinocytes are well established, the underlying mechanisms remain poorly understood. We report here that interferon regulatory factor 6 (IRF6), an IRF family member with an essential role in epidermal development, is induced in differentiation through a Notch-dependent mechanism and is a primary Notch target in keratinocytes and keratinocyte-derived SCC cells. Increased IRF6 expression contributes to the impact of Notch activation on growth/differentiation-related genes, while it is not required for induction of 'canonical' Notch targets like p21(WAF1/Cip1), Hes1 and Hey1. Down-modulation of IRF6 counteracts differentiation of primary human keratinocytes in vitro and in vivo, promoting ras-induced tumour formation. The clinical relevance of these findings is illustrated by the strikingly opposite pattern of expression of Notch1 and IRF6 versus epidermal growth factor receptor in a cohort of clinical SCCs, as a function of their grade of differentiation. Thus, IRF6 is a primary Notch target in keratinocytes, which contributes to the role of this pathway in differentiation and tumour suppression.     

Optimization of pH induced flocculation of marine and freshwater microalgae via central composite design

Microalgae harvesting via pH induced flocculation along with utilization of recovered medium after flocculation is one of the most economical methods for separating the microalgal biomass in order to reduce the dewatering cost. In this study, optimization of marine and freshwater microalgae flocculation by pH adjustment was investigated via central composite design methodology. One molar of KOH and NaOH solutions were used to increase the pH level of the microalgal culture. Increasing pH value of the medium provided the highest flocculation efficiency up to 92.63 and 86.18% with pH adjusted to 10.5 with KOH and NaOH solutions for marine microalgae Nannochloropsis oculata and freshwater microalgae Chlorella minutissima, respectively. Also, it was revealed that microalgae cells were still alive after flocculation process and their biochemical composition was not changed, and flocculated medium can be used again for the next microalgal production. According to the results, it can be said that this method is cheap and effective, simple to operate and provides the utilization of flocculated medium again.