Diversity of Archaea in Brazilian savanna soils

Although the richness of Bacteria and Fungi in Cerrado’ soils has been reported, here we report, for the first time, the archaeal community in Cerrado’s soils. DNA extracted from soil of two distinct vegetation types, a dense subtype of sensu strict (cerrado denso) and riverbank forest (mata de galeria), was used to amplify Archaea-specific 16S rRNA gene. All of the fragments sequenced were classified as Archaea into the phylum Thaumarchaeota, predominantly affiliated to groups I.1b and I.1c. Sequences affiliated to the group I.1a were found only in the soil from riverbank forest. Soils from ‘cerrado denso’ had greater Archaea richness than those from ‘mata de galeria’ based on the richness indexes and on the rarefaction curve. β-Diversity analysis showed significant differences between the sequences from the two soil areas studied because of their different thaumarchaeal group composition. These results provide information about the third domain of life from Cerrado soils.     

Neuroprotection from stroke in the absence of MHCI or PirB

Recovery from stroke engages mechanisms of neural plasticity. Here we examine a role for MHC class I (MHCI) H2-Kb and H2-Db, as well as PirB receptor. These molecules restrict synaptic plasticity and motor learning in the healthy brain. Stroke elevates neuronal expression not only of H2-Kb and H2-Db, but also of PirB and downstream signaling. KbDb knockout (KO) or PirB KO mice have smaller infarcts and enhanced motor recovery. KO hippocampal organotypic slices, which lack an intact peripheral immune response, have less cell death after in?vitro ischemia. In PirB KO mice, corticospinal projections from the motor cortex are enhanced, and the reactive astrocytic response is dampened after MCAO. Thus, molecules that function in the immune system act not only to limit synaptic plasticity in healthy neurons, but also to exacerbate brain injury after ischemia. These results suggest therapies for stroke by targeting MHCI and PirB.     

The plasminogen activator family from the salivary gland of the vampire bat Desmodus rotundus: cloning and expression

Complementary DNAs coding for four Desmodus rotundus salivary plasminogen activators (DSPAs) were isolated and characterized. The predicted amino acid sequences display structural features also found in tissue-type plasminogen activator. The largest forms (DSPA alpha 1 and -alpha 2) contain a signal peptide, a finger (F), an epidermal growth factor (EGF), a kringle, and a serine protease domain, whereas DSPA beta and -gamma lack the F and F-EGF domains, respectively. Additional differences between the four forms suggest that distinct genes code for the members of the DSPA family. Transfection of DSPA-encoding cDNAs, placed under the control of the simian virus 40 late promoter, into COS-1 cells resulted in the secretion of highly fibrin-dependent PAs.     

Carrier-mediated transport of riboflavin in Ashbya gossypii

The filamentous hemiascomycete Ashbya gossypii is used for industrial riboflavin production. We examined riboflavin uptake and excretion at the plasma membrane using riboflavin auxotrophic and overproducing mutants. The riboflavin uptake system had low activity [Vmax = 20 +/- 4 nmol min(-1) g(-1) mycelial dry weight (dw)] and high affinity (KM = 40 +/- 12 microM). Inhibitor studies with the analogs FMN and FAD revealed high specificity of the uptake system. Excretion of riboflavin was not the consequence of non-specific permeability of the plasma membrane. Excretion rates in the mid-production phase were determined to be 2.5 nmol min(-1) g(-1) dw for wild-type cells and 66.7 nmol min(-1) g(-1) dw for an overproducing mutant, respectively. Inhibition of the reverse reaction, riboflavin uptake, led to an increase in apparent riboflavin efflux in the early production phase, indicating the presence of a separate excretion carrier. Riboflavin accumulation in A. gossypii vacuoles leading to product retention was found to be a secondary transport process. To address the question of whether a flux from the vacuoles back into the cytoplasm is present, we characterized efflux in hyphae in which the plasma membrane was permeabilized with digitonin. Efflux kinetics across the vacuolar membrane were unaffected by the lack of vacuolar H+ATPase activity and ATP, suggesting a passive mechanism. Based on the characterization of riboflavin transport processes in this study, the design of new production strains with improved riboflavin excretion may be possible.     

Anamylopsoraceae — a new family of lichenized ascomycetes with stipitate apothecia (Lecanorales: Agyriineae)

The anatomy, chemistry and developmental morphology ofAnamylopsora pulcherrima is investigated. Some characters, including the ascus structure, suggest a close affinity with theAgyriaceae. However, the chemistry and the pycnidial structure differ as well as the ascoma ontogeny.Anamylopsora has a gymnocarpous ascoma development and the ascogonia are produced in stipes.Trapelia coarctata, as a typical member of theAgyriaceae, shows a hemiangiocarpous ascoma ontogeny. The anatomical, chemical and ontogenetical characters of several families are compared withAnamylopsora and it is shown that the genus is best placed in a monotypic familyAnamylopsoraceae Lumbsch & Lunke, fam. nova, which is placed in theAgyriineae (Lecanorales).This paper is dedicated to Prof. DrAino Henssen (Marburg) on the occasion of the 70th birthday.     

The effect of light levels on daily patterns of chlorophyll fluorescence and organic acid accumulation in the tropical CAM treeClusia hilariana

Sandy plains are characteristic of the coastal region of Brazil. We investigated the diel patterns of changes in organic acid levels, leaf conductance and chlorophylla fluorescence for sun-exposed and shaded plants ofClusia hilariana, one of the dominant woody species in the sandy coastal plains of northern Rio de Janeiro state. Both exposed and shaded plants showed a typical CAM pattern with considerable diel oscillations in organic acid levels. The degradation of both malic and citric acids during the midday stomatal closure period could lead to potential CO₂ fixation rates of 28 mol m^-2 s^-1 in exposed leaves. Moreover, exposed leaves exhibited large increases in total non-photochemical quenching (q_N) accompanied by a substantial decrease in effective quantum yield during the course of the day. However, these potential high rates of CO₂ fixation and the increases inqn of exposed plants were not enough to maintain the primary electron acceptor of photosystem II (q_A) in a low reduction state, similar to that of shaded plants. As a result, there was a moderate increase in the reduction state of q_A throughout the day. Most of the decline in photochemical efficiency of exposed leaves ofC. hilariana was reversible, as evidenced by the high levels of pre-dawn potential quantum yields (F_v/F_m) and their rapid recovery after sunset. However, the depletion of the organic acid pool in the afternoon resulted in an accentuated subsequent drop in F_v/F_m, suggesting that prolonged periods of water stress accompanied by high irradiance levels may expose plants ofC. hilariana in unprotected habitats to the danger of photoinhibition.     

Ordovician (Dobrotivá Formation) ostracodes and trilobites from Ejpovice (Bohemia) and their relations to faunas of northern and western Europe

For the first time a complete ostracode and trilobite fauna is described from the Dobrovitá Formation (Ordovician) of Perunica. In contrast to the trilobite fauna the ostracode fauna evidences close relations to both Armorica and Baltica. The trilobite fauna comprises 11 species out of 11 genera, the ostracode fauna comprises 15 (5 new) species out of 15 (1 new) genera.