High-yield production of oxalic acid for metal leaching processes by Aspergillus niger

Abstract The complex-forming compound oxalic acid can effectively solubilise metals such as aluminium, iron, lithium, and manganese. In order to produce high amounts of oxalic acid for biohydrometallurgical processes, it was the aim of this work to optimise oxalic acid production by Aspergillus niger , a fungus well known for its ability to produce oxalic acid. A. niger excreted 427 mmol oxalic acid 1⁻¹ if it was cultivated in a pH-controlled (pH 6.0) fed-batch run in a 2-1 stirred tank reactor. Sucrose and lactose permeate were suitable carbon sources for oxalic acid production. In sucrose medium, A. niger produced high amounts of gluconic and oxalic acids, whereas in lactose permeate medium only oxalic acid was produced. Cultivation in green syrup and molasses media lead to high yields of biomass, but low oxalic acid production (<20 mmol 1⁻¹).     

LapB (YciM) orchestrates protein–protein interactions at the interface of lipopolysaccharide and phospholipid biosynthesis

The outer membrane (OM) of Gram-negative bacteria functions as an essential barrier and is characterized by an asymmetric bilayer with lipopolysaccharide (LPS) in the outer leaflet. The enzyme LpxC catalyzes the first committed step in LPS biosynthesis. It plays a critical role in maintaining the balance between LPS and phospholipids (PL), which are both derived from the same biosynthetic precursor. The essential inner membrane proteins YejM (PbgA, LapC), LapB (YciM), and the protease FtsH are known to account for optimal LpxC levels, but the mechanistic details are poorly understood. LapB is thought to be a bi-functional protein serving as an adaptor for FtsH-mediated turnover of LpxC and acting as a scaffold in the coordination of LPS biosynthesis. Here, we provide experimental evidence for the physical interaction of LapB with proteins at the biosynthetic node from where the LPS and PL biosynthesis pathways diverge. By a total of four in vivo and in vitro assays, we demonstrate protein–protein interactions between LapB and the LPS biosynthesis enzymes LpxA, LpxC, and LpxD, between LapB and YejM, the anti-adaptor protein regulating LapB activity, and between LapB and FabZ, the first PL biosynthesis enzyme. Moreover, we uncovered a new adaptor function of LapB in destabilizing not only LpxC but also LpxD. Overall, our study shows that LapB is a multi-functional protein that serves as a protein–protein interaction hub for key enzymes in LPS and PL biogenesis presumably by virtue of multiple tetratricopeptide repeat (TPR) motifs in its cytoplasmic C-terminal region.     

Rapid Phosphorylation of Phospholipase Cγ 1 by Brain-Derived Neurotrophic Factor and Neurotrophin-3 in Cultures of Embryonic Rat Cortical Neurons

Abstract: Phospholipase Cγ1 (PLC-γ1) is involved at an early step in signal transduction of many hormones and growth factors and catalyzes the hydrolysis of phosphatidylinositol (PI) 4,5-bisphosphate to diacylglycerol and inositol trisphosphate, two potent intracellular second messenger molecules. The transformation of PC12 cells into neuron-like cells induced by nerve growth factor is preceded by a rapid stimulation of PLC-γ1 phosphorylation and PI hydrolysis. The present study analyzed the effects of brain-derived neurotrophic factor (BDNF) and neurotrophin-3 (NT-3) on phosphorylation of PLC-γ1 in primary cultures of embryonic rat brain cells. BDNF and NT-3 stimulated the phosphorylation of PLC-γ1, followed by hydrolysis of PI. The stimulation of PLC-γ1 phosphorylation occurred within 20 s after addition of BDNF or NT-3 and lasted up to 30 min, with a peak after 4 min. ED₅₀ values were similar for BDNF and NT-3, with τ25 ng/ml. Phosphorylation of PLC-γ1 by BDNF and NT-3 was found in cultures from all major brain areas. K-252b, a compound known to inhibit selectively neurotrophin actions by interfering with the phosphorylation of trk -type neurotrophin receptors, prevented the BDNF- and NT-3-stimulated phosphorylation of PLC-γ1. Receptors of the trk type were coprecipitated with anti-PLC-γ1 antibodies. The presence of trkB mRNA in the cultures was substantiated by northern blot analysis. The action of BDNF and NT-3 seems to be neuron specific because no phosphorylation of PLC-γ1 was observed in cultures of nonneuronal brain cells. The results provide evidence that developing neurons of the cerebral cortex and other brain areas are responsive to BDNF and NT-3, and they indicate that the transduction mechanism of BDNF and NT-3 in the brain involves rapid phosphorylation of PLC-γ1 followed by PI hydrolysis.     

Fungal succession on pine needles in Germany

The mycofloral succession on the needles ofPinus sylvestris was investigated in Tübingen, southwest Germany. Dead needles attached to the branches (D-type), those caught on branches (C-type) and three types of fallen needles, i.e., freshly fallen (L-type), slightly discolored (OL-type) and almost black needles (F-type) were examined for their fungal flora. Common primary saprophytes were rich on the dead needles on the tree, and on the L-type needles. They were replaced by successive species that contained the well-known species preferring pine needles as their substratum, such asVerticicladium trifidum orSympodiella acicola. Their ecological niches in pine leaf litter and their distribution patterns from a biogeographical viewpoint were discussed.     

Autophosphorylation of cGMP-dependent protein kinase is stimulated only by occupancy of one of the two cGMP binding sites

cGMP-Dependent protein kinase contains, per subunit, 2 binding sites for cGMP. The apparent KD values for site 1 and 2 were 12 and 55 nM. The analogues 8-benzyl-amino-cAMP and N2-monobutyryl-cGMP bind preferentially to site 1 and 2, respectively. Both analogues stimulate autophosphorylation of the enzyme at concentrations at which only half of the phosphotransferase activity of the enzyme is expressed. Complete expression of the phosphotransferase activity requires a high concentration of each analogue and is accompanied by inhibition of the autophosphorylation reactions. It is concluded that occupancy of site 1 or 2 stimulates autophosphorylation while occupancy of both sites prevents autophosphorylation.     

Hybrid cell lines Arabidopsis thaliana + Brassica campestris: No evidence for specific chromosome elimination

Summary Protoplasts from callus tissue of Arabidopsis thaliana and from leaves of Brassica campestris were fused using the PEG-high pH-high Ca⁺⁺-technique. Single dividing fusion products were isolated mechanically and cultured further in 1 l microdroplets. 31 cell lines each originating from a single fusion event have been obtained. Cytological analysis of 6 cell lines was conducted 4–7 months after isolation. All metaphases examined contained chromosomes of both species. Both Arabidopsis and Brassica specific chromosomes were still retained in cells of 7 month old cultures. Reconstituted di- and multiconstrictional chromosomes were also observed. Biochemical analysis of 12 cell lines was performed in 6–7-month old cultures. Electrophoresis on PAG and specific staining for esterase, lactate dehydrogenase, and peroxidase activities revealed isozymes of both parents to be present in all cell lines. The data obtained are interpreted as evidence for retention and functional activity in hybrid cells of specific chromosomes from each species for at least 7 months of culture.     

Peptidoglycantyp und Zusammensetzung der Zellwandpolysaccharide vonCellulomonas cartalyticum und einigen coryneformen Organismen

Cellulomonas cartalyticum was found to contain a peptidoglycan type different from that of the other species ofCellulomonas. The diamino acid is lysine instead of ornithine and the interpeptide bridge consists ofd-Asp-d-Ser. The same peptidoglycan type occurs inCorynebacterium manihot, Brevibacterium liticum andArthrobacter luteus. These non cellulolytic organisms are most likely not closely related withCellulomonas cartalyticum, as indicated by the very different G+C content of their DNA, although they formed a narrow cluster includingC. cartalyticum when numeric taxonomical methods were applied.

     

Quantitative analyses of C-banded karyotypes,and systematics in the cultivated species of theScilla siberica group (Liliaceae)

Quantified C-band karyograms are presented for the related speciesScilla siberica, S. mordakiae, S. ingridae, S. amoena, andS. mischtschenkoana. Chromosome structure, banding style, and heterochromatin characters suggest a systematic grouping of two more closely related species pairs:S. siberica andS. mordakiae, S. ingridae andS. amoena; they are part of a larger aggregate, well separated fromS. mischtschenkoana. Four different heterochromatin fractions can be recognized inS. siberica and its relatives, but only two inS. mischtschenkoana. C-bands do not replace, but they are added to euchromatin. The particular origin and history of the cultivatedS. amoena and the triploidS. siberica cv. Spring Beauty appear to be responsible for their karyotype constancy, but chromosome conservatism obviously is genuine inS. mischtschenkoana. The banding data support the systematic grouping proposed on a morphological basis, and provide additional evolutionary evidence.Evolution ofScilla and Related Genera, IV.     

Undegraded vitellogenin polysomes from female insect fat bodies

Fat body cells of vitellogenic females of the cockroach $\text{Leucophaea maderae}$ contain a prominent population of large polysomes of approximately 35–40 ribosomes whereas fat bodies of non-vitellogenic females or males of any age do not have these polysomes. Anti-vitellogenin recognizes newly synthesized nascent vitellogenin associated with these large polysomes. Adenosine labelled RNA is likewise precipitated by anti-vitellogenin primarily in the region of this class of polysomes. It is concluded that the class of large polysomes represents the vitellogenin polysomes.     

Die Ästheten vonAcanthochiton fascicularis (Mollusca,Polyplacophora)

Zusammenfassung Im Gegensatz zu allen anderen bisher untersuchten Polyplacophorenarten hatAcanthochiton fascicularis L. zwei Typen von Ästheten in den Schalenplatten. Im medianen Trakt gleichen sie den bisher bekannten Formen, in den lateralen Feldern sind sie extrem klein. Hier hat der stark entwickelte Gürtel das Tegmentum zurückgedrängt; dieses bildet in diesem Bereich um jeden Ästheten eine säulenstumpfartige Erhebung. Die beiden Ästhetentypen sind in ihrem Aufbau ähnlich: keulenförmige Sekretzellen und dünne Zentralzellen nehmen den meisten Raum in diesen Organen ein. Meist zweigen seitlich einige wenige Mikrästheten nach oben hin ab. Diese unterscheiden sich bei den beiden Ästhetentypen stark in ihrer Feinstruktur. Vor allem differieren die zwei Typen in ihren Sehzellen, die seitlich im Ästheten liegen. Median sind es rhabdomere Sehzellen, wie sie alle anderen bisher untersuchten Arten aufweisen, lateral hingegen ciliäre Lamellenzellen.

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The aesthetes ofAcanthochiton fascicularis (mollusca, polyplacophora)

Summary In contrast to all other investigated species the polyplacophoranAcanthochiton fascicularis L. has two types of aesthetes in their shell plates. Those which are situated in the median part of the shells are of a normal size and shape, whereas the aesthetes in the lateral fields are the smallest hitherto known. Here the tegmentum is repressed by the exuberantly developed girdle and forms trunklike structures around every aesthete. On the whole both aesthete types are similar: clubshaped secretory cells and thin central cells fill most of the organ. Up to a few micraesthetes may branch from the main part towards the shell surface. But there are also marked differences. In the median aesthetes rhabdomeric visual cells are present; in the lateral ones they have become ciliary lamellate cells which are probably also active photoreceptors.