Effect of glutamine on penicillin formation in Penicillium chrysogenum

Summary Resting-cell studies in Penicillium chrysogenum have indicated that penicillin formation is inhibited by glutamine concentrations higher than 1 mM. Total inhibition was obtained with 10 mM glutamine. This action was neither reverted by the amino acid precursors of the antibiotic moiety nor glutamin affected the in vitro activity of the first enzyme of the penicillin formation pathway. The inhibition was prevented by 1 mM glutathione by mechanisms not related to limitation in the glutamine incorporation nor connected with degradation of the tripeptide.     

Tissue-specific patterns of changes in 3,5,3'-triiodo-L-thyronine concentrations in thyroidectomized rats infused with increasing doses of the hormone. Which are the regulatory mechanisms?

We have measured 3,5,3'triiodothyronine (T3) in 12 tissues from thyroidectomized (Tx) rats infused with increasing doses of T3, and related them to their corresponding plasma levels. Young adult Wistar rats were surgically Tx. After 4 weeks, the animals were infused with placebo or T3 (0.25, 0.50, 0.75, 1.00 or 2.00 microg/100 g body weight/day). Placebo-infused intact rats served as euthyroid controls. Plasma and samples of cerebral cortex, cerebellum, brown adipose tissue (BAT), pituitary, liver, heart, lung, kidney, spleen, skeletal muscle, ovary and adrenal were obtained after 12-13 days of infusion. We determined plasma T3 and thyrotropin (TSH), and tissue T3 and thyroxine (T4), the latter being virtually undetectable. Results were compared with the relationships between tissue and plasma T3 in Tx rats on T4 infusions. Most tissues presented changes which paralleled those in plasma T3, irrespective of its source (infusion of T3, or generation from infused T4). However, at similar plasma T3 concentrations, cerebral cortex, cerebellum and BAT (containing type II 5' iodothyronine deiodinase (DII) activity), reached much lower T3 levels in the T3-infused Tx rats, than in Tx rats on T4, and required elevated plasma T3 levels for normal tissue T3. In these tissues, and in the pituitary, T3 concentrations were always lower than expected from plasma T3 levels. On the contrary, the lung and ovary of the T3-infused Tx rats contained more T3 than expected from plasma T3. Unexpectedly, both the ovary and adrenal attained higher tissue T3 concentrations in Tx rats on T3 than on T4 at comparable plasma T3 levels. In conclusion, the patterns of changes of the concentrations of T3 as a function of increasing plasma T3 are not only tissue-specific when T4 is provided, but also when circulating T3 is the only source of this iodothyronine. Further studies are needed to identify the mechanisms involved in the regulation of tissue T3 concentrations.     

Oogenesis in the egg-brooding frog Gastrotheca riobambae produces large oocytes with fewer nucleoli and low RNA content in comparison to Xenopus laevis

Abstract. The dissimilarities between oocytes of the eggbrooding frog, Gastrotheca riobambae , and Xenopus laevis suggest that oogenesis is modified according to the mode of reproduction. Oocytes of G. riobambae are large, yolky, and measure about 3 mm in diameter. In spite of the large oocyte size of Gastrotheca , the amplification of ribosomal genes, the number of nucleoli, and the amount of 18S and 28S rRNA are lower than in Xenopus oocytes. In Gastrotheca , the lower RNA content of oocytes is associated with a slow rate of development. A prolonged period of development is possible due to the protection given by the maternal pouch.     

Microbial induced corrosion of metallic antiquities and works of art: a critical review

Metallic antiquities and works of art are no exception to the phenomenon of microbial corrosion. Thus, all those which are buried, sunk or poorly conserved are susceptible to microbial corrosion. Although the last few decades have seen a marked development in the study of microbial corrosion of metals in industrial use, the same cannot be said for metallic antiquities and works of art. This work reviews the practical cases published, historical materials affected, and the micro-organisms involved and their mechanisms of action. Despite the great social importance of recovering these metallic cultural properties, and conserving them in a good state, there is a lack of documentation and of research groups dedicated to their study. The bringing together of researchers in works of art, microbiology and corrosion in metallic materials is shown to be necessary.     

Coenzyme B12-dependent and independent photoregulation of carotenogenesis across Myxococcales

Light-induced carotenogenesis in Myxococcus xanthus is controlled by the B₁₂-based CarH repressor and photoreceptor, and by a separate intricate pathway involving singlet oxygen, the B₁₂-independent CarH paralogue CarA and various other proteins, some eukaryotic-like. Whether other myxobacteria conserve these pathways and undergo photoregulated carotenogenesis is unknown. Here, comparative analyses across 27 Myxococcales genomes identified carotenogenic genes, albeit arranged differently, with carH often in their genomic vicinity, in all three Myxococcales suborders. However, CarA and its associated factors were found exclusively in suborder Cystobacterineae, with carA-carH invariably in tandem in a syntenic carotenogenic operon, except for Cystobacter/Melittangium, which lack CarA but retain all other factors. We experimentally show B₁₂-mediated photoregulated carotenogenesis in representative myxobacteria, and a remarkably plastic CarH operator design and DNA binding across Myxococcales. Unlike the two characterized CarH from other phyla, which are tetrameric, Cystobacter CarH (the first myxobacterial homologue amenable to analysis in vitro) is a dimer that combines direct CarH-like B₁₂-based photoregulation with CarA-like DNA binding and inhibition by an antirepressor. This study provides new molecular insights into B₁₂-dependent photoreceptors. It further establishes the B₁₂-dependent pathway for photoregulated carotenogenesis as broadly prevalent across myxobacteria and its evolution, exclusively in one suborder, into a parallel complex B₁₂-independent circuit.     

Genomes of the wild beets Beta patula and Beta vulgaris ssp. maritima

We present draft genome assemblies of Beta patula, a critically endangered wild beet endemic to the Madeira archipelago, and of the closely related Beta vulgaris ssp. maritima (sea beet). Evidence‐based reference gene sets for B. patula and sea beet were generated, consisting of 25 127 and 27 662 genes, respectively. The genomes and gene sets of the two wild beets were compared with their cultivated sister taxon B. vulgaris ssp. vulgaris (sugar beet). Large syntenic regions were identified, and a display tool for automatic genome‐wide synteny image generation was developed. Phylogenetic analysis based on 9861 genes showing 1:1:1 orthology supported the close relationship of B. patula to sea beet and sugar beet. A comparative analysis of the Rz2 locus, responsible for rhizomania resistance, suggested that the sequenced B. patula accession was rhizomania susceptible. Reference karyotypes for the two wild beets were established, and genomic rearrangements were detected. We consider our data as highly valuable and comprehensive resources for wild beet studies, B. patula conservation management, and sugar beet breeding research.