Screening method for microorganisms producing L-aminoacids from D,L-5-monosubstituted hydantoins

Summary The ability of microorganisms to produce hydantoinase and L-N-carbamoylase could be established by an overlay assay. Enzyme producing strains form clear areas around their colonies caused by the cleavage of D,L-indolylmethylhydantoin. A second overlayer with a tryptophan-auxotroph yeast enables us to detect microorganisms which are able to produce L-tryptophan from D,L-indolylmethylhydantoin.     

A modular approach to situation identification of the dynamics of bacterial populations synthesizing poly-β-hydroxybutyrate

Biotechnological processes involving bacteria are strongly nonlinear. Therefore, both their productivity and the final product quality may be considerably improved by applying appropriate control strategies to modulate behavior of the bacteria during transitional states. This requires advance identification of indicative signals by off-line investigation (i.e. experimental analysis) and on-line monitoring, (i.e. real time evaluation). A modular scheme is presented for doing this, which incorporates an Extended Kalman Filter and a prediction filter. If this is based on a suitable process-feature vector, which must be chosen in advance, the system can provide sufficient information to trigger appropriate feedback signals. Thus, it can provide a key element in modular situation control, allowing continuously periodic process management. In this publication the individual modules involved, and their assembly into an integrated system are described. Potential problems concerning selection of the feature vector, and experimental results are also discussed.     

Climate‐driven rampant speciation of the Cape flora

Aim To test whether the radiation of the extremely rich Cape flora is correlated with marine‐driven climate change. Location Middle to Late Miocene in the south‐east Atlantic and the Benguela Upwelling System (BUS) off the west coast of South Africa. Methods We studied the palynology of the thoroughly dated Middle to Late Miocene sediments of Ocean Drilling Program (ODP) Site 1085 retrieved from the Atlantic off the mouth of the Orange River. Both marine upwelling and terrestrial input are recorded at this site, which allows a direct correlation between changes in the terrestrial flora and the marine BUS in the south‐east Atlantic. Results Pollen types from plants of tropical affinity disappeared, and those from the Cape flora gradually increased, between 10 and 6 Ma. Our data corroborate the inferred dating of the diversification in Aizoaceae c. 8 Ma. Main conclusions Inferred vegetation changes for the Late Miocene south‐western African coast are the disappearance of Podocarpus‐dominated Afromontane forests, and a change in the vegetation of the coastal plain from tropical grassland and thicket to semi‐arid succulent vegetation. These changes are indicative of an increased summer drought, and are in step with the development of the southern BUS. They pre‐date the Pliocene uplift of the East African escarpment, suggesting that this did not play a role in stimulating vegetation change. Some Fynbos elements were present throughout the recorded period (from 11 Ma), suggesting that at least some elements of this vegetation were already in place during the onset of the BUS. This is consistent with a marine‐driven climate change in south‐western Africa triggering substantial radiation in the terrestrial flora, especially in the Aizoaceae.     

Interaction of extracellular Pseudomonas lipase with alginate and its potential use in biotechnology

Summary Extracellular Pseudomonas lipase is able to interact directly or indirectly with alginate as deduced from the following results: (i) During adsorption chromatography of exolipase the enzyme adsorbed quantitatively to glass beads in the absence of alginate, but not after its preincubation in the presence of the polysaccharide; pretreatment of glass beads with alginate did not prevent enzyme adsorption. (ii) In the presence of alginate exolipase was much more resistant to heat inactivation than in its absence. (iii) In the presence of alginate the increase in exolipase activity caused by the non-ionic detergent Triton X-100 was drastically reduced. (iv) Exolipase could be rapidly and almost completely harvested from cell-free culture fluid of P. aeruginosa 5940 by ethanolic coprecipitation with alginate. After dissolving the coprecipitate in detergent-containing buffer exolipase and polysaccharide could be easily separated by ion-exchange chromatography on DEAE-Sephadex A-25. The coprecipitation method was also successfully applied to exolipases produced by Pseudomonas sp., Chromobacierium viscosum and Rhizopus delamar, thus suggesting potential use of this method in biotechnology.     

The lipopolysaccharide of the phototrophic bacterium Ectothiorhodospira vacuolata

The lipopolysaccharide of Ectothiorhodospira vacuolata was obtained by the phenol-water procedure. It contained a 3-O-methyl-hexose, glucose, galacturonic and glucuronic acids. The finding of d-glycero-d-mannoheptose and 2-keto-3-deoxyoctonate (tentatively identified) suggested a core-structure. The lipid fraction of the lipopolysaccharide contained phosphate and both, 2,3-diamino-2,3-dideoxy-d-glucose and d-glucosamine. The major fatty acids were amine-bound 3-OH-10:0 and 3-OH-12:0 and esterbound 14:0 and 16:0 Sodium deoxycholate gel-electrophoresis, showing a single band only, indicated R-type character of the lipopolysaccharide of Ectothiorhodospira vacuolata.Abbreviations DOC sodium deoxycholate - GC/MS combined gasliquid chromatography - PAGE polyacrylamide gel-electrophoresis     

Formation of dimethylsulfide and methanethiol from methoxylated aromatic compounds and inorganic sulfide by newly isolated anaerobic bacteria

Formation of gas and of methylated sulfur compounds was observed in anaerobic enrichment cultures with methoxylated aromatic compounds as substrates. Via direct dilution of mud samples in defined reduced media supplemented with trimethoxybenzoate or syringate two new strains of anaerobic homoacetogenic bacteria (strain TMBS4 and strain SA2) were obtained in pure culture. Both strains produced dimethylsulfide and methanethiol during growth on methoxylated aromatic compounds. Growth tests and determination of stoichiometries demonstrated that the volatile sulfur compounds were formed from the methyl group at the aromatic ring and the sulfide added as reducing agent to the medium (R = aromatic residue): 2 R - O - CH₃ + H₂ S 2 R - OH + (CH₃)₂SDimethylsulfide was the major organic sulfur compound formed, whereas methanethiol appeared only as intermediate in small quantities. The isolates grew also with trihydroxybenzenes such as gallate, phloroglucinol, or pyrogallol without formation of methylated sulfur compounds. The aromatic compounds were degraded to acetate. The freshwater strain TMBS4 also fermented pyruvate. Other aliphatic or aromatic compounds were not utilized. External electron acceptors (sulfate, nitrate, fumarate) were not reduced. Both strains were mesophilic and formed rod-shaped, non-motile, Gram-negative cells. Spore formation was not observed. Tentatively, both isolates can be affiliated to the genus Pelobacter.Abbreviations TMB 3,4,5-trimethoxybenzoate - MT methanethiol - DMS dimethylsulfide     

The production and utilization of nitric oxide by a new,denitrifying strain of Pseudomonas aeruginosa

When a new strain of Pseudomonas aeruginosa was grown aerobically and then transferred to anaerobic conditions, cells reduced NO ₃ ^– quantitatively to NO ₂ ^– in NO ₃ ^– -respiration. In the absence of nitrate, NO ₂ ^– was immediately reduced to NO or N₂O but not to N₂ indicating that NO ₂ ^– -reductase but not N₂O-reductase was active. The formation of the products NO or N₂O depended on the pH in the medium and the concentration of NO ₂ ^– present. When P. aeruginosa was grown anaerobically for at least three davs N₂O-reductase was also active. Such cells reduced NO to N₂ via N₂O. The new strain generated a H⁺-gradient and grew by reducing N₂O to N₂ but not by converting NO to N₂O. For comparison, Azospirillum brasilense Sp7 showed the same pattern of NO-reduction. In contrast, Paracoccus denitrificans formed 3.5 H⁺/NO during the reduction of NO to N₂O in oxidant pulse experiments but could not grow in the presence of NO. Thus the NO-reduction pattern in P. denitrificans on one side and P. aeruginosa and A. brasilense on the other was very different. The mechanistic implications of such differences are discussed.     

On the Lichen generaPlacocarpus andPlacidiopsis (Verrucariaceae)

Verrucaria schaereri (Fr.)Nyl. is accorded generic status asPlacocarpus Trev. emend.O. Breuss. The main differences between the two genera concern the thallus anatomy and the spores which are halonate inPlacocarpus. The following new combinations are proposed:Placocarpus schaereri (Fr.)O. Breuss andPlacidiopsis cinerascens (Nyl.)O. Breuss.