Naturstoffe aus Mikroorganismen. 8. Mitteilung [1]. Optimale Gewinnung von Proferrorosamin A aus Pseudomonas roseus fluorescens J. C. MARCHAL 1937

Optimum Obtention of Proferrorosamine A from Pseudomonas roseus fluorescens J. C. MARCHAL 1937. We have developed the best conditions for the culture of Pseudomonas roseus fluorescens, and a quantitative isolation of the Proferrorosamine A produced in the culture solution, in order to study the incorporation of 1-[¹⁴C]-glycerol in this propigment.     

Impact of solar ultraviolet radiation on marine phytoplankton of Patagonia, Argentina

Patagonia area is located in close proximity to the Antarctic ozone "hole" and thus receives enhanced ultraviolet B (UV-B) radiation (280-315 nm) in addition to the normal levels of ultraviolet A (UV-A; 315-400 nm) and photosynthetically available radiation (PAR; 400-700 nm). In marine ecosystems of Patagonia, normal ultraviolet radiation (UVR) levels affect phytoplankton assemblages during the three phases of the annual succession: (1) prebloom season (late summer-fall), (2) bloom season (winter-early spring) and (3) postbloom season (late spring-summer). Small-size cells characterize the pre- and postbloom communities, which have a relatively high photosynthetic inhibition because of high UVR levels during those seasons. During the bloom, characterized by microplankton diatoms, photosynthetic inhibition is low because of the low UVR levels reaching the earth's surface during winter; this community, however, is more sensitive to UV-B when inhibition is normalized by irradiance (i.e. biological weighting functions). In situ studies have shown that UVR significantly affects not only photosynthesis but also the DNA molecule, but these negative effects are rapidly reduced in the water column because of the differential attenuation of solar radiation. UVR also affects photosynthesis versus irradiance (P vs E) parameters of some natural phytoplankton assemblages (i.e. during the pre- but not during the postbloom season). However, there is a significant temporal variability of P vs E parameters, which are influenced by the nutrient status of cells and taxonomic composition; taxonomic composition is in turn associated with the stratification conditions (e.g. wind speed and duration). In Patagonia, wind speed is one of the most important variables that conditions the development of the winter bloom by regulating the depth of the upper mixed layer (UML) and hence the mean irradiance received by cells. Studies on the interactive effects of UVR and mixing show that responses of phytoplankton vary according to the taxonomic composition and cell structure of assemblages; therefore cells use UVR if >90% of the euphotic zone is being mixed. In fact, cell size plays a very important role when estimating the impact of UVR on phytoplankton, with large cells being more sensitive when determining photosynthesis inhibition, whereas small cells are more sensitive to DNA damage. Finally, in long-term experiments, it was determined that UVR can shape the diatom community structure in some assemblages of coastal waters, but it is virtually unknown how these changes affect the trophodynamics of marine systems. Future studies should consider the combined effects of UVR on both phytoplankton and grazers to establish potential changes in biodiversity of the area.     

Field and pressure response of Yb compounds close to a quantum critical point

YbCu_5−x Al _x provides the possibility to tune ground state properties by a change of the valence due to the Cu/Al substitution, by pressure as well as by the application of a magnetic field. Near to the critical concentration x _cr≈1.5 non-Fermi-liquid properties (NFL) are obvious, obeying hyperscaling. If magnetic order sets in for x>1.5, the application of moderate magnetic fields quenches order and again NFL features become evident. Hyperscaling in this case indicates strongly interacting spin fluctuations.     

Abundant stable gauge field hair for black holes in anti-de Sitter space

We present new hairy black hole solutions of SU(N) Einstein-Yang-Mills (EYM) theory in asymptotically anti-de Sitter (AdS) space. These black holes are described by N+1 independent parameters and have N-1 independent gauge field degrees of freedom. Solutions in which all gauge field functions have no zeros exist for all N, and for a sufficiently large (and negative) cosmological constant. At least some of these solutions are shown to be stable under classical, linear, spherically symmetric perturbations. Therefore there is no upper bound on the amount of stable gauge field hair with which a black hole in AdS can be endowed.     

Induction of mycosporine-like amino acids (MAAs) in cyanobacteria by solar ultraviolet-B radiation

Three filamentous and heterocystous N₂-fixing cyanobacteria, Anabaena sp., Nostoc commune and Scytonema sp. were tested for the presence of ultraviolet-absorbing mycosporine-like amino acids (MAAs) and their induction by solar ultraviolet-B (UV-B) radiation. High performance liquid chromatographic (HPLC) studies revealed the presence of only one type of MAAs in all three cyanobacteria, that was identified as shinorine, a bisubstituted MAA containing both glycine and serine groups having an absorption maximum at 334 nm and a retention time of around 2.8 min. There was a circadian induction in the synthesis of MAAs when the cultures were exposed to mid-latitude solar radiation (Playa Unión, Rawson, Chubut, Patagonia, Argentina) for 3 days, 4–6th February, 2000. Solar radiation was measured by an ELDONET (European Light Dosimeter Network) filter radiometer permanently installed on the roof of the Estación de Fotobiología Playa Unión (43°18′ S; 65°03′ W). The maximum irradiances were around 450–500, 45–50 and 1.0–1.2 W m⁻² for PAR (photosynthetic active radiation), UV-A (ultraviolet-A) and UV-B (ultraviolet-B), respectively. PAR and UV-A had no significant impact on MAA induction while UV-B induced the synthesis of shinorine in all three cyanobacteria. Shinorine was found to be induced mostly during the light period. During the dark period the concentration stayed almost constant. In addition to shinorine, another unidentified, water-soluble, brownish compound with an absorption maximum at 315 nm was found to be induced by UV-B only in Scytonema sp. and released into the medium. This substance was neither found in Anabaena sp. nor in Nostoc commune. Judging from the results, the studied cyanobacteria may protect themselves from deleterious short wavelength radiation by their ability to synthesize photoprotective compounds in response to UV-B radiation.     

Effects of solar radiation on the Patagonian macroalga Enteromorpha linza (L.) J. Agardh-Chlorophyceae.

The photosynthetic performance of Enteromorpha linza (L.) J. Agardh-Chlorophyceae was determined with a portable PAM instrument in situ and under seminatural radiation conditions in Patagonia, Argentina. Solar radiation was measured in parallel with a three-channel radiometer, ELDONET (Real Time Computer, M?hrendorf, Germany), in three wavelength ranges, UV-B (280-315 nm), UV-A (315-400 nm), and PAR (400-700 nm). The effective photosynthetic quantum yield decreased after 15-min exposure to solar radiation when the thalli were kept in a fixed position but recovered in the subsequent shade conditions within several hours. A 30-min exposure of free floating thalli, however, caused less photoinhibition. The photosynthetic quantum yield of E. linza was also followed over whole days under clear sky, partly cloudy and rainy conditions in a large reservoir of water (free floating thalli) and in situ (thalli growing in rock pools). Most of the observed effect was due to visible radiation; however, the UV wavelength range, and especially UV-B, caused a significant reduction of the photosynthetic quantum yield. Fluence rate response curves indicated that the species is a typical shade plant which showed non-photochemical quenching at intermediate and higher irradiances. This is a surprising result since these algae are found in the upper eulittoral where they are exposed to high irradiances. Obviously they utilize light only during periods of low irradiances (morning, evening, high tide) while they shut down the electron transport chain during intensive exposure. Fast induction and relaxation kinetics have been measured in these algae for the first time and indicated a rapid adaptation of the photosynthetic capacity to the changing light conditions as well as a fast decrease of PS II fluorescence upon exposure to solar radiation. There was a strong bleaching of chlorophyll due to exposure to solar radiation but less drastic bleaching of carotenoids.     

Naturstoffe aus Mikroorganismen. 9. Mitteilung [1]. Über die Biogenese von Proferrorosamin A

Preliminary results on the biogenesis of the proferrorosamine A. Pseudomonas roseus fluorescens has been grown in a Lasser-broth with 1-[¹⁴C]-glycerol and L -asparagine as sources of carbon and nitrogen. The total percentage of incorporation of the isotopic carbon atom in the proferrorosamine A attained 0,03%. The first results on the localization of ¹⁴C show that the pyrrolinecarboxylic acid moiety is built with the carbon atoms of glycerol while the pyridine skeleton seems to be formed mainly from L -asparagine.     

Vertical migration and motility responses in three marine phytoplankton species exposed to solar radiation

Diurnal vertical migration in the water column and the impact of solar radiation on motility were investigated in three marine phytoplankton species: Tetraselmis suecica, Dunaliella salina and Gymnodinium chlorophorum. Cells were exposed to solar radiation either in ultraviolet radiation (UVR, 280-400 nm) transparent Plexiglas tubes (45 cm length, 10 cm diameter) or in quartz tubes under three radiation treatments: PAB (280-700 nm), PA (320-700 nm) and P (400-700 nm). The three species displayed different behavior after exposure to solar radiation. Tetraselmis suecica was insensitive to UVR and under high solar radiation levels, cells accumulated preferentially near the surface. Exposure experiments did not indicate any significant changes in swimming speed nor in the percentage of motile cells after 5 h of exposure. On the other hand, D. salina was sensitive to UV-B displaying a significant decrease in swimming speed and percentage of motile cells after 2-3 h of exposure. Moreover, D. salina cells migrated deep in the water column when irradiance was high. The response of G. chlorophorum was in between that of the other two species tested, with a slight (but significant) decrease in swimming speed and percentage of motile cells in all radiation treatments after 5 h of exposure. While G. chlorophorum cells were more or less homogenously distributed in the water column, a slight (but significant) avoidance response to high radiation was observed at local noon, with cells migrating deep in the water column. Our data clearly indicate that these sub-lethal effects of solar radiation are species-specific and they might have important implications for the aquatic ecosystem.