The mechanism of pattern formation in the developing drosophila retina

The biological patterning of the drosophila retina in vivo has striking resemblance to liquid bubbles, in which the surface mechanics due to N-cadherin within a sub-group of retina cells can be mimicked by surface tension. In this work, the aggregating patterns were reasonably simplified into 2D clusters consisting of 2—6 identical bubbles confined within a shrinking boundary. By using a hybrid fluid dy-namics model proposed for liquid foams, the aggregating process of 2―6 retina cells was studied. Assuming the minimal perimeter for patterning cells to be the condition of stability patterns, the stable converged patterns we simulated in this work are the same as the experimental observations. More importantly, a new pattern of 6 cells was obtained which was found physically more stable than the other two reported by Hayashi and Carthew[1]. Aggregating perimeters of cells, i.e. the surface energy, showed a good linear fit with the cell numbers.     

Production of transgenic gentian plants by particle bombardment of suspension-culture cells

 Cell suspension cultures were established from leaf explants of gentian (Gentiana triflora×G. scabra) for the generation of transgenic plants by particle bombardment. The parameters for the bombardment of suspension culture cells with a particle gun were examined by monitoring the transient expression of a gene for β-glucuronidase driven by the cauliflower mosaic virus (CaMV) 35S promoter. We found that prior culture of suspension culture cells for 5 days on solid medium was optimum for successful particle bombardment. Putative transformed calli were obtained from bombarded cells after a two-step selection procedure. Cells were cultured first with 30 mg l^–1 hygromycin in liquid MS medium that contained 10 mg l^–1 N-phenyl-N′-1,2,3-thiadiazol-5-yl urea, 1 mg/l 1-naphthaleneacetic acid and 30 g l^–1 sucrose and then on solid medium prepared from the same liquid medium plus 2 g l^–1 gellan gum. After 12 weeks of selection on solid medium that contained 30 mg l^–1 hygromycin, two transgenic gentian plants were regenerated from each selected callus. Analysis by the polymerase chain reaction and Southern blotting revealed the stable integration of transferred DNA. Received: 3 June 1999 / Revision received: 21 September 1999 / Accepted: 20 September 1999     

Effects of agitation on the microalgae Phaeodactylum tricornutum and Porphyridium cruentum

The effect of mechanical agitation on the microalgae Phaeodactylum tricornutum and Porphyridium cruentum was investigated in aerated continuous cultures with and without the added shear protectant Pluronic F68. Damage to cells was quantified through a decrease in the steady state concentration of the biomass in the photobioreactor. For a given aeration rate, the steady state biomass concentration rose with increasing rate of mechanical agitation until an upper limit on agitation speed was reached. This maximum tolerable agitation speed depended on the microalgal species. Further increase in agitation speed caused a decline in the steady state concentration of the biomass. An impeller tip speed of >1.56 m s^–1 damaged P. tricornutum in aerated culture. In contrast, the damage threshold tip speed for P. cruentum was between 2.45 and 2.89 m s^–1. Mechanical agitation was not the direct cause of cell damage. Damage occurred because of the rupture of small gas bubbles at the surface of the culture, but mechanical agitation was instrumental in generating the bubbles that ultimately damaged the cells. Pluronic F68 protected the cells against damage and increased the steady state concentration of the biomass relative to operation without the additive. The protective effect of Pluronic was concentration-dependent over the concentration range of 0.01–0.10% w/v.     

Callus induction and thallus regeneration from callus of phycocolloid yielding seaweeds from the Indian coast

The tissue culture of phycocolloid yielding seaweeds included preparation of axenic explants, callus induction, subculture of excised callus and regeneration of plantlets from pigmented callus in the laboratory. Treatment of algal material with 0.1–0.5% detergent for 10 min and 1–2% betadine for 1–5 min and 3–5% antibiotic treatment for 48–72 h successively enabled viable axenic explants to be obtained as high as 60% for Gracilaria corticata, Sargassum tenerrimum and Turbinaria conoides and 10% for Hypnea musciformis. Callus induction was more conspicuous in T. conoides than in the other three species investigated. Of the irradiances investigated, 30 μmol photons m⁻² s⁻¹ produced calluses in as many as 40% explants in G. corticata and T. conoides and 10% in H. musciformis and S. tenerrimum. The explants cultured at 5 and 70 μmol photons m⁻² s⁻¹ did not produce any callus in all the species studied except for H. musciformis in which 10% explants developed callus at 5 μmol photons m⁻² s⁻¹. Most of the species investigated showed uniseriate filamentous Type of growths and buds from cut ends and from all over the surface of explants. Nevertheless, T. conoides had three Types of callus developments, namely (1) uniseriate filamentous Type of outgrowths from the centre of the cut end of explant, (2) bubbly Type of callus and (3) club-shaped callus clumps. The subculture of T. conoides callus embedded in 0.4% agar produced two Types of filamentous growth, namely filiform (with elongated cells) and moniliform filaments (with round cells) in the 2 months period after inoculation. Further, friable callus with loose cells was also found associated with excised callus. The moniliform filaments showed prolific growth of micro-colonies resembling to somatic embryo-like growth which, in liquid cultures, differentiated and developed into propagules with deformed shoots and distinct rhizoids. The shoots of these propagules remained stunted with abnormal leaf stalks without forming triangular shaped leaves as the parental plant and rhizoids had prolific growth in the laboratory cultures. The excised callus of G. corticata continued to grow when transferred to liquid cultures and showed differentiation of new shoots within 10 days. The shoots grew to a maximum length of 5–6 cm in the 2 months period in aerated cultures in the laboratory. Dedicated to the memory of Late Dr. Rangarajan.     

Stability validation of seeding cell control parameters in large-scale hybridoma cell culture

Stability and reproducibility of seeding cell performance in large-scale hybridoma cell culture has been reported by controlling only initial cell seeding density. The aim of the current study was to integrate multiple seeding cell control parameters to maintain stable and consistent cell physiological status for HAb18 cell expansion. Three parameters and their ranges were investigated, including initial cell seeding density in the range of 0.075–0.5×10⁶ cells ml⁻¹, “timepost” after cell passage between 8 and 36 h, and duration of subculture up to 6 months after cell revival. Cell performance was tested at the 1 L, 5 L, and 75 L scales. Desirable performance was found within the following parameter ranges: initial cell seeding density of 0.1–0.3×10⁶ cells ml⁻¹, “timepost” after cell passage between 14 and 22 h, and duration of subculture within 3 months of cell revival. Our results showed that cell growth rate and antibody productivity of three batches at 1 L, 5 L, and 75 L scale were found to be stably maintained within a range of 0.036–0.047 h⁻¹ and 0.577–0.747 pg cell⁻¹ h⁻¹, with the positivity rate of antigen-binding activity within 97–99.75%, and the intensity of fluorescence around 200. This study may provide a simple but effective method to maintain seeding cell physiological status stable and consistent by combining seeding cell control parameters.     

Occurrence of cell surface arabinogalactan-protein and extensin epitopes in relation to pericycle and vascular tissue development in the root apex of four species

Monoclonal antibodies recognizing two classes of developmentally regulated plant cell surface components – arabinogalactan-proteins (AGPs) and extensins – have been used to immunolabel cells at the root apices of four species with different characteristics of pericycle and vascular tissue development. Root apices of pea (Pisum sativum L.), radish (Raphanus sativus L.), carrot (Daucus carota L.) and onion (Allium cepa L.) were immunolabelled with the anti-AGP monoclonal antibodies JIM4 and JIM13 and anti-extensin monoclonal antibodies JIM11, JIM12, JIM19 and JIM20. All of these antibodies recognized subsets of pericycle cells in at least one, but never all, of these species. The restricted patterns of epitope occurrence also reflected vascular cell development. The differences in patterns of antibody recognition in the four species are discussed in relation to the possible roles of these cell surface molecules in cell differentiation and root patterning events. Received: 11 March 1997 / Accepted: 20 May 1997     

Ecophysiological characteristics of Avicennia germinans and Laguncularia racemosa coexisting in a scrub mangrove forest at the Indian River Lagoon, Florida

The purpose of this work is to increase ecological understanding of Avicennia germinans L. and Laguncularia racemosa (L.) Gaertn. F. growing in hypersaline habitats with a seasonal climate. The area has a dry season (DS) with low temperature and vapour pressure deficit (vpd), and a wet season (WS) with high temperature and slightly higher vpd. Seasonal patterns in interstitial soil water salinity suggested a lack of tidal flushing in this area to remove salt along the soil profile. The soil solution sodium/potassium (Na⁺/K⁺) ratio differed slightly along the soil profile during the DS, but during the WS it was significantly higher at the soil surface. Diurnal changes in xylem osmolality between predawn (higher) and midday (lower) were observed in both species. However, A. germinans had higher xylem osmolality compared to L. racemosa. Xylem Na⁺/K⁺ suggested higher selectivity of K⁺ over Na⁺ in both species and seasons. The water relations parameters derived from pressure–volume P–V curves were relatively stable between seasons for each species. The range of water potentials (Ψ), measured in the field, was within estimated values for turgor maintenance from P–V curves. Thus the leaves of both species were osmotically adapted to maintain continued water uptake in this hypersaline mangrove environment.     

Expression of the cystine-glutamate exchanger (xc −) in retinal ganglion cells and regulation by nitric oxide and oxidative stress

The cystine-glutamate exchanger, system x_c ⁻, mediates the Na⁺-independent exchange of cystine into cells, coupled to the efflux of intracellular glutamate. System x_c ⁻ plays a critical role in glutathione homeostasis. Early studies of brain suggested that system x_c ⁻ was present primarily in astrocytes but not neurons. More recent work indicates that certain brain neurons have an active system x_c ⁻. In the retina, system x_c ⁻ has been demonstrated in Müller and retinal pigment epithelial cells. We have recently suggested that two protein components of system x_c ⁻, xCT and 4F2hc, are present in ganglion cells of the intact retina. Here, we have used (1) molecular and immunohistochemical assays to determine whether system x_c ⁻ is present in primary ganglion cells isolated from neonatal mouse retinas and (2) functional assays to determine whether its activity is regulated by oxidative stress in a retinal ganglion cell line (RGC–5). Primary mouse ganglion cells and RGC–5 cells express xCT and 4F2hc. RGC–5 cells take up [³H]glutamate in the absence of Na⁺, and this uptake is blocked by known substrates of system x_c ⁻ (glutamate, cysteine, cystine, quisqualic acid). Treatment of RGC–5 cells with NO and reactive oxygen species donors leads to increased activity of system x_c ⁻ associated with an increase in the maximal velocity of the transporter with no significant change in the substrate affinity. This is the first report of system x_c ⁻ in primary retinal ganglion cells and RGC–5 cells. Oxidative stress upregulates this transport system in RGC–5 cells, and the process is associated with an increase in xCT mRNA and protein but no change in 4F2hc mRNA or protein. This work was supported by National Institutes of Health grants EY014560 and EY012830.     

Micropropagation ofDalbergia sissoo from nodal explants of mature trees

A method for micropropagation ofDalbergia sissoo has been developed. Single node segments obtained from coppice shoots of a mature tree (20 – 25 year old) produced 3–4 shoots per explant on Murashige and Skoog (MS) medium containing 4.4 x 10⁻⁶ M benzylaminopurine (BAP) and 4.4 × 10⁻⁷ M of Β-naphthoxy acetic acid (NOA) (shoot multiplication medium) within 4 weeks. Thein vitro regenerated shoots were 3 – 4 cm in length and provided 2 to 3 culturable nodal segments which on shoot multiplication medium again produced 3–4 shoots. Following this procedure 18–24 shoots were produced from single nodal segment within 60 d. 80 % of the shoots directly produced five roots when they were firstly treated with MS medium supplemented with 10⁻⁵ M indole-3-butyric acid (IBA) and subsequently transferred to half strength liquid MS medium containing 1 % activated charcoal followed by half strength liquid MS free hormones, vitamins and activated charcoal. Thein vitro raised plants were hardened for survival after transplantation to soil by exposing them to various humidity conditions, gradually from higher to low, with nearly 100 % transplant success. Acknowledgement: Authors are grateful to CSIR and DST, New Delhi for financial assistance.     

Detection Methanogens in Newly Settled Sediments from Xuanwu Lake in Nanjing, China

Sediments from Xuanwu Lake have been dredged in the past 3 years to improve the water quality, but methanogenesis should still exist in the newly settled sediment. Methane production, methanogens, and physiochemical parameters were detected in the surface sediments (0–5 cm) and/or vertical sediments (0–21 cm, segmented at interval of 3 cm). Methane flux at water–air interface varied among five detected sites. Principal component analysis showed that CH₄ flux, content of water and the concentration of total nitrogen (TN), CH₄ and organic matters (OM) weighed most heavily on the component I in surface sediments while different patterns were observed for vertical sediments. The copy number of the 16S rRNA gene for bacteria was lower in the surface sediment (0–6 cm) than that in deeper sediments (12–21 cm), while 16S rRNA genes of Archaea were almost evenly distributed in the vertical sediments. Representatives belonging to the orders Methanobacteriales, Methanomicrobiales, and Methanosarcinales were detected in all samples of the vertical sediments, except that no members of the Methanococcales were detected in the samples at 0–6 cm. The level of Methanobacteriales reached a highest density at 18.1 × 10⁴ copies g⁻¹ dry weight (dw) at 6–9 cm; for Methanosarcinales (76.89 × 10⁶ copies g⁻¹ dw) and Methanococcales (82.70 × 10³ copies g⁻¹ dw) at 12–15 cm, whereas for Methanomicrobiales (43.37 × 10⁶ copies g⁻¹ dw) at 9–12 cm. Methanosarcinaceae and Methanosaetaceae reached to their highest densities at 6–9 and 9–12 cm, respectively. These data provided useful information for better understanding the methanogenesis in the newly settled sediments of a recently dredged lake.     

Plant regeneration in <Emphasis Type="Italic">Robinia pseudoacacia</Emphasis> from cell suspension cultures

A method for plant regeneration in Robinia pseudoacacia L. from cell suspension culture was established. Non regenerative friable callus from hypocotyls and cotyledon explants from in vitro raised seedling induced on solid Murashige and Skoog (MS) medium supplemented with 0.05 mg dm⁻³ 2,4-dichlorophenoxyacetic acid (2,4-D) was used for initiation of cell suspension cultures on same MS medium but without agar. Single cells were isolated after 3 d and the optimum cell density was 1–3 × 10⁴ cells per cm³ of the liquid MS medium. Plating efficiency was 29.6 % and callus formed within 4 weeks was subcultured and transferred to solid MS medium supplemented with 0.6 mg dm⁻³ benzyladenine (BA) along with 0.05 mg dm⁻³ α-naphthalene-1-acetic acid (NAA) for the induction of adventitious bud primordia. The shoots developed were isolated and re-cultured on MS medium containing 0.6 mg dm⁻³ BA. These microshoots after dipping in 1–2 cm³ of 10 mg dm⁻³ indole-3-butyric acid (IBA) for 24 h in dark were cultured on half strength solid MS medium supplemented with 0.05 % charcoal and showed 80–82 % rooting within 4 weeks.     

Chicken Mhc alloantiserum cross-reactivity analysis by hemagglutination and flow cytometry

 The major histocompatibility complex (Mhc) haplotype in the chicken is generally determined by the use of alloantisera in a hemagglutination assay. This method restricts haplotype determination to antigens expressed on the surface of erythrocytes which includes class I (B – F) and class IV (B – G) antigens as well as any other polymorphic molecules on these cells. Alloantisera can result in complex cross-reactivity patterns. We describe here the analysis of 53 alloantisera made within Mhc-congenic lines. Each antiserum was tested by hemagglutination with erythrocytes and by flow cytometry with erythrocytes and peripheral white blood cells of seven Mhc haplotypes; B ² , B ⁵ , B ¹² , B ¹³ , B ¹⁵ , B ¹⁹ , and B ²¹ . Five types of antiserum were identified based on their reactivity to different cell subpopulations of the peripheral blood of the donor haplotype as well as in cross-reactivity for different haplotypes. RBC specific cross-reactive antigens attributed to B – G molecules were demonstrated for the B5 : B19, B12 : B19, and B19 : B21 cross-reactions. Cross-reactive antigens detected on RBC and thrombocytes attributable to B – G molecules on both types of cells were demonstrated for the B2 : B12, B2 : B15, B2 : B19, and B2 : B21 cross-reactions. In addition, cross-reactive antigens occurring on RBC and WBC were attributed to B – F (or RBC and lymphocyte-expressed B – G loci) and included the B12 : B13, B13 : B19, and B15 : B19 cross-reactions. Several antisera with specificity for B cells purportedly identifying B – L epitopes were found but their numbers were limited and cross-reactivities were not defined. The identities described here may be useful in understanding B haplotype similarities and differences in disease resistance and immune response. Received: 18 September 1995 / 15 November 1995     

The ecological niche of the consortium “Pelochromatium roseum”

A dense accumulation of the phototrophic consortium “Pelochromatium roseum” in a small, eutrophic, freshwater lake (Dagowsee, Brandenburg, Germany) was investigated. Within the chemocline, the number of epibionts of the consortia represented up to 19% of the total number of bacteria. Per “P. roseum” a mean value of 20 epibionts was determined. Similar to other aquatic habitats, consortia in the Dagowsee were found only at low light intensities (< 7 μmol quanta m^–2 s^–1) and low sulfide concentrations (0–100 μM). In dialysis cultures of “P. roseum”, bacterial cells remained in a stable association only when incubated at light intensities between 5 and 10 μmol quanta m^–2 s^–1. Intact consortia from natural samples had a buoyant density of 1046.8 kg m^–3, which was much higher than that of ambient chemocline water (995.8 kg m^–3). Under environmental conditions and without motility, this density difference would result in rapid sedimentation of consortia toward the lake bottom. Our results indicate that (1) consortia are adapted to a very narrow regime of light intensities and sulfide concentrations, (2) motility and tactic responses must be of ecological significance for the colonization of the free water column of lakes, and (3) phototrophic growth of consortia can be explained only by a cycling of sulfur species in the chemocline, possibly within the consortia themselves. Received: 27 May 1997 / Accepted: 16 September 1997     

Continuum limits of pattern formation in hexagonal-cell monolayers

Intercellular signalling is key in determining cell fate. In closely packed tissues such as epithelia, juxtacrine signalling is thought to be a mechanism for the generation of fine-grained spatial patterns in cell differentiation commonly observed in early development. Theoretical studies of such signalling processes have shown that negative feedback between receptor activation and ligand production is a robust mechanism for fine-grained pattern generation and that cell shape is an important factor in the resulting pattern type. It has previously been assumed that such patterns can be analysed only with discrete models since significant variation occurs over a lengthscale concomitant with an individual cell; however, considering a generic juxtacrine signalling model in square cells, in O’Dea and King (Math Biosci 231(2):172–185 2011), a systematic method for the derivation of a continuum model capturing such phenomena due to variations in a model parameter associated with signalling feedback strength was presented. Here, we extend this work to derive continuum models of the more complex fine-grained patterning in hexagonal cells, constructing individual models for the generation of patterns from the homogeneous state and for the transition between patterning modes. In addition, by considering patterning behaviour under the influence of simultaneous variation of feedback parameters, we construct a more general continuum representation, capturing the emergence of the patterning bifurcation structure. Comparison with the steady-state and dynamic behaviour of the underlying discrete system is made; in particular, we consider pattern-generating travelling waves and the competition between various stable patterning modes, through which we highlight an important deficiency in the ability of continuum representations to accommodate certain dynamics associated with discrete systems.     

Organic matter stabilization in soil microaggregates: implications from spatial heterogeneity of organic carbon contents and carbon forms

This study investigates the spatial distribution of organic carbon (C) in free stable microaggregates (20–250 μm; not encapsulated within macroaggregates) from one Inceptisol and two Oxisols in relation to current theories of the mechanisms of their formation. Two-dimensional micro- and nano-scale observations using synchrotron-based Fourier-transform infrared (FTIR) and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy yielded maps of the distribution of C amounts and chemical forms. Carbon deposits were unevenly distributed within microaggregates and did not show any discernable gradients between interior and exterior of aggregates. Rather, C deposits appeared to be patchy within the microaggregates. In contrast to the random location of C, there were micron-scale patterns in the spatial distribution of aliphatic C–H (2922 cm⁻¹), aromatic C=C and N–H (1589 cm⁻¹) and polysaccharide C–O (1035 cm⁻¹). Aliphatic C forms and the ratio of aliphatic C/aromatic C were positively correlated (r ² of 0.66–0.75 and 0.27–0.59, respectively) to the amount of O–H on kaolinite surfaces (3695 cm⁻¹), pointing at a strong role for organo-mineral interactions in C stabilization within microaggregates and at a possible role for molecules containing aliphatic C-H groups in such interactions. This empirical relationship was supported by nanometer-scale observations using NEXAFS which showed that the organic matter in coatings on mineral surfaces had more aliphatic and carboxylic C with spectral characteristics resembling microbial metabolites than the organic matter of the entire microaggregate. Our observations thus support models of C stabilization in which the initially dominant process is adsorption of organics on mineral surfaces rather than occlusion of organic debris by adhering clay particles.     

Variable optimization for the formation of three-dimensional self-organized heart muscle

Cardiac tissue-engineering research is focused on the development of functional three-dimensional (3D) heart muscle in vitro. These models allow the detailed study of critical events in organogenesis, such as the establishment of cell–cell communication and construction and modification of the extracellular matrix. We have previously described a model for 3D heart muscle, termed cardioids, formed by the spontaneous delamination of a cohesive monolayer of primary cells in the absence of any synthetic scaffolding material. In an earlier publication, we have shown that, upon electrical stimulation, cardioids generate a twitch force in the range of 200–300 μN, generate a specific force (twitch force normalized to total cross-sectional area) of 2–4 kN/m², and can be electrically paced at frequencies of up to 10 Hz without any notable fatigue. We have two objectives for the current study: model development and model optimization. Our model development efforts are focused on providing additional characterization of the cardioid model. In this study, we show for the first time that cardioids show a pattern of gene expression comparable to that of cells cultured in two dimensions on tissue culture plastic and normal mammalian heart muscle. Compared with primary cardiac cells cultured on tissue culture plastic, the expression of α-myosin heavy chain (MHC), β-MHC, SERCA2, and phospholamban was significantly higher in cardioids. Our second objective, model optimization, is focused on evaluating the effect of several cell culture variables on cardioid formation and function. Specifically, we looked at the effect of plating density (1.0–4.0 × 10⁶ cells per cardioid), concentration of two adhesion proteins (laminin at 0.2–2.0 μg/cm² and fibronectin at 1–10 μg/cm²), myocyte purity (using preplating times of 15 and 60 min), and ascorbic acid stimulation (1–100 μl/ml). For our optimization studies, we utilized twitch force in response to electrical stimulation as our endpoint metric. Based on these studies, we found that cardioids formed with a plating density in the range 3–4 × 10⁶ cells per cardioid generated the maximum twitch force, whereas increasing the surface adhesion protein (using either laminin or fibronectin) and increasing the myocyte purity both resulted in a decrease in twitch force. In addition, increasing the ascorbic acid concentration resulted in an increase in the baseline force of cardioids, which was recorded in the absence of electrical stimulation. Based on the model development studies, we have shown that cardioids do indeed exhibit a gene expression pattern similar to normal mammalian heart muscle. This provides further validity for the cardioid model. Based on the model optimization studies, we have identified specific cell culture regimes which support cardioid formation and function. These results are specific to the cardioid model; however, they may be translated and applied to other tissue-engineering models. Collectively, the work described in this study provides insight into the formation of functional 3D heart muscle and the effect of several cell culture variables on tissue formation and function.     

AMPA and Kainate Receptors in Turtle Retina: An Immunocytochemical Study

Summary 1. Glutamate is one of the main neurotransmitters in the retina. Its effects are mediated by a large number of ionotropic and metabotropic receptors. 2. The distribution of ionotropic AMPA receptor subunits GluR1–4, kainate receptor subunits GluR5–7 and KA2, as well as delta receptors 1–2 was studied in turtle retina. Indirect immunofluorescence was used to localize the different receptor subunits viewed using light microscopy. 3. Results show that all subunits, with excerption of GluR1 and GluR5, are widely distributed in the turtle retina. 4. They are mainly located in the both plexiform layers of the retina where punctate staining, a sign for synaptic localization, is observed. 5. The vast majority of the subunits possess specific pattern of staining that allow to suppose that they are involved in different retinal circuits. 6. It can be assumed that the GluR2/3 and GluR6/7 subunits are expressed on the dendrites of a subpopulation of bipolar cells that are immunopositive for α-isoform of protein kinase C (PKCα). The GluR2/3 and GluR6/7 subunits are most probably used by the same PKCα immunopositive bipolar cells in their synaptic contacts with the third-order retinal neurons, the amacrine and ganglion cells.     

Derivatization of bioactive carbazoles by the biphenyl-degrading bacterium <Emphasis Type="Italic">Ralstonia</Emphasis> sp. strain SBUG 290

Different 9H-carbazole derivatives have been investigated within the last decades due to their broad range of pharmacological applications. While the metabolism of 9H-carbazole has previously been reported, nothing was known about the bacterial transformation of 2,3,4,9-tetrahydro-1H-carbazole and 9-methyl-9H-carbazole. Thus, for the first time, the bacterial biotransformation of 2,3,4,9-tetrahydro-1H-carbazole and 9-methyl-9H-carbazole was analyzed using biphenyl-grown cells of Ralstonia sp. strain SBUG 290 expressing biphenyl 2,3-dioxygenase. This strain accumulated 3-hydroxy-1,2,3,5,6,7,8,9-octahydrocarbazol-4-one and 6′-iminobicyclohexylidene-2′,4′-dien-2-one as major products during the incubation with 2,3,4,9-tetrahydro-1H-carbazole. Carbazol-9-yl-methanol was verified as the primary oxidation product of 9-methyl-9H-carbazole. In addition, 9H-carbazol-1-ol, 9H-carbazol-3-ol, and 3-hydroxy-1,2,3,9-tetrahydrocarbazol-4-one where detected in lower concentrations during the transformation of carbazol-9-yl-methanol and 9-methyl-9H-carbazole. Products were identified by high-performance liquid chromatography, gas chromatography–mass spectrometry, liquid chromatography–mass spectrometry, as well as ¹H and ¹³C nuclear magnetic resonance analyses.     

Limnological characteristics of the freshwater ecosystems of Byers Peninsula, Livingston Island, in maritime Antarctica

A limnological survey of 15 lakes and 6 streams was carried out on Byers Peninsula (Livingston Island, South Shetland Islands, Antarctica) during austral summer 2001–2002. Most of the surface waters had low conductivities (20–105 μS cm⁻¹) and nutrients (total phosphorus 0.01–0.24 μM), but some coastal lakes were enriched by nutrient inputs from seal colonies and marine inputs. Plankton communities in the lakes contained picocyanobacteria (10²–10⁴ cells ml⁻¹), diatoms, chrysophytes and chlorophytes, and a large fraction of the total biomass was bacterioplankton. Zooplankton communities were dominated by Boeckella poppei and Branchinecta gainii; the benthic cladoceran Macrothrix ciliata was also recorded, for the first time in Antarctica. The chironomids Belgica antarctica and Parochlus steinenii, and the oligochaete Lumbricillus sp., occurred in stream and lake benthos. The phytobenthos included cyanobacterial mats, epilithic diatoms and the aquatic moss Drepanocladus longifolius. These observations underscore the limnological richness of this seasonally ice-free region in maritime Antarctica and its value as a long-term reference site for monitoring environmental change.     

Biomass, carbonate standing stock and production of the mediterranean coralCladocora caespitosa (L.)

Summary The Mediterranean coralCladocora caespitosa often occurs in large beds, i.e. populations of hemispherical clonies with stock densities varying between 1.9 and 4 coloneis ·m⁻². Laboratory measurements of volume, skeleton weight, surface and number of corallites per colony, coupled with mean annual growth rates evaluated through sclerochronology, allowed for the estimation of biomass, skeleton bulk density, calcimass (carbonate standing stock) and secondary production (both organic and inorganic) of twoC. caespitosa beds at 4 and 9 m depth. The mean colony biomass varied between 0.73 and 0.99 kg dw ·m⁻², corresponding to a calcimass between 2 and 5 kg CaCO₃·m⁻². Organic secondary production was 215.5–305.4 g dw of polyps ·m⁻²·y⁻¹, while the potential (mineral) production was 1.1–1.7 kg CaCO₃·m⁻²·y⁻¹, for the year 1996–1997. These values show thatC. caespitosa is one of the major carbonate producers within the Mediterranean and one of the major epibenthic species originating stable carbonate frameworks both in recent and past times.