Studies withSalmonella typhimurium mutants defective in enzymes of the propionate catabolism

Salmonella typhimurium LT-2 mutants defective in the propionate degradative pathway were isolated after mutagenesis with ethyl-methane-sulfonate. From the analysis of the mutants it is possible to deduce that the phosphoenolpyruvate synthase and the phosphoenolpyruvate carboxylase act as an anaplerotic sequence essential to the catabolic route of the propionate via acrylate. A genetic locus for the Prp-phenotype maps at approximately 97 min on theS. typhimurium chromosome.     

Insights into the mechanisms of transport and regulation of the arabidopsis high-affinity K+ transporter HAK51

The high-affinity K⁺ transporter HAK5 from Arabidopsis (Arabidopsis thaliana) is essential for K⁺ acquisition and plant growth at low micromolar K⁺ concentrations. Despite its functional relevance in plant nutrition, information about functional domains of HAK5 is scarce. Its activity is enhanced by phosphorylation via the AtCIPK23/AtCBL1-9 complex. Based on the recently published three-dimensionalstructure of the bacterial ortholog KimA from Bacillus subtilis, we have modeled AtHAK5 and, by a mutational approach, identified residues G67, Y70, G71, D72, D201, and E312 as essential for transporter function. According to the structural model, residues D72, D201, and E312 may bind K⁺, whereas residues G67, Y70, and G71 may shape the selective filter for K⁺, which resembles that of K⁺shaker-like channels. In addition, we show that phosphorylation of residue S35 by AtCIPK23 is required for reaching maximal transport activity. Serial deletions of the AtHAK5 C-terminus disclosed the presence of an autoinhibitory domain located between residues 571 and 633 together with an AtCIPK23-dependent activation domain downstream of position 633. Presumably, autoinhibition of AtHAK5 is counteracted by phosphorylation of S35 by AtCIPK23. Our results provide a molecular model for K⁺ transport and describe CIPK-CBL-mediated regulation of plant HAK transporters.

Structure-function analysis of a high-affinity root K⁺ transporter reveals residues involved in transport, regulation by a protein kinase, and autoinhibition.     

A novel in vitro tissue culture approach to study salt stress responses in citrus

In citrus, a major crop throughout the world, growth and yield are seriously affected by salinity. Different approaches, including agronomical, physiological and molecular methods, have been used to address this problem. In this work, an in vitro experimental system has been developed to study the toxic effect of NaCl on three citrus genotypes, avoiding the ion filter that represents the root system. To carry out the experiments, shoots were obtained from nodal segments of Cleopatra mandarin, Carrizo citrange and citrumelo CPB4475 plants growing in a greenhouse. Shoots were cultured in control or NaCl-supplemented media. After testing several salt concentrations, 60 mM NaCl was selected as saline treatment. Shoots accumulated similar levels of chloride when cultured without roots and exhibited similar leaf damage. No increases in malondialdehyde levels were observed in any genotype (as a measure of oxidative stress). Similar patterns of hormonal signalling (in terms of abscisic acid and salicylic acid contents) were exhibited in the three genotypes, despite their different tolerance under field conditions. All data together indicate that, without root system, all genotypes had the same behaviour under salt stress. The in vitro culture system has been proved as a useful tool to study biochemical processes involved in the response of citrus to salt stress.     

N-Nitrosopiperidine and N-Nitrosodibutylamine induce apoptosis in HepG2 cells via the caspase dependent pathway

The human hepatoma cell line (HepG2) exhibited a dose and time-dependent apoptotic response following treatment with N-Nitrosopiperidine (NPIP) and N-Nitrosodibutylamine (NDBA), two recognized human carcinogens. Our results showed a significant apoptotic cell death (95%) after 24 h treatment with NDBA (3.5 mM), whereas it was necessary to use high doses of NPIP (45 mM) to obtain a similar percentage of apoptotic cells (86%). In addition, both extrinsic (caspase-8) and intrinsic pathway (caspase-9) could be implicated in the N-Nitrosamines-induced apoptosis. This study also addresses the role of reactive oxygen species (ROS) as intermediates for apoptosis signaling. A significant increase in ROS levels was observed after NPIP treatment, whereas NDBA did not induce ROS. However, N-acetylcysteine (NAC) did not block NPIP-induced apoptosis. All these findings suggest that NPIP and NDBA induce apoptosis in HepG2 cells via a pathway that involves caspases but not ROS.     

The glial design of a teleost optic nerve head supporting continuous growth.

This study demonstrates the peculiarities of the glial organization of the optic nerve head (ONH) of a fish, the tench (Tinca tinca), by using immunohistochemistry and electron microscopy. We employed antibodies specific for the macroglial cells: glutamine synthetase (GS), glial fibrillary acidic protein (GFAP), and S100. We also used the N518 antibody to label the new ganglion cells' axons, which are continuously added to the fish retina, and the anti-proliferating cell nuclear antigen (PCNA) antibody to specifically locate dividing cells. We demonstrate a specific regional adaptation of the GS-S100-positive Müller cells' vitreal processes around the optic disc, strongly labeled with the anti-GFAP antibody. In direct contact with these Müller cells' vitreal processes, there are S100-positive astrocytes and S100-negative cells ultrastructurally identified as microglial cells. Moreover, a population of PCNA-positive cells, characterized as glioblasts, forms the limit between the retina and the optic nerve in a region homologous to the Kuhnt intermediary tissue of mammals. Finally, in the intraocular portion of the optic nerve there are differentiating oligodendrocytes arranged in rows. Both the glioblasts and the rows of developing cells could serve as a pool of glial elements for the continuous growth of the visual system.     

Novel microsatellite loci in the threatened European long-snouted seahorse (<Emphasis Type="Italic">Hippocampus guttulatus</Emphasis>) for genetic diversity and parentage analysis

The long-snouted seahorse Hippocampus guttulatus is one of the two European seahorse species. We describe the isolation of the first 12 microsatellite loci in this threatened species. These new markers were tested in non-invasive samples of 32 seahorses from NW Spain. The number of alleles ranged from 2 to 15 (mean: 6.3) and expected heterozygosity from 0.031 to 0.912 (mean: 0.500). All loci conformed to Hardy–Weinberg expectations and no genotypic disequilibrium was observed between any pair of loci. The theoretical exclusion probabilities for this set of loci, when no parental information exists or when one parent is known, were 0.973 and 0.998, respectively. This study indicates the usefulness of these novel loci for population analysis and kinship studies in Hippocampus guttulatus. Their potential application is extended to the other European seahorse species, since all loci were successfully cross-amplified in H. hippocampus.     

A comparison of municipal wastewater treatment plants for big centres of population in Galicia (Spain)

Background, Aims and Scope  

It is clear that a wastewater treatment plant brings about an enhanced quality of wastewater; however, it also implies such environmental side effects as material and energy consumption as well as involving the generation of waste. This study is maintained within the boundaries of a research project that aims at the evaluation, from an environmental perspective, of the most common technical options focused on the removal of the organic matter present in urban wastewater. In particular, the paper presents the results for four centres of population with more than 50,000 inhabitants. The differences present among the facilities on their configurations will allow their comparison and the definition of the less environmentally damaging scheme for the treatment of this type of wastewater.     

Dynamics of protozoan and metazoan communities in a full scale wastewater treatment plant by rotating biological contactors

Performance of a full-scale wastewater treatment plant by rotating biological contactors (RBC) system was monitored during a year by physico-chemical and microbial characterisation. Six points along wastewater treatment were selected in the plant: three points along the water line (influent, sedimentation tank and effluent) and three points along RBC system (RBC1, RBC2 and RBC3). Although a large seasonal change in the values of physico-chemical parameters was observed, operation of the plant was optimal during all year (90% of removal in BOD5 and SS influent content). Microbial characterisation was approached by determining the structure and dynamics of protozoan and metazoan communities. Protozoa were the most abundant in all stages in the plant, heterotrophic flagellates being the most representative group in the water line and ciliates in the RBC system. The same seasonal preference was only observed for heterotrophic flagellates in the water line and green flagellates in the RBC system, both groups having highest abundances in summer and spring, respectively. Identification of ciliated protozoa populations rendered 58 species of ciliates in the plant. Most of these species are typical of aerobic wastewater treatment systems except three of them, which are cited for the first time in this type of ecosystems: Chaenea stricta, Holosticha mancoidea and Oxytricha lanceolata. Along the water line 34 species were identified, and half of them only appeared occasionally (once in all the study), while along the RBC system biofilms 55 species were observed, and the majority appeared permanently in this system. Our results indicate that the type of habitat, rather than the physico-chemical water parameters, was the primary factor in determining the different distribution of protozoan and metazoan communities in the plant. In RBC biofilms, the structure of ciliate protozoa community was found to be quite sensitive to changes in physico-chemical parameters, mainly to organic loading (BOD5) variations.     

Systemic approaches to biodegradation

Biodegradation, the ability of microorganisms to remove complex chemicals from the environment, is a multifaceted process in which many biotic and abiotic factors are implicated. The recent accumulation of knowledge about the biochemistry and genetics of the biodegradation process, and its categorization and formalization in structured databases, has recently opened the door to systems biology approaches, where the interactions of the involved parts are the main subject of study, and the system is analysed as a whole. The global analysis of the biodegradation metabolic network is beginning to produce knowledge about its structure, behaviour and evolution, such as its free-scale structure or its intrinsic robustness. Moreover, these approaches are also developing into useful tools such as predictors for compounds' degradability or the assisted design of artificial pathways. However, it is the environmental application of high-throughput technologies from the genomics, metagenomics, proteomics and metabolomics that harbours the most promising opportunities to understand the biodegradation process, and at the same time poses tremendous challenges from the data management and data mining point of view.