Comparative analysis of the Salmonella typhi and Escherichia coli ompC genes

The nucleotide (nt) sequence of the gene encoding the Salmonella typhi OmpC outer membrane protein, and its deduced amino acid (aa) sequence are presented here. The S. typhi ompC gene consists of an open reading frame of 1134 nt, corresponding to a protein of 378 aa; with a 21-aa signal peptide. This protein is 11 aa longer than Escherichia coli OmpC, but it has an identical leader peptide. The mature OmpC sequence shows 79% similarity for both bacteria at the aa level, and 77% similarity at the nt level. Seven main variable regions in the OmpC protein were identified. Five of them correspond to hydrophilic regions and contain aa observed most frequently in turn configurations in soluble proteins. This suggests that these aa stretches could be located on the exterior of the outer membrane. To probe into the genus and species specificity of the main variable regions, we have constructed complementary oligodeoxyribonucleotides. The use of one of them with a small number of DNA samples is illustrated here; no restriction fragment length polymorphism or nt sequence heterogeneity could be found between S. typhi and Salmonella typhimurium.     

The legacy of forest logging on organic matter inputs and storage in tropical streams

Riparian forests play an important role in stream ecosystems, as they support biodiversity, reduce water erosion, and provide litter that fuels aquatic biota. However, they are affected by great array of anthropogenic threats (e.g., fire, logging, and organic pollution), which alter species composition and their physical structure. Although forest recovery after disturbance such as logging can take decades, the legacy of forest clear-cut logging on key processes in tropical riparian ecosystems is mostly unknown. Here, we investigated how litter inputs (leaves, twigs, and reproductive parts) and storage, key processes for carbon and nutrient recycling and for forest and stream biota, are influenced by riparian vegetation undergoing succession (after 28 years from logging) through the comparison of reference and logged forest sites in the Cerrado biome. Litterfall was overall similar between forest types, but litterfall of twigs was twofold higher at logged than reference sites. Similarly, litter inputs from the bank to the stream (i.e., lateral inputs) and streambed storage were 50–60% higher at logged than reference sites. The higher litterfall observed in logged forests could be related to higher proportion of tree species that are characteristic of primary and secondary successional stages, including fast-growing and liana species, which often are more productive and common in anthropogenic areas. Our results showed that the legacy impact of clear-cut logging, even if residual woody vegetation is maintained in riparian buffers, can shift the type, quantity, and seasonality of litter subsidies to tropical streams. This knowledge should be considered within the context of management and conservation of communities and ecosystem processes in the forest-stream interfaces.     

Partial trisomy 16q resulting from maternal translocation 11p/16q

A 3 1/2-year-old male with partial trisomy of the long arm of chromosome 16 resulting from a maternal balanced translocation 11p;16q is described. Clinical findings are compared with similar case reports from the literature.     

Heterogeneity of glutamine synthetase polypeptides in Neurospora crassa

Purified preparations of Neurospora crassa glutamine synthetase contain two nonidentical polypeptides that can be separated by acrylamide gel electrophoresis in the presence of sodium dodecyl sulfate and 7 M urea. These polypeptides are synthesized both in vivo and in a heterologous cell-free protein-synthesizing system. The data presented indicate that both polypeptides contain an active site for glutamine synthetase activity and suggest that there is not a precursor-product relationship between them.     

Physiology of the yeast Kluyveromyces marxianus during batch and chemostat cultures with glucose as the sole carbon source

Growth, substrate consumption, metabolite formation, biomass composition and respiratory parameters of Kluyveromyces marxianus ATCC 26548 were determined during aerobic batch and chemostat cultivations, using mineral medium with glucose as the sole carbon source, at 30 degrees C and pH 5.0. Carbon balances closed within 95-101% in all experiments. A maximum specific growth rate of 0.56 h(-1), a biomass yield on glucose of 0.51 g g(-1), and a maximum specific consumption of oxygen of 11.1 mmol g(-1) h(-1) were obtained during batch cultures. The concentration of excreted metabolites was very low at the culture conditions applied, representing 6% of the consumed carbon at most. Acetate and pyruvate were excreted to a larger extent than ethanol under the batch conditions, and the protein content accounted for 54.6% of the biomass dry weight. Steady states were obtained during chemostats at dilution rates of 0.1, 0.25 and 0.5 h(-1). At the two former dilution rates, cells grew at carbon limitation and the biomass yield on glucose was similar to that obtained under the batch conditions. Metabolite formation was rather low, accounting for a total of 0.005 C-mol C-mol(-1) substrate. At 0.5 h(-1), although the biomass yield on glucose was similar to the value obtained under the above-mentioned conditions, the cultivation was not under carbon limitation. Under this condition, 2-oxoglutarate, acetate, pyruvate and ethanol were the prevalent metabolites excreted. Total metabolite formation only accounted to 0.056 C-mol C-mol(-1) of substrate. A very high protein and a low carbohydrate content (71.9% and 9.6% of biomass dry weight, respectively) were measured in cells under this condition. It is concluded that K. marxianus aligns with the so-called aerobic-respiring or Crabtree-negative yeasts. Furthermore, it has one of the highest growth rates among yeasts, and a high capacity of converting sugar into biomass, even when carbon is not the limiting nutrient. These results provide useful data regarding the future application of K. marxianus in processes aimed at the production of biomass-linked compounds, with high yields and productivities.     

Impact of phosphorus application on drought resistant responses of Eucalyptus grandis seedlings

Eucalyptus grandis is the most widely planted tree species worldwide and can face severe drought during the initial months after planting because the root system is developing. A complete randomized design was used to study the effects of two water regimes (well‐watered and water‐stressed) and phosphorus (P) applications (with and without P) on the morphological and physio‐biochemical responses of E. grandis. Drought had negative effects on the growth and metabolism of E. grandis, as indicated by changes in morphological traits, decreased net photosynthetic rates (P_n), pigment concentrations, leaf relative water contents (LRWCs), nitrogenous compounds, over‐production of reactive oxygen species (ROS) and higher lipid peroxidation. However, E. grandis showed effective drought tolerance strategies, such as reduced leaf area and transpiration rate (E), higher accumulation of soluble sugars and proline and a strong antioxidative enzyme system. P fertilization had positive effects on well‐watered seedlings due to improved growth and photosynthesis, which indicated the high P requirements during the initial E. grandis growth stage. In drought‐stressed seedlings, P application had no effects on the morphological traits, but it significantly improved the LRWC, P_n, quantum efficiency of photosystem II (F_v/F_m), chlorophyll pigments, nitrogenous compounds and reduced lipid peroxidation. P fertilization improved E. grandis seedling growth under well‐watered conditions but also ameliorated some leaf physiological traits under drought conditions. The effects of P fertilization are mainly due to the enhancement of plant N nutrition. Therefore, P can be used as a fertilizer to improve growth and production in the face of future climate change.     

Negative osmoregulation of the Salmonella ompS1 porin gene independently of OmpR in an hns background

The ompS1 gene encodes a quiescent porin in Salmonella enterica serovars Typhi and Typhimurium. By using random mariner transposon mutagenesis, mutations that caused derepression of ompS1 expression were isolated, one in S. enterica serovar Typhi and two in S. enterica serovar Typhimurium. All of them mapped in the hns gene in the region coding for the carboxy terminus of the H-NS nucleoid protein. The derepressed ompS1 expression was subject to negative regulation at high osmolarity, both in the presence and in the absence of OmpR. This observation was possible due to the fact that there are two promoters: P1, which is OmpR dependent, and P2, which does not require OmpR for activation (rather, OmpR represses P2). The sequences upstream from position -88, a region previously shown to be involved in the negative regulation of ompS1, can form a static bend, and the integrity of this region was required for function and binding of H-NS and for osmoregulation, as determined with gene reporter fusions of different lengths and with a 31-bp deletion mutant. This is consistent with the notion that this region determines a structure required for repression. Hence, ompS1 shares negative regulation by H-NS with other loci, such as the bgl operon and the ade gene.     

Do Insectivorous Birds use Volatile Organic Compounds from Plants as Olfactory Foraging Cues? Three Experimental Tests

Some insectivorous birds orient towards insect‐defoliated trees even when they do not see the foliar damage or the herbivores. There are, however, only a few studies that have examined the mechanisms behind this foraging behaviour. Previous studies suggest that birds can use olfactory foraging cues (e.g. volatile organic compounds (VOCs) emitted by defoliated plants), indirect visual cues or a combination of the two sensory cues. VOCs from insect‐defoliated plants are known to attract natural enemies of herbivores, and researchers have hypothesized that VOCs could also act as olfactory foraging cues for birds. We conducted three experiments across a range of spatial scales to test this hypothesis. In each experiment, birds were presented with olfactory cues and their behavioural responses or foraging outcomes were observed. In the first experiment, two different VOC blends, designed to simulate the volatile emissions of mountain birch (Betula pubescens ssp. czerepanovii) after defoliation by autumnal moth (Epirrita autumnata) larvae, were used in behavioural experiments in aviaries with pied flycatchers (Ficedula hypoleuca). The second experiment was a field‐based trial of bird foraging efficiency; the same VOC blends were applied to mountain birches, silver birches (B. pendula) and European white birches (B. pubescens) with plasticine larvae attached to the trees to serve as artificial prey for birds and provide a means to monitor predation rate. In the third experiment, the attractiveness of silver birch saplings defoliated by autumnal moth larvae versus intact controls was tested with great tits (Parus major) and blue tits (Cyanistes caeruleus) in an aviary. Birds did not orient towards either artificial or real trees with VOC supplements or towards herbivore‐damaged saplings when these saplings and undamaged alternatives were hidden from view. These findings do not support the hypothesis that olfactory foraging cues are necessary in the attraction of birds to herbivore‐damaged trees.     

Imatinib ameliorates renal morphological changes in Cyp1a1-Ren2 transgenic rats with inducible ANG II-dependent malignant hypertension

The present study was performed to assess the effects of the platelet-derived growth factor (PDGF) receptor kinase inhibitor imatinib mesylate on the renal morphological changes occurring during the development of malignant hypertension in transgenic rats with inducible expression of the Ren2 gene [TGR(Cyp1a1Ren2)]. Arterial blood pressure was measured by radiotelemetry in male Cyp1a1-Ren2 rats during control conditions and during dietary administration of indole-3-carbinol (I3C; 0.3%) for 14 days to induce malignant hypertension. Rats induced with I3C (n = 5) had higher mean arterial pressures (178 ± 4 vs. 109 ± 2 mmHg, P < 0.001) and increased urinary albumin excretion (Ualb; 13 ± 5 vs. 0.6 ± 0.2 mg/day) compared with noninduced rats (n = 5). Chronic administration of imatinib (60 mg·kg(-1)·day(-1) in drinking water, n = 5) did not alter the magnitude of the hypertension (176 ± 8 mmHg) but prevented the increase in Ualb (1.6 ± 0.3 mg/day). Quantitative analysis of proliferating cell nuclear antigen using immunohistochemistry demonstrated increased proliferating cell number in cortical tubules (38 ± 5 vs. 18 ± 1 cells/mm(2)) and cortical interstitium (40 ± 7 vs. 13 ± 6 cells/mm(2)) of hypertensive rat kidneys. Renal cortical fibrosis evaluated by picrosirius red staining showed increased collagen deposition in kidneys of the hypertensive rats (1.6 ± 0.1 vs. 0.4 ± 0.1% of cortical area). Imatinib attenuated the increase in proliferating cell number in cortical tubules and interstitium (22 ± 5 vs. 38 ± 5 and 22 ± 6 vs. 40 ± 7 cells/mm(2), respectively) and reduced the degree of collagen deposition (0.8 ± 0.2 vs. 1.6 ± 0.1%) in the kidneys of hypertensive rats. These findings demonstrate that the renal pathological changes that occur during the development of malignant hypertension in Cyp1a1-Ren2 rats involve activation of PDGF receptor kinase.