Pseudomonas expression of an oxygen sensing prolyl hydroxylase homologue regulates neutrophil host responses in vitro and in vivo

Background: Pseudomonas species are adapted to evade innate immune responses and can persist at sites of relative tissue hypoxia, including the mucus-plugged airways of patients with cystic fibrosis and bronchiectasis. The ability of these bacteria to directly sense and respond to changes in local oxygen availability is in part consequent upon expression of the 2-oxoglutarate oxygenase, Pseudomonas prolyl hydroxylase (PPHD), which acts on elongation factor Tu (EF-Tu), and is homologous with the human hypoxia inducible factor (HIF) prolyl hydroxylases. We report that PPHD expression regulates the neutrophil response to acute pseudomonal infection. Methods: In vitro co-culture experiments were performed with human neutrophils and PPHD-deficient and wild-type bacteria and supernatants, with viable neutrophil counts determined by flow cytometry. In vivo consequences of infection with PPHD deficient P. aeruginosa were determined in an acute pneumonia mouse model following intra-tracheal challenge. Results: Supernatants of PPHD-deficient bacterial cultures contained higher concentrations of the phenazine exotoxin pyocyanin and induced greater acceleration of neutrophil apoptosis than wild-type PAO1 supernatants in vitro. In vivo infection with PPHD mutants compared to wild-type PAO1 controls resulted in increased levels of neutrophil apoptosis and impaired control of infection, with higher numbers of P. aeruginosa recovered from the lungs of mice infected with the PPHD-deficient strain. This resulted in an overall increase in mortality in mice infected with the PPHD-deficient strain. Conclusions: Our data show that Pseudomonas expression of its prolyl hydroxylase influences the outcome of host-pathogen interactions in vitro and in vivo, demonstrating the importance of considering how both host and pathogen adaptations to hypoxia together define outcomes of infection. Given that inhibitors for the HIF prolyl hydroxylases are in late stage trials for the treatment of anaemia and that the active sites of PPHD and human HIF prolyl hydroxylases are closely related, the results are of current clinical interest

Physiological and biochemical responses to low non-freezing temperature of two Eucalyptus globulus clones differing in drought resistance

Abstract – We have compared the metabolic responses of leaves and roots of two Eucalyptus globulus L. clones CN5 and ST51 that differ in their sensitivity to water deficits (ST51 is more drought sensitive), with regard to the effect of chilling (10/5 ◦C, day/night). We studied changes in growth, osmotic potential and osmotically active compounds, soluble proteins, leaf pigments, and membrane lipid composition. Our data showed that both clones have the ability to acclimatize to chilling temperatures. As a result of 10 days of acclimation, an increase of soluble sugars in leaves of treated plants of both clones was observed that disappeared later on. Differences between clones were observed in the photosynthetic pigments and soluble protein content which were more stable in CN5 under chilling. It also was apparent that CN5 presented a less negative predawn water potential (ψpd) and a higher leaf turgor than ST51 throughout the chilling treatment. In the case of the CN5, increased total lipids (TFA) and concomitant increase of linolenic acid (C18:3) in leaves after acclimatization may be related to a better clone performance under chilling temperatures. Moreover, a higher constitutive investment in roots in the case of CN5 as compared to ST51 may benefit new root regeneration under low temperatures favoring growth after cold Mediterranean winter

Molluscan diversity caught by trawling fisheries: a case study in southern Portugal

The effects of commercial trawling on the malacological communities (except for the Cephalopoda) were examined, based on a study undertaken between 1996 and 2000 on the continental shelf and slope of southern Portugal. More than 50% of species caught by trawling in southern Portugal were discarded, with molluscs representing about 19%. Forty-four species of molluscs (15 bivalves, 28 gastropods and one polyplacophoran) were identified from the discarded specimens. Crustacean trawlers accounted for 34 molluscs species, and fish trawlers for 24. Twenty species were only caught by the crustacean trawl, compared with 10 species by the fish trawl, and 14 species were common to both trawls. The bivalve Venus nux Gmelin was the most numerous species discarded in the fish trawl, accounting for 42.0% of the total number of individuals, followed by the gastropods Ampulla priamus (Meuschen) (7.8%) and Ranella olearium (L.) (7.3%). In the crustacean trawl, the most numerous species discarded were the bivalve Anadara diluvii (Lamarck) (19.4%), the gastropod Calliostoma granulatum (Born) (15.5%), and the bivalve V. nux (15.1%). The third most discarded species from fish trawls in Algarve waters, the gastropod species R. olearium, is a species listed in Annex II of the Bern Convention. The difficulties of managing the real impact of fisheries on the molluscan populations and in defining a conservation strategy are discussed

Mecanismos de regeneração natural em diferentes ambientes de remanescente de Floresta Ombrófila Mista, São Francisco de Paula, RS Mechanisms of natural regeneration in different environments in the remaining Mixed Rain Forest, São Francisco de Paula, RS

O objetivo deste trabalho foi avaliar os mecanismos de regeneração natural em três agrupamentos florísticos em remanescente de Floresta Ombrófila Mista, localizado em São Francisco de Paula, RS. A coleta dos dados foi realizada em seis conglomerados de um hectare, subdivididos em 16 parcelas cada, nas quais foram coletadas amostras da chuva de sementes, do banco de sementes no solo e do banco de plântulas. Os grupos florísticos apresentaram diferenças significativas para a densidade de indivíduos na chuva de sementes e no banco de plântulas. Para o banco de sementes no solo, o grupo G1 diferiu dos grupos G2 e G3. A riqueza de espécies observada no banco de plântulas sugere que este pode ser o mecanismo principal de manutenção da diversidade no remanescente. A chuva de sementes foi abundante e representou uma fonte expressiva de propágulos para abastecer o banco de sementes e banco de plântulas local e das áreas circunvizinhas. O banco de sementes do solo não apresentou potencial florístico para representar a riqueza de espécies presentes na vegetação arbórea, corroborando o estágio sucessional avançado desta floresta, uma vez que o banco de sementes é formado principalmente de espécies pioneiras.<br>The aim of this study was to evaluate the natural regeneration mechanisms in three floristic groups of the remaining Mixed Rain Forest, located in San Francisco de Paula, RS. The data were collected in six conglomerates of one hectare, subdivided into 16 plots, in which seed rain, soil seed bank, and seedling bank were collected. The groups presented differences in the density of individuals in the seed rain and in the seedling banks. For the soil seed bank, the group G1 differed from the groups G2 and G3. The seedlings bank, due to the wealth of species, may be the primary mechanism for maintaining diversity in the remnant. Seed rain was abundant and represented an expressive source of seeds to supply the seed bank and the seedling bank site and surrounding areas. The seed bank of soil did not show potential to replace the floristic richness of species in the arboreal vegetation, confirming the advanced stage of forest succession, once the seed bank is composed mainly of pioneer specie