Phytogeography of the bryophyte floras of oak forests and páramo of the Cordillera de Talamanca, Costa Rica

Aim Central America is a biogeographically interesting area because of its location between the rich and very different biota of North and South America. We aim to assess phytogeographical patterns in the bryophyte floras of oak forests and páramo of the Cordillera de Talamanca, Costa Rica. Location Tropical America, in particular the montane area of Cordillera de Talamanca, Costa Rica. Methods The analysis is based on a new critical inventory of the montane bryophyte flora of Cordillera de Talamanca. All species were assigned to phytogeographical elements on the basis of their currently known distribution. Absolute and percentage similarities were employed to evaluate floristic affinities. Results A total of 401 species [191 hepatics (liverworts), one hornwort, 209 mosses] are recorded; of these, 251 species (128 hepatics, one hornwort, 122 mosses) occur in oak forests. Ninety‐three per cent of all oak forest species are tropical in distribution, the remaining 7% are temperate (4%) and cosmopolitan (3%) species. The neotropical element includes almost 74% of the species, the wide tropical element (pantropical, amphi‐atlantic, amphi‐pacific) only 19%. A significant part of the neotropical species from oak forests are species with tropical Andean‐centred ranges (27%). As compared with bryophyte species, vascular plant genera in the study region are represented by fewer neotropical, more temperate and more amphi‐pacific taxa. Bryophyte floras of different microhabitats within the oak forest and epiphytic bryophyte floras on Quercus copeyensis in primary, early secondary and late secondary oak forest show a similar phytogeographical make‐up to the total oak forest bryophyte flora. Comparison of oak forest and páramo reveals a greater affinity of the páramo bryophyte flora to temperate regions and the great importance of the páramo element in páramo. Surprisingly, oak forests have more Central American endemics than páramo. Main conclusions (1) Providing first insights into the phytogeographical patterns of the bryophyte flora of oak forests and páramo, we are able to confirm general phytogeographical trends recorded from vascular plant genera of the study area although the latter were more rich in temperate taxa. (2) Andean‐centred species are a conspicuous element in the bryophyte flora of Cordillera de Talamanca, reflecting the close historical connection between the montane bryophyte floras of Costa Rica and South America. (3) High percentages of Central American endemics in the bryophyte flora of the oak forests suggest the importance of climatic changes associated with Pleistocene glaciations for allopatric speciation.     

Retinoic acid modulates the pattern of cell division in embryos ofLymnaea stagnalis (Mollusca)

All-trans retinoic acid is well known as a modulator of positional specification in vertebrate development. A similar mechanism may operate in molluscan development. Molluscan development is characterized by an invariant pattern of cell divisions, which allows the study of individual cells in the developing organism. Low concentrations of exogenous retinoic acid applied during gastrulation affect the cell division pattern in the early larval stage of the molluscLymnaea stagnalis. A few cells from the apical plate, a larval organ consisting of seven large cleavage-arrested cells, were induced by retinoic acid to resume cell division. They typically formed an area of proliferating small cells that resembles the adjacent areas of precursor cells of adult ectoderm. The identification of individual cells that are transformed by retinoic acid may provide new insights into the mechanisms underlying positional specification within the embryo.     

Characterization of an Escherichia coli rotA mutant, affected in periplasmic peptidyl-prolyl cis/trans isomerase

The rotA gene of Escherichia coli encodes a peptidyl-prolyl cis/trans isomerase (PPlase), which is supposed to catalyse protein folding in the periplasm. To investigate the importance of the enzyme, the rotA gene was cloned and a chromosomal deletion mutant was created. The rotA mutant was normally viable. No residual PPlase activity could be detected in the periplasmic fraction of the mutant. Comparison of the patterns of periplasmic and outer membrane proteins by SDS-PAGE revealed no differences in protein composition between the rotA mutant and its parental strain. Similarly, the kinetics of periplasmic protein folding and outer membrane protein assembly appeared unaffected by the rotA mutation. Our results show that the periplasmic PPlase of E. coli is not essential and that the protein does not play an important role in protein folding.     

Xylose anaerobic conversion by open-mixed cultures

Xylose is, after glucose, the dominant sugar in agricultural wastes. In anaerobic environments, carbohydrates are converted into volatile fatty acids and alcohols. These can be used as building blocks in biotechnological or chemical processes, e.g., to produce bioplastics. In this study, xylose fermentation by mixed microbial cultures was investigated and compared with glucose under the same conditions. The product spectrum obtained with both substrates was comparable. It was observed that, in the case of xylose, a higher fraction of the carbon was converted into catabolic products (butyrate, acetate, and ethanol) and the biomass yield was approximately 20% lower than on glucose, 0.16 versus 0.21 Cmol X/Cmol S. This lower yield is likely related to the need of an extra ATP during xylose uptake. When submitted to a pulse of glucose, the population cultivated on xylose could instantaneously convert the glucose. No substrate preference was observed when glucose and xylose were fed simultaneously to the continuously operated bioreactor.     

Peripheral CD8+ T cell proliferation is prognostic for patients with advanced thoracic malignancies

There is a complex interplay between the immune system and a developing tumor that is manifest in the way that the balance of T cell subsets in the local tumor environment reflects clinical outcome. Tumor infiltration by CD8⁺ T cells and regulatory T cells (Treg) is associated with improved and reduced survival, respectively, in many cancer types. However, little is known of the prognostic value of immunological parameters measured in peripheral blood. In this study, peripheral CD8⁺ T cells and Treg from 43 patients with malignant mesothelioma or advanced non-small-cell lung cancer scheduled to commence palliative chemotherapy were assessed by flow cytometry and evaluated for association with patient survival. Patients had a higher proportion of peripheral Treg, proliferating CD8⁺ T cells and CD8⁺ T cells with an activated effector phenotype compared with age-matched healthy controls. Higher proportions of Treg and proliferating CD8⁺ T cells were both associated with poor survival in univariate analyses (hazard ratio [HR] 3.81, 95 % CI 1.69–8.57; p < 0.01 and HR 2.86, 95 % CI 1.26–6.50; p < 0.05, respectively). CD8⁺ T cell proliferation was independently predictive of reduced survival in multivariate analysis (HR 2.58, 95 % CI 1.01–6.61; p < 0.05). These findings suggest that peripheral CD8⁺ T cell proliferation can be a useful prognostic marker in patients with thoracic malignancies planned for palliative chemotherapy.     

Multifactorial diversity sustains microbial community stability

Maintenance of a high degree of biodiversity in homogeneous environments is poorly understood. A complex cheese starter culture with a long history of use was characterized as a model system to study simple microbial communities. Eight distinct genetic lineages were identified, encompassing two species: Lactococcus lactis and Leuconostoc mesenteroides. The genetic lineages were found to be collections of strains with variable plasmid content and phage sensitivities. Kill-the-winner hypothesis explaining the suppression of the fittest strains by density-dependent phage predation was operational at the strain level. This prevents the eradication of entire genetic lineages from the community during propagation regimes (back-slopping), stabilizing the genetic heterogeneity in the starter culture against environmental uncertainty.     

A highly active adipyl-cephalosporin acylase obtained via rational randomization

There is strong interest in creating an enzyme that can deacylate natural cephalosporins such as cephalosporin C in order to efficiently acquire the starting compound for the industrial production of semisynthetic cephalosporin antibiotics. In this study, the active site of the glutaryl acylase from Pseudomonas SY-77 was randomized rationally. Several mutations that were found in previous studies to enhance the activity of the enzyme towards adipyl-7-aminodesacetoxycephalosporanic acid (ADCA) and cephalosporin C have now been combined, and libraries have been made in which random amino acid substitutions at these positions are joined. The mutants were expressed in a leucine-deficient Escherichia coli strain and subjected to growth selection with adipyl-leucine or amino-adipyl-leucine as sole leucine source. The mutants growing on these media were selected and purified, and their hydrolysis activities towards adipyl-7-ADCA and cephalosporin C were tested. Several mutants with highly improved activities towards the desired substrates were found in these rationally randomized libraries. The best mutant was selected from a library of totally randomized residues: 178, 266, and 375. This mutant comprises two mutations, Y178F + F375H, which synergistically improve the catalytic efficiency towards adipyl-7-ADCA 36-fold. The activity of this mutant towards adipyl-7-ADCA is 50% of the activity of the wild-type enzyme towards the preferred substrate glutaryl-7-aminocephalosporanic acid, and therefore the characteristics of this mutant approach those needed for industrial application.     

Behavioral patterns of two fiddler crab species Uca rapax and Uca tangeri in a seminatural mangrove system

Zoos increasingly transform their exhibitions from traditional one‐species enclosures to more natural exhibits, that is, environments that capture part of an ecosystem including a selection of animals and plants that occur there. Thus, enhancing the experience of its human visitors while also allowing its residents to possibly show more natural behavior. In 2017 Royal Burger's Zoo (Arnhem, The Netherlands) created and opened a mangrove‐like environment containing fiddler crabs. Fiddler crabs display a broad range of behaviors, and this research examines which wild‐type behavior and behavioral patterns can be observed on a seminatural mudflat. The behavior shown by Uca rapax and Uca tangeri on the mudflat was counted each hour between 07:00 and 17:00. An asymmetric tidal regime was present in the enclosure including two high water periods. Various known fiddler crab behaviors, including waving and combat, were observed but no copulation. A clear pattern in exposed crabs on the mudflat was found, with low numbers visible in the early morning and the highest numbers present in the early afternoon, while number of visitors did not have a significant effect on this pattern. Interestingly, the highest abundances were not observed around the ebbing tide (07:00–09:00), as observed in the wild, but somewhat later, possibly due to the asymmetric tidal scheme or the interaction of tidal and daily rhythms. This study shows that in captivity, fiddler crabs indeed show a range of natural behaviors which is linked to the tidal and possibly daily rhythm as well.     

Kinetics and mass-transfer phenomena in anaerobic granular sludge

The kinetic properties of acetate-degrading methanogenic granular sludge of different mean diameters were assessed at different up-flow velocities (V(up)). Using this approach, the influence of internal and external mass transfer could be estimated. First, the apparent Monod constant (K(S)) for each data set was calculated by means of a curve-fitting procedure. The experimental results revealed that variations in the V(up) did not affect the apparent K(S)-value, indicating that external mass-transport resistance normally can be neglected. With regard to the granule size, a clear increase in K(S) was found at increasing granule diameters. The experimental data were further used to validate a dynamic mathematical biofilm model. The biofilm model was able to describe reaction-diffusion kinetics in anaerobic granules, using a single value for the effective diffusion coefficient in the granules. This suggests that biogas formation did not influence the diffusion-rates in the granular biomass.     

Post-genomics of lactic acid bacteria and other food-grade bacteria to discover gut functionality

Recent years have seen an explosion in the number of complete or almost complete genomic sequences of lactic acid bacteria and other food-grade bacteria that are used in functional foods to increase the health of the consumer. These have been instrumental in the development of functional, comparative and other post-genomics approaches that provide the possibility to detect, unravel and understand their functionality in the human intestinal tract. In conjunction with other high-throughput approaches, these advances can be exploited in the functional food innovation cycle for developing new or designed probiotic and other bacterial products that impact gut health.