Bacterial colonization of the phyllosphere of nineteen plant species and antimicrobial activity of their leaf secondary metabolites against leaf associated bacteria

Summary. The scope of this work was to examine whether leaf constitutive secondary metabolites play a role in determining bacterial colonization of the phyllosphere. To this aim, we surveyed nineteen native or cultivated plant species that share a common bacterial pool in a North Mediterranean area, and estimated the size of total and ice nucleation active (INA) bacterial populations on their leaves. Large differences in the colonization of their phyllosphere were found; the population size of epiphytic bacteria ranged from 7.5 × 10² to 1 × 10⁶ CFU/g fresh weight, in eucalypt and celery, respectively. Species native in Mediterranean-type climate areas, particularly those belonging to the group of aromatic plants, are characterized by scarce presence of INA bacteria. The antibacterial activity of essential oils, surface phenolics and leaf tissue extracts was also estimated against the INA strains P. syringae and E. herbicola, isolated from two of these plant species. E. herbicola proved more sensitive than P. syringae. Of the species examined, oregano [Origanum vulgare L. subsp. hirtum (Link.) Ietswaart], an aromatic plant, had the highest antimicrobial activity, whereas six species showed no activity at all. Further experiments were performed with oregano and bean (Phaseolus vulgaris L.) that represent two extremes in their secondary metabolite content. Both plants were inoculated with P. syringae. By the end of incubation, the bacterial population on bean plants was about 100 times higher than that on oregano leaves. Scanning electron micrographs showed that bacterial growth on oregano leaves was confined to sites away from glandular hairs. Results from the bacterial colonization survey together with those from the toxicity tests showed that all species rich in antibacterial secondary metabolites harbored low leaf bacterial populations. These results provide substantial evidence that leaf secondary metabolites function as constitutive defense chemicals against microbial invasions. However, the fact that species with non- or moderately active leaf secondary metabolites are not always highly colonized suggests mediation of other unknown factors, the contribution of which requires further investigation.     

Composting of vegetable waste.

The effects of the aeration, seeding, and agitation on the composting of vegetable waste were studied in a laboratory-scale reactor. Experimental results showed that the final product at the end of a 4-day composting period met multiple maturity indices suggested by many researchers. The evolution of carbon dioxide during the composting process could be modelled with a modified Gompertz equation that described the bacteria growth successfully. Multivariate regression analysis was used to study the effects of operating parameters on the carbon conversion. The response surface contour plots were constructed using the regression equation for the examination of the dependence of carbon conversion on operating parameters. The maximum carbon conversion of 14.54% was obtained when the percentage of seeding was set at 14.5%, the air suction rate was set at 2.6 L kg(-1) dry-solid min(-1), and the agitator operated half of the time, alternating on and off for every 5 min. Future work will focus on the application of the data and the experience gained in this work to composters of pilot and semi-commercial scales.     

Presence–Absence versus Abundance Data for Monitoring Threatened Species

Abstract:  Effective detection of population trend is crucial for managing threatened species. Little theory exists, however, to assist managers in choosing the most cost-effective monitoring techniques for diagnosing trend. We present a framework for determining the optimal monitoring strategy by simulating a manager collecting data on a declining species, the Chestnut-rumped Hylacola ( Hylacola pyrrhopygia parkeri ), to determine whether the species should be listed under the IUCN (World Conservation Union) Red List. We compared the efficiencies of two strategies for detecting trend, abundance, and presence–absence surveys, under financial constraints. One might expect the abundance surveys to be superior under all circumstances because more information is collected at each site. Nevertheless, the presence–absence data can be collected at more sites because the surveyor is not obliged to spend a fixed amount of time at each site. The optimal strategy for monitoring was very dependent on the budget available. Under some circumstances, presence–absence surveys outperformed abundance surveys for diagnosing the IUCN Red List categories cost-effectively. Abundance surveys were best if the species was expected to be recorded more than 16 times/year; otherwise, presence–absence surveys were best. The relationship between the strategies we investigated is likely to be relevant for many comparisons of presence–absence or abundance data. Managers of any cryptic or low-density species who hope to maximize their success of estimating trend should find an application for our results.     

Separation of fine binary mixtures under vibration in a gas-solid fluidized bed with dense medium.

The coke-slag mixture discharged from water-air generators not only causes a serious environmental problem, but also is a potential resource. In order to obtain a high economic return, separation of fine binary mixtures in a vibrating fluidized bed with dense media was experimentally investigated. The effects of volume ratio (mono-component volume to dense medium volume or binary mixture volume to dense medium volume), the fluidization velocity and vibration parameters on separation efficiency are discussed. The experimental results show that vibration can prevent the coalescence and growth of bubbles and improve fluidization properties of particles and the stability of bed density. The major factors associated with separating efficiency are discussed. Based on the experiments, the ratio of the volume of particles to bed volume and the vibration conditions are also reported. It was found that the separation efficiency for a fine coke-slag mixture was greater than 70% and close to 80% under optimal conditions.     

Use of Ordination Techniques to Follow Community Succession from Oil Impact to Recovery in the Field

Much effort has been directed toward elucidating pollution effects on marine benthic communities (Pearson and Rosenberg, 1978; Sanders et al., 1980; NAS 1985). Less effort has been directed at methods of data analysis which will identify distribution patterns and relationships between communities. Traditional community structure summary parameters such as species richness and various indices of diversity utilize only part of the information contained in a data set and are not very useful in elucidating relationships between communities of animals.     

Negotiations after the sale: The roots and ramifications of conflict in an acquisition

This paper presents a case study of negotiations over the combination of a small manufacturing firm into a multi-billion dollar conglomerate following its 'white knight' acquisition. It focuses on the strategic and tactical conflicts between the two firms and traces these to the party's emotional reactions to the combination. Feeling of loss versus gain in the two firms, each party's sense of uncertainty and threat, and their moves toward proactive versus reactive control in the combination are analysed to identify the roots of strategic conflict. These feelings, plus incompatibilities in the two company's managements, business systems, corporate cultures, and goals for combination ramify in conflict in the negotiations themselves. The paper concludes with a more generic model illustrating contextual features of combinations that shape human reactions and conflicts in negotiations after the sale.     

Density, velocity and flow relationships for closely packed crowds

Work undertaken to quantify the relationships between crowd velocities, flow rates and densities for uni-directional motion is reviewed. Most of the available data has been generated for underground stations in the UK; similar work for commuter stations in Japan is introduced and developed. Maximum observed flow rates from this work are compared with those suggested in the ‘Green Guide’ for the evacuation of sports grounds. The ‘Green Guide’ figures are higher than the maximum values obtained from the work reviewed.