The Role of Demography in the Transition to Sustainable Societies

Currently, although the global population has surpassed 7.5 billion and continues to increase in about 80 million each year, attention to demography is almost absent in most of the studies and publications related to the current situation of planetary emergency and the necessary transition to sustainable societies. For this reason, our first aim in this paper has been to discuss if this current lack of attention to demography is justified or not. With this purpose, we begin considering the scientific meaning of Sustainability, in order to overlay distorted and impoverish views of this concept that may hinder our study. Then, we analyse the reasons given by experts for and against the incidence of demographic growth in the current unsustainable situation of planetary emergency. Finally, we present proposals to face the ensemble of interconnected socio-environmental problems (including demographic evolution), to make possible an appropriate transition to sustainable societies. Aunque la población mundial ha sobrepasado los 7500 millones y continúa aumentando anualmente en alrededor de 80 millones, la atención a la demografía está hoy prácticamente ausente en la mayoría de los estudios y publicaciones acerca de la actual situación de emergencia planetaria y la necesidad de una transición a sociedades sostenibles. Con el propósito de analizar si esta falta de atención a la demografía está o no justificada, en esta contribución comenzamos discutiendo el significado científico de Sostenibilidad socioambiental, para evitar concepciones distorsionadas y empobrecidas de este concepto que pueden dificultar dicho análisis. A continuación estudiaremos las razones dadas por distintos expertos a favor y en contra de la incidencia del crecimiento demográfico en la insostenible situación actual de emergencia planetaria. Finalmente presentamos propuestas para hacer frente al conjunto de problemas estrechamente interconectados - incluido el problema demográfico - que caracterizan dicha situación, para hacer así posible una adecuada transición a sociedades sostenibles

Wheat seed embryo excision enables the creation of axenic seedlings and Koch’s postulates testing of putative bacterial endophytes

Early establishment of endophytes can play a role in pathogen suppression and improve seedling development. One route for establishment of endophytes in seedlings is transmission of bacteria from the parent plant to the seedling via the seed. In wheat seeds, it is not clear whether this transmission route exists, and the identities and location of bacteria within wheat seeds are unknown. We identified bacteria in the wheat (Triticum aestivum) cv. Hereward seed environment using embryo excision to determine the location of the bacterial load. Axenic wheat seedlings obtained with this method were subsequently used to screen a putative endophyte bacterial isolate library for endophytic competency. This absence of bacteria recovered from seeds indicated low bacterial abundance and/or the presence of inhibitors. Diversity of readily culturable bacteria in seeds was low with 8 genera identified, dominated by Erwinia and Paenibacillus. We propose that anatomical restrictions in wheat limit embryo associated vertical transmission, and that bacterial load is carried in the seed coat, crease tissue and endosperm. This finding facilitates the creation of axenic wheat plants to test competency of putative endophytes and also provides a platform for endophyte competition, plant growth, and gene expression studies without an indigenous bacterial background

Effect of bacterial distribution and activity on conjugal gene transfer on the phylloplane of bush bean (Phaseolus vulgaris). Appl Environ Microbiol 64

2 , corresponding to about one-third of the recipient population. At 25% RH, numbers of transconjugants were below the detection limit. Immediately after inoculation onto the leaves, the per-cell metabolic activity of the inocula increased by up to eight times (100% RH), followed by a decrease to the initial level after 96 h. The metabolic activity of the bacteria was not rate limiting for conjugation, and no correlation between the two parameters was observed. Apparently, leaf exudates insured that the activity of the bacteria was above a threshold value for transfer to occur. Transconjugants were primarily observed in junctures between epidermal cells and in substomatal cavities. The distribution of the transconjugants was similar to the distribution of indigenous bacteria on nonsterile leaves. Compared to polycarbonate filters, with cell densities equal to the overall density on the leaves, transfer ratios on leaves were up to 30 times higher. Thus, aggregation of the bacteria into microhabitats on the phylloplane had a great stimulatory effect on transfer

Green Fluorescent Protein-Marked Pseudomonas fluorescens: Localization, Viability, and Activity in the Natural Barley Rhizosphere

The gfp-tagged Pseudomonas fluorescens biocontrol strain DR54-BN14 was introduced into the barley rhizosphere. Confocal laser scanning microscopy revealed that the rhizoplane populations of DR54-BN14 on 3- to 14-day-old roots were able to form microcolonies closely associated with the indigenous bacteria and that a majority of DR54-BN14 cells appeared small and almost coccoid. Information on the viability of the inoculant was provided by a microcolony assay, while measurements of cell volume, the intensity of green fluorescent protein fluorescence, and the ratio of dividing cells to total cells were used as indicators of cellular activity. At a soil moisture close to the water-holding capacity of the soil, the activity parameters suggested that the majority of DR54-BN14 cells were starving in the rhizosphere. Nevertheless, approximately 80% of the population was either culturable or viable but nonculturable during the 3-week incubation period. No impact of root decay on viability was observed, and differences in viability or activity among DR54-BN14 cells located in different regions of the root were not apparent. In dry soil, however, the nonviable state of DR54-BN14 was predominant, suggesting that desiccation is an important abiotic regulator of cell viability