Biodiversity,science and development. Towards a new partnership. Edited by F. di Castri and T. Youne´s

World Journal of Microbiology and Biotechnology -     

Osmoregulation in Rhizobium meliloti: inhibition of growth by salts

A defined medium of low osmolarity was developed permitting growth of Rhizobium meliloti with generation times of approximately 2.8 h doubling^-1. The effects of sodium, potassium, magnesium, ammonium, chloride, sulfate, phosphate, bicarbonate and acetate ions on the growth rate of R. meliloti were determined. Sodium, potassium and ammonium ions had little effect on growth at concentrations of 100 mEq or less; magnesium ion inhibited growth severely at concentrations of 50 mEq (25 mM). Of the anions, chloride and sulfate appeared to have little effect while phosphate, bicarbonate, and acetate inhibited growth at concentrations of as little as 25 mEq. The addition of proline, glutamate, or betaine to cells growing in inhibitory concentrations of NaCl did not relieve the inhibition. When grown in the presence of inhibitory levels of NaCl, the intracellular concentration of glutamate but not of proline or gamma amino butyric acid increased 5-fold.     

Frequency responses of age-structured populations: Pacific salmon as an example

Increasing evidence of the effects of changing climate on physical ocean conditions and long-term changes in fish populations adds to the need to understand the effects of stochastic forcing on marine populations. Cohort resonance is of particular interest because it involves selective sensitivity to specific time scales of environmental variability, including that of mean age of reproduction, and, more importantly, very low frequencies (i.e., trends). We present an age-structured model for two Pacific salmon species with environmental variability in survival rate and in individual growth rate, hence spawning age distribution. We use computed frequency response curves and analysis of the linearized dynamics to obtain two main results. First, the frequency response of the population is affected by the life history stage at which variability affects the population; varying growth rate tends to excite periodic resonance in age structure, while varying survival tends to excite low frequency fluctuation with more effect on total population size. Second, decreasing adult survival strengthens the cohort resonance effect at all frequencies, a finding that addresses the question of how fishing and climate change will interact.     

Gut microbiota composition is associated with environmental landscape in honey bees

There is growing recognition that the gut microbial community regulates a wide variety of important functions in its animal hosts, including host health. However, the complex interactions between gut microbes and environment are still unclear. Honey bees are ecologically and economically important pollinators that host a core gut microbial community that is thought to be constant across populations. Here, we examined whether the composition of the gut microbial community of honey bees is affected by the environmental landscape the bees are exposed to. We placed honey bee colonies reared under identical conditions in two main landscape types for 6 weeks: either oilseed rape farmland or agricultural farmland distant to fields of flowering oilseed rape. The gut bacterial communities of adult bees from the colonies were then characterized and compared based on amplicon sequencing of the 16S rRNA gene. While previous studies have delineated a characteristic core set of bacteria inhabiting the honey bee gut, our results suggest that the broad environment that bees are exposed to has some influence on the relative abundance of some members of that microbial community. This includes known dominant taxa thought to have functions in nutrition and health. Our results provide evidence for an influence of landscape exposure on honey bee microbial community and highlight the potential effect of exposure to different environmental parameters, such as forage type and neonicotinoid pesticides, on key honey bee gut bacteria. This work emphasizes the complexity of the relationship between the host, its gut bacteria, and the environment and identifies target microbial taxa for functional analyses.     

Connectivity and resilience of coral reef metapopulations in marine protected areas: matching empirical efforts to predictive needs

Design and decision-making for marine protected areas (MPAs) on coral reefs require prediction of MPA effects with population models. Modeling of MPAs has shown how the persistence of metapopulations in systems of MPAs depends on the size and spacing of MPAs, and levels of fishing outside the MPAs. However, the pattern of demographic connectivity produced by larval dispersal is a key uncertainty in those modeling studies. The information required to assess population persistence is a dispersal matrix containing the fraction of larvae traveling to each location from each location, not just the current number of larvae exchanged among locations. Recent metapopulation modeling research with hypothetical dispersal matrices has shown how the spatial scale of dispersal, degree of advection versus diffusion, total larval output, and temporal and spatial variability in dispersal influence population persistence. Recent empirical studies using population genetics, parentage analysis, and geochemical and artificial marks in calcified structures have improved the understanding of dispersal. However, many such studies report current self-recruitment (locally produced settlement/settlement from elsewhere), which is not as directly useful as local retention (locally produced settlement/total locally released), which is a component of the dispersal matrix. Modeling of biophysical circulation with larval particle tracking can provide the required elements of dispersal matrices and assess their sensitivity to flows and larval behavior, but it requires more assumptions than direct empirical methods. To make rapid progress in understanding the scales and patterns of connectivity, greater communication between empiricists and population modelers will be needed. Empiricists need to focus more on identifying the characteristics of the dispersal matrix, while population modelers need to track and assimilate evolving empirical results.     

Seed dormancy release and germination characteristics of <i>Corispermum lehmannianum</i> Bunge,an endemic species in the Gurbantunggut desert of China

Seed dormancy release and germination of Corispermum lehmannianum Bunge were tested using various treatments: temperature, cold stratification, gibberelins (GA3), dry storage and sand burial. Results showed that temperature and light did not affect the germination of fresh seeds, cold stratification and GA3 could improve seed germination, whereas dry storage and sand burial did not. The germination percentage was highest at 35/20 °C after the cold stratification and GA3 treatments. Corispermum lehmannianum seeds were classified as non-deep, Type-2, physiological dormancy (PD), whose seed dormancy could be released by cold stratification and GA3.