ZOOTAXA

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Ecological importance of soil bacterivores for ecosystem functions

BackgroundBacterivores, mostly represented by protists and nematodes, are a key component of soil biodiversity involved in soil fertility and plant productivity. In the current context of global change and soil biodiversity erosion, it becomes urgent to suitably recognize and quantify their ecological importance in ecosystem functioning.ScopeUsing meta-analysis tools, we aimed at providing a quantitative synthesis of the ecological importance of soil bacterivores on ecosystem functions. We also intended to produce an overview of the ecological factors that are expected to drive the magnitude of bacterivore effects on ecosystem functions.ConclusionsBacterivores in soil contributed significantly to numerous key ecosystem functions. We propose a new theoretical framework based on ecological stoichiometry stressing the role of C:N:P ratios in soil, microbial and plant biomass as important parameters driving bacterivore-effects on soil N and P availability for plants, immobilization of N and P in the bacterial biomass, and plant responses in nutrition and growth

Pseudomonas fluorescens CHA0 maintains carbon delivery to Fusarium graminearum-infected roots and prevents reduction in biomass of barley shoots through systemic interactions

Soil bacteria such as pseudomonads may reduce pathogen pressure for plants, both by activating plant defence mechanisms and by inhibiting pathogens directly due to the production of antibiotics. These effects are hard to distinguish under field conditions, impairing estimations of their relative contributions to plant health. A split-root system was set up with barley to quantify systemic and local effects of pre-inoculation with Pseudomonas fluorescens on the subsequent infection process by the fungal pathogen Fusarium graminearum. One root half was inoculated with F. graminearum in combination with P. fluorescens strain CHA0 or its isogenic antibiotic-deficient mutant CHA19. Bacteria were inoculated either together with the fungal pathogen or in separate halves of the root system to separate local and systemic effects. The short-term plant response to fungal infection was followed by using the short-lived isotopic tracer 11CO2 to track the delivery of recent photoassimilates to each root half. In the absence of bacteria, fungal infection diverted carbon from the shoot to healthy roots, rather than to infected roots, although the overall partitioning from the shoot to the entire root system was not modified. Both local and systemic pre-inoculation with P. fluorescens CHA0 prevented the diversion of carbon as well as preventing a reduction in plant biomass in response to F. graminearum infection, whereas the non-antibiotic-producing mutant CHA19 lacked this ability. The results suggest that the activation of plant defences is a central feature of biocontrol bacteria which may even surpass the effects of direct pathogen inhibition

The holistic rhizosphere: integrating zones, processes, and semantics in the soil influenced by roots

Despite often being conceptualized as a thin layer of soil around roots, the rhizosphere is actually a dynamic system of interacting processes. Hiltner originally defined the rhizosphere as the soil influenced by plant roots. However, soil physicists, chemists, microbiologists, and plant physiologists have studied the rhizosphere independently, and therefore conceptualized the rhizosphere in different ways and using contrasting terminology. Rather than research-specific conceptions of the rhizosphere, the authors propose a holistic rhizosphere encapsulating the following components: microbial community gradients, macroorganisms, mucigel, volumes of soil structure modification, and depletion or accumulation zones of nutrients, water, root exudates, volatiles, and gases. These rhizosphere components are the result of dynamic processes and understanding the integration of these processes will be necessary for future contributions to rhizosphere science based upon interdisciplinary collaborations. In this review, current knowledge of the rhizosphere is synthesized using this holistic perspective with a focus on integrating traditionally separated rhizosphere studies. The temporal dynamics of rhizosphere activities will also be considered, from annual fine root turnover to diurnal fluctuations of water and nutrient uptake. The latest empirical and computational methods are discussed in the context of rhizosphere integration. Clarification of rhizosphere semantics, a holistic model of the rhizosphere, examples of integration of rhizosphere studies across disciplines, and review of the latest rhizosphere methods will empower rhizosphere scientists from different disciplines to engage in the interdisciplinary collaborations needed to break new ground in truly understanding the rhizosphere and to apply this knowledge for practical guidance

Interview with Rosetta Daylie

Length: 71 minutes Oral history interview of Rosetta Daylie by Sarah Bonkowsk

Including food systems, biodiversity, nutrition and health in the Post-2020 Global Biodiversity Framework: a submission from the Alliance of Bioversity International and the International Center for Tropical Agriculture.

Tice_etal.2016.SupplementalText.pdf. Supplementary text that includes: an extended materials and methods section, details of light microscope observations, and a discussion on the justification for taxonomic reassignment of Stereomyxa ramosa ATCC® 50982™. (PDF 524 kb

Technologies for tissue culture electrophysiologic recording

The development of tissue culture electrophysiology has been hindered by these numerous technological problems. The function of this thesis was to identify and propose solutions to these technological problems and concurrently develop a system for prolonged intracellular GME monitoring (30 to 40 hours) of membrane parameters from cells grown in tissue culture. The technological problems identified in the present study and for which solutions have been proposed are: (1) Maintenance of a sterile environment for an open tissue culture vessel in which GME measurements can be made for periods exceeding 30 to 40 hours.; (2) Elimination of environmental electrical interference which normally interferes with GME recording and data displaying.; (3) Design of an optical instrumentation system that is compatible with microelectrode penetration needs and tissue culture cell observation.; (4) Elimination of building and peripheral instrument vibrational influences at the microelectrode recording site.; (5) A method of microelectrode preparation that would produce consistent glass microelectrodes meeting the peculiar needs of tissue culture electrophysiology.; (6) Design of a culture recording chamber which would permit: (a) culturing of cells using standard tissue culture techniques.; (b) easy access of cells for microelectrode penetration.; (c) continuous optical observation.; (d) continuous temperature regulation of cultured cells for periods exceeding 30 to 40 hours.; (e) shielding against electrical field disturbances during microelectrode recording.; (f) rapid perfusion of media to the chamber without causing harsh turbulence allowing continuous intracellular recording via glass microelectrode even during perfusion of substances.; (g) microelectrodes penetration of cells over a wide range of angles.; (7) Design of a complete intracellular tissue culture electrophysiology monitoring system.; and (8) Development of explant and culturing procedures to provide cell substrate to test the effectiveness of the tissue culture electrophysiology system design

Organic matter composition and the protist and nematode communities around anecic earthworm burrows

By living in permanent burrows and incorporating organic detritus from the soil surface, anecic earthworms contribute to soil heterogeneity, but their impact is still under-studied in natural field conditions. We investigated the effects of the anecic earthworm Lumbricus centralis on fresh carbon (C) incorporation, soil organic matter composition, protists, and nematodes of a Cambisol under grassland. We used plant material labelled with stable isotope tracers to detect fresh C input around earthworm-occupied burrows or around burrows from which the earthworm had been removed. After 50 days, we sampled soil (0–10 cm depth) in concentric layers around the burrows, distinguishing between drilosphere (0–8 mm) and bulk soil (50–75 mm). L. centralis effectively incorporated fresh C into the drilosphere, and this shifted soil organic matter amount and chemistry: total soil sugar content was increased compared to unoccupied drilosphere and bulk soil, and the contribution of plant-derived sugars to soil organic matter was enhanced. Earthworms also shifted the spatial distribution of soil C towards the drilosphere. The total abundance of protists and nematodes was only slightly higher in earthworm-occupied drilosphere, but strong positive effects were found for some protist clades (e.g. Stenamoeba spp.). Additional data for the co-occurring anecic earthworm species Aporrectodea longa showed that it incorporated fresh C less than L. centralis, suggesting that the two species may have different effects on soil C distribution and organic matter quality

Larval development and breeding ecology of Ziegler's crocodile newt, Tylototriton ziegleri Nishikawa, Matsui and Nguyen, 2013 (Caudata: Salamandridae), compared to other Tylototriton representatives

We describe for the first time the larval development and stages of the recently described Ziegler's Crocodile Newt (Tylototriton ziegleri), an endemic species to northern Vietnam. Diagnostic morphological characters are provided for Grosse (1997, 2013) stages 27-32, 35-36, and 44-45, as well as comparisons with larval stages of other Tylototriton representatives. In addition, natural history data and an ecological assessment of the breeding niche are presented for T. ziegleri as well as for T. vietnamensis, from whom the former species was only recently taxonomically separated. We provide data extending the known breeding season of these two cryptic species in the North of Vietnam, which in fact lasts from April until July. On average, the clutches of T. ziegleri consisted of 67 +/- 32 eggs, were found on rock and soil substrates with a distance of 50 +/- 28 cm from water, whereas the clutches of T. vietnamensis were significantly smaller (43 +/- 19 eggs), found only on soil and were further distant from water (80 +/- 41 cm). The known maximum altitudinal distribution of T. vietnamensis is herein increased to 980 m above sea level. Based on the examples of T. ziegleri and T. vietnamensis, this study highlights how important it is to uncover cryptic species, define their exact distribution range, and investigate potential differences in ecological adaptations in order to assess the conservation status, develop proper conservation planning and provide suitable conditions for potential ex situ breeding programs