Search

Premise: Mycoheterotrophic plants rely on fungi to obtain their carbon requirements. Recent experiments demonstrated the presence of endophytic bacteria associated with mycoheterotrophs. Although mycoheterotrophs show high specificity for their fungal partners, it is not known whether they also show high specificity for associated bacteria or whether the bacteria have a definite function in the symbiosis. Methods: Two 16S rRNA sequencing experiments were designed to explore endophytic microbial community composition and function in root ball fractions of the mycoheterotroph Pterospora andromedea (Ericaceae), and rhizosphere soil and control soil 5 m away from each plant. One experiment compared microbial assemblages in fractions of six plants to those in rhizosphere and control soil samples. Another experiment documented bacterial endophyte diversity in root balls of 97 plants from across North America. Results: Soil samples were similar in bacterial community structure but were significantly more diverse and less consistently structured than were bacterial communities within root balls. The proportion of endophytic bacterial species varied slightly but not their community composition despite differences in P. andromedea lineage, geography, conifer species, and fungi. Predictive metagenomic profiling of the endophytes in P. andromedea‐only root ball fractions showed many of the bacterial endophytes likely function in N‐metabolism and N‐fixation. Conclusions: Our results document a consistent and largely invariant community of endophytic bacteria in P. andromedea across biotic and abiotic environmental conditions at a continental scale. It is unknown what role these bacteria may play in the quad‐partite symbiotic network centered on P. andromedea; however, the predictive metagenomic profiling suggests a possible function in N‐metabolism or N‐fixation. Discovery of a ubiquitous community of endophytic bacteria with a putative function centered on N‐metabolism or N‐fixation could have a previously unrecognized impact on understanding of mycoheterotroph ecophysiology. [ABSTRACT FROM AUTHOR]

Recent declines in coral populations along the Florida reef tract have prompted the establishment of coral restoration programs which raise coral species, such as the threatened Acropora cervicornis, in nurseries ready for outplanting. Large numbers of nursery-reared coral colonies have been outplanted along the Florida reef tract in recent years, yet few studies have characterized benthic habitats that are considered optimal for colony survival. In 2016, we surveyed 23 A. cervicornis restoration sites, located at six different reefs in the upper Florida Keys. We examined the condition of the outplanted corals and quantified the benthic assemblages adjacent to the outplanted coral colonies. We found that where A. cervicornis survived for more than 1 year, the substrate significantly supported less brown macroalgae of the genus Dictyota than at sites where A. cervicornis had died. Coral survival was highest at sites with less than 15% Dictyota cover. These results suggest that the habitat conditions that supported Dictyota spp. were not conducive to A. cervicornis growth and survival. Restoration practitioners should avoid attaching nursery-raised corals to substrate with Dictyota spp. cover greater than 15%. [ABSTRACT FROM AUTHOR]

One of the deleterious effects of acute nerve agent exposure is the induction of status epilepticus (SE). If SE is not controlled effectively, it causes extensive brain damage. Here, we review the neuropathology observed after nerve agent-induced SE, as well as the ensuing pathophysiological, neurological, and behavioral alterations, with an emphasis on their time course and longevity. Limbic structures are particularly vulnerable to damage by nerve agent exposure. The basolateral amygdala (BLA), which appears to be a key site for seizure initiation upon exposure, suffers severe neuronal loss; however, GABAergic BLA interneurons display a delayed death, perhaps providing a window of opportunity for rescuing intervention. The end result is a long-term reduction of GABAergic activity in the BLA, with a concomitant increase in spontaneous excitatory activity; such pathophysiological alterations are not observed in the CA1 hippocampal area, despite the extensive neuronal loss. Hyperexcitability in the BLA may be at least in part responsible for the development of recurrent seizures and increased anxiety, while hippocampal damage may underlie the long-term memory impairments. Effective control of SE after nerve agent exposure, such that brain damage is also minimized, is paramount for preventing lasting neurological and behavioral deficits. [ABSTRACT FROM AUTHOR]

Amorphous Boron Nitride (a-BN) is an important starting material for the synthesis of cubic BN (c-BN). However, information on the synthesis methods and the characteristics of a-BN are not sufficiently discussed in the literature. The purpose of this study is to understand the conversion of precursor chemicals to a-BN and to illustrate the effects of starting material and heat treatment conditions on the formation and characteristics of a-BN. Boric acid (H3BO3) and melamine (C3H6N6) were used as starting materials and the starting composition range was selected to be between 1:1 and 6:1 molar ratios (H3BO3:C3H6N6). Two-step solid state reaction method was applied for the synthesis of a-BN: First heat-treatment at 200°C for 2 hours in air and the second heat treatment at selected temperatures for 3 hours in N2 gas atmosphere. To determine the condition region for the synthesis of a-BN, synthesized powders were characterized using Xray diffraction, Raman and FTIR spectroscopies which showed different sensitivity for detecting crystalline phase in the powders. The condition regions for the synthesis of a-BN were determined to be between 400°C and 600°C for the composition range of 1:1 and 1.5:1. Crystallization was observed at lower temperatures for the samples with higher H3BO3 content in the H3BO3-C3H6N6 system. [ABSTRACT FROM AUTHOR]

• Russula brevipes is common ectomycorrhizal (EM) fungus that is associated with several hosts across temperate forest ecosystems. A previous study has demonstrated that substructuring across large geographic distances (1500 km) occurs in the western USA. • To examine genetic structure over a more localized scale, basidiocarps of Russula brevipes from three subpopulations, separated by distances of 230–1090 m, were collected over two consecutive years in an oak/pine woodland. Microsatellite loci were used to test for population differentiation both among subpopulations and by year. • No significant population differentiation was detected between subpopulations (θST = 0.01) or between years (θST = 0.01). Most loci were consistent with a Hardy–Weinburg equilibrium and 82% of the genets between seasons from similar sampling localities constituted new genotypes. • These results indicate that R. brevipes constitutes a randomly mating population with no genetic differentiation between locations or across successive fruiting seasons. [ABSTRACT FROM AUTHOR]

Presents a study which documented the changes in nutrient fluxes associated with internal tidal bores arriving on Florida Keys coral reefs. Background of studies on the anthropogenic factors associated with reductions in herbivore populations and the input of dissolved nutrients to reef environments; Methods used; Characteristics of temperature variability across reef sites; Analysis of hydrography and nutrients; Estimates of nitrogen and phosphorus input.

Summary • The spatial mapping of genets from sporocarps allows determination of the primary modes of reproduction of ectomycorrhizal fungi. The goals of this research were to determine the relative size, density, and persistence of genets of Russula brevipes , a late successional basidiomycete, in mature stands of lodgepole pine ( Pinus contorta ) and Sitka spruce ( Picea sitchensis ). • Sporocarps were mapped and genets were identified using species-specific hypervariable microsatellite markers. • Most of the sporocarps sampled in clumped aggregations were the same genet and occupied areas less than 3 m. The largest distance measured between two sporocarps of the same genet was 18 m. In local populations of R. brevipes associated with Sitka spruce, genets were comprised of largely related individuals, whereas in lodgepole pine, most genets appeared unrelated. • High genotypic diversity in Sitka spruce stands suggests frequent mating and recombination between local inhabitants from primary establishment of basidiospores. In lodgepole pine, fewer, unrelated genotypes of R. brevipes indicates that multiple sources of colonization arose from infrequent, long distance spore dispersal events. [ABSTRACT FROM AUTHOR]