Flooding Greatly Affects the Diversity of Arbuscular Mycorrhizal Fungi Communities in the Roots of Wetland Plants

The communities of arbuscular mycorrhizal fungi (AMF) colonizing the roots of three mangrove species were characterized along a tidal gradient in a mangrove swamp. A fragment, designated SSU-ITS-LSU, including part of the small subunit (SSU), the entire internal transcribed spacer (ITS) and part of the large subunit (LSU) of rDNA from samples of AMF-colonized roots was amplified, cloned and sequenced using AMF-specific primers. Similar levels of AMF diversity to those observed in terrestrial ecosystems were detected in the roots, indicating that the communities of AMF in wetland ecosystems are not necessarily low in diversity. In total, 761 Glomeromycota sequences were obtained, which grouped, according to phylogenetic analysis using the SSU-ITS-LSU fragment, into 23 phylotypes, 22 of which belonged to Glomeraceae and one to Acaulosporaceae. The results indicate that flooding plays an important role in AMF diversity, and its effects appear to depend on the degree (duration) of flooding. Both host species and tide level affected community structure of AMF, indicating the presence of habitat and host species preferences

Effect of water hardness on peracetic acid toxicity to zebrafish, Danio rerio, embryos

The use of peracetic acid (PAA) in aquaculture has been suggested as an alternative therapeutic agent. Few data are available concerning fish toxicity by PAA or factors that modify this toxicity. The aim of this study was to investigate the influence of water hardness on the acute toxicity of PAA products to embryos of zebrafish (Danio rerio). Embryos were exposed to PAA ranging from 0 to 9 mg/L in low-hardness (1. 4 °dH or 25 mg/L hardness as CaCO3), medium-hardness (14 °dH or 250 mg/L hardness as CaCO3) and high-hardness (140 °dH or 2,500 mg/L hardness as CaCO3) waters. The lowest LC50 value was 2. 24 mg/L PAA in the low-hardness water, and the highest LC50 value was 7. 14 mg/L PAA in the high-hardness water. Toxicity of PAA to embryos was found to be negatively correlated with water hardness. The pH decreased with increasing concentrations of PAA, and the test waters were observed to become more acidic in low hardness. In conclusion, aquaculturists using PAA should pay attention to water hardness to avoid acidosis. © 2012 Springer Science+Business Media Dordrecht

Advances in Arbuscular Mycorrhizal Taxonomy

Taxonomy, the science of classifying organisms, describes names, identifies organisms, and generates tools for taxonomic identification of fungi. The products of taxonomy are used by taxonomists and ecologists. Correct species names are deliberately used for instance on land management systems to compare ecological interactions between the different components. Current classification systems of Arbuscular mycorrhizal fungi (AMF, Glomeromycota) involve both morphological and molecular tools and their progress shows in some measure a natural organization and understanding of the relationships among species. Several research groups have been discussing the taxonomy, systematics, and evolution of AMF. The researchers may propose their classification system; however, most biologists believe that these developing systems only reflect our knowledge at time. This chapter presents an overview of data showing AMF classification, and recent advances are here compiled. Our goal was to provide nonspecialists such as researchers in other fields and land managers with information on historical and recent changes in AMF classification

How useful is the mutualism-parasitism continuum of arbuscular mycorrhizal functioning?

BACKGROUND A recent review in this journal puts forward the premise that our recent studies have resulted in our questioning the validity of the so-called mutualism-parasitism continuum of functioning of arbuscular mycorrhizas. This premise is incorrect and appears largely to result from a misunderstanding of terminology. SCOPE AND CONCLUSIONS We clarify a comment in one of our publications that influenced the previous review, which contains several statements that do not accurately represent our views. Our research has overturned not the continuum concept itself, but some past ideas about the balance of resources traded between AM fungi and plants. Of course, we recognize that outcomes of AM symbiosis in relation to the non-mycorrhizal (NM) state are strongly influenced by many environmental factors. Nevertheless, underlying resource trade is always a key determinant of costs and benefits of the symbiosis for both partners. In this context, we address uncertainties and contradictory ideas about mechanisms, causes, effects and outcomes in AM symbioses that occur in the literature, and issues of relevance of research at different scales. We also discuss semantics that can cause confusion. Finally, we assess how useful the mutualism-parasitism continuum is for design of hypothesis-driven experiments to disentangle the complex interactions that determine growth of AM plants, i.e. the so-called emergent properties.F. Andrew Smith & Sally E. Smit