Witnessing history: comparison of a century of sedimentary and written records in a California protected area

We use a combination of proxy records from a high-resolution analysis of sediments from Searsville Lake and adjacent Upper Lake Marsh and historical records to document over one and a half centuries of vegetation and socio-ecological change-relating to logging, agricultural land use change, dam construction, chemical applications, recreation, and other drivers-on the San Francisco Peninsula. A relatively open vegetation with minimal oak (Quercus) and coast redwood (Sequoia sempervirens) in the late 1850s reflects widespread logging and grazing during the nineteenth century. Forest and woodland expansion occurred in the early twentieth century, with forests composed of coast redwood and oak, among other taxa, as both logging and grazing declined. Invasive species include those associated with pasturage (Rume x, Plantago), landscape disturbance (Urtica, Amaranthaceae), planting for wood production and wind barriers (Eucalyptus), and agriculture. Agricultural species, including wheat, rye, and corn, were more common in the early twentieth century than subsequently. Wetland and aquatic pollen and fungal spores document a complex hydrological history, often associated with fluctuating water levels, application of algaecides, raising of Searsville Dam, and construction of a levee. By pairing the paleoecological and historical records of both lakes, we have been able to reconstruct the previously undocumented impacts of socio-ecological influences on this drainage, all of which overprinted known climate changes. Recognizing the ecological manifestations of these impacts puts into perspective the extent to which people have interacted with and transformed the environment in the transition into the Anthropocene.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10113-023-02056-9.

Oligosaccharides production from coprophilous fungi: An emerging functional food with potential health-promoting properties

Functional foods are essential food products that possess health-promoting properties for the treatment of infectious diseases. In addition, they provide energy and nutrients, which are required for growth and survival. They occur as prebiotics or dietary supplements, including oligosaccharides, processed foods, and herbal products. However, oligosaccharides are more efficiently recognized and utilized, as they play a fundamental role as functional ingredients with great potential to improve health in comparison to other dietary supplements. They are low molecular weight carbohydrates with a low degree of polymerization. They occur as fructooligosaccharide (FOS), inulooligosaccharadie (IOS), and xylooligosaccahride (XOS), depending on their monosaccharide units. Oligosaccharides are produced by acid or chemical hydrolysis. However, this technique is liable to several drawbacks, including inulin precipitation, high processing temperature, low yields, and high production costs. As a consequence, the application of microbial enzymes for oligosaccharide production is recognized as a promising strategy. Microbial enzymatic production of FOS and IOS occurs by submerged or solid-state fermentation in the presence of suitable substrates (sucrose, inulin) and catalyzed by fructosyltransferases and inulinases. Incorporation of FOS and IOS enriches the rheological and physiological characteristics of foods. They are used as low cariogenic sugar substitutes, suitable for diabetics, and as prebiotics, probiotics and nutraceutical compounds. In addition, these oligosaccharides are employed as anticancer, antioxidant agents and aid in mineral absorption, lipid metabolism, immune regulation etc. This review, therefore, focuses on the occurrence, physico-chemical characteristics, and microbial enzymatic synthesis of FOS and IOS from coprophilous fungi. In addition, the potential health benefits of these oligosaccharides were discussed in detail.

Identification of cyclosporin C from Amphichorda felina using a Cryptococcus neoformans differential temperature sensitivity assay

We used a temperature differential assay with the opportunistic fungal pathogen Cryptococcus neoformans as a simple screening platform to detect small molecules with antifungal activity in natural product extracts. By screening of a collection extracts from two different strains of the coprophilous fungus, Amphichorda felina, we detected strong, temperature-dependent antifungal activity using a two-plate agar zone of inhibition assay at 25 and 37 °C. Bioassay-guided fractionation of the crude extract followed by liquid chromatography-mass spectrometry (LC-MS) and nuclear magnetic resonance spectroscopy (NMR) identified cyclosporin C (CsC) as the main component of the crude extract responsible for growth inhibition of C. neoformans at 37 °C. The presence of CsC was confirmed by comparison with a commercial standard. We sequenced the genome of A. felina to identify and annotate the CsC biosynthetic gene cluster. The only previously characterized gene cluster for the biosynthesis of similar compounds is that of the related immunosuppressant drug cyclosporine A (CsA). The CsA and CsC gene clusters share a high degree of synteny and sequence similarity. Amino acid changes in the adenylation domain of the CsC nonribosomal peptide synthase's sixth module may be responsible for the substitution of L-threonine compared to L-α-aminobutyric acid in the CsA peptide core. This screening strategy promises to yield additional antifungal natural products with a focused spectrum of antimicrobial activity.

The ecological consequences of megafaunal loss: giant tortoises and wetland biodiversity

The giant tortoises of the Galápagos have become greatly depleted since European discovery of the islands in the 16th Century, with populations declining from an estimated 250 000 to between 8000 and 14 000 in the 1970s. Successful tortoise conservation efforts have focused on species recovery, but ecosystem conservation and restoration requires a better understanding of the wider ecological consequences of this drastic reduction in the archipelago's only large native herbivore. We report the first evidence from palaeoecological records of coprophilous fungal spores of the formerly more extensive geographical range of giant tortoises in the highlands of Santa Cruz Island. Upland tortoise populations on Santa Cruz declined 500–700 years ago, likely the result of human impact or possible climatic change. Former freshwater wetlands, a now limited habitat-type, were found to have converted to Sphagnum bogs concomitant with tortoise loss, subsequently leading to the decline of several now-rare or extinct plant species.