Shona M. Duncan

Wood-Destroying Soft Rot Fungi in the Historic Expedition Huts of Antarctica

ABSTRACT Three expedition huts in the Ross Sea region of Antarctica, built between 1901 and 1911 by Robert F. Scott and Ernest Shackleton, sheltered and stored the supplies for up to 48 men for 3 years during their explorations and scientific investigation in the South Pole region. The huts, built with wood taken to Antarctica by the early explorers, have deteriorated over the past decades. Although Antarctica has one of the coldest and driest environments on earth, microbes have colonized the wood and limited decay has occurred. Some wood in contact with the ground contained distinct microscopic cavities within secondary cell walls caused by soft rot fungi. Cadophora spp. could be cultured from decayed wood and other woods sampled from the huts and artifacts and were commonly associated with the soft rot attack. By using internal transcribed spacer sequences of ribosomal DNA and morphological characteristics, several species of Cadophora were identified, including C. malorum, C. luteo-olivacea, and C. fastigiata. Several previously undescribed Cadophora spp. also were found. At the Cape Evans and Cape Royds huts, Cadophora spp. commonly were isolated from wood in contact with the ground but were not always associated with soft rot decay. Pure cultures of Cadophora used in laboratory decay studies caused dark staining of all woods tested and extensive soft rot in Betula and Populus wood. The presence of Cadophora species, but only limited decay, suggests there is no immediate threat to the structural integrity of the huts. These fungi, however, are widely found in wood from the historic huts and have the capacity to cause extensive soft rot if conditions that are more conducive to decay become common.

Effects of oil spills on microbial heterotrophs in Antarctic soils

Abstract. Oil spillage on the moist coastal soils of the Ross Sea region of Antarctica can impact on populations of microbial heterotrophs in these soils, as determined by viable plate counts and a most probable number technique. Elevated numbers of culturable hydrocarbon degraders, bacteria and fungi were detected in surface and subsurface soils from oil-contaminated sites, compared with nearby control sites. Culturable yeasts were not detected in soil from coastal control sites, yet reached >105 organisms g–1 dry weight in contaminated soils. The presence of hydrocarbons in soils resulted in a shift in the genera of culturable filamentous fungi. Chrysosporium dominated control soils, yet Phialophora was more abundant in oil-contaminated soils. Hydrocarbon degraders are most likely bacteria; however, fungi could play a role in degradation of hydrocarbons or their metabolites. Depleted levels of nitrate detected in some contaminated soils and decreased pH may be the result of growth of hydrocarbon degraders. Numbers and diversity of culturable microbes from Antarctic soil varied depending on whether a pristine site or a human-impacted (in this case, by fuel spills) site is studied.

Synergy between pretreatment lignocellulose modifications and saccharification efficiency in two brown rot fungal systems

Brown rot wood-degrading fungi distinctly modify lignocellulose and completely hydrolyze polysaccharides (saccharification), typically without secreting an exo-acting glucanase and without removing lignin. Although each step of this two-step approach evolved within the same organism, it is unknown if the early lignocellulose modifications are made to specifically facilitate their own abbreviated enzyme system or if enhancements are more general. Because commercial pretreatments are typically approached as an isolated step, answering this question has immense implication on bioprocessing. We pretreated spruce and pine blocks with one of two brown rot fungi, Gloeophyllum trabeum or Fomitopsis pinicola. Wood harvested at weeks 1, 2, 4, and 8 showed a progression of weight loss from time zero due to selective carbohydrate removal. Hemicellulose losses progressed faster than cellulose loss. This “pretreated” material was then saccharified with commercially relevant Trichoderma reesei cellulases or with cellulases from the brown rot fungi responsible for degrading the wood to test for synergy. With increased decay, a significant increase in saccharification efficiency was apparent but not limited to same-species enzyme sources. We also calculated total sugar yields, and calculations that compensate for sugars consumed by fungi suggest a shorter residence time for fungal colonization than calculations based solely on saccharification yields.

Improved pretreatment of lignocellulosic biomass using enzymatically-generated peracetic acid.

Release of sugars from lignocellulosic biomass is inefficient because lignin, an aromatic polymer, blocks access of enzymes to the sugar polymers. Pretreatments remove lignin and disrupt its structure, thereby enhancing sugar release. In previous work, enzymatically generated peracetic acid was used to pretreat aspen wood. This pretreatment removed 45% of the lignin and the subsequent saccharification released 97% of the sugars remaining after pretreatment. In this paper, the amount of enzyme needed is reduced tenfold using first, an improved enzyme variant that makes twice as much peracetic acid and second, a two-phase reaction to generate the peracetic acid, which allows enzyme reuse. In addition, the eight pretreatment cycles are reduced to only one by increasing the volume of peracetic acid solution and increasing the temperature to 60 °C and the reaction time to 6h. For the pretreatment step, the weight ratio of peracetic acid to wood determines the amount of lignin removed.

Survey of potential sapstain fungi on Pinus radiata in New Zealand

Abstract A nationwide survey of New Zealand sapstain fungi on Pinus radiata was undertaken between 1996 and 1998 with collections of 1958 samples of material from 869 sites in the North and South Islands. Material was collected from mills, ports, forest plantations of native, exotic, or P. radiata, nurseries, farms, and urban areas. Material collected included branches, twigs, needles or leaves, cones, logs, wood chips, timber, and veneer. From these collections, 2154 potential sapstain fungi, representing 14 known species plus a number of unidentified species, were isolated. The predominant sapstain fungi isolated were Sphaeropsis sapinea, Ophiostoma ips, O. floccosum, O. piliferum, Leptographium procerum, and O. querci. S. sapinea was isolated from all material sampled including collections from the forest floor (including branches, twigs, needles, leaves, cones, and logs) as well as from logs and timber. In contrast Ophiostoma species were mainly found on logs, timber, and wood chips.

Lignocellulose modifications by brown rot fungi and their effects, as pretreatments, on cellulolysis

Brown rot fungi Gloeophyllum trabeum and Postia placenta were used to degrade aspen, spruce, or corn stover over 16 weeks. Decayed residues were saccharified using commercial cellulases or brown rot fungal extracts, loaded at equal but low endoglucanase titers. Saccharification was then repeated for high-yield samples using full strength commercial cellulases. Overall, brown rot pretreatments enhanced yields up to threefold when using either cellulase preparation. In the best case, aspen degraded 2 weeks by G. trabeum yielded 72% glucose-from-cellulose, a 51% yield relative to original glucan. A follow-up trial with more frequent harvests showed similar patterns and demonstrated interplay between tissue modifications and saccharification. Hemicellulose and vanillic acid (G6) or vanillin (G4) lignin residues were good predictors of saccharification potential, the latter notable given lignins potential active role in brown rot. Results show basic relationships over a brown rot time course and lend targets for controlling an applied bioconversion process.

Screening fungi isolated from historic Discovery Hut on Ross Island, Antarctica for cellulose degradation

Abstract To survive in Antarctica, early explorers of Antarcticas Heroic Age erected wooden buildings and brought in large quantities of supplies. The introduction of wood and other organic materials may have provided new nutrient sources for fungi that were indigenous to Antarctica or were brought in with the materials. From 30 samples taken from Discovery Hut, 156 filamentous fungi were isolated on selective media. Of these, 108 were screened for hydrolytic activity on carboxymethyl cellulose, of which 29 demonstrated activities. Endo-1, 4-β-glucanase activity was confirmed in the extracellular supernatant from seven isolates when grown at 4°C, and also when they were grown at 15°C. Cladosporium oxysporum and Geomyces sp. were shown to grow on a variety of synthetic cellulose substrates and to use cellulose as a nutrient source at temperate and cold temperatures. The research findings from the present study demonstrate that Antarctic filamentous fungi isolated from a variety of substrates (wood, straw, and food stuffs) are capable of cellulose degradation and can grow well at low temperatures.

Introduced and indigenous fungi of the Ross Island historic huts and pristine areas of Antarctica

This review summarizes research concerning Antarctic fungi at the century-old historic huts of the Heroic Period of exploration in the Ross Dependency 1898–1917 and fungi in pristine terrestrial locations. The motivation of the research was initially to identify potential fungal causes of degradation of the historic huts and artifacts. The research was extended to study fungal presence at pristine sites for comparison purposes and to consider the role of fungi in the respective ecosystems. We employed classical microbiology for isolation of viable organisms, and culture-independent DNA analyses. The research provided baseline data on microbial biodiversity. Principal findings were that there is significant overlap of the yeasts and filamentous fungi isolated from the historic sites, soil, and historic-introduced materials (i.e., wood, foodstuffs) and isolated from environmental samples in pristine locations. Aerial spore monitoring confirmed that winter spore counts were high and, in some cases, similar to those found in summer. Microbial diversity varied between the three Ross Island historic sites, and one historic site showed noticeably higher diversity, which led to the conclusion that this is a variable that should not be generalized. Cultured fungi were cold active, and the broader scientific significance of this finding was that climate change (warming) may not adversely affect these fungal species unless they were out-competed by new arrivals or unfavorable changes in ecosystem domination occur.

Environmental pollutants from the Scott and Shackleton expeditions during the 'Heroic Age' of Antarctic exploration

EarlyexplorerstoAntarcticabuiltwoodenhutsandbroughthugequantitiesofsuppliesandequipmentto support their geographical and scientific studies for several years. When the expeditions ended and relief ships arrived, a rapid exodus frequently allowed only essential items to be taken north. The huts and thousands of items were left behind. Fuel depots with unused containers of petroleum products, asbestos materials, and diverse chemicals were also left at the huts. This investigation found high concentrations of polyaromatic hydrocarbons in soils under and around the historic fuel depots, including anthracene, benzo(b)fluoranthene, benzo(k)fluoranthene, chrysene, fluorene, and pyrene, as well as benzo(a)anthracene, benzo(a)pyrene, and fluoranthene, which are recognized carcinogens. Asbestos materials within the huts have been identified and extensive amounts of fragmented asbestos were found littering the ground around the Cape Evans hut. These materials are continually abraded and fragmented as tourists walk over them and the coarse scoria breaks and grinds down the materials. A chemical spill, within the Cape Evans hut, apparently from caustic substances from one of the scientific experiments, has caused an unusual deterioration and defibration on affected woods. Although these areas are important historic sites protected by international treaties, the hazardous waste materials left by the early explorers should be removed and remedial action taken to restore the site to as pristine a condition as possible. Recommendations are discussed for international efforts to study and clean up these areas, where the earliest environmental pollution in Antarctica was produced.