Showing papers by "Robert A. Blanchette published in 2011"

Distribution and abundance of soil fungi in Antarctica at sites on the Peninsula, Ross Sea Region and McMurdo Dry Valleys

Abstract: Fungal abundance and diversity were studied from 245 soil samples collected in 18 distinct ice-free locations in Antarctica including areas in the McMurdo Dry Valleys, Ross Sea Region, and the Antarctic Peninsula. Cultivable fungal abundance in soil was found to be most positively correlated with percent carbon and nitrogen based on a Spearman’s rank correlation test of six soil parameters. Soil moisture and C/N ratio were also positively correlated with fungal abundance while pH and conductivity were negatively correlated. These results suggest that nutrient limitations in these highly oligotrophic environments are a primary factor in determining the distribution and abundance of indigenous fungi. Other effects of the extreme Antarctic environment likely affect fungi indirectly by limiting the distribution and abundance of plant-derived sources of carbon.

Significant Alteration of Gene Expression in Wood Decay Fungi Postia placenta and Phanerochaete chrysosporium by Plant Species

Abstract: Identification of specific genes and enzymes involved in conversion of lignocellulosics from an expanding number of potential feedstocks is of growing interest to bioenergy process development. The basidiomycetous wood decay fungi Phanerochaete chrysosporium and Postia placenta are promising in this regard because they are able to utilize a wide range of simple and complex carbon compounds. However, systematic comparative studies with different woody substrates have not been reported. To address this issue, we examined gene expression of these fungi colonizing aspen (Populus grandidentata) and pine (Pinus strobus). Transcript levels of genes encoding extracellular glycoside hydrolases, thought to be important for hydrolytic cleavage of hemicelluloses and cellulose, showed little difference for P. placenta colonizing pine versus aspen as the sole carbon source. However, 164 genes exhibited significant differences in transcript accumulation for these substrates. Among these, 15 cytochrome P450s were upregulated in pine relative to aspen. Of 72 P. placenta extracellular proteins identified unambiguously by mass spectrometry, 52 were detected while colonizing both substrates and 10 were identified in pine but not aspen cultures. Most of the 178 P. chrysosporium glycoside hydrolase genes showed similar transcript levels on both substrates, but 13 accumulated >2-fold higher levels on aspen than on pine. Of 118 confidently identified proteins, 31 were identified in both substrates and 57 were identified in pine but not aspen cultures. Thus, P. placenta and P. chrysosporium gene expression patterns are influenced substantially by wood species. Such adaptations to the carbon source may also reflect fundamental differences in the mechanisms by which these fungi attack plant cell walls.

Fungal colonization of exotic substrates in Antarctica

Abstract: Throughout the history of polar exploration and up to recent times, wood and other exotic materials have been brought to the Antarctic continent and left there. While the possible transportation of exotic fungal species on these materials is sometimes considered, the effects of these exotic substrates on indigenous fungal communities have not been previously evaluated. This study reports results from seven plots where organic materials were used in baiting studies to determine the fungal diversity present in soils. Four plots were on islands in the Palmer Archipelago on the Antarctic Peninsula and three at Ross Island, Antarctica. Samples of sterile wood and cellulose with and without nutrients added were buried in soil and left for either two or four years before being removed and evaluated for fungal colonization. There was a significant increase in fungal colony-forming units (CFU) from soil in direct contact with introduced, sterile wood and cellulose substrates compared to background soil levels. The type of substrate, 2 or 4 year incubation period in the field, or nutrient addition did not have a significant effect on culturable densities in soil. Fungal abundance on soil adhering to substrates was found to be similar to that found in non-polar soils indicating that lack of organic material may be the most significant limiting factor affecting densities of Antarctic fungal populations. Based on a high degree of colonization, these exotic substrates appear to have a significant effect on indigenous soil fungal abundance.

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

Abstract: 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.

Puccinia psidii infecting cultivated Eucalyptus and native myrtaceae in Uruguay

Abstract: Eucalyptus or guava rust caused by Puccinia psidii is a serious disease of Eucalyptus and other Myrtaceae. In Uruguay, it has been previously found on Eucalyptus globulus and Psidium brasiliensis. Almost nothing is known regarding the occurrence of this pathogen on other Eucalyptus species or native Myrtaceae in that country. In this study, we determined the presence of P. psidii on Eucalyptus species and native Myrtaceae trees in Uruguay and evaluated the pathogenicity of specimens from native myrtaceous hosts on E. globulus and E. grandis. Phylogenetic analyses based on the internal transcribed spacer (ITS) region of the nuclear ribosomal DNA operon were used to confirm pathogen identity. Comparisons of ITS sequences confirmed the identity of P. psidii on Eucalyptus globulus, E. grandis, Myrcianthes pungens, and Myrrhinium atropurpureum var. octandrum. This is the first report of P. psidii on M. atropurpureum var. octandrum. Pathogenicity tests showed that isolates from native Myrtaceae could infect both Eucalyptus species tested, indicating a strong biological relationship between both introduced and native Myrtaceae. This study supplies relevant field data, morphological information, molecular phylogenetic analyses and infection studies that contribute to a better understanding of an important and little studied pathogen.