University of Maine

About: University of Maine is a education organization based out in Orono, Maine, United States. It is known for research contribution in the topics: Population & Ice sheet. The organization has 8637 authors who have published 16932 publications receiving 590124 citations. The organization is also known as: University of Maine at Orono.

Lignocellulosic polysaccharides and lignin degradation by wood decay fungi: the relevance of nonenzymatic Fenton-based reactions

Abstract: The brown rot fungus Wolfiporia cocos and the selective white rot fungus Perenniporia medulla-panis produce peptides and phenolate-derivative compounds as low molecular weight Fe 3? -reductants. Phenolates were the major compounds with Fe 3? -reducing activity in both fungi and displayed Fe 3? -reducing activity at pH 2.0 and 4.5 in the absence and presence of oxalic acid. The chemical structures of these compounds were identified. Together with Fe 3? and H2O2 (mediated Fenton reaction) they pro- duced oxygen radicals that oxidized lignocellulosic poly- saccharides and lignin extensively in vitro under conditions similar to those found in vivo. These results indicate that, in addition to the extensively studied Gloeophyllum trabeum— a model brown rot fungus—other brown rot fungi as well as selective white rot fungi, possess the means to promote Fenton chemistry to degrade cellulose and hemicellulose, and to modify lignin. Moreover, new information is pro- vided, particularly regarding how lignin is attacked, and either repolymerized or solubilized depending on the type of fungal attack, and suggests a new pathway for selective white rot degradation of wood. The importance of Fenton reactions mediated by phenolates operating separately or synergistically with carbohydrate-degrading enzymes in brown rot fungi, and lignin-modifying enzymes in white rot fungi is discussed. This research improves our understand- ing of natural processes in carbon cycling in the environ- ment, which may enable the exploration of novel methods for bioconversion of lignocellulose in the production of biofuels or polymers, in addition to the development of new and better ways to protect wood from degradation by microorganisms.

Associations of methanotrophs with the roots and rhizomes of aquatic vegetation.

Abstract: Results of an in vitro assay revealed that root-associated methane consumption was a common attribute of diverse emergent wetland macrophytes from a variety of habitats. Maximum potential uptake rates (Vmaxp) varied between about 1 and 10 micromol g (dry weight)-1 h-1, with no obvious correlation between rate and gross morphological characteristics of the plants. The Vmaxp corresponded to about 2 x 10(8) to 2 x 10(9) methanotrophs g (dry weight)-1, assuming that the root-associated methanotrophs have cell-specific activities comparable to those of known isolates. Vmaxp varied seasonally for an aquatic grass, Calamogrostis canadensis, and for the cattail, Typha latifolia, with highest rates in the late summer. Vmaxp was well correlated with ambient temperature for C. canadensis but weakly correlated for T. latifolia. The seasonal changes in Vmaxp, as well as inferences from apparent half-saturation constants for methane uptake (Kapp; generally 3 to 6 microM), indicated that oxygen availability might be more important than methane as a rate determinant. In addition, roots incubated under anoxic conditions showed little or no postanoxia aerobic methane consumption, indicating that root-associated methanotrophic populations might not tolerate variable oxygen availability. Hybridization of oligodeoxynucleotide probes specific for group I or group II methylotrophs also varied seasonally. The group II-specific probe consistently hybridized to a greater extent than the group I probe, and the relative amount of group II probe hybridization to C. canadensis root extracts was positively correlated with Vmaxp.

Statistical mechanical simulation of polymeric DNA melting with MELTSIM.

Abstract: MOTIVATION MELTSIM is a windows-based statistical mechanical program for simulating melting curves of DNAs of known sequence and genomic dimensions under different conditions of ionic strength with great accuracy. The program is useful for mapping variations of base compositions of sequences, conducting studies of denaturation, establishing appropriate conditions for hybridization and renaturation, determinations of sequence complexity, and sequence divergence. RESULTS Good agreement is achieved between experimental and calculated melting curves of plasmid, bacterial, yeast and human DNAs. Denaturation maps that accompany the calculated curves indicate non-coding regions have a significantly lower (G+C) composition than coding regions in all species examined. Curves of partially sequenced human DNA suggest the current database may be heavily biased with coding regions, and excluding large (A+T)-rich elements. AVAILABILITY MELTSIM 1.0 is available at: //www.uml.edu/Dept/Chem/UMLBIC/Apps/MEL TSIM/MELTSIM-1.0-Win/meltsim. zip. Melting curve plots in this paper were made with GNUPLOT 3.5, available at: http://www.cs.dartmouth.edu/gnuplot_inf o.html Contact : blake@maine.maine.edu;