The fungi in Century 21. The XXI Fungal Genetics Conference, Pacific Grove, California, March 13-18, 2001

As an important opportunistic pulmonary pathogen, Pneumocystis carinii has been the focus of extensive research over the decades. The use of laboratory animal models has permitted a detailed understanding of the host-parasite interaction but an understanding of the basic biology of P. carinii has lagged due in large part to the inability of the organism to grow well in culture and to the lack of a tractable genetic system. Molecular techniques have demonstrated extensive heterogeneity among P. carinii organisms isolated from different host species. Characterization of the genes and genomes of the Pneumocystis family has supported the notion that the family comprises different species rather than strains within the genus Pneumocystis and contributed to the understanding of the pathophysiology of infection. Many of the technical obstacles in the study of the organisms have been overcome in the past decade and the pace of research into the basic biology of the organism has accelerated. Biochemical pathways have been inferred from the presence of key enzyme activities or gene sequences, and attempts to dissect cellular pathways have been initiated. The Pneumocystis genome project promises to be a rich source of information with regard to the functional activity of the organism and the presence of specific biochemical pathways. These advances in our understanding of the biology of this organism should provide for future studies leading to the control of this opportunistic pathogen.     

Abstracts of Platform Presentations from the Phytoremediation Session at the 14th Annual West Coast Conference on Contaminated Soils,Sediments, and Water (March 15–18, San Diego,CA)

Previous field studies indicate that zucchini (Cucurbita pepo) has a unique ability to phytoextract persistent organic pollutants from soil. It is unlikely that C. pepo evolved a unique mechanism favoring POP extraction and uptake, but all plants have evolved means to facilitate nutrient acquisition from soil. We have hypothesized that the exudation of organic acids as a means to acquire phosphorus could facilitate the uptake of persistent organic pollutants by increasing contaminant bioavailability to the plants. In one study, we assessed DDE uptake and organic acid exudation by zucchini (an uptaker of POPs) and cucumber (a non-uptaker of POPs) under various cultivation and nutrient conditions. Under dense planting (5 plants in a 5-kg pot of DDE-contaminated soil), zucchini accumulated significant and expected amounts of DDE but surprisingly, under these stressed conditions, cucumber phytoextracted greater amounts of DDE. The cucumber rhizosphere concentrations of organic acids were significantly higher than that of zucchini, suggesting that the increased organic acid exudation promoted DDE uptake by cucumber. Conversely, under non-stressed conditions zucchini phytoextracted significantly greater quantities of pollutant than cucumber but no differences in organic acid content of the rhizosphere of the two species were observed. Separately, zucchini and other species were grown under field conditions and weekly amendments of different nutrients were made (nitrogen, phosphorus, nitrogen/phosphorus, aluminum sulfate to bind phosphorus in the soil). The uptake and translocation of the weathered pollutant and inorganic elements was found to vary with nutrient amendments. Lastly, data will be presented from rhizotron units constructed to facilitate not only the direct in situ isolation of exuded organic acids but also the isolation of xylem sap and rhizosphere soil pore water from individual plants. The role of cultivation conditions and nutrient availability in controlling root morphology, organic acid exudation, and contaminant uptake will be discussed.