23 research outputs found
Abundances of Iron-Binding Photosynthetic and Nitrogen-Fixing Proteins of Trichodesmium Both in Culture and In Situ from the North Atlantic
Marine cyanobacteria of the genus Trichodesmium occur throughout the oligotrophic tropical and subtropical oceans, where they can dominate the diazotrophic community in regions with high inputs of the trace metal iron (Fe). Iron is necessary for the functionality of enzymes involved in the processes of both photosynthesis and nitrogen fixation. We combined laboratory and field-based quantifications of the absolute concentrations of key enzymes involved in both photosynthesis and nitrogen fixation to determine how Trichodesmium allocates resources to these processes. We determined that protein level responses of Trichodesmium to iron-starvation involve down-regulation of the nitrogen fixation apparatus. In contrast, the photosynthetic apparatus is largely maintained, although re-arrangements do occur, including accumulation of the iron-stress-induced chlorophyll-binding protein IsiA. Data from natural populations of Trichodesmium spp. collected in the North Atlantic demonstrated a protein profile similar to iron-starved Trichodesmium in culture, suggestive of acclimation towards a minimal iron requirement even within an oceanic region receiving a high iron-flux. Estimates of cellular metabolic iron requirements are consistent with the availability of this trace metal playing a major role in restricting the biomass and activity of Trichodesmium throughout much of the subtropical ocean
Isolement et caractérisation des champignons du sol halotolérant des Great Salt Plains de l'Oklahoma, USA
Les Great Salt Plains (GSP) de l\u27Oklahoma est un environnement hypersalin sur voie terrestre oĂč les saumures saturĂ©es laissent des croĂ»tes Ă©vaporites de NaCl. Le prĂ©sent rapport examine la communautĂ© fongique, en complĂ©ment des rapports antĂ©rieurs sur les communautĂ©s bactĂ©riennes et archĂ©es. Vingt-cinq isolats fongiques du GSP sols ont Ă©tĂ© obtenus sur un milieu contenant 10 de NaCl et caractĂ©risĂ©. BasĂ© sur l\u27analyse de la sĂ©quence du gĂšne rRNA 18S, tous les isolats relĂšvent des ascomycĂštes, avec une prĂ©dominance de Trichocomaceae, reprĂ©sentĂ©e par les espĂšces de Aspergillus, Eurotium, et Penicillium. Les reprĂ©sentants de Anthrinium, Cladosporium, Debaryomyces, Fusarium, et Ulocladium ont Ă©galement Ă©tĂ© isolĂ©s. Globalement les isolats Ă©taient largement halotolĂ©rants, avec la meilleure croissance observĂ©e Ă des salinitĂ©s infĂ©rieures et aucun halophilisme. Les genres fongiques observĂ©s Ă©taient tous cosmopolites, sans une forte spĂ©cialisation. Pris ensemble, ces rĂ©sultats appuient la conclusion que les zones hypersalines n\u27ont pas une communautĂ© caractĂ©ristique, contrairement Ă ce qui a Ă©tĂ© observĂ© Ă la GSP pour les bactĂ©ries et les archĂ©es.The Great Salt Plains (GSP) of Oklahoma is an inland terrestrial hypersaline environment where saturated brines leave evaporite crusts of NaCl. The current report examines the fungal community, complementing earlier reports on the bacterial and archaeal communities. Twenty-five fungal isolates from GSP soils were obtained on medium containing 10 NaCl and characterized. Based on 18S rRNA gene sequence analysis, all of the isolates fall within the ascomycetes, with a predominance of Trichocomaceae, represented by Aspergillus, Eurotium, and Penicillium species. Representatives of Anthrinium, Cladosporium, Debaryomyces, Fusarium, and Ulocladium also were isolated. Overall the isolates were widely halotolerant, with best growth observed at lower salinities and no halophilism. The fungal genera observed were all cosmopolitan, without strong specialization. Taken together, these results support the conclusion that hypersaline environments do not have a characteristic community, in contrast to what was observed at the GSP for bacteria and archaea.</p