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G M Seager

Publications and source records attributed to G M Seager.

5 recordsLinked to original sources
PubMed1994

Seasonal and spatial population dynamics of the nitrogen-efficient guild in a desert bajada grassland.

This study examined the temporal and spatial variation in the populations of bacteria from a Chihuahuan desert bajada grassland that could grow on nearly nitrogen-free medium, a nitrogen-efficient guild (NEG). A Curtis similarity index of 0.876 and nearly identical diversity and equability indexes (H' = 1.22, J = 0.46 and H' = 1.27, J = 0.48 for the crown edge and interplant samples, respectively) indicated that there was no qualitative difference between the NEG assemblages isolated from samples taken at Bouteloua eriopoda plant crowns and in nonvegetated areas 45 cm from crowns. The difference in NEG populations between the crown and interplant samples was only 2-fold, despite a 9.5-fold difference in root biomass between the sites. These differences, while consistent, were statistically significant at only 50% of the sampling times. There was over an order of magnitude difference in NEG numbers in root-associated soil and in bulk soil from the crown or intercrown sites. The typical trend for temporal variation in NEG numbers was that they increased in the spring, fluctuated dramatically over the summer, and declined at the summer's end. The pattern of soil moisture change was the only abiotic variable which showed the same fluctuation pattern as NEG numbers.

Bacteria↗
PubMed1993

Effect of water and nitrogen additions on free-living nitrogen fixer populations in desert grass root zones.

In this study we measured changes in population levels of free-living N2-fixing bacteria in the root zones of potted Bouteloua eriopoda and Sporobolus flexuosus plants as well as the photosynthetic indices of the plants in response to added nitrogen, added water, and added water plus nitrogen treatments. In addition, N2 fixer population changes in response to added carbon source and nitrogen were measured in plant-free soil columns. There were significant increases in the numbers of N2 fixers associated with both plant species in the water and the water plus nitrogen treatments. Both treatments increased the photosynthetic index, suggesting that plant exudates were driving N2 fixer population changes. Population increases were greatest in the water plus nitrogen treatments, indicating that added nitrogen was synergistic with added water and suggesting that nitrogen addition spared bacteria the metabolic cost of N2 fixation, allowing greater reproduction. Plant-free column studies demonstrated a synergistic carbon-nitrogen effect when carbon levels were limiting (low malate addition) but not when carbon was abundant (high malate), further supporting this hypothesis. The results of this study indicate the presence of N2 fixer populations which interact with plants and which may play a role in the nitrogen balance of desert grasslands.

Acetylene↗
PubMed1985

Granulomas of the vocal cords caused by Sporothrix schenckii.

A 42-year-old female acquired an acute respiratory infection one week after working in a sphagnum moss packing plant. Three and one half months later direct laryngoscopic examination, done because of persistent hoarseness, revealed granulomas of the left true cord. Initial biopsy showed noncaseating granulomas, and a repeat biopsy with fungal cultures grew Sporothrix schenckii. The patient was treated with an oral solution of saturated potassium iodide and gradually improved although mild hoarseness has persisted.

Adult↗
PubMed1982

Malakoplakia of palatine tonsil.

This paper's purpose is to document a case of unilateral tonsillar malakoplakia. Escherichia coli was repeatedly cultured from the lesion, and the isolate was studied by expert microbiologists who found no abnormalities in its biologic properties. The course of the lesion was followed by repeated punch biopsies before, and after the institution of antibiotic therapy. Following treatment, healing was characterized histologically by the disappearance of edema, granulocytes and bacilli, a striking initial increase in the number of Michaelis-Gutmann (MG) bodies and other calcified particles, and an increase in the number of foamy plasma cells, before the eventual resolution of the lesion.

Aged↗