The physiological implications of urease inhibitors on N metabolism during germination of Pisum sativum and Spinacea oleracea seeds.

The development of new nitrogen fertilizers is necessary to optimize crop production whilst improving the environmental aspects arising from the use of nitrogenous fertilization as a cultural practice. The use of urease inhibitors aims to improve the efficiency of urea as a nitrogen fertilizer by preventing its loss from the soil as ammonia. However, although the action of urease inhibitors is aimed at the urease activity in soil, their availability for the plant may affect its urease activity.

High irradiance increases NH(4)(+) tolerance in Pisum sativum: Higher carbon and energy availability improve ion balance but not N assimilation.

The widespread use of NO(3)(-) fertilization has had a major ecological impact. NH(4)(+) nutrition may help to reduce this impact, although high NH(4)(+) concentrations are toxic for most plants. The underlying tolerance mechanisms are not yet fully understood, although they are thought to include the limitation of C, the disruption of ion homeostasis, and a wasteful NH(4)(+) influx/efflux cycle that carries an extra energetic cost for root cells.

Increase of resistance to macrolides in invasive Streptococcus pneumoniae in Spain (2000-2001).

This study examined the antimicrobial resistance of 1,278 invasive Streptococcus pneumoniae isolates from 41 Spanish laboratories participating in the European Antimicrobial Resistance Surveillance System (EARSS) during 2000 and 2001. Twenty-nine laboratories participated during both years and provided 950 of the isolates. Each laboratory used its own susceptibility testing methods.

Molecular basis of rifampicin resistance in Haemophilus influenzae.

Objectives: To determine the molecular basis of rifampicin resistance in Haemophilus influenzae.

Methods: Mutations in the rifampicin-resistance determining region of the rpoB gene of H. influenzae were analysed by gene amplification and sequencing in 12 rifampicin resistant, one intermediate and four susceptible isolates.