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Spread of Novel Aminoglycoside Resistance Gene aac(6')-Iad among Acinetobacter Clinical Isolates in Japan. Yohei Doi, 2004.A novel aminoglycoside resistance gene, aac(6')-Iad, encoding aminoglycoside 6'-N-acetyltransferase, was identified in Acinetobacter genospecies 3 strain A-51 . The gene encoded a 144-amino-acid protein, which shared modest identity (up to 36.7%) with some of the aminoglycoside 6'-N-acetyltransferases . The results of high-pressure liquid chromatography assays confirmed that the protein is a functional aminoglycoside 6'-N-acetyltransferase . The enzyme conferred resistance to amikacin, tobramycin, sisomicin, and isepamicin but not to gentamicin . The prevalence of this gene among Acinetobacter clinical isolates in Japan was then investigated . Of 264 Acinetobacter sp . strains isolated from geographically diverse areas in Japan in 2002, 16 were not susceptible to amikacin, and aac(6')-Iad was detected in 7 . Five of the producers of aminoglycoside 6'-N-acetyltransferase type Iad were identified as Acinetobacter baumannii, and two were identified as Acinetobacter genospecies 3 . These results suggest that aac(6')-Iad plays a substantial role in amikacin resistance among Acinetobacter spp . in Japan . Two Distinct Pathways for Trehalose Assimilation in the Yeast Saccharomyces cerevisiae. Matthieu Jules, 2004.The yeast Saccharomyces cerevisiae can synthesize trehalose and also use this disaccharide as a carbon source for growth . However, the molecular mechanism by which extracellular trehalose can be transported to the vacuole and degraded by the acid trehalase Ath1p is not clear . By using an adaptation of the assay of invertase on whole cells with NaF, we showed that more than 90% of the activity of Ath1p is extracellular, splitting of the disaccharide into glucose . We also found that Agt1p-mediated trehalose transport and the hydrolysis of the disaccharide by the cytosolic neutral trehalase Nth1p are coupled and represent a second, independent pathway, although there are several constraints on this alternative route . First, the AGT1/MAL11 gene is controlled by the MAL system, and Agt1p was active in neither non-maltose-fermenting nor maltose-inducible strains . Second, Agt1p rapidly lost activity during growth on trehalose, by a mechanism similar to the sugar-induced inactivation of the maltose permease . Finally, both pathways are highly pH sensitive and effective growth on trehalose occurred only when the medium was buffered at around pH 5.0 . The catabolism of trehalose was purely oxidative, and since levels of Ath1p limit the glucose flux in the cells, batch cultures on trehalose may provide a useful alternative to glucose-limited chemostat cultures for investigation of metabolic responses in yeast . Potential Role for Fish in Transmission of Mycobacterium ulcerans Disease (Buruli Ulcer): an Environmental Study. Miriam Eddyani, 2004. Luminescence Resonance Energy Transfer-Based High-Throughput Screening Assay for Inhibitors of Essential Protein-Protein Interactions in Bacterial RNA Polymerase. Veit Bergendahl, 2003.The binding of sigma factors to core RNA polymerase is essential for the specific initiation of transcription in eubacteria and is thus critical for cell growth . Since the responsible protein-binding regions are highly conserved among all eubacteria but differ significantly from eukaryotic RNA polymerases, sigma factor binding is a promising target for drug discovery . A homogeneous assay for sigma binding to RNA polymerase (Escherichia coli) based on luminescence resonance energy transfer (LRET) was developed by using a europium-labeled  70 and an IC5-labeled fragment of the ß' subunit of RNA polymerase (amino acid residues 100 through 309) . Inhibition of sigma binding was measured by the loss of LRET through a decrease in IC5 emission . The technical advances offered by LRET resulted in a very robust assay suitable for high-throughput screening, and LRET was successfully used to screen a crude natural-product library . We illustrate this method as a powerful tool to investigate any essential protein-protein interaction for basic research and drug discovery .
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