Aquatic Hyphomycete Species Are Screened by the Hyporheic Zone of Woodland Streams

Aquatic hyphomycetes strongly contribute to organic matter dynamics in streams, but their abilities to colonize leaf litter buried in streambed sediments remain unexplored. Here, we conducted field and laboratory experiments (slow-filtration columns and stream-simulating microcosms) to test the following hypotheses: (i) that the hyporheic habitat acting as a physical sieve for spores filters out unsuccessful strategists from a potential species pool, (ii) that decreased pore size in sediments reduces species dispersal efficiency in the interstitial water, and (iii) that the physicochemical conditions prevailing in the hyporheic habitat will influence fungal community structure. Our field study showed that spore abundance and species diversity were consistently re- duced in the interstitial water compared with surface water within three differing streams. Significant differences occurred among aquatic hyphomycetes, with dispersal efficiency of filiform-spore species being much higher than those with compact or branched/tetraradiate spores. This pattern was remarkably consistent with those found in laboratory experiments that tested the influence of sediment pore size on spore dispersal in microcosms. Furthermore, leaves inoculated in a stream and incubated in slow-filtration columns exhibited a fungal assemblage dominated by only two species, while five species were codominant on leaves from the stream-simulating microcosms. Results of this study highlight that the hyporheic zone exerts two types of selec- tion pressure on the aquatic hyphomycete community, a physiological stress and a physical screening of the benthic spore pool, both leading to drastic changes in the structure of fungal community

A target-protection mechanism of antibiotic resistance at atomic resolution: insights into FusB-type fusidic acid resistance

Antibiotic resistance in clinically important bacteria can be mediated by proteins that physically associate with the drug target and act to protect it from the inhibitory effects of an antibiotic. We present here the first detailed structural characterization of such a target protection mechanism mediated through a protein-protein interaction, revealing the architecture of the complex formed between the FusB fusidic acid resistance protein and the drug target (EF-G) it acts to protect. Binding of FusB to EF G induces conformational and dynamic changes in the latter, shedding light on the molecular mechanism of fusidic acid resistance

Satellyptus: analysis and database of microsatellites from ESTs of Eucalyptus

The main goal of our research was to search for SSRs in the Eucalyptus EST FORESTs database (using a software for mining SSR-motifs). With this objective, we created a database for cataloging Eucalyptus EST-derived SSRs, and developed a bioinformatics tool, named Satellyptus, for finding and analyzing microsatellites in the Eucalyptus EST database. The search for microsatellites in the FORESTs database containing 71,115 Eucalyptus EST sequences (52.09 Mb) revealed 20,530 SSRs in 15,621 ESTs. The SSR abundance detected on the Eucalyptus ESTs database (29% or one microsatellite every four sequences) is considered very high for plants. Amongst the categories of SSR motifs, the climeric (37%) and trimeric ones (33%) predominated. The AG/CT motif was the most frequent (35.15%) followed by the trimeric CCG/CGG (12.81%). From a random sample of 1,217 sequences, 343 microsatellites in 265 SSR-containing sequences were identified. Approximately 48% of these ESTs containing microsatellites were homologous to proteins with known biological function. Most of the microsatellites detected in Eucalyptus ESTs were positioned at either the 5′ or 3′ end. Our next priority involves the design of flanking primers for codominant SSR loci, which could lead to the development of a set of microsatellite-based markers suitable for marker-assisted Eucalyptus breeding programs