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AmpC ß-Lactamase in an Escherichia coli Clinical Isolate Confers Resistance to Expanded-Spectrum Cephalosporins. Hedi Mammeri, 2004.Cloning, sequencing, and biochemical analysis identified a novel AmpC-type ß-lactamase conferring resistance to extended-spectrum cephalosporins in an Escherichia coli clinical isolate . This enzyme, exhibiting 14 amino acid substitutions compared to a reference AmpC cephalosporinase of E . coli, hydrolyzed ceftazidime and cefepime significantly . Mating Type Sequences in Asexually Reproducing Fusarium Species. Zoltán Kerényi, 2004.To assess the potential for mating in several Fusarium species with no known sexual stage, we developed degenerate and semidegenerate oligonucleotide primers to identify conserved mating type (MAT) sequences in these fungi . The putative  and high-mobility-group (HMG) box sequences from Fusarium avenaceum, F . culmorum, F . poae, and F . semitectum were compared to similar sequences that were described previously for other members of the genus . The DNA sequences of the regions flanking the amplified MAT regions were obtained by inverse PCR . These data were used to develop diagnostic primers suitable for the clear amplification of conserved mating type sequences from any member of the genus Fusarium . By using these diagnostic primers, we identified mating types of 122 strains belonging to 22 species of Fusarium . The
box and the HMG box from the mating type genes are transcribed in F . avenaceum, F . culmorum, F . poae, and F . semitectum . The novelty of the PCR-based mating type identification system that we developed is that this method can be used on a wide range of Fusarium species, which have proven or expected teleomorphs in different ascomycetous genera, including Calonectria, Gibberella, and Nectria .
Crystal Structures of Mycobacterium smegmatis RecA and Its Nucleotide Complexes. S. Datta, 2003.The crystal structures of Mycobacterium smegmatis RecA (RecAMs) and its complexes with ADP, ATP  S, and dATP show that RecAMs has an expanded binding site like that in Mycobacterium tuberculosis RecA, although there are small differences between the proteins in their modes of nucleotide binding . Nucleotide binding is invariably accompanied by the movement of Gln 196, which appears to provide the trigger for transmitting the effect of nucleotide binding to the DNA-binding loops . These observations provide a framework for exploring the known properties of the RecA proteins .
Analysis of the Sulfate-Reducing Bacterial and Methanogenic Archaeal Populations in Contrasting Antarctic Sediments. K. J. Purdy, 2003.The distribution and activity of communities of sulfate-reducing bacteria (SRB) and methanogenic archaea in two contrasting Antarctic sediments were investigated . Methanogenesis dominated in freshwater Lake Heywood, while sulfate reduction dominated in marine Shallow Bay . Slurry experiments indicated that 90% of the methanogenesis in Lake Heywood was acetoclastic . This finding was supported by the limited diversity of clones detected in a Lake Heywood archaeal clone library, in which most clones were closely related to the obligate acetate-utilizing Methanosaeta concilii . The Shallow Bay archaeal clone library contained clones related to the C1-utilizing Methanolobus and Methanococcoides and the H2-utilizing Methanogenium . Oligonucleotide probing of RNA extracted directly from sediment indicated that archaea represented 34% of the total prokaryotic signal in Lake Heywood and that Methanosaeta was a major component (13.2%) of this signal . Archaea represented only 0.2% of the total prokaryotic signal in RNA extracted from Shallow Bay sediments . In the Shallow Bay bacterial clone library, 10.3% of the clones were SRB-like, related to Desulfotalea/Desulforhopalus, Desulfofaba, Desulfosarcina, and Desulfobacter as well as to the sulfur and metal oxidizers comprising the Desulfuromonas cluster . Oligonucleotide probes for specific SRB clusters indicated that SRB represented 14.7% of the total prokaryotic signal, with Desulfotalea/Desulforhopalus being the dominant SRB group (10.7% of the total prokaryotic signal) in the Shallow Bay sediments; these results support previous results obtained for Arctic sediments . Methanosaeta and Desulfotalea/Desulforhopalus appear to be important in Lake Heywood and Shallow Bay, respectively, and may be globally important in permanently low-temperature sediments .
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