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Identification and Functional Characterization of the Lactococcus lactis rfb Operon, Required for dTDP-Rhamnose Biosynthesis. Ingeborg C. Boels, 2004.dTDP-rhamnose is an important precursor of cell wall polysaccharides and rhamnose-containing exopolysaccharides [EPS] in Lactococcus lactis . We cloned the rfbACBD operon from L . lactis MG1363, which comprises four genes involved in dTDP-rhamnose biosynthesis. When expressed in Escherichia coli, the lactococcal rfbACBD genes could sustain heterologous production of the Shigella flexneri O antigen, providing evidence of their functionality. Overproduction of the RfbAC proteins in L . lactis resulted in doubled dTDP-rhamnose levels, indicating that the endogenousRfbAC activities control the intracellular dTDP-rhamnose biosynthesisrate . However, RfbAC overproduction did not affect rhamnose-containing B40-EPS production levels . A nisin-controlled conditional RfbBD mutant was unable to grow in media lacking the inducer nisin, indicating that the rfb genes have an essential role in L . lactis. Limitation of RfbBD activities resulted in the production of altered EPS . The monomeric sugar of the altered EPS consistedof glucose, galactose, and rhamnose at a molar ratio of 1:0.3:0.2,which is clearly different from the ratio in the native sugar.Biophysical analysis revealed a fourfold-greater molecular massand a twofold-smaller radius of gyration for the altered EPS,indicating that these EPS are more flexible polymers with changedviscosifying properties . This is the first indication that enzymeactivity at the level of central carbohydrate metabolism affectsEPS composition. Distribution of Giardia duodenalis Genotypes and Subgenotypes in Raw Urban Wastewater in Milwaukee, Wisconsin. Irshad M. Sulaiman, 2004.Giardia cysts in 131 raw wastewater samples from Milwaukee, Wis., were genotyped by sequence analysis of the triosephosphate isomerase gene which showed the presence of two distinct genotypes (assemblages A and B) of Giardia duodenalis . Of the 131 samples, 111 belonged to assemblage A, and the remaining samples belonged to assemblage B . A high degree of genetic polymorphism was evident within the assemblage B cluster, with 10 distinct subgenotypes identified, eight of which have not been reported before . Distinctive Protein Signatures Provide Molecular Markers and Evidence for the Monophyletic Nature of the Deinococcus-Thermus Phylum. Emma Griffiths, 2004.The Deinococcus-Thermus group of species is currently recognized as a distinct phylum solely on the basis of their branching in 16S rRNA trees . No unique biochemical or molecular characteristics that can distinguish this group from all other bacteria are known at present . In this work, we describe eight conserved indels (viz., inserts or deletions) in seven widely distributed proteins that are distinctive characteristics of the Deinococcus-Thermus phylum but are not found in any other group of bacteria . The identified signatures include a 7-amino-acid (aa) insert in threonyl-tRNA synthetase, 1- and 3-aa inserts in the RNA polymerase ß' subunit, a 5-aa deletion in signal recognition particle (Ffh/SR54), a 2-aa insert in major sigma factor 70 (  70), a 2-aa insert in seryl-tRNA synthetase (SerRS), a 1-aa insert in ribosomal protein L1, and a 2-aa insert in UvrA homologs . By using PCR primers for conserved regions, fragments of these genes were amplified from a number of Deinococcus-Thermus species, and all such fragments (except SerRS in Deinococcus proteolyticus) were found to contain the indicated signatures . The presence of these signatures in various species from all three known genera within this phylum, viz., Deinococcus, Thermus, and Meiothermus, provide evidence that they are likely distinctive characteristics of the entire phylum which were introduced in a common ancestor of this group . The signature in SerRS, which is absent in D . proteolyticus, was likely introduced after the branching of this species . Phylogenetic studies as well as the nature of the inserts in some of these proteins (viz.,
70 and SerRS) also support a sister group relationship between the Thermus and the Meiothermus genera . The identified signatures provide strong evidence for the monophyletic nature of the Deinococcus-Thermus phylum . These molecular markers should prove very useful in the identification of new species related to this group .
Novel Derivatives of 9,10-Anthraquinone Are Selective Algicides against the Musty-Odor Cyanobacterium Oscillatoria perornata. Kevin K. Schrader, 2003.Musty "off-flavor" in pond-cultured channel catfish (Ictalurus punctatus) costs the catfish production industry in the United States at least $30 million annually . The cyanobacterium Oscillatoria perornata (Skuja) is credited with being the major cause of musty off-flavor in farm-raised catfish in Mississippi . The herbicides diuron and copper sulfate, currently used by catfish producers as algicides to help mitigate musty off-flavor problems, have several drawbacks, including broad-spectrum toxicity towards the entire phytoplankton community that can lead to water quality deterioration and subsequent fish death . By use of microtiter plate bioassays, a novel group of compounds derived from the natural compound 9,10-anthraquinone have been found to be much more selectively toxic towards O . perornata than diuron and copper sulfate . In efficacy studies using limnocorrals placed in catfish production ponds, application rates of 0.3 µM (125 µg/liter) of the most promising anthraquinone derivative, 2-[methylamino-N-(1'-methylethyl)]-9,10-anthraquinone monophosphate (anthraquinone-59), dramatically reduced the abundance of O . perornata and levels of 2-methylisoborneol, the musty compound produced by O . perornata . The abundance of green algae and diatoms increased dramatically 2 days after application of a 0.3 µM concentration of anthraquinone-59 to pond water within the limnocorrals . The half-life of anthraquinone-59 in pond water was determined to be 19 h, making it much less persistent than diuron . Anthraquinone-59 appears to be promising for use as a selective algicide in catfish aquaculture .
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