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The Escherichia coli Fis Protein Stimulates Bacteriophage 
Integrative Recombination In Vitro.Dominic Esposito, 2003.The Escherichia coli nucleoid-associated protein Fis was previously shown to be involved in bacteriophage lambda site-specific recombination in vivo, enhancing the levels of both integrative recombination and excisive recombination . While purified Fis protein was shown to stimulate in vitro excision, Fis appeared to have no effect on in vitro integration reactions even though a 15-fold drop in lysogenization frequency had previously been observed in fis mutants . We demonstrate here that E . coli Fis protein does stimulate integrative lambda recombination in vitro but only under specific conditions which likely mimic natural in vivo recombination more closely than the standard conditions used in vitro . In the presence of suboptimal concentrations of Int protein, Fis stimulates the rate of integrative recombination significantly . In addition, Fis enhances the recombination of substrates with nonstandard topologies which may be more relevant to the process of in vivo phage lambda recombination . These data support the hypothesis that Fis may play an essential role in lambda recombination in the host cell . Mutational Analysis of the TolA C-Terminal Domain of Escherichia coli and Genetic Evidence for an Interaction between TolA and TolB. Jean François Dubuisson, 2002.The Tol proteins are involved in the outer membrane stability of gram-negative bacteria . The C-terminal domain of TolA was mutagenized to identify residues important for its functions . The isolation of suppressor mutants of tolA mutations in the tolB gene confirmed an interaction between TolAIII and the N-terminal domain of TolB . Determination of In Situ Bacterial Growth Rates in Aquifers and Aquifer Sediments. Brian J. Mailloux, 2003.Laboratory and field-scale studies with stained cells were performed to monitor cell growth in groundwater systems . During cell division, the fluorescence intensity of the protein stain 5-(and 6-)-carboxyfluorescein diacetate succinimidyl ester (CFDA/SE) for each cell is halved, and the intensity can be tracked with a flow cytometer . Two strains of bacteria, Comamonas sp . strain DA001 and Acidovorax sp . strain OY-107, both isolated from a shallow aquifer, were utilized in this study . The change in the average generation or the average fluorescence intensity of the CFDA/SE-stained cells could be used to obtain estimates of doubling times . In microcosm experiments, the CFDA/SE-based doubling times were similar to the values calculated by total cell counting and were independent of cell concentration . Intact and repacked sediment core experiments with the same bacteria indicated that changes in groundwater chemistry were just as important as growth rates in determining planktonic cell concentrations . The growth rates within the sediment cores were similar to those calculated in microcosm experiments, and preferential transport of the daughter cells was not observed . The experiments indicated that the growth rates could be determined in systems with cell losses due to other phenomena, such as attachment to sediment or predation . Application of this growth rate estimation method to data from a field-scale bacterial transport experiment indicated that the doubling time was approximately 15 days, which is the first known direct determination of an in situ growth rate for bacteria in an aquifer .
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