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Triclosan (2, 4, 4′-trichloro-2′-hydroxydiphenyl ether) is a bisphenol antimicrobial agent that can promote antibiotic resistance in bacteria. The purpose of the present study was to determine a possible association between triclosan exposure and bacterial susceptibility of the staphylococci to the antibiotic ciprofloxacin. Determining this relationship will allow a deeper understanding of triclosan's affects on the development of antibiotic resistance. For this study, a one month double-blind and randomized home hygiene intervention trial was conducted that consisted of 12 participants. Half of these individuals were randomly assigned to use a non-antibacterial soap, while the other half were assigned to use a similar appearing liquid soap containing 0.2%triclosan. The participants were required to use only those products that were assigned to them, and were asked not to change any of their other normal hygiene practices. If any of these participants were found to use any other home hygiene product that was not assigned to them, they were automatically dropped from this study. A hand-wash culture from each participant was taken before and after the use of the soap for the period of one month. These cultures were then plated on increasing concentrations of the antibiotic ciprofloxacin to determine if ciprofloxacin minimal inhibitory concentrations (MICs) and susceptibility trends changed in response to triclosan exposure. Although our sample size was not large enough for our results to be considered significant, the results do suggest that antibacterial soap containing triclosan does indeed decrease ciprofloxacin susceptibility in the staphylococci.
Spores of the fern Ceratopteris richardii can develop as either males or hermaphrodites; the difference in sex is determined by the pheromone antheridiogen secreted by the hermaphrodite. During spore germination, the first spores to germinate are hermaphrodites, which will secrete antheridiogen into the surroundings. Antheridiogen will induce later germinating spores to develop as males. Previous studies have shown that antheridiogen is necessary for both induction and maintenance of males. In the present study, fully developed males were isolated from hermaphrodites in order to test the effects of various parameters on their conversion to hermaphrodites. The results show that in the absence of antheridiogen, males converted to hermaphrodites. However, males exposed to higher levels of antheridiogen converted more slowly than males exposed to lower levels. Furthermore, males exposed to antheridiogen for an extended period converted at a lower frequency than males exposed for a shorter period. When test spores were sown in the presence of converted males, all germinated and developed as males, indicating that converted males have the ability to secrete antheridiogen as do normal hermaphrodites. Finally, converted males were able to self-fertilize and produce healthy, fertile sporophyte offspring.
The study of embryonic development in Drosophila melanogaster has contributed major insights into the mechanisms of development, gene regulation and evolution. We have explored the role of heat shock factor (HSF) in regulation of an even-skipped (eve) transgene in Drosophila embryos. The traditional role of HSF is to activate transcription of the heat shock proteins (HSPs) in response to stresses. Previous work had not implicated HSF in regulating non-HSP targets in embryos. Our results demonstrate that HSF is capable of regulating a developmental gene in embryos. This is the first demonstration that HSF is capable of activity in embryos that is not related to environmental stress.
The polymerase chain reaction (PCR) is an important technique for biology students to learn. PCR utilizes DNA polymerases isolated from archaea or bacteria, like Thermus aquaticus (Taq), to amplify target DNA sequences. In this paper we describe lab activities where students clone the gene for, express, and purify Taq DNA polymerase and assay for its activity. These lab activities employ plasmids containing multiple components of the lac operon thereby giving students practical experience with a genetic regulatory system they learn about in the classroom. Taq DNA polymerase purification simply involves cell lysis, a heat incubation step, and centrifugation, with the resulting supernatant containing highly pure and active Taq DNA polymerase.