Role of Fly Cleaning Behavior on Carriage of Escherichia coli and Pseudomonas aeruginosa.

Flies are known to be mechanical vectors of bacterial, viral, and parasitic diseases. Although flies are known to transmit disease, the effects of cleaning behavior have not been well studied. This study quantified the cleaning effectiveness and behavior of three fly species: Sarcophaga bullata, Musca domestica L., and Drosophila virilis. Flies were transferred to plates of Escherichia coli or Pseudomonas aeruginosa and allowed to walk on the bacteria for a total of 5 min. After the flies were contaminated, they were either immediately collected to quantify bacteria or were placed onto sterile plates to clean for 5 or 10 min. After cleaning, flies were placed into tubes with 1 ml of sterile 0.85% saline and were gently shaken for 1 min to remove bacteria. A serial dilution was made and 50-µl spot titers were plated. Cleaning behavior was also monitored and scored for a period of 5 min. Results demonstrate a bacterial reduction for both bacteria on all three fly species. Sarcophaga bullata and D. virilis both showed a significant reduction of both bacteria within 10 min, whereas M. domestica only showed a significant reduction in P. aeruginosa. Cleaning behavior increased significantly in flies that were exposed to bacteria compared to flies that were not exposed to bacteria. This study is important, as it demonstrates that fly cleaning could affect mechanical transmission of disease, and additional studies should look at flies' abilities to remove other types of microorganisms.

Regulation of the ferritin heavy-chain homologue gene in the yellow fever mosquito, Aedes aegypti.

In the yellow fever mosquito Aedes aegypti, the ferritin heavy-chain homologue (HCH) gene is induced by blood feeding. This suggests that ferritin may serve as a cytotoxic protector against the oxidative challenge of the blood meal and may be essential for the survival of the insect. In this study, various cis-acting elements for the gene were identified and mapped. Transfection assays showed that the strength and activity of a subset of these elements are orientation-dependent. The shift observed for the ferritin HCH cis-acting elements is unique among known ferritin genes. DNase I footprinting data together with Transfac analyses identified a number of putative sites known for their involvement in developmental and cell proliferation processes.

Identification and mapping of the promoter for the gene encoding the ferritin heavy-chain homologue of the yellow fever mosquito Aedes aegypti.

Mosquitoes are responsible for the transmission of numerous human diseases. The recent development of transgenic mosquitoes provides a new tool to examine molecular interactions between insect vectors and the pathogens they transmit. One focus in generating transgenic mosquito lies on expressing anti-pathogenic proteins at primary sites of pathogenic invasions, specifically the mosquito gut. Promoters that direct the expression of anti-pathogenic proteins in the mosquito gut are thus sought after because they may provide ways to hinder pathogenic development in the mosquito. Here, we report the identification and mapping of a strong promoter from the Aedes aegypti ferritin heavy-chain homologue (HCH) gene. All known insect ferritin HCH genes are expressed in the gut and inducible by an iron overload. Our transfection assays and DNase I footprinting analyses show that the mosquito ferritin HCH-gene contains regulatory elements both upstream and downstream of the transcriptional start site. The promoter of this gene contains a CF2 site, two GATA-binding sites, an E2F site, a TATA-box, an AP-1 site and a C/EBP binding site.

Influence of infected cell growth state on bacteriophage reactivation levels.

Reactivation of UV-C-inactivated Pseudomonas aeruginosa bacteriophages D3C3, F116, G101, and UNL-1 was quantified in host cells infected during the exponential phase, during the stationary phase, and after starvation (1 day, 1 and 5 weeks) under conditions designed to detect dark repair and photoreactivation. Our experiments revealed that while the photoreactivation capacity of stationary-phase or starved cells remained about the same as that of exponential-phase cells, in some cases their capacity to support dark repair of UV-inactivated bacteriophages increased over 10-fold. This enhanced reactivation capacity was correlated with the ca. 30-fold-greater UV-C resistance of P. aeruginosa host cells that were in the stationary phase or exposed to starvation conditions prior to irradiation. The dark repair capacity of P. aeruginosa cells that were infected while they were starved for prolonged periods depended on the bacteriophage examined. For bacteriophage D3C3 this dark repair capacity declined with prolonged starvation, while for bacteriophage G101 the dark repair capacity continued to increase when cells were starved for 24 h or 1 week prior to infection. For G101, the reactivation potentials were 16-, 18-, 10-, and 3-fold at starvation intervals of 1 day, 1 week, 5 weeks, and 1. 5 years, respectively. Exclusive use of exponential-phase cells to quantify bacteriophage reactivation should detect only a fraction of the true phage reactivation potential.

Structure and location of a ferritin gene of the yellow fever mosquito Aedes aegypti.

We have isolated and sequenced a genomic clone encoding the 24- and 26-kDa ferritin subunits in the mosquito Aedes aegypti (Rockefeller strain). The A. aegypti gene differs from other known ferritin genes in that it possesses an additional intron and an unusually large second intron. The additional intron is located within the 5' untranslated region, between the CAP site and the start codon. The second intron contains numerous putative transposable elements. In addition, unlike the human and rat ferritin genes, the A. aegypti ferritin gene is a single copy gene, located at 88.3% FLpter on the q-arm of chromosome 1. Primer extension analysis indicates that the A. aegypti ferritin gene has multiple transcriptional start sites. A differential usage of these sites is observed with varied cellular iron concentrations.

The effects of ultraviolet radiation on the moderate halophile Halomonas elongata and the extreme halophile Halobacterium salinarum.

Both the moderately halophilic bacterium, Halomonas elongata, and the extremely halophilic archaea, Halobacterium salinarum, can be found in hypersaline environments (e.g., salterns). On complex media, H. elongata grows over a salt range of 0.05-5.2 M, whereas, H. salinarum multiplies over a salt range of 2.5-5.2 M. The purpose of this study was to illustrate the effect that solar (UV-A and UV-B) and germicidal radiation (UV-C) had on the growth patterns of these bacteria at varied salt concentrations. Halomonas elongata grown on a complex medium at 0.05, 1.37, and 4.3 M NaCl was found to be more sensitive to UV-A and UV-B radiation, as the salt concentration of the medium increased. Halobacterium salinarum grown on a complex medium at 3.0 and 4.3 M NaCl did not show a significant drop in viability after 39.3 kJ.m-2 of UV-A and UV-B exposure. When exposed to UV-C, H. elongata exhibited substantially more sensitivity than H. salinarum. In H. elongata, differential sensitivity to UV-C was observed. At 0.05 M NaCl, H. elongata was less sensitive to UV-C than at 1.37 and 4.3 M NaCl. Both bacteria showed some photoreactivation when incubated under visible light following both UV-A, UV-B, and UV-C exposure. Mutagenesis following UV-C exposure was demonstrated by both organisms.

Characterization of Pseudomonas aeruginosa bacteriophage UNL-1, a bacterial virus with a novel UV-A-inducible DNA damage reactivation phenotype.

UNL-1, a lytic virus of Pseudomonas aeruginosa, was observed to express a novel inducible DNA damage reactivation activity in UV-A-irradiated P. aeruginosa host cells. The expression of bacteriophage reactivation was quantified in hosts exposed to either UV-C or UV-A radiation. While reactivation of UV-C-damaged UNL-1 was not inducible in UV-C-irradiated host cells, an approximately 13-fold induction was observed in UV-A-irradiated host cells. When host cells were exposed to sunlight, reactivation of damaged UNL-1 virus increased eightfold. The UV-A induction of UNL-1 DNA damage reactivation was supported in hosts lacking recA gene function. This report is the first description of a recA-independent, UV-inducible virus DNA damage repair system. Our findings suggest that a combination of both host and virus DNA repair processes contribute to the persistence and sustained replication of some bacterial viruses in aquatic environments.

Float polishing of optical materials.

The float-polishing technique has been studied to determine its suitability for producing supersmooth surfaces on optical materials, yielding a roughness of <2 A rms. An attempt was made to polish six different materials including fused quartz, Zerodur, and sapphire. The low surface roughness was achieved on fused quartz, Zerodur, and Corning experimental glass-ceramic materials, and a surface roughness of <1 A rms was obtained on O-cut single-crystal sapphire. Presumably, similar surface finishes can also be obtained on CerVit and ULE quartz, which could not be polished satisfactorily in this set of experiments because of a mismatch between sample mounting and machine configuration.

Bender-bimorph scanner analysis.

The bender-bimorph beam steerer is a piezoelectrically driven optical device capable of pointing a light beam of several centimeters diameter anywhere in a several degree wide field of view with a control bandwidth of several hundred hertz. Its operation depends on the mechanical motion of a piezoelectric bender-bimorph to tilt a mirror, which in turn deflects the light beam. Fundamental relationships governing the operation of such a device constrain the product of mirror diameter, scan amplitude, and control bandwidth so that optimization of a bender-bimorph beam steerer system is a matter of trade-off considerations. A theoretical analysis of bender-bimorph performance is carried out. Expressions are derived for the resonant frequency of a loaded bimorph and its deflection. Graphs of these expressions are presented with several parameters treated as variables. For the numerical calculations, a very light beryllium mirror the same width as the bimorph is assumed. Some experimental data were collected and compared with the predicted performance (i.e., resonant frequency and deflection). The comparison verified the theoretical expressions.