Scandium 45 in meteoritic irons

This report presents the results of determinations of cosmogenic ^Sc and light noble gases in iron meteorites. Sc and REE were simultaneously determined using radiochemical neutron activation method. This method is sensitive enough for detection of as little as lower than 10^gSc/g, compared to the level of cosmic ray effects in irons which are usually in the range of 10^-10^gSc/g. The lowest concentration found in irons was 2×10^gSc/g in the Campo del Cielo and similar contents were observed in the Gibeon, DRP-78008 (and Brenham-metal). Even at these low levels, Sc seems mostly attributable to cosmic ray production. The Sc content in irons is best compared with cosmogenic ^4He. The ratio of Sc to ^4He, approximately 1×10^gSc/1×10^cc ^4He, or an average atomic ratio of 1 : 19±3,was observed independent of shielding. Technical aspects of metal phase separation from ordinary chondrites were studied. In one Peace River metal sample, 0.9 ppbSc was found. This number corresponds to 0.01% of the stone phase in the metal. This level of contamination seems still higher than the cosmogenic level of 0.2 ppbSc expected in the metal phase of this meteorite

Protozoal ciliate promotes bacterial autoinducer-2 accumulation in mixed culture with Escherichia coli

We have previously demonstrated conjugation of Escherichia coli into vacuoles of the protozoal ciliate (Tetrahymena thermophila). This indicated a possible role of ciliates in evoking bacterial quorum sensing, directly connecting bacterial survival via accumulation in the ciliate vacuoles. We therefore assessed if ciliates promoted bacterial autoinducer (AI)-2 accumulation with vacuole formation, which controls quorum sensing. E. coli AI-2 accumulation was significantly enhanced in the supernatants of a mixed culture of ciliates and bacteria, likely depending on ciliate density rather than bacterial concentration. As expected, AI-2 production was significantly correlated with vacuole formation. The experiment with E. coli luxS mutants showed that ciliates failed to enhance bacterial AI-2 accumulation, denying a nonspecific phenomenon. Fluorescence microscopy revealed accumulation of fragmented bacteria in ciliate vacuoles, and, more importantly, expulsion of the vacuoles containing disrupted bacteria into the culture supernatant. There was no increase in the expression of luxS (encoding AI-2) or ydgG (a transporter for controlling bacterial export of AI-2). We conclude that ciliates promote bacterial AI-2 accumulation in a mixed culture, via accumulation of disrupted bacteria in ciliate vacuoles followed by expulsion of the vacuoles, independently of luxS or ydgG gene induction. This is believed to be the first demonstration of a relationship between E. coli AI-2 dynamics and ciliates. In the natural environment, ciliate biotopes may provide a survival advantage to bacteria inhabiting such biotopes, via evoking quorum sensing

Ciliates promote the transfer of the gene encoding the extended-spectrum -lactamase CTX-M-27 between Escherichia coli strains

OBJECTIVES:The mechanism by which Escherichia coli acquires multidrug resistance genes from other bacteria in the natural environment or livestock is still unclear. The ability of ciliates to promote the transfer of genes encoding extended-spectrum β-lactamases (ESBLs) between the CTX-M-27 donor and clinically isolated recipient E. coli strains was investigated. METHODS:Equal amounts (∼10(9) cfu) of donor cefotaxime-resistant E. coli and recipient ciprofloxacin-resistant E. coli strains were mixed together in the presence or absence of 10(5) ciliates in Page's amoeba saline for 24 h, in the presence or absence of certain drugs (cytochalasin D, cycloheximide and latrunculin B). RESULTS:Gene transfer frequency in the presence of ciliates was estimated at ∼10(-6); in the absence of ciliates it was ∼10(-10). Protein synthesis (cycloheximide) or phagocytosis (cytochalasin D or latrunculin B) inhibitors significantly reduced the frequency of gene transfer. CONCLUSIONS:Ciliates promote the transfer of genes encoding ESBLs between E. coli strains, implying that the presence of ciliates may provide a significant impact on emerging multidrug-resistant bacteria

Ciliates rapidly enhance the frequency of conjugation between Escherichia coli strains through bacterial accumulation in vesicles

The mechanism underlying bacterial conjugation through protozoa was investigated. Kanamycin-resistant Escherichia coli SM10λ+ carrying pRT733 with TnphoA was used as donor bacteria and introduced by conjugation into ciprofloxacin-resistant E. coli clinical isolate recipient bacteria. Equal amounts of donor and recipient bacteria were mixed together in the presence or absence of protozoa (ciliates, free-living amoebae, myxamoebae) in Page's amoeba saline for 24 h. Transconjugants were selected with Luria Broth agar containing kanamycin and ciprofloxacin. The frequency of conjugation was estimated as the number of transconjugants for each recipient. Conjugation frequency in the presence of ciliates was estimated to be approximately 10^[-6], but in the absence of ciliates, or in the presence of other protozoa, it was approximately 10^[-8]. Conjugation also occurred in culture of ciliates at least 2 h after incubation. Successful conjugation was confirmed by polymerase chain reaction. Addition of cycloheximide or latrunculin B resulted in suppression of conjugation. Heat killing the ciliates or bacteria had no effect on conjugation frequency. Co-localization of green fluorescent protein-expressing E. coli and PKH67-vital stained E. coli was observed in the same ciliate vesicles, suggesting that both donor and recipient bacteria had accumulated in the same vesicle. In this study, the conjugation frequency of bacteria was found to be significantly higher in vesicles purified from ciliates than those in culture suspension. We conclude that ciliates rapidly enhance the conjugation of E. coli strains through bacterial accumulation in vesicles