Highly selective acridine and ethidium staining of bacterial DNA and RNA

Detection of dsRNA by Acridine Orange Staining

Acridine orange is a nucleic acid binding dye that emits green fluorescence when bound to double-stranded DNA or RNA and red fluorescence when bound to single-stranded DNA or RNA under ultraviolet light. This unique characterization allows it to be used for distinguishing or visualization of dsRNA. Here, we present a convenient and efficient protocol for detecting dsRNA in polyacrylamide gels.

Self-assembled nanocomposite film with tunable enhanced fluorescence for the detection of DNA

In this study, a simple and environmentally friendly, silver nanocomposite film was prepared via the in situ reduction of silver ions in self-assembled chitosan (CS)/sodium alginate film matrixes. Negatively charged DNA containing the fluorescent intercalator acriflavine (Acf) was assembled on the surface of the silver nanocomposite film, to facilitate the detection of DNA. A tunable fluorescence enhancement was achieved for the Acf in the silver nanocomposite film simply by changing the thickness of the interlayer between the DNA and the silver nanocomposite film. Using the interlayer prepared by an assembly of poly(acrylic acid) and CS, a significant enhancement in the fluorescence of Acf was obtained. Owing to the ability of Acf to intercalate into DNA, this hybrid system with an enhanced Acf fluorescence could be used to monitor the template-independent DNA elongation process in a facile, high-efficiency, label-free fashion.

The progression of the intra-erythrocytic cell cycle of Plasmodium falciparum and the role of the centriolar plaques in asynchronous mitotic division during schizogony

The cell division cycle and mitosis of intra-erythrocytic (IE) Plasmodium falciparum are poorly understood aspects of parasite development which affect malaria molecular pathogenesis. Specifically, the timing of the multiple gap (G), DNA synthesis (S) and chromosome separation (M) phases of parasite mitosis are not well defined, nor whether genome divisions are immediately followed by cleavage of the nuclear envelope. Curiously, daughter merozoite numbers do not follow the geometric expansion expected from equal numbers of binary divisions, an outcome difficult to explain using the standard model of cell cycle regulation. Using controlled synchronisation techniques, confocal microscopy to visualise key organelles and fluorescence in situ hybridization (FISH) to follow the movements and replication of genes and telomeres, we have re-analysed the timing and progression of mitotic events. The asynchronous duplications of the P. falciparum centrosome equivalents, the centriolar plaques, are established and these are correlated with chromosome and nuclear divisions in a new model of P. falciparum schizogony. Our results improve the resolution of the cell cycle and its phases during P. falciparum IE development, showing that asynchronous, independent nuclear division occurs during schizogony, with the centriolar plaques playing a major role in regulating mitotic progression.

Ex vivo gingival-biofilm consortia

AIMS

To develop a protocol for harvesting ex vivo samples of gingival-biofilm consortia and to investigate their basic characteristics.

METHODS AND RESULTS

Gingival epithelial cells with attached biofilm were collected from healthy subjects by taking a smear. The bacterial viability was estimated via the alteration of the membrane permeability and metabolic activity via the double/single-stranded nucleic acid ratio using a confocal laser-scanning microscope. Morphological analysis was performed by scanning and transmission electron microscopy. Additionally, microbiological estimations were made. The electron microscopy revealed fimbriae-mediated adhesion and the formation of a biofilm matrix. Most bacteria were viable and had a high metabolic activity.

CONCLUSIONS

The presented study offers an easy to follow approach for harvesting samples of gingival-biofilm consortia. The latter differs considerably from the supragingival plaque in viability and zonal distribution. Related to free-living and in vitro-grown biofilms, the gingiva-associated biofilm revealed an atypically high metabolic activity.

SIGNIFICANCE AND IMPACT OF THE STUDY

Biofilm fragments should possess the basic features of the entire gingiva-associated biofilm; which as yet cannot be simulated in vitro. Thus, samples of ex vivo gingival-biofilm consortia can be used to investigate the resistance of oral biofilms against antibiotics and biocides.

The use of blue-excitable nucleic-acid dyes for the detection of bacteria in well water using a simple field fluorometer and a flow cytometer

The blue-excitable nucleic acid dyes Coriphosphine O (CPO), YOYO-1, and YOPRO-1 were evaluated to rapidly detect the presence of bacteria in well water samples using a simple field fluorometer (Turner Designs, Sunnyvale, CA, Model 10-AU-005) and a tabletop flow cytometer (Coulter Epics XL). The dyes were first titrated on the Turner Designs Model 10-AU field fluorometer with log-fold dilutions of Esherichia coli, since this organism is the indicator organism for water contamination. A detection limit of 10(4) Colony Forming Units per ml (CFU/ml) was established for YOPRO-1 and 10(5) CFU/ml for YOYO-1. The detection limit with CPO was determined to be 10(7) CFU/ml due to the high background fluorescence of the dye. The dyes were also evaluated with ragweed pollen to gauge the effect of a biological interferent. Ten well-water samples were subsequently analyzed using the technique. The results showed that only YOYO-1 correctly detected all the samples that were positive according to the reference laboratory. YOPRO-1 correctly detected only one of four positive samples. Analysis with the CPO dye was inconclusive due to high background fluorescence. The samples were then subjected to analysis on the flow cytometer. Results obtained with YOYO-1 compared well to those obtained on the fluorometer and by the reference techniques. YOPRO-1 performed better on the flow cytometer than with the simple fluorometer, correctly detecting three of four positive samples. Although the CPO results showed a very slight increase of green fluorescence with positive samples, they were largely indistinguishable from negative samples. This study suggests YOYO-1 could be useful with either a simple fluorometer or with a tabletop flow cytometer in screening water samples for the presence of bacterial contamination.