RESUMEN
AIM: Development of a new chromatic (colorimetric/fluorescence) bacterial sensor, for rapid, sensitive and versatile detection of bacterial proliferation. METHODS AND RESULTS: We constructed agarose-embedded chromatic films which produce dramatic colour changes and fluorescence transformations in response to bacterial growth. The sensing constructs comprise glass-supported Langmuir-Schaeffer phospholipid/polydiacetylene films that undergo both blue-red transformations and induction of intense fluorescence following interactions with bacterially secreted amphiphilic compounds that diffuse through the agarose. The agarose matrix coating the sensor film further contains growth nutrients, facilitating signal amplification through promotion of bacterial culture proliferation. The agarose layer also constitutes an effective barrier for reducing background signals not associated with the bacteria. We demonstrate the applications of the new sensor for the detection of Gram-negative and Gram-positive bacteria, and for screening specimens of physiological fluids (blood and urine) and foods (meat) for bacterial contaminations. CONCLUSIONS: The experiments demonstrate that the new agarose-embedded film constructs are capable of bacterial detection through visible colour transitions and fluorescence emission recorded in conventional apparatuses. SIGNIFICANCE AND IMPACT OF THE STUDY: This work demonstrated a new simple chromatic platform for bacterial detection, based on the generation of easily recorded colour and fluorescence changes. The new bacterial detection scheme is highly generic and could be employed for varied practical uses, in which, rapid reporting on bacterial presence is required.
Asunto(s)
Bacterias/aislamiento & purificación , Microbiología de Alimentos , Adsorción , Materiales Biomiméticos , Colorimetría/métodos , Liposomas , Nanotecnología , Polímero Poliacetilénico , Polímeros , Poliinos , Sefarosa , Espectrometría de FluorescenciaRESUMEN
Four dogs with Rocky Mountain spotted fever developed extensive dermal necrosis. Factors contributing to this complication included delay in initiation of appropriate therapy.
Asunto(s)
Enfermedades de los Perros/patología , Fiebre Maculosa de las Montañas Rocosas/veterinaria , Piel/patología , Animales , Perros , Femenino , Masculino , Necrosis , Fiebre Maculosa de las Montañas Rocosas/patologíaRESUMEN
The DNA-damaging agents mitomycin C and UV irradiation, as well as the DNA-synthesis inhibitors nalidixic acid, novobiocin and coumermycin, induce the de novo synthesis of luciferase and in vivo luminescence in dark variant cells of the luminous bacteria Photobacterium leiognathi. Mitomycin C and nalidixic acid also cause the induction of luminescence in wild-type cells in the absence of its natural inducer. In spite of the high level of in vivo luminescence of the treated dark-variant cells, none of these agents result in the appearance of genetically luminous revertants. The possibility is discussed that these agents phenotypically induce luminescence through their ability to trigger 'SOS functions', which in turn leads to the transitory inactivation of certain repressors.
Asunto(s)
Luciferasas/biosíntesis , Mutación/efectos de los fármacos , Photobacterium/genética , Aminocumarinas , Cumarinas/farmacología , Activación Enzimática , Mitomicinas/farmacología , Mutación/efectos de la radiación , Ácido Nalidíxico/farmacología , Novobiocina/farmacología , Photobacterium/efectos de la radiación , Pirroles/farmacología , Rayos UltravioletaRESUMEN
Acridine dyes and other DNA-intercalating agents such as ethidium bromide, theophylline, and caffeine induce luminescence in dark variants (K variants) different luminous species of bacteria, as well as in their wild-type luminous cells, prior to induction. The increase in luminescence appears 10-20 min after addition of these agents and is inhibited by chloramphenicol or rifampicin. Addition of these agents affects the synthesis of both luciferase and aldehyde-synthesizing enzymes. It is hypothesized that these agents, through their intercalation into DNA, cause configurational changes resulting in derepressed transcription of the luminescence operon.
Asunto(s)
Acridinas/farmacología , Sustancias Intercalantes/farmacología , Mediciones Luminiscentes , Photobacterium/efectos de los fármacos , Inducción Enzimática/efectos de los fármacos , Luciferasas/biosíntesis , Luciferasas/genética , Transcripción Genética/efectos de los fármacosRESUMEN
A spontaneous dark variant of the luminous bacterium Photobacterium leiognathi was isolated. The reversion frequency of this variant to genetic-hereditary luminescent cells is greatly increased by nanogram quantities of different base-substitution and frameshift agents. This makes it possible to detect mutagenic compounds at concentrations 100 times lower than that detected by the Ames Test. Curing agents, such as acridine dyes, ethidium bromide and sodium dodecyl sulfate, are also very active in the reversion of this dark variant to the luminous state, but fail to revert it to a genetic-hereditary luminescent type. The nature of the primary mutation in the dark variant, and the potential use of this luminescence system for detecting different classes of carcinogenic chemical, are discussed.
Asunto(s)
Evaluación Preclínica de Medicamentos/métodos , Mutágenos , Photobacterium/genética , Técnicas Genéticas , Variación Genética , Mediciones Luminiscentes , MutaciónRESUMEN
The synthesis of killer double-stranded ribonucleic acid (dsRNA) in Saccharomyces cerevisiae was examined in seven different cell division cycle mutants (cdc) that are defective in nuclear deoxyribonucleic acid replication and contain the "killer character." In cdc28, cdc4, and cdc7, which are defective in the initiation of nuclear deoxyribonucleic acid synthesis, and in cdc23 or in cdc14, defective in medial or late nuclear division, an overproduction of dsRNA at the restrictive temperature was observed. In contrast to the above mutants, the synthesis of killer dsRNA is not enhanced at the restrictive temperature in either cdc8 or cdc21, which are defective in deoxyribonucleic acid chain elongation. Examination of killer sensitive strains (cdc7 K- and cdc4 K-) has shown that the complete killer dsRNA genome is essential for the overproduction of dsRNA at the restrictive temperature.