Intracellular pH determination of pristinamycin-producing Streptomyces pristinaespiralis by image analysis

Intracellular pH (pH(i)) is an essential parameter in the regulation of intracellular processes. Thus, its measurement might provide clues regarding the physiological state of cells cultivated in vitro. pH(i) of the filamentous, pristinamycin-producing Streptomyces pristinaespiralis was determined by epifluorescence microscopy and image analysis using the pH-sensitive fluorescent probe BCECF-AM [2', 7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein, acetoxymethyl ester]. Staining cell culture samples (OD(660)=1) of S. pristinaespiralis with 20 microM BCECF at 28 degrees C for 30 min yielded a green/red fluorescence ratio (R:(527/600)) that correlated with the pH(i) of the cells for values ranging from 6.5 to 8.5. When S. pristinaespiralis was cultivated in pristinamycin-producing conditions (in batch mode, with a constant external pH of 6.8), the measured pH(i) varied between 6.3 and 8.7. In fact, pH(i) correlated with the excretion of pristinamycins and glucose consumption during the production process.

Biomass quantification by image analysis

Microbiologists have always rely on microscopy to examine microorganisms. When microscopy, either optical or electron-based, is coupled to quantitative image analysis, the spectrum of potential applications is widened: counting, sizing, shape characterization, physiology assessment, analysis of visual texture, motility studies are now easily available for obtaining information on biomass. In this chapter the main tools used for cell visualization as well as the basic steps of image treatment are presented. General shape descriptors can be used to characterize the cell morphology, but special descriptors have been defined for filamentous microorganisms. Physiology assessment is often based on the use of fluorescent dyes. The quantitative analysis of visual texture is still limited in bioengineering but the characterization of the surface of microbial colonies may open new prospects, especially for cultures on solid substrates. In many occasions, the number of parameters extracted from images is so large that data-mining tools, such as Principal Components Analysis, are useful for summarizing the key pieces of information.

Physiological investigations by image analysis

Modern quantitative image analysis has been extensively used to characterize the morphology of microorganisms, especially those of the filamentous type. More recently physiological features have been quantified, making use of classical stains as well as fluorescent dyes. The potential of the technique is illustrated by a detailed analysis of the differentiation of Streptomyces ambofaciens. Three different staining procedures have been used to monitor the thinning and septation of hyphae (with propidium iodide staining), the leakage of cellular components through the membrane (with carbol gentian violet staining) and the respiration (with INT staining) in a batch submerged culture.

Crystal data for antimony molybdenum oxide Sb2MoO6

The powder data for antimony molybdenum oxide Sb2MoO6 are reported. This compound is triclinic, P{\bar 1}, with a = 7.481(4), b = 7.504(3), c = 10.120(1) Å, α = 70.43(3), β = 70.91(4), γ = 83.34(7)°; U = 505.9(5) Å3; Z = 4; Dx = 5.74 Mg m−3. The structure is of the fluorite type but it is distorted. Pseudo-monoclinic cells as reported by Parmentier, Courtois & Gleitzer [Bull. Soc. Chim. Ft. (1974), 1–2, 75–77] or that obtained with program TRACER [Lawton & Jacobson (1965). Mobil Oil Corporation Research Department; Lawton (1967). Mobil Oil Corporation Research Department] are also considered and discussed. Neutron diffraction gives further evidence of the triclinic lattice. The JCPDS Diffraction File No. for Sb2MoO6 is 33–1491.