Spores viability

One of the long-standing criticisms of Bis is that the incubation period required in order to confirm a satisfactory sterilization process imposes an undesirable delay on the release of the product. This problem has been overcome, with respect to steam sterilization at least, by the use of a detection system in which a spore enzyme, a-glucosidase (reflective of spore viability), converts a non-fluorescent substrate into a fluorescent product in as little as Ihour. 

Nabais AMA, da Fonseca MMR (1995) The effect of solid medium composition on growth and sporulation of Streptomyces clavuligerus spore viability dming storage at 4°C. Biotechnol Tech 9 361- 364... 

Table 8.3 Relatedness within the cactophilic G+C groups for Starmera (a), Phajfomices (h) and Pichia (c). The upper triangle has DNA-DNA reassociation values and the lower triangle has hybrid spore viabilities, a, b, 33 mol% G+C Species c, 30 mol% G+C Species. Sources are listed at the bottom of the table. Spaces indicate that no data are available. Pichia heedii has 33 mol% G+C, but shows only background homology with either Starmera or Phajfomyces species. Pichia barkeri has 36 mol% G+C, but has a remarkably high DNA-DNA homology of 20% with P. kluyveri.

Relatively less work has been done on immobilization of plant and animal cells and spores of microbes in silica matrixes. The main drawback is less viability of the cells in sol-gel matrices. Thus more refined methods are required to utilize harness of the whole cells entrapped in sol-gel matrices and biosensing applications. At the same time studies such as interactions between sol-gel matrices and whole cells and metabolic changes during immobilization have to be closely monitored for the exploration of new matrices and methods. 

Experiments on board the NASA Long Duration Exposure facility have been performed with spores from the bacterium Bacillus subtilis, allowing them to be exposed to the extreme conditions of space. Low pressures and highly energetic particles are dominant in space and most importantly around the Sun, including an intense UV radiation field. It is the latter that is the most destructive in terms of viability of the spores, and under controlled conditions the extreme UV exposure is four orders of magnitude more likely to kill the cells than when screened. Crucially, however, not all spores were killed. Protection of the spores from the UV field for example within the interior of the meteorite suggests that the spores... 

The dye 4, 6-Diamidino-2-PhenyIindole (DAPI) in 0.001%W/V aqueous solution can be used directly on smears, ciyosections and embedded specimens to locate and count culture bacteria, without regard to their viability, in cheese and other cultured products. The dye reacts with nucleic acids by intercalation. Excitation at 360nm is best for this dye. It is worth noting two other facts about its use. DAPI cross reacts with dairy proteins, but the color of the protein-dye complex is different from that of the nucleic acid-dye complex (the latter is a steely blue/white) and so the two reactions may be discriminated. The dye also may take up to 15 minutes to enter bacterial cells, particularly spores, before fluorescence is observed. An alternative nucleic acid dye, Ethidium Bromide, has less contrast between the fluorescence induced in cells and the fluorescence of cross-reacting dairy proteins. It should be tried in other products such as meats if DAPI is not successful. 

Berny, J. F., and Hennebert, G. L. (1991), Viability and stability of yeast cells and filamentous fungus spores during freeze-drying Effects of protectants and cooling rates, Mycologia, 83, 805-815. 

Yang, W. -W. East Viability Assessment of Clostridium spores - Survival in Extreme Environments. California Institute of Technology Pasadena, CA, 2009. 

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