Uptake of UVc induced photoproducts of dipicolinic acid by Bacillus subtilis spores - Effects on the germination and UVc resistance of the spores.

Dipicolinic acid (DPA) is a specific molecule of bacterial spores which is essential to their resistance to various stresses such as ultraviolet (UV) exposure and to their germination. DPA has a particular photochemistry that remains imperfectly understood. In particular, due to its ability to absorb UVc radiation, it is likely to form in vitro a wide variety of photoproducts (DPAp) of which only about ten have been recently identified. The photochemical reactions resulting in DPAp, especially those inside the spores, are still poorly understood. Only one of these DPAp, which probably acts as a photosensitizer of DNA upon exposure to UVc, has been identified as having an impact on spores. However, as UVc is required to form DPAp, it is difficult to decouple the overall effect of UVc exposure from the possible effects of DPAp alone. In this study, DPAp were artificially introduced into the spores of the FB122 mutant strain of Bacillus subtilis, one that does not produce DPA. These experiments revealed that some DPAp may play a positive role for the spore. These benefits are visible in an improvement in spore germination rate and kinetics, as well as in an increase in their resistance to UVc exposure.

[The mucus: a medium of life]. / Le mucus : un milieu de vie.

OBJECTIVES: To investigate whether mucus, with its complex structure and specific functional properties, is a medium for life? PATIENTS AND METHODS: We compared cervical and nasal mucus samples collected from 45 ovulatory women consulting for sterility and 5 menopausal women respectively. We analyzed the physicochemical and functional characteristics. We also performed 266 sperm penetrability tests. We studied 32 samples using scanning electron microscope, according to Hexamethyl-Disilasane technique and the critical point drying method. RESULTS: Both types of mucus had 10cm spin abilities and typical ferning patterns. The pH were similar (8.09±0.58 and 8.46±0.32 for cervical and nasal mucus, respectively) as well as the percentages of positive sperm penetration test (55.6 and 40.6 respectively). We observed similar patterns of spermatozoa mobility in both types of mucus. Under the scanning electron microscope, structures resembled woven fabric, with a stretched and rigid framework. Filaments of different diameters formed variable loose meshes. Thinner filaments linked together thicker filaments measuring between 300 and 400nm. The intermediate filaments varied between 100 and 200nm. Very thin and sparse filaments crossed the meshes, measuring between 10 to 100nm. Spermatozoa, bacteria and unspecified round cells were enmeshed in the mucus. DISCUSSION AND CONCLUSION: From this first comparative study of nasal and cervical mucus giving the proof of sperm penetration in the both mucus and the discovery of mucus produced by archaea living in extreme conditions, we suggested that mucus, from all origins, is a medium of life.