Regulation of the initial phase of embryo implantation may involve the recognition interplay of glycoconjugates and respective receptors such as endogenous lectins on both cellular surfaces. Whereas changes in glycoconjugate composition have been detected in preparation for embryo implantation and described in detail, knowledge on endogenous lectins has remained scant. Affinity probes (carrier-immobilized carbohydrate structures as ligand part on a histochemically inert backbone) are used in the present investigation in order to gain further insights in this area. Cryostat sections of rabbit Fallopian tubes and uteri in nonpregnant and early pregnant [tubes: 3 days post coitum (d p.c); uteri: 3, 5, 7 and 9 d p.c] states were studied for binding patterns of a series of biotinylated (neo)glycoproteins. A high density of binding sites was detected with β-galactosides. (with decreasing intensity: β-D-galactose-BSA, asialofetuin with its triantennary glycan chains, lactose-BSA). Considerably less binding (but with the same pattern) was obtained with β-N-acetyl-D-glucosaminide-BSA and is interpreted to originate from a cross-reactivity of such sites which may bind physiologically to Gal-βl¾-GlcNAc sequences. In contrast, no evidence for the presence of binding molecules with specificities for a-D-mannose-BSA, maltose-BSA, N-acetyl-galactosaminide-BSA and N-acetyl-D-neuraminic acid-BSA was obtained in these tissues under the same conditions. The epithelium of the Fallopian tube showed a high density of β-galactoside-binding sites at the apical cell poles (including the cytoplasm and membrane region) already in the nonpregnant state. At 3 d p.c, a strong reaction in all epithelial cells of the isthmus and a marked decrease in the ampulla were noted. The putative lectin(s) appear(s) to be synthesized and secreted by the tubal epithelium. A physiological role in forming the mucoprotein layer of the blastocyst coverings by precipitating the appropriate mucin-type molecules can be considered. Within the endometrium, the β-galactoside-binding molecules were almost exclusively localized at the apical cell pole of epithelial cells, whereas there was hardly any binding in the epithelial cytoplasm or in the endometrial stroma. The reaction was very weak in the non-pregnant state but increased considerably until 5 d p.c, starting in the luminal-most parts of the epithelium. While the reaction was rather homogeneous at the surface of the luminal epithelium at 5 d p.c, the degree of heterogeneity increased stepwise from 7 to 9 d p.c. In the implantation chamber, the density of these β-galactoside-specific ‘receptors’ was further enhanced in particular at the epithelial surface of the placental folds. In contrast, the reaction was less intense at the antimesometrial uterine epithelium and in interblastocyst segments of the uterus, and it remained weak in the middle and deep crypts. The trophoblast showed a high density of galacto-side-binding sites at its surface, and less in the cytoplasm. Neoglycoprotein binding to the blastocyst c...

The complex regulatory network in Bacillus, known as quorum sensing, offers many opportunities to modify bacterial gene expression and hence to control bioprocesses. One target regulated by this mechanism is the activity of the PsrfA promoter, which is engaged in the formation of lipopeptide surfactin. It was hypothesised that deletion of rapC, rapF and rapH, encoding for prominent Rap-phosphatases known to affect PsrfA activity, would enhance surfactin production. Therefore, these genes were deleted in a sfp+ derivative of B. subtilis 168 with subsequent evaluation of quantitative data. Up to the maximum product formation of the reference strain B. subtilis KM1016 after 16 h of cultivation, the titers of the rap deletion mutants did not exceed the reference. However, an increase in both product yield per biomass YP/X and specific surfactin productivity qsurfactin was observed, without any considerable effect on the ComX activity. By extending the cultivation time, a 2.7-fold increase in surfactin titer was observed after 24 h for strain CT10 (ΔrapC) and a 2.5-fold increase for CT11 (ΔrapF) compared to the reference strain KM1016. In addition, YP/X was again increased for strains CT10 and CT11, with values of 1.33 g/g and 1.13 g/g, respectively. Interestingly, the effect on surfactin titer in strain CT12 (ΔrapH) was not as distinct, although it achieved the highest promoter activity (PsrfA-lacZ). The data presented support the possibility of involving the quorum sensing system of Bacillus in bioprocess control as shown here on the example of lipopeptide production.

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