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The reliable production of heterologous proteins is important in the field of industrial biotechnology. This can be achieved by applying auto-inducible gene expression systems. The development of a Bacillus subtilis expression plasmid harboring SigB-dependent ohrB promoter was reported. The expression system was subjected to high cell density cultivation to produce xylanase as a stable model protein. The recombinant strain was cultured in a synthetic medium containing glucose as the carbon source. The exponential fed-batch feeding strategy was applied to prevent substrate inhibition. A sharp increase of xylanase activity (about 6-fold) at the end of the fermentation was observed as a result of sigma factor B (SigB) protein activation, supporting auto-inducibility of the expression system. For the control strain a specific induction of the xylanase activity was not observed. The recombinant strain was capable to offer a 5-fold increase in xylanase activity in comparison with the control strain. In addition, the constructed system displayed catabolite repression resistance ability. This SigB-dependent expression system can be considered as a biotechnology tool and an alternative to eliminate the cost of conventional inducers, e.g. isopropyl-β-galactopyranoside.

It is shown that the recombinant protein GST-HSV2gG, containing the immunodominant regions of glycoprotein G of HSV-2 is accumulated in the form of inclusion bodies or in soluble form in the Escherichia coli BL21 (DE3) cells. The ratio between protein fractions varied depending on the physiological state of cells before biosynthesis. The kinetic parameters of bacterial populations were determined by mathematical modeling of growth curves based on the Verhulst logistic function. It was established that the induction of biosynthesis in the growth acceleration phase (at OD600 = 0.3) with 0.1 mM IPTG gives the maximum yield of soluble protein (26.75 mg/l or 17.6 mg/g biomass). The target protein was purified using the immobilized metal ion affinity and affinity chromatography technologies. Antigenic activity of the soluble form of recombinant protein GST-HSV2gG, was significantly (three times) higher than that of the protein purified from inclusion bodies (p < 0.05) and was comparable with the activity of the commercial analog (p > 0.05), that allows using this product in the immunosorbent test kits for diagnosis of IgG to HSV-2.

A model of the simplest epigene was constructed to have two alternative states, which proved to be stable and transmittable through Escherichia coli cell generations. A switch from one to another state was induced by thermal and chemical external signals. The results gave further insight into the dynamic mechanism of preservation, coding, and transmission of the genetic information.

It is known that binding of specific anti-Fas antibodies to Fas-receptor induces apoptosis in various cell lines. But the mechanisms of functional regulation and realization of apoptosis remain so far unknown. We obtained HeLa cells transfected with cDNA of Fas-antigen, whose expression was located under the promoter controlled by isopropoyl beta-D-thiogalactopiranoside. Analysis of transfectants has shown that expression of Fas above a certain critical level leads to redistribution of Fas in the cells and is accompanied by changes in the cell cycles and cell sensitivity to the cytotoxic effects of anti-Fas and tumor necrosis factor (TNF). We propose that the sensitivity of cells to Fas-mediated apoptosis depends on the ratio of transmembrane, intracellular and soluble Fas-antigen in the cells.

The effect of cyclic 3',5'-adenosine monophosphate (cAMP) on the rate of beta-galactosidase biosynthesis was studied in the cells of Escherichia coli M-17 growing in MPB and mineral media with glucose and maltose, i.e. under the conditions of various catabolite repression, as well as upon lac-operon induction by isopropyl-beta-D-galactopyranoside (IPGP). The stimulating action of exogenous cAMP was found only in a medium with salts and glucose. The induction by IPGP was highest during the growth in a medium with glucose and maltose. When the medium contained IPGP, cAMP accelerated the enzyme synthesis in all media, but only at the early growth phases, while cAMP eliminated the effect of IPGP at the stationary phase of growth. The regulation of beta-galactosidase biosynthesis by cAMP demonstrated for the first time that this effect depended on the physiological state of E. coli: the expression of catabolite-sensitive E. coli genes was subject to both positive and negative regulation in one and the same inducible system. The effect exerted by cAMP depended on the nature of a carbon source in the growth medium.