pH-dependent activation of the alternative transcriptional factor sigmaB in Bacillus subtilis.

The expression of the sigB gene of Bacillus subtilis was analysed in response to a mild acid shock. This gene is subject to sigmaB-dependent regulation. It has been found that the expression of sigB is induced as part of the acid-tolerant response. In that respect sigB is similar to the previously described gene gsiB which is also a member of the sigmaB regulon. Through this induction, the sigmaB regulon provides protection against acid shock. Besides its protective role against acid shock, no other general function could be directly associated with the sigmaB regulon. An acidification of the cytoplasmic environment induces synthesis of general stress proteins in B. subtilis.

[Genetic marker analysis in head and neck cancer] / Genetikai marker-vizsgálatok fej-nyaki daganatokban.

Prognostication of head and neck cancer (HNCC) involves molecular identification of residual tumor cells, prediction of recurrence, distant metastases or secondary tumors and prediction of the sensitvity to therapy. Biomarkers of HNCC are mutations of p53, p16 and amplification of Cyclin D and E2F4. One hundred and fifty-two HNCC cases have been evaluated for p53, hMLH1, Cyclin D and p16 gene alterations using PCR-SSCP and Western blot analysis. P53 mutations of HNCC have been found in 37.5% of cases. However, 11% of the cases showed p53 mutations in the normal peritumoral mucosa suggesting "field cancerization" process. Mismatch-repair gene mutations (MMR: hMHL1 and hMSH2) occurred with 17 and 8.6% frequency, respectively, while E2F4 mutations were even more frequent (21.4%) in HNCC. Our data suggest that E2F4 overexpression can be caused by the inactivation of the p16 gene in HNCC, while its mutations are most probably associated to the mutations of the MMR genes. These molecular informations can help to predict the biological potential of HNCC as well as the probability of the development of secondary HNCCs.

Stress related changes of cell surface hydrophilicity in Bacillus subtilis.

The changes of cell surface hydrophilicity in Bacillus subtilis were analyzed in response to oxygen-limitation, heat shock, salt stress, pH-shock, phosphate- and carbon-limitation. Although cell surface hydrophilicity varied during growth phases, an increase of surface hydrophilicity was observed under several of these stress conditions. An observed drop in intracellular GTP and/or ATP may be an element of the signal transduction pathway leading to an increase in surface hydrophilicity in response to environmental stresses. Attachment of cells to soil particles under salt stress conditions is strongly influenced by the degS/degU two-component system, which thereby provides a mechanism for the bacteria to escape from the hostile environment.