The bacterial stringent response is a pleiotrophic physiological response that is evoked when bacteria are subjected to nutrient stress and is mediated through the accumulation of hyperphosphorylated guanine nucleotides ((p)ppGpp) which are synthesized by the combined action of the relA and spoT gene products. The relA and spoT genes were cloned from Neisseria gonorrhoeae strain MS11 and various insertional and deletion mutants were constructed. Deletion of the gonococcal relA gene abrogated the production of (p)ppGpp when the organism was starved for the amino acid serine. Also, N. gonorrhoeaeDeltarelA null mutants were impaired for growth when propagated on rich medium, a phenotype that could be relieved by deleting the spoT gene. Sequence analysis of the gonococcal SpoT polypeptide indicated a strong similarity to its Escherichia coli counterpart. However, in contrast to studies with E. coli, insertional spoT mutants could be obtained that still accumulated (p)ppGpp when gonococci were starved for nutrients provided that the non-polar insertions were located downstream of the putative phosphohydrolase active site. In time course studies, it is also shown that gonococci rapidly accumulate (p)ppGpp (within 5 min) when encountering nutrient deprivation.

Abstract. Health care associated infections are the fourth leading cause of disease in industrialized countries, and the most common complication affecting hospitalized patients. Recently a polymerized siloxane coating substrate was suggested as a promising candidate for the coating of materials which are aimed to be used in cardiovascular tissue engineering. To reduce the risk of tissue remodeling failure after implantation of such engineered tissue implants, coatings substrates for tissue engineering scaffolds might be helpful to lower the risk of bacterial attachment and growth during and after implantation.In the presented study a coating based on polymerized siloxanes was tested with respect to these properties. Tests were performed with aerobic nosocomial bacteria (Escherichia coli and Staphylococcus epidermidis) and an exemplary selection of materials (stainless steel, polycarbonate, soda-lime glass). The siloxane coating was able to significantly reduce bacterial adherence, and it is supposed that this effect is mainly a result of the high hydrophobicity of the coating substrate.