Starvation-Induced Multiresistance in Enterococcus faecalis JH2-2

Compared with growing bacteria, carbohydrate-starved cells of Enterococcus faecalis show development of a multiresistance state against heat, H₂O₂, acid, and ethanol, but not against UV irradiation. The kinetics of acquisition of resistance is different according to the stress. Three hours of starvation provide maximal resistance against ethanol, while the tolerance to heat, H₂O₂, and acid increases progressively with the duration of starvation. Chloramphenicol treatment does not abolish the ethanol tolerance. Protein synthesis inhibition during the transitional growth phase and the first hours of starvation partially inhibit the acquisition of heat and oxidative resistances. Antibiotic treatment after 3 h of starvation does not affect the increase of these resistances. We suggest that synthesis of specific proteins revealed by 2-D gel analysis in the first 3 h of starvation, followed by a second mechanism related to protein degradation or alteration, is necessary for acquisition of maximal resistance towards heat and oxidative stresses.     

Plant Protoplasts Immobilized in Calcium Alginate: A Simple Method of Preparing Fragile Cells for Transmission Electron Microscopy

A simple method for electron microscopic preparation of plant protoplasts is described. The main problems in preparing these fragile protoplasts for electron microscopy have been cell collapse due to steep gradients between protoplasts and fixatives and unacceptable loss of material during the many steps of the procedure. These problems may be solved by immobilization of the protoplasts in calcium alginate beads. The free diffusion properties of this gel prevent steep gradients. The beads also simplify handling and prevent loss of material. Protoplasts isolated from hypocotyls of rape, Brassica napus (var. Niklas), have been used as a model system. Transmission electron microscopy of the immobilized protoplasts osmotically stabilized with glucose demonstrated adequate structural and ultrastructural preservation.     

Insights into the myosin II inhibitory potency of A-ring-modified (S)-blebbistatin analogs

Myosin II is an interesting target for therapeutic intervention, as it is involved in a large number of motility-based diseases. (S)-Blebbistatin is a known micromolar inhibitor of this protein. A new series of (S)-blebbistatin derivatives with a modified A-ring was synthesized and the myosin II inhibitory properties were evaluated in vitro. In this way, we gained insight into the influence of structural modifications in this part of the scaffold on myosin II inhibitory potency. Our results indicate there are few possibilities for potency enhancement via ring A modification of the blebbistatin scaffold.     

Plasmid Transfer by Electroporation and Conjugation in Tetragenococcus and Pediococcus Genera and Evidence of Plasmid-Linked Metabolic Traits

Various strains of Pediococcus genus were successfully transformed by electroporation using the broad host-range plasmid pSA3 and the lactococcal Rep22 based-replicon pUCB304. Failure to transform Tetragenococcus strains by electroporation have led to use conjugation as an alternative plasmid DNA transfer mechanism. Intergeneric matings conducted with the broad host-range conjugative plasmid pVA797 from Lactococcus lactis subsp. lactis SL2/797A to Tetragenococcus halophilus and Pediococcus pentosaceus strains have shown that Tetragenococcus strains are not impervious to plasmid DNA transfer. Plasmid and metabolic profiles of wild and mutant strains of Pediococcus pentosaceus NCDO990 have shown that many metabolic traits including lactose utilization are plasmid linked.