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.     

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.     

The reproductive system of Osedax (Annelida,Siboglinidae): ovary structure,sperm ultrastructure,and fertilization mode

Osedax is a genus of siboglinid annelids in which the females live on dead vertebrate bones on the seafloor. These females have a posterior end that lies within the bone and contains the ovarian tissue, as well as the “roots” involved with bone degradation and nutrition. The males are microscopic and live as “harems” in the lumen of the gelatinous tube that surrounds the female trunk, well away from the ovary. Females are known to spawn fertilized primary oocytes, suggesting internal fertilization. However, little is known about sperm transfer, sperm storage, or the location of fertilization, and the morphology of the female reproductive system has not been described and compared with the reproductive systems of other siboglinids. A 3D‐reconstruction of the ovisac of Osedax showed ovarian tissue with multiple lobes and mature oocytes stored in a “uterus” before being released through the single oviduct. The oviduct emerges as a gonopore on the trunk and travels along the trunk to finally open to the seawater as a thin cylindrical tube among the crown of palps. Light and transmission electron microscopy of mature Osedax sperm revealed elongate heads consisting of a nucleus with helical grooves occupied by mitochondria. In contrast to other Siboglinidae, Osedax sperm are not packaged into spermatophores or spermatozeugmata, and Osedax females lack a discrete region for sperm storage. Transmission electron microscopy and fluorescence microscopy allowed detection of sperm associated with ovarian tissue of the female ovisac of four different Osedax species. This provides the first evidence for the site of internal fertilization in Osedax. A heart body was found in the circulatory system, as seen in other siboglinids and some other annelids. The possible presence of nephridia in the anterior ovisac region was also documented. These morphological features provide new insights for comparing the regionalization of Osedax females in relation to other siboglinids.     

A RAPD study of the Sarcostemma group of Cynanchum (Apocynaceae-Asclepiadoideae-Asclepiadeae)

One hundred and thirty-seven accessions of Cynanchum viminale and its relatives, formerly known as Sarcostemma, were studied using randomly amplified polymorphic DNA (RAPD). A fingerprinting technique was used because sequencing had failed to differentiate between morphologically separable groups. Chromosome counts were conducted to establish the ploidy level of the accessions. The banding patterns resulting from RAPD analysis were evaluated with Canonical Analysis of Principal Coordinates, Permanova and neighbour-joining. A strong geographic component was found in the structure of the group. Taxa considered species or subspecies based on morphology often formed coherent groups. The data are interpreted to reflect at least two cycles of diversification: the first one from Madagascar and the second one most likely from the East African–Arabian region, reaching Madagascar again. In mainland Africa, polyploidisation has occurred several times.