Characterization of Inverted Membrane Vesicles from the Halophilic Archaeon Haloferax volcanii

Membrane-related processes in archaea, the third and most-recently described domain of life, are in general only poorly understood. One obstacle to a functional understanding of archaeal membrane-associated activities corresponds to a lack of archaeal model membrane systems. In the following, characterization of inverted archaeal membrane vesicles, prepared from the halophilic archaeon Haloferax volcanii, is presented. The inverted topology of the vesicles was revealed by defining the orientation of membrane-bound enzymes that in intact cells normally face the cytoplasm or of other protein markers, known to face the exterior medium in intact cells. Electron microscopy, protease protection assays and lectin-binding experiments confirmed the sealed nature of the vesicles. Upon alkalinization of the external medium, the vesicles were able to generate ATP, reflecting the functional nature of the membrane preparation. The availability of preparative scale amounts of inverted archaeal membrane vesicles provides a platform for the study of various membrane-related phenomena in archaea. Received: 27 March 2001/Revised: 13 June 2001     

Feeding in the two phytophagous beetles Hydromedion sparsutum and Perimylops antarcticus from South Georgia

Summary The consumption of fresh plant materials by adults and larvae of Hydromedion sparsutum and Perimylops antarcticus (Col., Perimylopidae) was estimated from the production of faecal pellets and amount of excreted plant remnants as dry weight. Adults and larvae of Hydromedion consumed large quantities of grasses, including the alien Poa annua, but smaller amounts of the indigenous great burnet, Acaena magellanica. Both stages of Perimylops consumed much smaller quantities of grasses and Acaena. Different species of mosses were eaten in both species, and appeared to be a major source of food for Perimylops in addition to microphytes on rocks. The consumption of mosses and microphytes reflects the adaptation of Perimylops to living in habitats at higher altitudes (e.g. above 200 m), where other plants are scarce.