Glutathione Status and Protein Synthesis during Drought and Subsequent Rehydration in Tortula ruralis

Glutathione status and its relationship to protein synthesis during water deficit and subsequent rehydration have been examined in the drought-tolerant moss, Tortula ruralis. During slow drying there is a small decrease in total glutathione but the percentage of oxidized glutathione (GSSG) increases. During rapid drying there is little change in total glutathione but a small increase in GSSG. On rehydration of slowly dried moss, GSSG rapidly declines to normal level. But when rapidly dried moss is rehydrated, there is an immediate, sharp increase in GSSG as a percentage of total glutathione. After 2 hours of rehydration GSSG starts declining and reaches a normal level in about 6 hours. When an increasing degree of steady state water deficit is imposed on the moss tissue with polyethylene glycol 6000, there is a progressive decrease in protein synthesis but an increase in oxidized glutathione. When 5 millimolar GSSG is supplied exogenously during rehydration of rapidly dried or slowly dried moss, protein synthesis is strongly inhibited. In vitro protein synthesis supported by moss mRNA is also inhibited by more than 85% by 150 micromolar GSSG. The role of glutathione status in water deficit-induced inhibition of protein synthesis is discussed.     

The influence of immobilization and reduced water activity on gaseous-alkene oxidation by Mycobacterium PY1 and Xanthobacter PY2 in a gas-solid bioreactor

Immobilization of Mycobacterium PY1 and Xanthobacter PY2 in alginate and in or on hydroculture has a minor influence on the maximum rate of oxidation of propene and ethane. The apparent K(m) values of the immobilized cells are slightly higher than those of the free cells, indicating the presence of diffusion limitation in the immobilized systems. Both bacterial strains rapidly lose their alkene-oxidizing activity when the water activity is decreased. This decrease in activity is so rapid that most of the activity is lost already when the pores of the pertinent supports are still filled with water. Therefore, it is not possible with this system to study the transition of mass transfer of substrates entirely in the water phase to mass transfer to substrates entirely through the gas phase.     

A Comprehensive Study of Genic Variation in Natural Populations of Drosophila melanogaster. III. Variations in Genetic Structure and Their Causes between Drosophila melanogaster and Its Sibling Species Drosophila simulans

The natural populations of Drosophila melanogaster and Drosophila simulans were compared for their genetic structure. A total of 114 gene-protein loci were studied in four mainland (from Europe and Africa) and an island (Seychelle) populations of D. simulans and the results were compared with those obtained on the same set of homologous loci in fifteen worldwide populations of D. melanogaster. The main results are as follows: (1) D. melanogaster shows a significantly higher proportion of loci polymorphic than D. simulans (52% vs. 39%, P<0.05), (2) both species have similar mean heterozygosity and mean number of alleles per locus, (3) the two species share some highly polymorphic loci but they do not share loci that show high geographic differentiation, and (4) D. simulans shows significantly less geographic differentiation than D. melanogaster. The differences in genetic differentiation between the two species are limited to loci located on the X and second chromosomes only; loci on the third chromosome show similar level of geographic differentiation in both species. These two species have previously been shown to differ in their pattern of variation for chromosomal polymorphisms, quantitative and physiological characters, two-dimensional electrophoretic (2DE) proteins, middle repetitive DNA and mitochondrial DNA. Variation in niche-widths and/or genetic "strategies" of adaptation appear to be the main causes of differences in the genetic structure of these two species.