Glycine betaine and polar lipid composition in halophilic archaebacteria in response to growth in different salt concentrations

Abstract Examples of halophilic archaebacteria contain low levels of between 1 and 20 mM trimethyl glycine (glycine betaine). In disrupted cell preparations, the glycine betaine is associated with the membrane fraction and is not detectable in cell supernatants. Cells of Natronococcus occultus grown in different salt concentrations show an increase in cell-associated glycine betaine along with an increase in the ratio of phosphatidyl glycerophosphate (PG) to phosphatidyl glycerol (PG) in the cell membrane.     

Haloarcula spp able to biosynthesize exo- and endopolymers

Three halobacteria strains (T5, T6, T7), growing optimally at a sodium chloride concentration of 3.5 M, were isolated from samples collected in the Tunisian marine saltern located close to Monastir. Although they were different in colony and cell morphology, the isolates were similar in most respects and all produced a homopolyester identified spectroscopically as polyhydroxybutyrate when grown on carbohydrates. Under the same conditions, the isolates formed acidic exopolysaccharides. Acid methanolysis of their complex lipids released archaeol (2,3-di-O-phytanyl-sn-glycerol). All the isolates had polar lipid patterns characteristic of representatives of the genus Haloarcula. Partial sequence analysis of 16S rRNA genes from strain T5 confirmed its assignment to the genus Haloarcula. Although strain T5 differed phenotypically from the species Haloarcula japonica in several respects, DNA–DNA hybridization indicated that the T5 isolate is a new strain of H. japonica. Received 10 June 1998/ Accepted in revised form 29 July 1999     

Zur genetischen interpretation morphologischer gesetzmäßigkeiten der degenerativen evolution

Complex organs such as the eyes of vertebrates are based upon highly polygenic systems. So, remarkable differences in the eyes of cave fishes and their overground ancestors are caused by several mutations. Although in cavernicolous populations natural selection seems to play no part in eye degeneration, there is evidence for morphologic regularities in the degenerative process. These morphologic regularities are due to pleiotropic effects of the mutating genes.     

Ornamental colors reveal age in the king penguin

We investigated whether delayed plumage maturation occurred in king penguins (Aptenodytes patagonicus). Therefore we examined the relationships between age and sex on spectral properties and size of two colored plumage patches and a UV-reflective beak spot, using known-age cohorts. Unlike the colored patch on the breast, we found age differences in ear and beak coloration. These results suggest that head ornaments in king penguins could signal sexual maturity or social status. No sex differences were found in the intensity of colored ornaments, which can result from mutual mate choice or genetic correlation between sexes. Size of colored patches did not relate to age or sex.     

Regularity of isoprenoid biosynthesis in the ether lipids of archaebacteria

The location of paired and unpaired ¹³C atoms in the 16,16′-biphytanyl components of the lipids of Caldariella acidiophila following incorporation of acetate-[1,2-¹³C₂] shows that the overall process of isoprenoid biosynthesis in this archaebacterial species follows a normal pattern and that the head-to-head linkage of the two tetraprenyl chains occurs stereoselectively.     

A Desaturase Gene Involved in the Formation of 1,14-Nonadecadiene in Synechococcus sp. Strain PCC 7002

The marine cyanobacterium Synechococcus sp. strain PCC 7002 synthesizes two alkenes, 1-nonadecene and 1,14-nonadecadiene. Whereas the genetic basis for the biosynthesis of the terminal double bond in both alkenes has been characterized, the origin of the internal double bond in 1,14-nonadecadiene has not. In this study, we demonstrate that a gene encoding an uncharacterized desaturase is involved in the formation of the internal double bond of 1,14-nonadecadiene. Further, at low temperatures, the desaturase gene is essential for growth, and in wild-type cells the levels of 1,14-nonadecadiene increase relative to that of cells grown at 38°C. These data suggest that 1,14-nonadecadiene plays a role in responding to cold stress.     

Effects of temperature on ether lipid composition of Caldariella acidophila

The composition of the ether lipids of a strain of Caldariella acidophila, with respect to the different numbers of cyclizations of the biphytanyl components, is shown to differ between the various complex lipid classes, but the degree of cyclization increases systematically with the growth temperature in the range 75–89°. The problem of distinguishing adaptive from phyletic features in archaebacterial lipids is considered.