Effect of Bracteoles on Seed Germination and Dispersal of Two Species of Atriplex

The influence of bracteoles on the germination response of asalt marsh annual, Atriplex prostrata, and a salt desert perennial,A. griffithii, was determined. Attached bracteoles did not inhibitgermination of A. prostrata but completely inhibited germinationof A. griffithii seeds. Germination of seeds ofA. griffithiiwas also somewhat inhibited in the presence of detached bracteoles.The osmotic potential of dissolved substances in water-saturatedbracteoles was -4.8 ± 0.05 MPa for A. griffithii and-2.4 ± 0.15 MPa for A. prostrata. Ash content of bracteoleson a dry weight basis was 28.7 ± 0.37% for A. prostrataand 30.0 ± 0.29% for A. griffithii. The presence of relativelyhigh concentrations of dissolved salts in bracteoles may explainthe reduced germination of A. griffithii. Germination of seedsof the perennial A. griffithii may also be inhibited mechanicallyby the presence of persistent bracteoles, whereas the annualA. prostrata has ephemeral bracteoles that may serve to limitgermination in the autumn but are not present during the normalspring germination period. Bracteoles could affect the dispersalof seeds by water since some fruiting structures of A. griffithiiand A. prostrata are able to float in 1.0% NaCl solutions for5 and >30 d, respectively, compared with a maximum of 4 and3 d for seeds without bracteoles. Fruiting structures of A.prostrata floated for longer over a range of salinities thandid those ofA. griffithii ; this may play a significant rolein the dispersal of this salt marsh species. Copyright 2001Annals of Botany Company Atriplex, bracteoles, dispersal, flotation, germination, salinity, temperature     

Isolation and characterization of a new poly(3-hydroxybutyrate)-degrading, denitrifying bacterium from activated sludge

One hundred and forty isolates of thermophilic bacteria from the genus Thermus were screened for the presence of restriction endonuclease activity. Thermostable isoschizomers of restriction endonucleases, such as AceIII, BbvI, BglI, BsePI, FnuDII, HgiAI, MaeII, MboI, MseI, PvuII, StuI, TaqI, Tsp4CI, TspEI, XhoI and XmaIII, were isolated. Two restriction enzymes, TatI and TauI, recognizing novel degenerate sequences 5'-W (downward arrow)GTACW-3' and 5'-GCSG (downward arrow)C-3' respectively were partially purified and the recognition and cleavage sites were determined.     

Salinity tolerance in some mangrove species from Pakistan

Growth, ionic and water relations of three mangrove species viz. Avicennia marina, Ceriops tagal and Rhizophora mucronata werestudied in different seawater concentrations (0, 25, 50, 75 and 100%).All mangrove species showed optimal growth at 50% seawater. Relativelymore biomass was accumulated by R. mucronata while C. tagalhad the tallest individuals. Tissue water potential became more negativewith the increase in salinity and stomatal conductance was decreased in allplants. Higher stomatal conductance was noted in R. mucronata,followed by A. marina and C. tagal. Sodium and chloride ionsincreased with the increase in salinity and this accumulation was muchhigher in A. marina.     

The Neisseria gonorrhoeae lpxLII gene encodes for a late-functioning lauroyl acyl transferase, and a null mutation within the gene has a significant effect on the induction of acute inflammatory responses

LPS is a fundamental constituent of the outer membrane of all Gram-negative bacteria, and the lipid A domain plays a central role in the induction of inflammatory responses. We identified genes of the Neisseria gonorrhoeae lipid A biosynthetic pathway by searching the complete gonococcal genome sequence with sequences of known enzymes from other species. The lpxLII gene was disrupted by an insertion-deletion in an attenuated aroA mutant of the gonococcal strain MS11. Lipopolysaccharide (LPS) and lipid A analysis demonstrated that the lpxLII mutant had synthesized an altered LPS molecule lacking a single lauric fatty acid residue in the GlcN II of the lipid A backbone. LPS of the lpxLII mutant had a markedly reduced ability to induce the proinflammatory cytokines tumour necrosis factor (TNF)-alpha, interleukin (IL)-1beta, IL-6 and IL-8 from human macrophages and IL-8 from polymorphonuclear cells. This study demonstrates that the lpxLII gene in gonococci encodes for a late-functioning lauroyl acyl transferase that adds a lauric acid at position 2' in the lipid A backbone. The presence of lauric acid at such a position appears to be crucial for the induction of full inflammatory responses by N. gonorrhoeae LPS.