Suspended cultivation of Gracilaria in the sea

Suspended rope cultivation systems for Gracilaria or Gracilariopsis can be seeded from spores but vegetative propagation is used for those which are currently commercially successful. Such systems and methods have been recently developed for the shallow lagoon areas around Lüderitz, Namibia and deeper open water sites off the Araya Peninsula, Venezuela. Various sites, substrata, depths and seeding methods have been assessed and have resulted in average commercial growth rates of about 3.5% per day. Netlon ‘Superope’ has been demonstrated to be more suitable than laid rope as a substratum for outplanted vegetative Gracilaria gracilis in Namibia as it does not compress the thalli as they grow. An efficient method, using hooks, has been developed to ‘seed’ the Superope. There is a very low incidence of algal epiphytism: mainly Ceramium and Ulva sp. In Venezuela, pilot rope cultivation systems for Gracilariopsis tenuifrons proved successful and have good commercial prospects.     

Bacterial Characteristics Determining the Potential Host Range of Bacteriophage T4

Many members of the Enterobacteriaceae, but not other gram-negative organisms, apparently carry a specific recognition site for the T4 tail tube on their cytoplasmic membranes.     

Saccharomyces cerevisiae strain expressing a plant fatty acid desaturase produces polyunsaturated fatty acids and is susceptible to oxidative stress induced by lipid peroxidation

Although oxygen is essential for aerobic organisms, it also forms potentially harmful reactive oxygen species. For its simplicity, easy manipulation, and cultivation conditions, yeast is used as an attractive model in oxidative stress research. However, lack of polyunsaturated fatty acids in yeast membranes makes yeast unsuitable for research in the field of lipid peroxidation. Therefore, we have constructed a yeast strain expressing a Delta12 desaturase gene from the tropical rubber tree, Hevea brasiliensis. This yeast strain expresses the heterologous desaturase in an active form and, consequently, produces Delta9/Delta12 polyunsaturated fatty acids under inducing conditions. The functional expression of the heterologous desaturase did not affect cellular morphology or growth, indicating no general adverse effect on cellular physiology. However, the presence of polyunsaturated fatty acids changed the yeast's sensitivity to oxidative stress induced by addition of paraquat, tert-butylhydroperoxide, and hydrogen peroxide. This difference in sensitivity to the latter was followed by the formation of 4-hydroxy-2-nonenal, one of the end products of linoleic fatty acid peroxidation, which is known to play a role in cell growth control and signaling. Here we show that this yeast strain conditionally expressing the Delta12 desaturase gene provides a novel and well-defined eukaryotic model in lipid peroxidation research. Its potential to investigate the molecular basis of responses to oxidative stress, in particular the involvement of reactive aldehydes derived from fatty acid peroxidation, especially 4-hydroxy-2-nonenal, will be addressed.