No description available.

Twenty-three marine and two terrestrial gram-negative bacteria were examined by electron microscopy for the effect on the outer membrane of the cells of washing the organisms successively in 0.5M NaCl and 0.5M sucrose. Six marine bacteria lost their outer membranes completely, three lost large segments but not all of their outer membranes, and six retained their outer membranes but with either gross distortions of the outer membrane and/or segments of outer membrane removed from some cells. The remaining eight marine and two terrestrial bacteria appeared to have continuous outer membranes after application of the wash procedure. / Eighteen of the twenty-three marine bacteria employed in the wash treatment study and two terrestrial bacteria were examined for the effect of washing and suspending the organisms in various solutions with respect to lysis of the cells and Optical Density (O.D.) changes of suspensions. / A spectrum of lytic susceptibility was observed among the marine bacteria ranging from those organisms which lysed in distilled water after exposure to Mg('2+) through organisms which lysed upon suspension in distilled water after pre-exposure to NaCl but which failed to lyse in distilled water if pre-exposed to Mg('2+) to organisms which failed to lyse in distilled water even after exposure to NaCl. E. coli and Ps. aeruginosa also fell within this spectrum. / After exposure to NaCl and subsequent suspension of these organisms in decreasing concentrations of either NaCl, KCl or MgCl(,2), concentrations of KCl two to three times that of NaCl or ten to four hundred times that of MgCl(,2) could protect most marine organisms from lysis or larger decreases in the O.D. of their suspensions. However, three marine and both terrestrial bacteria required only equal concentrations of KCl or NaCl to effect protection. / No overall distinction can therefore be made between marine and terrestrial bacteria with respect to the status of the outer membrane of these organisms after washing them in NaCl and sucrose solutions or the sensitivity of the two groups of organisms to lysis in distilled water after pre-exposure to NaCl or MgCl(,2).

Utilizing non-metabolizable substrates as valuable tools to differentiate between transport and subsequent metabolism, the possibility was explored whether there was a relationship between the sodium requirement by marine bacterial cella for growth and a sodium requirement for uptake of substrates. Various aspects of the transport phenomenen in these organisms were studied and the following findings are claimed to constitute a contribution to knowledge. [...]

No description available.

Epiphytic bacterial communities on the surfaces of marine algae are poorly characterised. Most information available on marine bacterial epiphytes is derived from culture-based studies. With the rapid development of molecular community analysis technologies, it is now possible to obtain a more comprehensive picture of marine microbial populations on living surfaces. The intertidal macroalga Ulva australis, belongs to the cosmopolitan group of green marine algae (Ulvales) known to require the presence of bacteria for normal growth and has been suggested to employ specific bacteria for the defence against fouling by micro- and macro-organisms. This thesis has examined the composition and structure of the surface associated bacterial community on Ulva australis using 16S rRNA gene clone library, denaturing gradient gel electrophoresis (DGGE), and catalysed reporter deposition ??? fluorescence in situ hybridisation (CARD-FISH) analysis. The 16S rRNA gene clone library revealed that the five main bacterial groups present in the surface associated community were Bacteriodetes, Planctomycetes, Alpha-, Gamma-, and Delta-Proteobacteria. Twenty-two sequence phylotypes were identified, suggesting that the epiphytic community was of relatively low diversity. A clone similar to an algal morphogenesis inducing Cytophaga strain was identified, indicating that U. australis harbours bacteria important for thallus structural maintenance. DGGE analysis showed that while the bacterial community varied over spatial and temporal (seasons) scales it also included a stable subpopulation consistently associated with the seaweed surface. Sequencing of selected DGGE bands suggested that members of the Alphaproteobacteria and the Bacteriodetes belonged to the stable subpopulation. Using CARD-FISH with different phylogenetic probes demonstrated that Alphaproteobacteria (~ 70%) and Cytophaga-Flavobacteria (~13%) constituted the majority of bacterial cells on the surface of U. australis. A comparison of the results provided by the molecular community analysis methods, employed in this thesis, and those of culturing of epiphytic bacteria from U. australis revealed that each approach provides different patterns of phylogeny and extent of diversity. For example, the culture collection and the clone library detected a relatively high amount of Gammaproteobacteria, however, DGGE and CARD-FISH did not. Also, low species diversity clone sequences and isolates of Alphaproteobacteria contrasted with the high numbers detected by the DGGE analysis. In addition to the phylogentic determination of the epiphytic bacterial community, CARDFISH was also used to assess the organisation and distribution of bacterial cells across different zonal regions on seaweed surface. It was found that approximately 40% of bacterial cells clustered in aggregates, or microcolonies. These aggregations were considered to be heterogeneous in composition and were mainly comprised of multiply species. The occurrence of more non-viable solitary single rather than aggregated cells suggests that aggregates might offer greater protection to bacterial cells from the harsh conditions in the intertidal zone. More broadly, CARD-FISH was found to be a useful tool for studying microcolonies and was also successfully applied to detect slow growing soil microcolonies cultivated using a novel soil substrate membrane system culturing technique without the need to perform an rRNA enrichment incubation. The findings in this thesis, as described from the application of a number of molecular community analysis techniques such as clone library, DGGE and CARD-FISH, have improved our understanding of the diversity and structure of the epiphytic bacterial community associated with U. australis. Morevover, the information provided may to design future studies in the ecology of bacteria-seaweed interactions, including symbiotic interactions, and aid in marine biotechnology applications such as identifying bacteria which produce bioactive secondary metabolites.

Thesis (Ph. D.)--University of Washington, 1998. / Vita. Includes bibliographic references (p. [81]-94).

Thesis (Ph. D.)--Rutgers University, 2008. / "Graduate Program in Oceanography." Includes bibliographical references (p. 85-92).

Thesis (M.Sc.)--Memorial University of Newfoundland, 1997. / Restricted until June 1998. Bibliography: leaves 106-116.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Biology, 1981. / Supervised by Holger W. Jannasch. Vita. Includes bibliographical references (leaves 359-373).

No description available.