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 Hong Kong, 2008. / Also available in print.

Thesis (M.S.)--University of North Carolina Wilmington, 2007. / Includes bibliographical references (leaves: 43-46)

No description available.

During the evolution of multicellularity from unicellular ancestors, cells transition from being evolutionary individuals to components of more complex, multicellular evolutionary individuals. The volvocine green algae provide a powerful model system for understanding the genetic and morphological changes that underlie and are caused by the evolution of multicellularity. This dissertation concerns the role of cell cycle regulation, cellular differentiation, and sexual traits during the evolution of multicellularity. While some of these are shown to be causally important in the origins of multicellularity (Appendix B), others are driven by the evolution of multicellularity (Appendix D). We provide a review of recent mathematical models on the evolution of multicellularity, which are found to focus heavily on the later, subsequent stages of the evolution of multicellular complexity. We found that many of these models assume multicellular ancestors and instead evolve cellular differentiation, bringing attention to a gap in our understanding of the events in the initial stages of the evolution of multicellularity. We show that a focus on the early stages of the evolution of multicellularity reveals a powerful and critical role for regulation of the cell cycle at the origins of multicellularity (Appendix B). We further find that the genetic basis for cellular differentiation evolved sometime after the evolution of cell cycle regulation. We find that while the genetic basis for cellular differentiation evolved after cell cycle regulation, it also evolved earlier than previously predicted in the volvocine green algae, suggesting an important role in undifferentiated species (Appendix C). Lastly, having elucidated the origins and evolution of multicellularity, we find that multicellularity causes the evolution of sexual traits including anisogamy, internal fertilization, and subsequently sexual dimorphism (Appendix D). This work emphasizes the important role that multicellularity plays in driving the evolution of sexual diversity seen across the eukaryotic tree and well as informs critical hypotheses on the evolution of anisogamous sex, among the most challenging problems in evolutionary theory.

1-substituted 1,2,4-triazoles form a class of agricultural chemicals known as sterol-inhibiting fungicides (SIFs). These fungicides function through the inhibition of sterol synthesis, which ultimately affects cell membrane fluidity and permeability. Of the two main types of sterols in plants, free sterols (FSs) are thought to be incorporated into membranes while conjugated sterols such as steryl esters (SEs), hypothetically, regulate homeostasis by inserting or removing FSs from cell membranes under changing environmental conditions. Non-target algae species possess sterol synthesis pathways that are affected by a range of SIFs. One of the main objectives of the current study was to determine the reason for the observed sensitivity of C. fusca and the tolerance of C. kessleri to SIFs relative to total lipid, FS, SE and FFA composition. These parameters were measured using gas chromatography and mass spectroscopy techniques. Both quantitative and qualitative differences in sterol number and type were noted relative to the FS and SE composition of the two species of algae over time. Notably, SEs were detected in both species of algae, although presence and amount varied with the organism. While SEs were more abundant in C. kessleri, higher amounts of FSs were found in C. fusca. The FS/SE ratios were 64/36 and 88/12 percent of the total sterol in C. kessleri and C. fusca, respectively. Treatment of C. fusca with 2, 4, and 6 ppm and C. kessleri with 6,12, and 24 ppm propiconazole caused an accumulation of methylated precursor sterols, resulting in slightly more FSs in both algae. Only 3 of the FSs produced following treatment were different from the control in C. fusca while 9 new sterols were found in C. kessleri. Treatment also altered the SE fraction in both species, with fewer SEs produced compared to the control, but more novel sterols in C. kessleri, suggesting a possible inverse relationship between FSs and SEs in both organisms. Several studies have implicated lipid/sterol concentrations with the potential for cellular bioaccumulation of lipophilic xenobiotics as they relate to membrane permeability. Cell age and environmental parameters can also affect lipid composition of algae. Although cell age did not affect the qualitative sterol composition of C. fusca and C. kessleri, quantitative differences were observed. Plants exposed to chemical and other environmental stresses accumulate free fatty acids (FFAs), which may be linked to biophysical membrane changes. SIF sensitive C. fusca, had inherently higher levels of FFAs than C. kessleri. Qualitatively, C. fusca exhibited higher percentages of 18:1 and lower ratios of 18:2/18:3 FFAs than C. kessleri. In response to increasing SIF treatment, the ratio of 18:2/18:3 FFAs increased in C. kessleri and declined in C. fusca. The amount of total lipid produced in the cells of C. fusca was higher than in C. kessleri during all growth stages. Variations were observed in lipid measured as a percent dry weight compared to lipid/cell as the cultures age. Inherent differences in FS, SE, and lipid composition of C. fusca and C. kessleri as well as age related changes could account for the differences in the susceptibility of the two algae to propiconazole. / Master of Science

Indiana University-Purdue University Indianapolis (IUPUI) / This project examines the impact of confounding variables that have limited the accuracy of remotely predicting phycocyanin in three Indiana drinking and recreational water reservoirs. In-situ field reflectance spectra were collected from June to November 2006 over a wide range of algal bloom conditions using an ASD Fieldspec (UV/VNIR) spectroradiometer. Groundtruth samples were analyzed for chlorophyll a, phycocyanin, total suspended matter, and other water quality constituents. Previously published spectral algorithms for the detection of phycocyanin were evaluated against lab measured pigment concentrations using linear least squares regression. Algorithm performance varied across study sites (best performing models by reservoir resulted in r2 values of 0.32 to 0.84). Residuals of predicted versus measured pigment concentrations were analyzed against concentration of potential confounding water constituents. Residual analysis revealed optically active constituents contributed between 25% and 95% of original phycocyanin model errors. Inclusion of spectral variables into models to account for significant confounders resulted in improved spectral estimates of phycocyanin (r2 = 0.56 to 0.93).

The work in this thesis is an extension of a large study carried out by this college at Rothamsted Experimental Station (J. Featherstone-Witty, Ph.D thesis, 1974; with Keay, and Froggatt in press) and was aimed at scaling down the fieldwork to lysimeter investigations in order to elucidate the true value of algal inoculation as a replacement for synthetic fertilizers. Two lysimeters (each measuring 5m. x 3m.) were constructed above ground on concrete rafts with a built in facility to collect drainage water from the four quarters of each lysimeter. Both units were filled with calcareous soil (pH. 8). Each unit was divided into 4 treatments and sown to spring wheat. Previous indications were that this variety would benefit more from algal release of nitrogen than winter wheat because of a later maturation, and hence greater likelihood of the ears receiving nitrogen released from algal cells during late summer. A continuous record was kept of variations in soil, crop and drainage water nitrogen together with surface nitrogen fixation measurements (using the acetylene reduction technique), so that estimates of the efficiency of algal inoculation, to increase soil-N levels, could be made. Laboratory studies have suggested nitrogen fixation occurs only in soils low in nitrogen (less than about 4ppm) and algal cells apparently release very little extracellular nitrogen when grown on solid surfaces. These low levels of nitrogen would not support crop yields equivalent to those achieved by the application of synthetic fertilizers. Results from the two year lysimeter study suggest no improvement in crop yield for the algal inoculated treatments, compared with the controls, though total crop nitrogen, for the algal treatments was approximately 7% higher than the fertilizer treatments and 60% higher than the mean value for the two controls; ear nitrogen was as much as 46% higher than the controls. Algal inoculation, together with herbicide application, proved the best treatment, improving both crop dry weight and nitrogen composition significantly.

No description available.

The purpose of this investigation is to determine the effect of varying geosmin concentrations on the growth of selected cyanophytes which did not produce a notable odor in culture.