Scholarly Work - Center for Biofilm Engineering
Permanent URI for this collectionhttps://scholarworks.montana.edu/handle/1/9335
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Item Nutrient resupplementation arrests bio-oil accumulation in Phaeodactylum tricornutum(2013-08) Valenzuela, Jacob J.; Carlson, Ross P.; Gerlach, Robin; Cooksey, Keith E.; Peyton, Brent M.; Bothner, Brian; Fields, Matthew W.Phaeodactylum tricornutum is a marine diatom in the class Bacillariophyceae and is important ecologically and industrially with regards to ocean primary production and lipid accumulation for biofuel production, respectively. Triacylglyceride (TAG) accumulation has been reported in P. tricornutum under different nutrient stresses, and our results show that lipid accumulation can occur with nitrate or phosphate depletion. However, greater lipid accumulation was observed when both nutrients were depleted as observed using a Nile Red assay and fatty acid methyl ester (FAME) profiles. Nitrate depletion had a greater effect on lipid accumulation than phosphate depletion. Lipid accumulation in P. tricornutum was arrested upon resupplementation with the depleted nutrient. Cells depleted of nitrogen showed a distinct shift from a lipid accumulation mode to cellular growth post resupplementation with nitrate, as observed through increased cell numbers and consumption of accumulated lipid. Phosphate depletion caused lipid accumulation that was arrested upon phosphate resupplementation. The cessation of lipid accumulation was followed by lipid consumption without an increase in cell numbers. Cells depleted in both nitrate and phosphate displayed cell growth upon the addition of both nitrate and phosphate and had the largest observed lipid consumption upon resupplementation. These results indicate that phosphate resupplementation can shut down lipid accumulation but does not cause cells to shift into cellular growth, unlike nitrate resupplementation. These data suggest that nutrient resupplementation will arrest lipid accumulation and that switching between cellular growth and lipid accumulation can be regulated upon the availability of nitrogen and phosphorus.Item New technologies for studying biofilms(2015-08) Franklin, Michael J.; Chang, Connie B.; Akiyama, Tatsuya; Bothner, BrianThe results of recent biofilm characterizations have helped reveal the complexities of these surface-associated communities of microorganisms. The activities of the cells and the structure of the extracellular matrix material demonstrate that biofilm bacteria engage in a variety of physiological behaviors that are distinct from planktonic cells (1 – 3 ). For example, bacteria in biofilms are adapted to growth on surfaces, and most produce adhesins and extracellular polymers that allow the cells to firmly adhere to the surfaces or to neighboring cells ( 4 – 6 ). The extracellular material of biofilms contains polysaccharides, proteins, and DNA that form a glue-like substance for adhesion to the surface and for the three-dimensional (3D) biofilm architecture ( 4 ). The matrix material, although produced by the individual cells, forms structures that provide benefits for the entire community, including protection of the cells from various environmental stresses ( 7 – 9 ). Biofilm cells form a community and engage in intercellular signaling activities ( 10 – 19 ). Diffusible signaling molecules and metabolites provide cues for expression of genes that may benefit the entire community, such as genes for production of extracellular enzymes that allow the biofilm bacteria to utilize complex nutrient sources ( 18 , 20 – 22 ). Biofilm cells are not static. Many microorganisms have adapted to surface-associated motility, such as twitching and swarming motility ( 23 – 28 ). Cellular activities, including matrix production, intercellular signaling, and surface-associated swarming motility suggest that biofilms engage in communal activities. As a result, biofilms have been compared to multicellular organs where cells differentiate with specialized functions ( 2 , 29 ). However, bacteria do not always cooperate with each other. Biofilms are also sites of intense competition. The bacteria within biofilms compete for nutrients and space by producing toxic chemicals to inhibit or kill neighboring cells or inject toxins directly into neighboring cells through type VI secretion ( 30 – 33 ). Therefore, biofilm cells exhibit both communal and competitive activities.