APEX Presentations
February 27, 2006
Linking Sugar Metabolism and Osmotic Tolerance in Agrobacterium tumefaciens
Name: Amanda Reed
Major: Biology
Academic and APEX Advisor: Dr. Brad Goodner
Location: Hiram College
Dr. Brad Goodner
Associate Professor
Hiram College, Hiram, OH 44234
330.569.5260
GoodnerBW@hiram.edu
Source of Funding: Howard Hughes Medical Institute Grant
Previous work in our lab has shown that there is functional redundancy for sucrose catabolism in Agrobacterium tumefaciens C58. The functional redundancy for this gross-level phenotype is in stark contrast to evidence indicating that the loss of the sucrose hydrolase enzyme leads to severe sensitivity to osmotic stress. This enzyme may not be that important for the breakdown of sucrose, but rather for the synthesis of the novel disaccharide mannosucrose.
In addition to the role of mannosucrose, we do not know if the two salt-tolerant biovars with the Agrobacterium genus, biovars 1 and 3, use common mechanisms for osmotic adjustment. In order to explore the genetic basis for the osmotic tolerance in A. tumefaciens we screened for mutants of A. tumefaciens C58 (biovar 1) and A. vitis S4 (biovar 3) unable to grow either under high salt conditions or with low levels of sucrose as a sole carbon source. Most of the mutants characterized so far have established a link between sugar metabolism and osmotic tolerance. Finally, an update will be given with our efforts to characterize the basis of the 3-ketosucrose pathway in A. tumefaciens C58.
Characteristics of herpetofaunal distribution at University of Notre Dame Environmental Research Center (UNDERC)
Name: Keely Davidson
Major: Biology
Academic Advisor: Dr. Matthew Hils
APEX Advisor: Dr. Dennis Taylor
Location: University of Notre Dame Environmental Research Center, Gogebic Co., Michigan
Dr. Karen Francl, Assistant Director of UNDERC-East
University of Notre Dame, 097 Galvin Life Science Bldg., Notre Dame, IN 46556
574.631.0970
francl.1.@nd.edu
Source of Funding: Bernard J. Hank Family Endowment
During the summer of 2006, I conducted a survey of the amphibians and reptiles of the UNDERC property 25 sites in 5 habitats: vernal ponds, lakes, open water bogs, deciduous forests, and mixed forests. Each site was surveyed for one week using pitfall traps with drift fences, visual encounter surveys, and incidental captures. All amphibians and reptiles found were counted and relative age (adult/juvenile) was noted for each. Microhabitat characteristics were measured for each site. Juveniles were found at too few sites to analyze relationships, so only adults were used for analyses. Habitat types differed significantly with regards to the number of R. clamitans (p=.013) and R. sylvatica (p=.000) captured. H. versicolor was positively correlated with leaf litter depth (p=.008). R. clamitans was positively correlated with canopy cover (p=.015). Rana pipiens captured was positively correlated to depth of live organic matter (p=.002) and dead organic matter (p=.032) and negatively correlated to canopy cover (p=.025). Rana sylvatica adults were positively related to soil moisture (p=.003) and percent open water in area surveyed (.000). These results can be applied to land management decisions within the home range of species of interest.
The functional differences of the two aconitases of Agrobacterium tumefaciens C58
Name: DaJuan Whiteside
Major: Biology
Academic Advisor: Dr. Sandy Madar
APEX Advisor: Dr. Brad Goodner
Location: Hiram College
Dr. Brad Goodner
Associate Professor
Hiram College, Hiram, OH 44234
330.569.5260
GoodnerBW@hiram.edu
Source of Funding: Howard Hughes Medical Institute Grant
Aconitases are monomeric iron-sulfur proteins whose primary function is to catalyze the interconversion of citrate to isocitrate in the citric acid cycle. Virtually all members of the Bacteria domain have two aconitases, AcnA and AcnB, except the alpha-Proteobacteria which usually have only AcnA. Interestingly, our main study organism, Agrobacterium tumefaciens C58 is a member of the alpha-Proteobacteria and it has both AcnA and AcnB.
According to a model developed in E. coli and B. subtilis, aconitases monitor oxidative stress and post-transcriptionally regulate the synthesis of additional aconitase protein as well as cellular processes such as motility. In E. coli, AcnA is induced during periods of stress while AcnB is the major enzyme involved in exponential growth. Mutations in acnA have no impact on motility, while mutations in acnB decreases motility.
To analyze the role of the two aconitases in A. tumefaciens C58, we generated mutations in each gene (AGR_C_4866 = acnA; AGR_L_294 = acnB). Contrary to the E. coli model, the acnA mutant is an auxotroph on minimal media and it shows a very hypermotile phenotype on rich medium. The acnB mutant shows a mild hypomotile phenotype. The hypermotility of the acnA mutant does not substantially impact virulence, due to the repression of motility by low pH conditions. I plan to present data on growth, motility, and virulence, as well as other experiments to dissect the role of the two aconitases.
Sink or Swim? Bone Density as a Mechanism for Buoyancy Control in Early Cetaceans
Name: Scott Wolfe
Major: Biology
Academic Advisor: Dr. Greg Szulgit
APEX Advisor: Dr. Sandy Madar
Location: Hiram College
Dr. Sandy Madar
Associate Professor
Hiram College, Hiram, OH 44234
330.569.5261
MadarSI@hiram.edu
Source of Funding: Howard Hughes Medical Institute Grant
Co-Researchers: Noel-Marie Gray, Kim Kainec, and Lucas Tomko
Previous analyses have shown that secondarily aquatic tetrapods, including whales, exhibit osteological adaptations to life in water, as part of their complex buoyancy control systems. These structural specializations of bone span hyperostosis through osteoporosis. Although members of one late family of archaic whale has been described with pachyostosis considered skeletal ballast, with few exceptions, modern cetaceans exhibit osteoporosis, and control buoyancy dynamically. The past fifteen years of paleontological effort has provided an unprescedented opportunity to examine the osteological transformation of whales as they make their transition to obligiate aquatic lifestyle over a ten million year period. Here we analyze the bone histology of five early cetacean families, including Pakicetidae, Ambulocetidae, Protocetidae, Remintonocetidae, and Basilosauridae. We can then examine whether whales manifest their osteological specialization in the same manner as extant semi-aquatic and fully aquatic mammals. While few gross morphological adaptations related to swimming are seen in the earliest whales, histological analysis clearly shows extreme bone density that is an attributable aquatic specialization.