Professional Education


  • Bachelor of Science, University of Minnesota Twin Cities (2012)
  • Doctor of Philosophy, University of California Berkeley (2018)

All Publications


  • A method of alternating characteristics with application to advection-dominated environmental systems COMPUTATIONAL GEOSCIENCES Georgiou, K., Harte, J., Mesbah, A., Riley, W. J. 2018; 22 (3): 851–65
  • Microbial community-level regulation explains soil carbon responses to long-term litter manipulations (vol 8, 1223, 2017) NATURE COMMUNICATIONS Georgiou, K., Abramoff, R. Z., Harte, J., Riley, W. J., Torn, M. S. 2018; 9: 173

    Abstract

    The original PDF version of this Article contained an error in Table 1. On the right-hand side of the third row, the third equation was missing a β as an exponent on the first CB. This has now been corrected in the PDF version of the Article. The HTML version was correct from the time of publication.

    View details for DOI 10.1038/s41467-017-02134-7

    View details for Web of Science ID 000419658500002

    View details for PubMedID 29317614

    View details for PubMedCentralID PMC5760661

  • The effects of heating, rhizosphere, and depth on root litter decomposition are mediated by soil moisture BIOGEOCHEMISTRY Castanha, C., Zhu, B., Pries, C., Georgiou, K., Torn, M. S. 2018; 137 (1-2): 267–79
  • Microbial community-level regulation explains soil carbon responses to long-term litter manipulations NATURE COMMUNICATIONS Georgiou, K., Abramoff, R. Z., Harte, J., Riley, W. J., Torn, M. S. 2017; 8: 1223

    Abstract

    Climatic, atmospheric, and land-use changes all have the potential to alter soil microbial activity, mediated by changes in plant inputs. Many microbial models of soil organic carbon (SOC) decomposition have been proposed recently to advance prediction of climate and carbon (C) feedbacks. Most of these models, however, exhibit unrealistic oscillatory behavior and SOC insensitivity to long-term changes in C inputs. Here we diagnose the source of these problems in four archetypal models and propose a density-dependent formulation of microbial turnover, motivated by community-level interactions, that limits population sizes and reduces oscillations. We compare model predictions to 24 long-term C-input field manipulations and identify key benchmarks. The proposed formulation reproduces soil C responses to long-term C-input changes and implies greater SOC storage associated with CO2-fertilization-driven increases in C inputs over the coming century compared to recent microbial models. This study provides a simple modification to improve microbial models for inclusion in Earth System Models.

    View details for DOI 10.1038/s41467-017-01116-z

    View details for Web of Science ID 000414032200026

    View details for PubMedID 29089496

    View details for PubMedCentralID PMC5663850

  • Dynamics of Mechanosensitive Neural Stem Cell Differentiation STEM CELLS Rammensee, S., Kang, M. S., Georgiou, K., Kumar, S., Schaffer, D. V. 2017; 35 (2): 497–506

    Abstract

    Stem cell differentiation can be highly sensitive to mechanical inputs from the extracellular matrix (ECM). Identifying temporal windows during which lineage commitment responds to ECM stiffness, and the signals that mediate these decisions, would advance both mechanistic insights and translational efforts. To address these questions, we investigate adult neural stem cell (NSC) fate commitment using an oligonucleotide-crosslinked ECM platform that for the first time offers dynamic and reversible control of stiffness. "Stiffness pulse" studies in which the ECM was transiently or permanently softened or stiffened at specified initiation times and durations pinpoint a 24-hour window in which ECM stiffness maximally impacts neurogenic commitment. Overexpression of the transcriptional coactivator Yes-associated protein (YAP) within this window suppressed neurogenesis, and silencing YAP enhanced it. Moreover, ablating YAP-β-catenin interaction rescued neurogenesis. This work reveals that ECM stiffness dictates NSC lineage commitment by signaling via a YAP and β-catenin interaction during a defined temporal window. Stem Cells 2017;35:497-506.

    View details for DOI 10.1002/stem.2489

    View details for Web of Science ID 000393573300019

    View details for PubMedID 27573749

    View details for PubMedCentralID PMC5285406

  • Toward more realistic projections of soil carbon dynamics by Earth system models GLOBAL BIOGEOCHEMICAL CYCLES Luo, Y., Ahlstrom, A., Allison, S. D., Batjes, N. H., Brovkin, V., Carvalhais, N., Chappell, A., Ciais, P., Davidson, E. A., Finzi, A., Georgiou, K., Guenet, B., Hararuk, O., Harden, J. W., He, Y., Hopkins, F., Jiang, L., Koven, C., Jackson, R. B., Jones, C. D., Lara, M. J., Liang, J., McGuire, A. D., Parton, W., Peng, C., Randerson, J. T., Salazar, A., Sierra, C. A., Smith, M. J., Tian, H., Todd-Brown, K. E., Torn, M., van Groenigen, K. J., Wang, Y. P., West, T. O., Wei, Y., Wieder, W. R., Xia, J., Xu, X., Xu, X., Zhou, T. 2016; 30 (1): 40-56
  • Toward improved model structures for analyzing priming: potential pitfalls of using bulk turnover time GLOBAL CHANGE BIOLOGY Georgiou, K., Koven, C. D., Riley, W. J., Torn, M. S. 2015; 21 (12): 4298–4302

    Abstract

    Many studies have shown that elevated atmospheric CO2 concentrations result in increased plant carbon inputs to soil that can accelerate the decomposition of native soil organic matter, an effect known as priming. Consequently, it is important to understand and quantify the priming effect for future predictions of carbon-climate feedbacks. There are potential pitfalls, however, when representing this complex system with a simple, first-order model. Here, we show that a multi-pool soil carbon model can match the change in bulk turnover time calculated from overall respiration and carbon stocks (a one-pool approach) at elevated CO2 , without a change in decomposition rate constants of individual pools (i.e., without priming). Therefore, the priming effect cannot be quantified using a one-pool model alone, and even a two-pool model may be inadequate, depending on the effect size as well as the distribution of soil organic carbon and turnover times. In addition to standard measurements of carbon stocks and CO2 fluxes, we argue that quantifying the fate of new plant inputs requires isotopic tracers and microbial measurements. Our results offer insights into modeling and interpreting priming from observations.

    View details for DOI 10.1111/gcb.13039

    View details for Web of Science ID 000364777400002

    View details for PubMedID 26182905

  • Explicitly representing soil microbial processes in Earth system models GLOBAL BIOGEOCHEMICAL CYCLES Wieder, W. R., Allison, S. D., Davidson, E. A., Georgiou, K., Hararuk, O., He, Y., Hopkins, F., Luo, Y., Smith, M. J., Sulman, B., Todd-Brown, K., Wang, Y., Xia, J., Xu, X. 2015; 29 (10): 1782–1800
  • Controls on terrestrial carbon feedbacks by productivity versus turnover in the CMIP5 Earth System Models BIOGEOSCIENCES Koven, C. D., Chambers, J. Q., Georgiou, K., Knox, R., Negron-Juarez, R., Riley, W. J., Arora, V. K., Brovkin, V., Friedlingstein, P., Jones, C. D. 2015; 12 (17): 5211–28
  • Targeted Polymersome Delivery of siRNA Induces Cell Death of Breast Cancer Cells Dependent upon Orai3 Protein Expression LANGMUIR Pangburn, T. O., Georgiou, K., Bates, F. S., Kokkoli, E. 2012; 28 (35): 12816–30

    Abstract

    Polymersomes, polymeric vesicles that self-assemble in aqueous solutions from block copolymers, have been avidly investigated in recent years as potential drug delivery agents. Past work has highlighted peptide-functionalized polymersomes as a highly promising targeted delivery system. However, few reports have investigated the ability of polymersomes to operate as gene delivery agents. In this study, we report on the encapsulation and delivery of siRNA inside of peptide-functionalized polymersomes composed of poly(1,2-butadiene)-b-poly(ethylene oxide). In particular, PR_b peptide-functionalized polymer vesicles are shown to be a promising system for siRNA delivery. PR_b is a fibronectin mimetic peptide targeting specifically the α(5)β(1) integrin. The Orai3 gene was targeted for siRNA knockdown, and PR_b-functionalized polymer vesicles encapsulating siRNA were found to specifically decrease cell viability of T47D breast cancer cells to a certain extent, while preserving viability of noncancerous MCF10A breast cells. siRNA delivery by PR_b-functionalized polymer vesicles was compared to that of a current commercial siRNA transfection agent, and produced less dramatic decreases in cancer cell viability, but compared favorably in regards to the relative toxicity of the delivery systems. Finally, delivery and vesicle release of a fluorescent encapsulate by PR_b-functionalized polymer vesicles was visualized by confocal microscopy, and colocalization with cellular endosomes and lysosomes was assessed by organelle staining. Polymersomes were observed to primarily release their encapsulate in the early endosomal intracellular compartments, and data may suggest some escape to the cytosol. These results represent a promising first generation model system for targeted delivery of siRNA.

    View details for DOI 10.1021/la300874z

    View details for Web of Science ID 000308260200015

    View details for PubMedID 22827285

  • Graceful switching in hybrid models Georgiou, K., Georgiou, T. T., IEEE IEEE. 2009: 3882–84