个人简介

1976 B.S. Biology, Heidelberg College, Tiffin, OH 1977 Comprehensive Science teaching credential, Heidelberg College, Tiffin, OH 1995 Ph.D. Microbiology, University of California at Davis 1977-78 High School Science Teacher, Rolling Hills Local School Dist. Byesville, OH 1978-81 Jr. High School Science Teacher, Kingman City School Dist. Kingman, AZ 1981-84 High School Science Teacher, Orford School Dist. Orford, NH 1984-88 Jr. High School Science Teacher, Silver Valley Local School Dist. Daggett, CA 1989-94 Teaching Assistant: Introduction to Biological Science, Bacteriology Laboratory, Microbial Ecology, U.C. Davis, Davis, CA 1990-94 Research Assistant: Physiology and genetics of symbiotic and diazotrophic cyanobacteria, U.C. Davis, Davis, CA 1995-98 Postdoctoral Research Associate: Physiology and genetics of phosphorous metabolism in free-living and symbiotic rhizobia, Montana State University, Bozeman, MT 1998-2003 Assistant Professor; 2003-2007 Associate Professor; 2007-Present Full Professor - California State University Northridge, Northridge, CA: teaching Principles of Microbiology, Bacterial Diversity, Molecular Genetics of Prokaryotes, Gentics of Bacteria and their Viruses, Graduate Seminars; researching physiology and genetics of cyanobacterial metabolism and cell development

研究领域

The research in my laboratory focuses on the problem of how bacteria regulate adaptive alterations of their cell morphology and physiology in response to environmental changes. I utilize the cyanobacterium Nostoc punctiforme for these studies. As illustrated in the left-hand panels of the figure below, the filaments cyanobacterium Nostoc punctiforme can differentiate from normal vegetative cells (V) into nitrogen fixing heterocysts (H) resistant akinetes (A) or motile hormogonia (Horm) that move by gliding motility. Our research focuses on identification of genes involved in cellular differentiation of akinetes. Akinetes are resting cells capable of surviving long periods of desiccation and cold that differentiate from normal vegetative cells due to low light or phosphate starvation. For an overview of the differentiation potential in N. punctiforme, please see our recent review. We have developed plasmid vectors to report gene transcription and have tested them for cell-type specific expression using known promoters. For instance in the figure below, the cells in panels A and B contain a green fluorescent protein (GFP) reporter fused to the promoter of hetR, known to be expressed in heterocysts. The right-hand pannel is a view using epifluorescence microscopy to excite the cells containing GFP. Similarly, the vegetative cell promoter to psaC (panels C and D) and akinete marker gene promoter avaK (panels E and F) are shown. If the plasmid reporter vector does not contain a promoter, no expression of GFP occurs (panels G and H). Please see the publication; Aguilar, Yuksek and Summers, 2004. J. Microbiol. Meth. 59:181 for details. We have developed a model system for the study of akinetes in this organism using a metabolic mutant lacking glucose-6-phosphate dehydrogenase (encoded by the zwf gene). The cells of this mutant synchronously turn into akinetes after several days in the dark if given a carbon source such as fructose. Please see Argueta and Summers, 2005, Arch. Microbiol. 183:338-346 for more information. Using differential display on RNA harvested from wild-type (grows in the dark as a heterotroph) and mutant (differentiates into akinetes) allowed us to identify genes more highly expressed in akinetes after a dark shift. Promoters from these genes have been tested using the reporter plasmids shown above and have been confirmed to be more highly expressed in developing akinetes, as shown below. Please see Argueta, C., K. Yuksek, R. Patel, and M.L Summers. 2006 for more information.

Bacterial physiology and genetics

近期论文

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Peramuna, A., R. Morton, and M.L. Summers. 2015. Enhancing alkane production in cyanobacterial lipid droplets: A model platform for industrially relevant compound production. Life 5(2):1111-1126. eLife link to publication Peramuna, A. and M.L. Summers. 2014. Composition and occurrence of lipid droplets in the cyanobacterium Nostoc punctiforme. Archives of Microbiology 196: 881-890. Gupta, D., T. Ip, M.L. Summers, and C. Basu. 2014. 2-Methyl-3-buten-2-ol (MBO) synthesis expression in Nostoc punctiforme leads to over production of phytols. Bioengeneered Published online January 3, 2015. Maldener, I., M.L. Summers and A. Sukenik. 2014. Cellular Differentiation in Filamentous Cyanobacteria, in The Cell Biology of Cyanobacteria. E. Flores and A. Herrero (ed). Caister Academic Press, Norfolk, UK. Gupta, D., M. L. Summers, and C. Basu. 2014. Engineering an isoprenoid pathwayin Escherichia coli for production of 2-Methyl-3-buten-2-ol: A potential biofuel. Molecular Biotechnology 56:516-523. Holmquist, C.P., G.P. Holmquist, and M.L. Summers. 2011. Comparing binding site information to binding affinity reveals that Crp/DNA complexes have several distinct binding conformers. Nucleic Acids Research 39(15):6813-24. click here to down-load paper Kaplan-Levy, R.N.; O., Hadas; M.L., Summers; J., Rücker; A., Sukenik. 2010. Akinetes: Dormant Cells of Cyanobacteria. Dormancy and resistance in harsh environments. E. Lubzens, J. Cerdà and M. Clark (Eds.), Topics in Current Genetics, Vol. 21. Springer-Verlag Berlin Heidelberg. Hedger, J , P.C. Holmquist, K.A. Leigh, K. Saraff, C. Pomykal, and M.L. Summers. 2009. Illumination stimulates cAMP receptor protein dependent transcriptional activation from regulatory regions containing type I, and II promoter elements in Synechocystis sp. PCC 6803. Microbiology 155: 2994-3004. (view manuscript as PDF file) Campbell, E.L., M.L. Summers, H. Christman, M.E. Martin, and J.C. Meeks. 2007. Global gene expression patterns of Nostoc punctiforme in steady state dinitrogen-grown heterocyst-containing cultures and at single time points during the differentiation of akinetes and hormogonia. Journal of Bacteriology 189:5247-5256. Argueta, C., K. Yuksek, R. Patel, and M.L Summers. 2006. Identification of Nostoc punctiforme akinete-expressed genes using differential display. Molecular Microbiology 61:748-757. Welty, L.A.Y., E.L. Heinrich, K. Garcia, L.R. Banner, M.L. Summers, L. Baresi, S. Metzenberg, C. Coyl-Thompson, and S.B. Oppenheimer. 2005. Analysis of Unconventional approaches for the rapid detection of surface lectin binding ligands on human cell lines. ACTA Histochemica 107:411-420. Argueta, C and M.L. Summers. 2005. Characterization of a model system for the study of Nostoc punctiforme akinetes. Archives of Microbiology 183:338-346. Argueta, C., K. Yuksek, and M.L. Summers. 2004. Construction and use of GFP reporter vectors for analysis of cell-type-specific gene expression in Nostoc punctiforme. Journal of Microbiological Methods 59:181-188. Meeks, J.C., E.L. Campbell, M.L. Summers, F.C. Wong. 2002. Cellular differentiation in the cyanobacterium Nostoc punctiforme. Archives of Microbiology 178:395-403. Summers, M.L., L. M. Botero, S.C. Busse, and Timothy R. McDermott. 2000. The Sinorhizobium meliloti Lon protease is involved in regulating exopolysaccharide synthesis and is required for nodulation of alfalfa. Journal of Bacteriology 182:2551-2558. Summers, M.L., M.C. Denton, T.R. McDermott. 1999. Genes coding for phosphotransacetylase and acetate kinase in Sinorhizobium meliloti are in an operon that is inducible by phosphate stress and controlled by PhoB. Journal of Bacteriology 181:2217-24. Summers, M.L., J.G. Elkins, B. Elliot, T.R. McDermott. 1998. Expression and regulation of phosphate starvation inducible genes in Rhizobium meliloti. Molecular Plant Microbe Interactions 11:1094-1101. Deng, S., M.L. Summers, M.L. Kahn, and T.R. McDermott. 1998. Cloning and characterization of a Rhizobium meliloti nonspecific acid phosphatase. Archives of Microbiology 170:18-26. Stout, R.G., M.L. Summers, T. Kerstetter, and T.R. McDermott. 1997. Heat- and acid-tolerance of a grass commonly found in geothermal areas within Yellowstone National Park. Plant Science 130:1-9. Al-Niemi, T.S., M.L. Summers, J.G. Elkins, M.L. Kahn, T.R. McDermott. 1997. Regulation of the phosphate stress response in Rhizobium meliloti by PhoB. Applied and Environmental Microbiology 63:4979-4981. Summers, M.L., and J.C. Meeks. 1996. Transcriptional regulation of zwf, encoding glucose-6-phosphate dehydrogenase, from the cyanobacterium Nostoc punctiforme strain ATCC 29133. Molecular Microbiology 22:473-480. Campbell, E.L, K.D. Hagen, M.F. Cohen, M.L. Summers, and J.C. Meeks. 1996. The devR gene product is characteristic of receivers of two-component regulatory systems and is essential for heterocyst development in the filamentous cyanobacterium Nostoc sp. strain ATCC 29133. Journal of Bacteriology 178:2037-2043. Summers, M.L., J.G. Wallis, E.L. Campbell, and J.C. Meeks. 1995 Genetic evidence of a major role for glucose-6-phosphate dehydrogenase in nitrogen fixation and dark growth of the cyanobacterium Nostoc sp. strain ATCC 29133. Journal of Bacteriology 177:6184-6194. Summers, M.L., J.C. Meeks, S. Chu, and R.E. Wolf, Jr. 1995. Nucleotide sequence of an operon in Nostoc sp. strain ATCC 29133 encoding four genes of the oxidative pentose phosphate cycle. Plant Physiology 107: 267-268.