The microbial symbiosis community at UW-Madison has positioned itself on the cutting edge of symbiosis research. Over twenty laboratories, including four faculty hired as part of the Symbiosis Cluster, are exploring beneficial microbial symbiosis in plants, animals, and biofilms. This interdisciplinary group brings together numerous faculty and students from departments and schools across the university. Symbiosis activities include monthly seminars, journal club, and a manuscript review; as well as a yearly symbiosis-related conference. Please join us as we delve into the spectacular diversity of interactions between microbes and the world!

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Faculty Papers

Terri Balser

 

Great Lakes Bioenergy Research Center | UW-Madison

"Investigation of the molecular ion structure for aldononitrile acetate derivatised muramic acid"

The muramic acid assay is a powerful tool for detecting both intact bacteria and bacterial debris. Past use of aldononitrile acetate derivatization for determining muramic acid in complex samples by gas chromatography/mass spectrometry met detection needs in many instances; however, questions have been raised regarding the interpretation of the derivative structure and its EI fragments. In this study, we applied different methods and proved that the aldononitrile acetate derivatised muramic acid yields a molecular weight of 398, associated with a lactam structure. We also presented evidence that the structure of aldononitrile acetate derivatized muramic acid is acetylated at five positions, 4 O-acetylations and 1N-acetylation. In practical manner, this communication provides a comprehensive reference to researchers using δ(13)C value or ion fragments of the muramic acid marker in biogeochemical studies.

Details : Liang C, Zhang X, Wei L, He H, Higbee AJ, Balser TC. J Microbiol Methods. 2011 May 19.

 

Papers of Interest

Angela Douglas

Department of Entomology | Cornell University | Ithaca, NY

 

"Low-diversity bacterial community in the gut of the fruitfly Drosophila melanogaster"

The bacteria in the fruitfly Drosophila melanogaster of different life stages was quantified by 454 pyrosequencing of 16S rRNA gene amplicons. The sequence reads were dominated by 5 operational taxonomic units (OTUs) at ≤ 97% sequence identity that could be assigned to Acetobacter pomorum, A. tropicalis, Lactobacillus brevis, L. fructivorans and L. plantarum. The saturated rarefaction curves and species richness indices indicated that the sampling (85 000-159 000 reads per sample) was comprehensive. Parallel diagnostic PCR assays revealed only minor variation in the complement of the five bacterial species across individual insects and three D. melanogaster strains. Other gut-associated bacteria included 6 OTUs with low %ID to previously reported sequences, raising the possibility that they represent novel taxa within the genera Acetobacter and Lactobacillus. A developmental change in the most abundant species, from L. fructivorans in young adults to A. pomorum in aged adults was identified; changes in gut oxygen tension or immune system function might account for this effect. Host immune responses and disturbance may also contribute to the low bacterial diversity in the Drosophila gut habitat.

 

Wong CN, Ng P, Douglas AE. Environ Microbiol. 2011 Jun1.

 

Wilmara Salgado-Pabon

 

Unité de Pathogénie Microbienne Moléculaire | Institut Pasteur | France

 

"The Shigella flexneri Type Three Secretion System Effector IpgD Inhibits T Cell Migration by Manipulating Host Phosphoinositide Metabolism"

Abstract: Shigella, the Gram-negative enteroinvasive bacterium that causes shigellosis, relies on its type III secretion system (TTSS) and injected effectors to modulate host cell functions. However, consequences of the interaction between Shigella and lymphocytes have not been investigated. We show that Shigella invades activated human CD4(+) T lymphocytes. Invasion requires a functional TTSS and results in inhibition of chemokine-induced T cell migration, an effect mediated by the TTSS effector IpgD, a phosphoinositide 4-phosphatase. Remarkably, IpgD injection into bystander T cells can occur in the absence of cell invasion. Upon IpgD-mediated hydrolysis of phosphatidylinositol 4,5-bisphosphate (PIP(2)), the pool of PIP(2) at the plasma membrane is reduced, leading to dephosphorylation of the ERM proteins and their inability to relocalize at one T cell pole upon chemokine stimulus, likely affecting the formation of the polarized edge required for cell migration. These results reveal a bacterial TTSS effector-mediated strategy to impair T cell function.

 

Details : Konradt C, Frigimelica E, Nothelfer K, Puhar A, Salgado-Pabon W, di Bartolo V, Scott-Algara D, Rodrigues CD, Sansonetti PJ, Phalipon A. Cell Host Microbe. 2011 Apr 21;9(4):263-72.