Microorganisms represent the major portion of biomass on Earth with enormous diversity in morphology, genetics, and metabolism, which implies huge application potentials. We are interested in using genetic, biochemical, and photochemical approaches to develop microbial systems that can be applied to environmental processes, such as remediation of hazardous substances, development of detection or monitoring systems, and production of high value products from agricultural or industrial by-products or wastes. Currently, we are focusing on the following projects:
1. Genetic engineering of the surface layer (S-layer) protein RsaA of Caulobacter crescentus for heavy metal retrieval. Caulobacter crescentus is a harmless dimorphic bacterium widely found in aquatic environments. In common with many other prokaryotic organisms, Caulobacter cells are coated with an orderly structured S-layer, which is composed of identical subunits of protein or glycoprotein. Because of their external location and crystalline arrangement, S-layer proteins become ideal carriers to display foreign peptides on the surface of a host cell, allowing us to build remediation bioreactors with heavy metal removal capacity or to fabricate nano-scale constructs for photodegradation of organic pollutants.
2. Site-directed mutagenesis of bacterial sensory rhodopsin for wanted optical properties. In Anabaena (Nostoc) sp. PCC7120, the light sensory rhodopsin ASR is responsible for sensing green light and activating a cascade of light-sensitive reactions in the cell body. In this project, we aim to generate ASR mutants that can absorb light at different wavelengths. The application of the results can be foreseen in a variety of aspects, such as development of molecular light switches in nanotechnology and light-induced gene expression in biotechnology. This project is in collaboration with Dr. Massimo Olivucci at the BGSU Department of Chemistry.
3. Genetic modification of cellulases to improve the enzyme catalytic efficiency, thermostability, and substrate specificity or stereoselectivity. Due to global energy crisis, developing renewable forms of energy like hydro, solar and bio-energy has become increasingly important. Energy from biomass has a promising future because it ensures self-reliance through the use of local resources with simple technologies and less production hazards. This project aims to utilize genetic tools to facilitate the hydrolysis of cellulose, which becomes useful as a food and energy source once it is broken down into soluble cellobiose (β-1,4 glucose dimer) and glucose
Han D, SM Norris, Xu Z*. Construction and transformation of a Thermotoga-E. coli shuttle vector. BMC Biotechnology. 12:2. 2012.
Xu Z*, Han D, Cao J, Saini, U. Cloning and characterization of the TneDI restriction-modification system of Thermotoga neapolitana. Extremophiles. 15(6):665-72. 2011.
Xu Z*, Dutton RJ, Gober JW. Direct interaction of FliX and FlbD is required for their regulatory activity in Caulobacter crescentus. BMC Microbiology. 11:89. 2011.
Ditty J, Kvaal C, Goodner B, Freyermuth S, Bailey C, Britton R, Gordon S, Heinhorst S, Reed K, Xu Z, Sanders-Lorenz E, Axen S, Kim E, Johns M, Scott K, Kerfeld, C*. Faculty incorporating genomics and bioinformatics across the life sciences curriculum: development and implementation of the integrated microbial genomes annotation collaboration toolkit (IMG-ACT). PLoS Biology. 8(8): e1000448. 2010.
Xu Z*, Lei Y, Patel J. Bioremediation of soluble heavy metals with recombinant Caulobacter crescentus. Bioengineered Bugs. 1(3):207-12. 2010.