title: Self-immobilization of recombinant Caulobacter crescentus and its application in removal of cadmium from water.
abstract: Microbial biofilms can be valuable in many biotechnological applications, including bioremediation. We have previously constructed a recombinant strain of Caulobacter crescentus JS4022/p723-6H by inserting a hexahistidine peptide to a permissive site of the host surface layer (S-layer) protein RsaA. This engineered strain is highly effective in removal of cadmium from water as free cells. In this communication, we examined the biofilms formed by self-immobilized JS4022/p723-6H and evaluated their ability to retrieve cadmium from contaminated water samples. According to light and electron microscopic observations, JS4022/p723-6H cells developed a uniform monolayer biofilm on borosilicate surfaces through their intrinsic appendage, a stalk with an adhesive holdfast. The density of the biofilms reached a maximum after 48 h of incubation and was not affected by exposure to at least 1 ppm cadmium. When 0.4 ppm Cd(II) was added to the growth medium, immobilized JS4022/p723-6H removed 76.9% of the total metal, whereas the control strain only removed 13.5%. When a water sample collected from Lake Erie was spiked with various amounts of CdCl2, immobilized JS4022/p723-6H was able to sequester 44 approximately 51% of the total metal, compared to 37 approximately 42% accumulated by the control strain. By combining two powerful techniques, cell surface display and self-immobilization, we achieved complete separation of dissolved heavy metals from contaminated water in a single step. This study laid down the foundation to cost-effectively construct large-scale bioreactors with high efficiency and specificity to retrieve environmental contaminants from water.
authors.affiliation: Department of Biological Sciences, Bowling Green State University, Bowling Green, OH 43403-0208, USA.
authors.forename: Jigar
authors.initials: J
authors.lastname: Patel
authors.forename: Gregory
authors.initials: G
authors.lastname: Wilson
authors.forename: R Michael L
authors.initials: RM
authors.lastname: McKay
authors.forename: Robert
authors.initials: R
authors.lastname: Vincent
authors.forename: Zhaohui
authors.initials: Z
authors.lastname: Xu
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D001673:Biodegradation, Environmental; D018441:Biofilms; D002104:Cadmium / Q000378:metabolism*; D016935:Caulobacter crescentus / Q000235:genetics / Q000502:physiology*; D052918:Environmental Restoration and Remediation / Q000379:methods*; D005818:Genetic Engineering; D014874:Water Pollutants, Chemical / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D014874:Water Pollutants, Chemical; D002104:Cadmium