Plasmid Extraction

Introduction

Chitobiase, from Vibrio harveyi, is a membrane bound lipoprotein involved in the degradation of chitin. Chitobiase is similar to and may share a common ancestry to the a-chain of human b-hexos-aminidase. Chitobiase is encoded by chb.

In this experiment, a restriction map for restriction enzymes Eco R1, Pst1 and Hind III using Southern hybridization and restriction analysis of pRSG 192. pRSG 192 is a recombinant plasmid derived from the chb gene and pUC 19, a 2.7kb engineered plasmid which encodes for ampicillin resistance, a portion of the lac operon and a multiple cloning region . The chb gene exists as a 3.6 kb insert in the mutiple cloning region of pUC 19.

The major goals of Experiment One will be to isolate pRSG 192 from an overnight culture of E. coli, amplify a region of the chb gene using PCR, and to map restriction sites within the chb gene using restriction analysis and Southern hybridization.

Methods

Plasmid Isolation

Four microfuge tubes containing cell pellets representing 3.0ml of cells(2 x 1.5ml) from an overnight culture of E. coli were prepared. The supernatant fluid was discarded and each pellet was resuspended in 150ul of TE buffer(10mM Tris-HCl, pH 8.0; 0.1 EDTA). 300ul of SDS(1% SDS, 0.2 N NaOH) was added to each pellet. The tubes were placed on ice for five minutes, after which, 225ul of ice-cold 3M potassium acetate(pH 4.8) was added. The tubes were again placed on ice for five minutes and subsequently microfuged for five minutes.

The supernatants were recovered and transferred to new tubes. One volume of phenol/chloroform was added to each new tube. The tubes were shaken vigorously for two minutes and centrifuged for five minutes. The upper, aqueous phase was recovered and transferred to a new tube.