Construction of Genomic Library of Magnetospirillnm magneticum AMB-I and Screening of Genes Involved in Magnetosome Synthesis

Abstract

Magnetospirillum magneticum AMB-1 is a fresh-water magnetic bacterium capable of synthesizing membrane- bound magnetic particle. called magnetosome, under microaerobic conditions. To screen and isolate genes involved in magnetosome synthesis, genomic library of M. magneticum AMB-1 was constructed using pJRD2l5 as a cosmid vector. The genomic DNA of AMB-1 was partially digested with Saµ3AI and ligated into BamHI digestion of pJRD215. The ligated DNA was packaged into bacteriophage λ particle and subsequently infected into Escherichia coli NM554 as a host strain. A thousand and five colonies of NM554 library carrying the recombinant cosmids were obtained that grew on luria agar supplemented with kanamycin (25 µg ml-1) and streptomycin (50 µg ml-1). Screening of the library by colony hybridization revealed that the library carried all DNA sequences or genes involved in magnetosome synthesis used as probes. The average of the genome size inserted in the library was approximately 10-40 kb. These large fragments would facilitate complementation analysis of genes involved in magnetosorne synthesis in this forming magnetic bacterium.