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Mutation in the rpsL gene are responsible for streptomycin resistance of Clavibacter michiganensis subsp. michiganensis

Qingyang Lyu: China Agricultural University

<div>Streptomycin is an aminoglycoside antibiotic effective against a wide variety of bacteria and has been used to control many plant bacterial diseases, including bacterial canker of tomato caused by <em>Clavibacter</em> <em>michiganensis</em> subsp. <em>michiganensis</em> (Cmm), but no resistant Cmm strain has been reported. The induced streptomycin-resistant (Sm<sup>r</sup>) mutant of Cmm was isolated by culturing the streptomycin-sensitive strain BT-0505 on streptomycin containing LB agar, the isolate can grow on LB agar in the presence of 512 μg/mL streptomycin while the minimum inhibitory concentration was more than 5000 μg/mL. The gene related with the streptomycin resistance was amplified from the Sm<sup>r</sup> mutant by PCR and confirmed by sequencing. There was an A to G point mutation in <em>rpsL</em> gene at nucleotide 128 in the Sm<sup>r</sup> mutant, resulting a lysine to arginine change in the RpsL protein. The complementation assay further confirmed that the point mutation in the <em>rpsL </em>gene was responsible for the streptomycin resistance in BT-0505. These results are consistent with the current understanding of the mechanism on streptomycin resistance in <em>Escherichia coli</em> and other bacteria.</div>