钟鸣
(2023-10-30 16:06):
#paper doi: 10.1128/jb.00165-23 Three genes controlling streptomycin susceptibility in Agrobacterium fabrum 链霉素是一种氨基糖苷类抗生素，通过干扰16S rRNA的正常工作阻碍细菌复制，实现抗菌效果。农杆菌的链霉素抗性通常由rpsL、rsmG（也称为gidB）和rrs突变引起。本课题中，作者使用链霉菌做连续培养筛选和分析，获取了在低浓度和高浓度抗生素下筛选到的耐药菌准，由于传代筛选过程中未引入外源基因，表明内源性基因的突变调控了耐药性。由于低浓度下的突变体的耐药性高于高浓度下的突变体，因此作者分别对这两批突变体进行了测序。作者首先发现高浓度突变株的rpsL发生了突变而低浓度的没有，对突变的rpsL等位基因进行转移实现，验证了该等位基因能赋予野生型耐药性。对6株低浓度突变体的测序发现，都发生了导致rsmG功能丧失的突变，随后的敲除和回补实证实了该基因突变对链霉素抗性的影响。
Three genes controlling streptomycin susceptibility in Agrobacterium fabrum
Robyn E. Howarth,
Curtis M. Pattillo,
Joel S. Griffitts,
Diana G. Calvopina-Chavez
Abstract:
ABSTRACT<br> <br> Streptomycin (Sm) is a commonly used antibiotic for its efficacy against diverse bacteria. The plant pathogen<br> <i>Agrobacterium fabrum</i><br> is a model for studying pathogenesis and interkingdom gene transfer. Streptomycin-resistant variants of<br> <i>A. fabrum</i><br> are commonly employed in genetic analyses, yet mechanisms of resistance and susceptibility to streptomycin in this organism have not previously been investigated. We observe that resistance to a high concentration of streptomycin arises at high frequency in<br> <i>A. fabrum</i><br> , and we attribute this trait to the presence of a chromosomal gene (<br> <i>strB</i><br> ) encoding a putative aminoglycoside phosphotransferase. We show how<br> <i>strB</i><br> , along with<br> <i>rpsL</i><br> (encoding ribosomal protein S12) and<br> <i>rsmG</i><br> (encoding a 16S rRNA methyltransferase), modulates streptomycin sensitivity in<br> <i>A. fabrum</i><br> .<br> <br> <br> IMPORTANCE<br> <br> The plant pathogen<br> <i>Agrobacterium fabrum</i><br> is a widely used model bacterium for studying biofilms, bacterial motility, pathogenesis, and gene transfer from bacteria to plants. Streptomycin (Sm) is an aminoglycoside antibiotic known for its broad efficacy against gram-negative bacteria.<br> <i>A. fabrum</i><br> exhibits endogenous resistance to somewhat high levels of streptomycin, but the mechanism underlying this resistance has not been elucidated. Here, we demonstrate that this resistance is caused by a chromosomally encoded streptomycin-inactivating enzyme, StrB, that has not been previously characterized in<br> <i>A. fabrum</i><br> . Furthermore, we show how the genes<br> <i>rsmG</i><br> ,<br> <i>rpsL</i><br> , and<br> <i>strB</i><br> jointly modulate streptomycin susceptibility in<br> <i>A. fabrum</i><br> .<br> <br>
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