The genomic organization and the functional features of SMAG elements are described herein. A total of 1650 SMAG elements were identified in the genome of the S. maltophilia K279a strain. The elements are 22–25 bp in size, and can be sorted into five distinct major
subfamilies because they have different stem and loop sequences. One fifth of the SMAG family is comprised of single units, 2/5 of elements located at a close distance from each other and 2/5 of elements grouped in tandem arrays of variable lengths. Altogether, SMAGs and intermingled DNA occupy 13% of the intergenic check details space, and make up 1.4% of the chromosome. Hundreds of genes are immediately flanked by SMAGs, and the level of expression of many may be influenced by the folding of the repeats in the mRNA. Expression analyses suggested that SMAGs function as RNA control sequences, either stabilizing upstream transcripts or favoring their degradation. Stenotrophomonas maltophilia is a nonfermentative Gram-negative bacterium that is ubiquitous in nature. It constitutes one of the dominant rhizosphere inhabitants (Ryan et al., 2009; Taghavi et al., 2009), but is also increasingly being described as an important nosocomial
pathogen in debilitated and immunodeficient patients, and has been associated with a broad spectrum of clinical syndromes. It has been isolated frequently old from cystic fibrosis Cabozantinib in vivo patients, and has emerged as a serious pathogen in cancer patients (Looney et al., 2009). Stenotrophomonas maltophilia displays an intrinsic resistance to many antibiotics, making the selection of optimal
therapy difficult (Crossman et al., 2008). Whether the bacterium is a mere colonizer or an infectious agent often remains unresolved, and virulence factors are still ill-defined. The chromosomes of the clinical K279a (Crossman et al., 2008) and the environmental R551-3 (Taghavi et al., 2009) strains exhibit extensive synteny, but each is punctuated by about 40 different GEIs or genomic islands (Rocco et al., 2009). Whether pathogenicity may be associated in part with the maintenance of specific GEIs in the S. maltophilia population remains to be established. Stenotrophomonas maltophilia is extremely heterogeneous at the genetic level (Coenye et al., 2004; Kaiser et al., 2009). We described a procedure to obtain a rapid genotyping of S. maltophilia isolates based on the measurement of length variations of genomic regions marked by arrays of palindromic sequences (Roscetto et al., 2008). In this paper, we describe the organization and the features of this peculiar class of repeats, called SMAG (Stenotrophomonas maltophilia GTAG), because they carry at one terminus the tetranucleotide GTAG.