tet -Dependent Gene Expression in Stenotrophomonas maltophilia.

Stenotrophomonas maltophilia is increasingly recognized as an important nosocomial pathogen among the Gram-negative bacteria. Intrinsic resistance to different classes of antibiotics makes treatment of infections challenging. A deeper understanding of S. maltophilia physiology and virulence requires molecular genetic tools. Here, we describe the implementation of tetracycline-dependent gene regulation ( regulation) in this bacterium. The exploited regulatory sequence of transposon Tn contained the gene and three intertwined promoters, one of which was required for regulated expression of a target gene or operon. The episomal architecture was tested with a variant as a quantifiable reporter. Fluorescence intensity was directly correlated with the concentration of the inducer anhydrotetracycline (ATc) applied and the duration of induction. Also, the expression of the operon of S. maltophilia K279a was subjected to control. These genes code for the synthesis of dTDP-l-rhamnose, an activated nucleotide sugar precursor of lipopolysaccharide (LPS) formation. A Δ mutant was complemented with a plasmid carrying this operon downstream of the sequence. In the presence of ATc, the LPS pattern was similar to that of wild-type S. maltophilia, whereas without the inducer, fewer and apparently shorter O-antigen chains were detected. This underscores the functionality and usefulness of the system for gene regulation and, prospectively, the validation of targets for new anti-S. maltophilia drugs. Stenotrophomonas maltophilia is an emerging pathogen in hospital settings and poses a threat to immunocompromised patients. Due to a high level of resistance to different types of antibiotics, treatment options are limited. We here adapted a tool for inducible expression of genes of interest, known as the system, to S. maltophilia. Genes relevant to producing surface carbohydrate structures (lipopolysaccharide [LPS]) were placed under the control of the system. In the presence of an inducer, the LPS pattern was similar to that of wild-type S. maltophilia, whereas in the "off" state of the system (without inducer), fewer and apparently shorter versions of LPS were detected. The system is functional in S. maltophilia and may be helpful to reveal gene-function relationships to gain a deeper understanding of the bacterium's physiology and virulence.