The flagellin N-methylase gene fliB and an adjacent serovar-specific IS200 element in Salmonella typhimurium

Abstract

The cloning and molecular genetic analysis of a locus mapping within the flagellar gene (fli) complex of Salmonella typhimurium is reported. A copy of the insertion element IS200 was located in a noncoding stretch of DNA upstream of the fliA gene. Comparative nucleotide sequence analysis showed that this copy of IS200 was 711 bp long and that its flanking regions contained no features common to other characterized insertion sites of this element. The element was located 37 bp downstream of an ORF whose product was shown by interspecific transfer and amino acid analysis to carry out N-methylation of selected lysine residues in Salmonella flagellin. The sequence and phenotype of this ORF identified it as fliB, encoding the only prokaryotic N-methylase acting on amino groups to have been characterized to date. It was found to be conserved among all clinically significant serovars of Salmonella. The IS200 insertion site is of particular interest since it was conserved in all but two rare evolutionary lines of 5. typhimurium, and was absent from 85 Salmonella strains belonging to 37 other serovars. It is thus a phylogenetically significant marker at the serovar level.

Genetic Types, Gene Repertoire, and Evolution of Isolates of the Salmonella enterica Serovar 4,5,12:i:− Spanish Clone Assigned to Different Phage Types

“…All were positive for the repA gene of the IncA/C plasmid group, consistent with the presence of pUO-STmR/RV1-like plasmids, and the ISCR2 (linked to sul2 in IncA/C plasmids [11]) and ISCR3 (also carried by the IncA/C plasmids; P. García, unpublished data) elements. The same result was obtained for recC (which encodes a subunit of exonuclease V involved in homologous recombination and DNA repair), for the insertion sequences IS200 (reported as a 1-kb fragment in the fliB-fliA intergenic region of S. Typhimurium [25]), and for IS26. None of the isolates was positive for traT.…”

The Flag-2 Locus, an Ancestral Gene Cluster, Is Potentially Associated with a Novel Flagellar System from Escherichia coli

“…Situated between Ec042-0260 and lfgN is a gene predicted to encode a 323-residue protein with significant similarity as determined by BLASTP analysis against nr to a hypothetical protein from Y. pestis KIM (E value, 1e-4) and two S. enterica FliB proteins (E value, 2e-4). FliB is a lysine-N-methylase that is required for posttranslational methylation of lysine residues in the flagellin of S. enterica but is not found in E. coli (12). The fliB gene is normally found adjacent to fliA, and in some S. enterica strains FliB has been found to be encoded by two adjacent genes (fliUV) (17).…”

“…In this area, Salmonella enterica serovar Typhimurium strain LT2 has been the most commonly used model organism (34,35). Nonetheless, it has been assumed that the genetics and physiology of flagellar systems are essentially the same in E. coli and S. enterica; minor differences include a tap receptor gene in E. coli but not in S. enterica and an fliB flagellar methylase gene and a phase 2 locus in S. enterica but not in E. coli (12,34). In a similar vein, we have recently concluded from comparative sequence analysis that the S. enterica-E. coli model of flagellar function holds up surprisingly well even when it is generalized to bacteria that are only distantly related to E. coli (43).…”

Multiplex PCR for Distinguishing the Most Common Phase-1 Flagellar Antigens of Salmonella spp

“…This new Salmonella phase-1 multiplex PCR developed with the newly designed and previously published (1,3,17) primers (Table 3) Two amplicons were identified for Salmonella serotype Enteritidis: one of 500 bp that corresponds to the G complex and one of 333 bp that is specific for this serotype (Fig. 1).…”