Diversity in the swimming motility and flagellar regulon structure of uropathogenic Morganella morganii strains

In current times, the opportunistic pathogen Morganella morganii is increasingly becoming a cause of urinary tract infections. The condition has been further complicated by the multiple drug resistance of most isolates. Swimming motility plays an important role in the development of urinary tract infections, allowing bacteria to colonize the upper urinary tract. We determined the differences between the growth, swimming motility, and biofilm formation of two M. morganii strains MM 1 and MM 190 isolated from the urine of patients who had community-acquired urinary tract infections. MM 190 showed a lower growth rate but better-formed biofilms in comparison to MM 1. In addition, MM 190 possessed autoaggregation abilities. It was found that a high temperature (37 °C) inhibits the flagellation of strains and makes MM 190 less motile. At the same time, the MM 1 strain maintained its rate of motility at this temperature. We demonstrated that urea at a concentration of 1.5% suppresses the growth and swimming motility of both strains. Genome analysis showed that MM 1 has a 17.7-kb-long insertion in flagellar regulon between fliE and glycosyltransferase genes, which was not identified in corresponding loci of MM 190 and 9 other M. morganii strains with whole genomes. Both strains carry two genes encoding flagellin, which may indicate flagellar antigen phase variation. However, the fliC2 genes have only 91% identity to each other and exhibit some variability in the regulatory region. We assume that all these differences influence the swimming motility of the strains.