coli strain HB101 and the bald fim2-negative
K. pneumoniae C3091∆fim∆mrk mutant was pursued. Yet again evidence of a fim2-associated phenotype was elusive and only apparent in HB101 and then too only when crystal violet-staining data were buy LEE011 standardised for total pre-wash cell numbers. Attempts to alleviate the observed growth retardation associated with over-expression of fim2 in a HB101 background by reducing incubation temperature to 30°C and by providing rare tRNAs in trans were unsuccessful. Furthermore, the observed growth retardation was highly reproducible even when newly generated HB101 strains possessing independently-constructed pFim2-Ptrc plasmids were used instead (van Aartsen and Rajakumar, unpublished data). Thus, it would appear that over-expression SN-38 cell line of fim2 in HB101 was specifically responsible for this phenotype, though no comparable effect occurred with over-expression of fim. The presence of fim2 in more than one species and its global spread suggests that this horizontally acquired locus has been maintained within a subset of the Klebsiella population due to positive selection. Hence, although the role fim2 remains elusive, given the glimpses of functionality hinted at by our data and the evolutionary survival
of this multi-gene entity, we hypothesize that putative Fim2 contributes to pathogenesis of infection and/or Akt inhibitor ic50 environmental persistence, at least under highly specific conditions. Conclusions In conclusion, we have described Etomidate the KpGI-5 island which possessed a novel γ1-type CU operon called fim2. Although fim2 was shown to be expressed at an mRNA level and its function was investigated using three distinct murine infection models, tissue culture experiments and biofilm assays, no obvious in vitro or in vivo role for the fim2 locus was identified, although there were subtle hints of involvement in urovirulence and in bacterial
dissemination from the respiratory tract. Nevertheless, as fim2 was found in approximately 13% of Klebsiella spp. isolates examined, we propose that fim2 has the potential to contribute beneficially to its host Klebsiella strains at least under specific conditions. Methods Bacterial strains, plasmids, and growth media Bacterial strains and plasmids used in this study are described in Table 3. K. pneumoniae KR116 is a human blood stream infection isolate obtained from the University Hospitals of Leicester. Unless otherwise specified, strains were routinely cultured at 37°C in LB medium supplemented with 50 μg/ml apramycin, 250 μg/ml ampicillin, 30 μg/ml chloramphenicol, 50 μg/ml kanamycin and/or 15 μg/ml tetracycline for K. pneumoniae, and 100 μg/ml ampicillin, 12.5 μg/ml chloramphenicol, 50 μg/ml kanamycin and/or 10 μg/ml tetracycline for E. coli.