Siderophore production by uropathogenic Escherichia coli.

Urinary tract infection (UTI) is one of the most frequently encountered problems in ambulatory medicine. The present study was designed to determine siderophore production as the urovirulence factor of Escherichia coli isolated from the patients of UTI. A total of 160 strains of E. coli isolated from urine of patients with clinically diagnosed UTI were included in the study and 50 fecal isolates of E. coli, siderophore production was seen in 156 (97.5%). In 50 fecal isolates, siderophore production was seen in 2 (4%). Siderophore production has been shown to be more frequent in E. coli from patients with UTI, than in fecal isolates. The results suggest that siderophore production positive strains can be considered as UPEC. Thus, although a great deal has been learned regarding E. coli virulence mechanisms in UTI, much remains to be learned and the practical application of our growing understanding of E. coli virulence factors to the prevention and treatment of UTI has to be continued.

Haemagglutination and siderophore production as the urovirulence markers of uropathogenic Escherichia coli.

A total of 160 strains of Escherichia coli isolated from urine of patients with clinically diagnosed urinary tract infection were included in the study and 50 faecal isolates of E. coli were studied. They were studied for virulence factors, namely mannose-resistant and mannose-sensitive haemagglutination (MRHA, MSHA) and siderophore production.Among 160 urinary isolates of E. coli , 40 (25%) showed MRHA, siderophore production was seen in 156 (97.5%). In 50 faecal isolates, two (4%) were MRHA, four (8%) MSHA and siderophore production in two (4%). The results suggest that MRHA and siderophore production positive strains can be considered as UPEC.

Iron mediated regulation of growth and siderophore production in a diazotrophic cyanobacterium Anabaena cylindrica.

Iron mediated regulation of growth and siderophore production has been studied in a diazotrophic cyanobacterium Anabaena cylindrica. Iron-starved cells of A. cylindrica exhibited reduced growth (30%) when the cells were growing under N2-fixing conditions. In contrast, N03-, NO2-, NH4' and urea grown cells exhibited almost 50% reduction in their growth in the absence of iron as compared to their respective counterparts cultured in the presence of iron. However, at 60 microM of iron, A. cylindrica cells exhibited almost equal growth regardless of the nitrogen source available. Siderophore production in A. cylindrica was started after day 2nd of the cell growth and attained its optimal level on day 5th when the cells were at their mid-log phase. No siderophore production was, however, recorded on day 2nd at all the concentrations of iron tested. The production of siderophore in A. cylindrica further increased with increase in iron concentration and attained its optimum level on day 5th at 60 microM iron. A. cylindrica cells took at least 3 days for initiation of siderophore production and produced about 60% siderophore on day 5th even under iron-starved condition. A. cylindrica produced dihydroxamate type of siderophore.

Studies on siderophore production of different diarrhoeagenic Escherichia coli.

In the present study, siderophore production capacity of various diarrhoeagenic E coli strains was tested on quantitative basis. The collected strains were classified under enteropathogenic E coli, enterotoxigenic E coli and entero-invasive E coli groups by using appropriate techniques. A few reference . enterotoxigenic E coli strains were also included in this study. The confirmation of various properties of enteropathogenic E coli, enterotoxigenic E coli and entero-invasive E coli strains was carried out by standard procedures. Several non-pathogenic E coli strains were also included in the study to assess their siderophore producing capacity. The results presented in the study showed that, the phenolate type of siderophore, that is enterochelin was predominantly produced by majority of these E coli strains. Only 30% of enteropathogenic E coli and 33% of enterotoxigenic E coli strains failed to produce any detectable level of enterochelin. On the other hand, only 50% of enteropathogenic E coli strains and all the entro-invasive E coli (100%) showed the positive aerobactin that is hydroxamate type of siderophore production ability. None of the enterotoxigenic E coli and non-pathogenic strains produced aerobactin.

Effect of metal ions on growth of Pseudomonas aeruginosa and siderophore and protein production.

Pseudomonas aeruginosa (GRC1) isolated from potato rhizosphere, grew better on succinate medium than tryptic soy medium and produced hydroxamate type of siderophore in iron-deficient succinate medium. When the strain GRC1 was grown in the presence of different metal ion compounds, viz. ZnSO4, MnSO4, MnCl2 and FeCl3 at 6 and 12 microM concentrations individually, ZnSO4 (12 microM) promoted siderophore production but suppressed the growth and protein content of test organism. MnCl2 and FeCl3 (12 microM) enhanced the growth, whereas MnCl2 and MnSO4 (12 microM) induced protein contents of strain GRC1.

Siderophore production by fluorescent pseudomonads colonizing roots of certain crop plants.

Twelve fluorescent Pseudomonas isolates colonizing roots of four crop plants, chilli, cotton, groundnut and soybean, were examined for extracellular siderophore production in different media under iron deficient conditions. While all the organisms produced siderophores, they varied in the quantity of siderophores produced and in their preference to the medium. The siderophores were invariably hydroxamates (pyoverdine) of trihydroxamate type which formed bidentate ligands with Fe III ions.

Influence of metham sodium on suppression of collar rot disease of peanut, in vitro antibiosis, siderophore production and root colonization by a fluorescent pseudomonad strain FPO4.

A hydroxamate type siderophore producing fluorescent Pseudomonas strain, isolated from the rhizoplane of paddy root showing plant growth promoting activity, exhibited a decreased in vitro antibiosis, production of siderophore and suppression of collar rot in presence of metham sodium. Use of herbicide had a detrimental effect on the plant growth promoting activity of this organism. The multiple drug resistant mutant strain derived from this rhizobacteria colonized the roots, but the herbicide application had a negative effect on their population. HPLC analysis of the siderophore showed five peaks of which the peak number three confirmed the antifungal activity.

Production of siderophores & effect of iron restriction on the protein profiles of Aeromonas species isolated from water & patients suffering from acute diarrhoeal disease.

Among 48 strains of Aeromonas species, 21 isolates from patients suffering from acute diarrhoea and 27 from metropolitan water samples grown under iron-restricted conditions, 45 strains produced siderophores. Forty one of the 46 strains tested produced siderophores on chrome azurol S (CAS) agar, while 43 isolates did so when the culture supernatants of the bacterial isolates grown in minimal medium were assayed with chrome azurol S assay solution. The whole cell protein profiles of A. hydrophila strains grown under iron restricted conditions expressed new proteins that were not detected in those cultured in iron rich conditions. Five high molecular weight proteins ranging from 70 to 96 kDa were distinctly absent in cultures grown in the presence of iron, indicating their role in iron acquisition by the aeromonads.

Regulation of siderophore production by iron Fe(III) in certain fungi and fluorescent pseudomonads.

Regulation of siderophore production in response to iron concentration in the medium was examined. Threshold concentration was recorded for twenty fungi and three rhizobacterial pseudomonads. Organisms showed difference in threshold values at which they stopped siderophore elaboration. In nine fungi (3 aspergilli, 1 penicillium, N. crassa, F. dimerum and 3 mucors) siderophore production was repressed at 3 microM Fe(III). Siderophore production was repressed at 27 microM of Fe (III) in 3 aspergilli, 2 penicillia and 3 pseudomonads. Rest of the fungi had cut off values at 6, 9, 15, 21 microM of Fe(III) concentration.