[Influence of iron on siderophore and photosynthetic pigments biosynthesis by siderophore-producing Rhodopesudomonnas palustris].

OBJECTIVE

To explore the regulation of iron on siderophore production, cell growth and photosynthetic pigments biosynthesis by siderophore-producing anoxygenic phototrophic bacteria.

METHODS

Siderophore production was determined using Chrome Azurol S (CAS) assay. The siderophore types were determined by Arnow method, Csaky test and Shenker test. The compositions and contents of photosynthetic pigments were determined by spectrophotometry and HPLC analysis.

RESULTS

Rhodopseudomonas palustris (Rps. palustris) CQV97 was capable of producing hydroxamate-type of siderophore. Siderophore production reached the highest yield in the absence of ferric chloride. With increasing ferric chloride concentrations, the lag phase of cell growth was shortened, and the cell growth rate, final biomass and the total amounts of carotenoid and bacteriochlorophyll a were increased significantly. The characteristic absorption maxima of carotenoids from pigment extracts were blueshifted. Iron concentration had little effect on the compositions and relative contents of bacteriochlorophylls a, whereas predominately affected carotenoid compositions, rhodopin was present as major carotenoid component instead of spirillxanthin. Culture tends to accumulate the Cars having shorter conjugated double bonds at the expense of longer conjugated double bonds as the ferric chloride concentration increased. The changes in carotenoid composition were consistent with those of the blue shift of absorption spectra of pigment extracts.

CONCLUSION

Rps. palustris CQV97 can produce siderophore and the changes in microbial growth, siderophore production and photosynthetic pigments accumulation of anoxygenic phototrophic bacteria are related to the iron concentration in the medium.