RESPONSE OF THIOBACILLUS-FERROOXIDANS TO PHOSPHATE LIMITATION

Phosphate ion is an essential nutrient for all cells. Consequently, st arvation for this component may constitute a stressing condition which affects the bioleaching capacity of the biomining microorganisms. The refore, we have studied the manner in which the chemolithotroph Thioba cillus ferrooxidans responds to phosphate limitation. Under these circ umstances the bacteria reduced its growth rate, capacity to oxidize fe rrous iron and to fix CO2. Concomitant with these changes, the cells s howed an increased synthesis of several proteins, some of which were e xclusively synthesized during phosphate starvation. When intact cells grown in the absence of phosphate were labelled with I-125, several pr oteins were iodinated in addition of those observed in control cells. suggesting that the lack of phosphate induces some proteins located in the membranes or the periplasmic space of the bacteria. It is expecte d that by measuring the levels of expression of some of the proteins i nduced by the shortage of phosphorus, it might be possible to estimate in situ the relative physioiogical condition of the bacteria in a giv en bioleaching operation.