Indium (In) is one of the most important metals for the modern technology due its use in high tech devices particularly for LCDs and monitors as it exhibits semiconductor and optoelectronic characteristics. It is mainly produced as a by-product of Zinc (Zn) and Zn mainly occurs as sulphides which can be leached by using iron and sulphur oxidising bacteria. Nonetheless, the In recovery could be inhibited by the formation of indium phosphate and indium arsenate, which are poorly soluble. Phosphate (PO43-) and Arsenic (As) are usually present in the bioleaching solutions. In this thesis, the effect of PO43- and As on the recovery of In during the bioleaching of a sulfidic concentrate (Pöhla concentrate) consisting of mainly sphalerite and a significant amount of arsenopyrite was studied. For this purpose, a series of bioleaching experiments of the Pöhla concentrate using Sulfobacillus thermosulfidooxidans were performed: i) using different solid load (SL) 1% ,2.5%, 5% and 10%. ii) using different PO43- concentrations- 10%=1.88 mg/L,50%=9.4 mg/L,200%=37.6 mg/L and 500%=94 mg/L of PO43 iii) using different concentrations (60 mg/L or 120 mg/L) of arsenite [As (III)] and (60 mg/L or 120 mg/L) of arsenate [As(V)] for 21 days, at 500C. It was found out that 1%SL was the optimum SL where effective recovery of both In (68%) and Zn (80%) was achieved. After ICPMS analysis of the PLS from the experiment with different PO43- concentration was done, 200%PO4 has the highest yield of In (81%) and Zn (86%). 500% PO4 has the lowest recovery of In (61%) and Zn (65%). The result of the experiment with different As (III) and As(V) concentration shows that 100% yield of In and Zn were achieved by biotic experiment B(V)60 and chemical control C(III)120. Whereas experiment with added As (III) have low yield of In (34%) and Zn (38%). The intermediate products confirmed by XRD analysis like jarosite, scorodite and elemental sulphur (S) were thought to be the main inhibitory agents for In and Zn recovery.