Acinetobacter calcoaceticus PUCM 1011 efficiently synthesized platinum nanoparticles (PtNP) of size 2-3 nm intracellularly when challenged with hexachloroplatinic acid. Salt concentration (1 mM), temperature (30 degrees C), pH (7) and incubation period (72 h) influenced the efficiency of monodisperse cuboidal PtNP synthesis. Resolution of ordered lattice fringes with "d" value of 0.23 nm corresponding to (1 I 1) plane and EDAX confirmed presence of metallic platinum. AFM, TEM and HR-TEM confirmed synthesis of PtNP and its effect on cell viability. Total cell protein profile for 120h with an interval of 24h after PtNP synthesis revealed prominent four protein bands (97, 66, 43 and 29,kDa) when compared to control. Combinations of three proteins initiated PtNP synthesis within 4 h in range of 1-4nm and few in picometers under HR-TEM. This is the first report of PtNP synthesis employing whole cell and total cell protein of A. calcoaceticus. (C) 2014 Elsevier Ltd. All rights reserved.