Microbial diversity studies of lignite mines of Rajpardi, Amod, Tadkeshwar and Panandhro, Gujarat, India, were carried out by substrate utilization-based, community-structure analysis. In Biologâ EcoPlates out of 31 different substrates, 1 to 28 substrates were metabolized. On the basis of these, similarity index and diversity indices were studied. From an extreme mine site Gram-positive, Gram-negative, fungi and yeasts were isolated and identified. One of the yeasts isolated is for the first time reported from a lignite mine ecosystem Apart from this auto- and heterotrophic iron oxidizers; sulphur oxidizers and sulphate reducers were also isolated. So, lignite mine ecosystems, inspite of the extreme environment showed rich microbial diversity.