Abstract

One hundred and sixty nine Nocardia isolates were recovered from 111 Iraqi soil samples on six cultivation media, using paraffin baiting and dilution techniques. The North of Iraq soil was the richest in Nocardia. Paraffin baiting technique was more efficient in the isolation of Nocardia than dilution technique. Glucose asparagine agar was more suitable for cultivating Nocardia isolates followed by Sabouraud dextrose agar. All the 169 presumptive Nocardia isolates recovered were subjected to primary screening of antibacterial activity, with 10-55 mm inhibition zones against standard Staphylococcus aureus (NCTC 6571) and 10-38 mm inhibition zones against standard Escherichia coli (ATCC 25922). Eleven isolates with the highest antibacterial activities were selected for chemo-taxonomic studies. These isolates exhibited high similar features of 87-89% with Nocardia brasiliensis. Therefore, it is suggested to give proposed names for these new taxa: Nocardia sp.1, N. sp. 2, N. sp. 3, N. sp. 4, N. sp. 5, N. sp. 6, N. sp. 7, N. sp. 8, N. sp. 9, N. sp. 10 and N. sp. 11. .

Key words: Secondary metabolite, Nocardia sp., antimicrobial activity.