Author(s): Mansour SR
An extensive study was carried out to investigate the occurrence and distribution of actinomycetes isolated from arid area, Saint Catherine, South Sinai, Egypt. Ten different soil samples were collected from different sites. Two hundred and eight actinomycetes cultures were isolated and identified. The existence of high population of actinomycetes, represented by total per gm soil, was significantly correlated (P less than 0.01) with organic matter and soil moisture percentages. The predominant genus in all soil samples was Streptomyces, which represented by 74 isolates. The second most common organism (50 isolates) was genus Nocardia. The other isolates were identified as Actinomadura, Nocardiopsis, Pesudonocardia, Rhodococcus, Micromonospora and Streptosporangium. Frequency of each genus was varied in each sample. Micromonospora isolates recorded in significantly higher count when the soil moisture increased. Genera diversity was varied which recorded the highest value in site 1 and site 8. Variation in the distribution of actinomycetes, expressed in frequency, richness and diversity of genera, indicate that climate in combination with soil properties play an important role in creation a specific niches for survival and propagation of actinomycetes.