ABSTRACT

Bacterial diversity and total viable counts of bacteria of the different soil samples from different localities in Khartoum State ( three regions : AL-Gaeli , Sharq EL-Neel and Omdurman North and eight sub-regions : Kunger, Gary , Wadi Gedad in AL-Gaeli region ; Soba, AL-Elafoona and Um Dawan Ban in Sharq EL-Neel region ; Karary and Khor Omer in Omdurman North region) were carried out. Soil physical and chemical characteristics (pH, EC, SP, soluble cations: Na, K, Ca, Mg and anion P, organic carbon , total nitrogen and soil texture in each of different studied sub-regions were measured. Soil samples reveal a total of more than 15 different species of bacteria, of which 2 are unidentified. The 11 species are classified under Bacillus genera and the remaining 2 species are classified under Micrococcus genera. Soil Actinomyces spp. and Streptomyces spp. were the most abundant microorganisms identified in the three habitats (regions) which directly may influence decomposition processes and nutrient cycling in the soil. In AL-Gaeli region soil samples, total bacterial counts ranged from 8.5X105 cfu g-1 to 1X104 with a mean of 3X104 cfu g-1. In Shaq EL-Neel region soil samples, total bacterial counts ranged from 9.5X104 cfu g-1 to 1X103 with a mean of 4X105 cfu g-1. In Omdurman North region soil samples, total bacterial counts ranged from 7.5 X 103 cfu g-1 to 1X104 with a mean of 4X104 cfu g-1. The higher bacterial counts CFUs observed in the Calotropis procera and Acacia tortilis ssp. tortilis rhizospheres (8.5X105) at surface layer of soil in Kunger sub-region and in Acacia seyal rhizosphere (9.5X104) at subsurface soil of Um Dawan Ban sub-region. This could be to better availability of nutrients and environmental conditions which favored their growth. The Shannon-Weiner diversity Index value for AL-Aelafoon sub-region (1.79361) was higher than the rest of the studied habitat. This is followed by Khor Omer sub-region (1.71261) and then Um Dawan Ban sub-region (1.5408) . The Simpson Index value for Um Dawan Ban sub-region (2.80) was higher than the rest of the studied sub-regions. This is followed by AL-Aelafoon sub-region (2.7213) and then Khor Omer sub-region (2.5). Data of the present study revealed that the number of total viable bacterial count was positively correlated with EC and soil texture. These factors are the major driving factors of bacterial communities in studied habitat soils in Khartoum State. There were obvious differences in correlation coefficients among the selecting criteria (49% from the total number of correlation coefficients were positively correlated between bacterial counts and soil physic-chemical properties, whereas 48% from the total number were positively correlated between plant type and bacterial counts.