Mvungi, Mussa Faraji2026-02-042026-02-042000https://www.suaire.sua.ac.tz/handle/20.500.14820/7287DisertationThe study reported herein was conducted to enumerate and evaluate the antimicrobial potential of Streptomyces from acid and alkaline soils. The soils were sampled from Morogoro, Coast and Iringa regions in Tanzania. Streptomyces were enumerated us ing starch-casein agar. Colour of aerial mycelium and morphology of spore chains were determined. The isolates were evaluated for tolerance to pH changes and as sessed for antibiosis against selected plant pathogenic bacteria. There were signifi cant (P=0.05) differences in populations of Streptomyces in soils of different pH lev- respectively) and were highest at pH 7.2, with a population of 5.4. Regressions analy sis revealed that only % clay was significantly (0.05) correlated with Streptomyces populations. The regression of Streptomyces on all soil pH values was not significant in the entire range. However, the relationship was significant (P=0.05) when Strep tomyces populations were regressed on pH levels ranging from 4.5 to 7.2. The Strep tomyces isolates displayed the following morphologies of spore chains: flexuous (60.9%), straight (12.4%), open spirals (13.3%), closed spirals (2.86%), open loops (7.62%), hooks (1.9%) and monoverticillate (0.95%). The colours of mature colonies of Streptomyces isolates were white (20%), gray (58.1%), pink (1.9%), red (1.9%), yellow (1.9%) and cream (16.2%). All isolates from acidic soils (pH 4.5 and 5.95) were able to proliferate at high pH up to 7.8 while those from alkalinity conditions (pH 7.85, 8.2 and 10.0) could not do well when tested on the acidic side (pH 4.5 and 5.95). els. The populations were lowest at pH 4.5 and at pH 10 (log io values of 3.2 and 3.5, About 84% of the strains produced antibiotics against Ciavibacter michiganensis sub sp michiganensis, Xanlhotnonas phaseoli, X. vascatoria, X. oryzae pv oryzae and Acidovorax avenae. Six isolates (about 16.2% of all isolates) did not produce antibio sis against any of the tested plant pathogens. Xanthamonas phaseolicoli var fuscoris was not inhibited by any of the isolates. The Acidovorax avenae was inhibited by the least number of isolates, mainly those from acidic soils.enAntimicrobialAlkaline soilsStreptomycesMonoverticillateThesis