Isolation, enumeration and evaluation of antimicrobial potential of streptomyces isolated from some acid and alkaline soils of Tanzania
No Thumbnail Available
Date
2000
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Sokoine Univerisity of Agriculture
Abstract
The 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.
Description
Disertation
Keywords
Antimicrobial, Alkaline soils, Streptomyces, Monoverticillate