Aerobic Heterotrophic Bacterial Flor1ff one of Shalla Hot Springs
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Date
1991-06
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Addis Ababa University
Abstract
Four sites in one of the hot springs of Shalla were
selected for the study. The water from the sites merge to form
a stream lqhich forms a temperature gradient. In this sttldy four'
media were compared for the cuI ti vation and isolation of
aerobic heterotrophic bacteria. The pH of the hot spring was
8.7 with a temperature of 96-560C. The formulated media were
adjusted to pH values of 7.0-13.0. However,high counts of
bacteria (lxl03-7xl01 cfu/ml) was only registered when the pH
lqas adjusted between 8.0 and 9.0. A medium containing normal
concentration of Trypton Soya Agar (TSA) was effective in
supporting the growth of bacteria than a medium containing onequarter
strength of TSA or supplement of tl'ace minerals.
Replacing trace minerals ld th hot spring water improved the
total number of bacteria growing and also the number of
isolates.
Thermophiles were numerous (lxl03-7xl01 cfu/ml) than
thermotolerants (2xl02-2xlOI cfu/ml) at all si tes. The
population of Bacillus brevis, Bacillus sphaericus, Bacillus
stearothermophilus and Hicrococcus sp. was found to be low at
lOlqer environmental temperatures than at higher environmental
temperatures.
In the course of this study a total of 44
microorganisms were isolated and characterized. Twenty nine
were identified. to the species level and were found to be
members of genus Bacillus. Three isolates were Gr~n-positive cocci identified
to the genus level - Micrococcus. The remaining 12 isolates
were either Gram-positive, filamentous or non-filamentous rods
which need a detailed biochemical analysis for identification.
To identify if any of the isolates may have
industrial applications, they were checked for production of
amylase and protease. Fifteen of the isolates produced
protease, 18 amylase and eleven produced both amylase and
protease.
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Biology