Effect of temperature, pH and media on the recovery of aerobic heterotrophic bacteria from the rabbitfish siganus rivulatus

Abstract EN

As part o f on goin g stu dies o n the micro biology of the rabbitfish Siganus rivulatus, farmed in sea cage sites at Jeddah, method s have been de vised fo r the e nume ration and recovery o f dominant ae ro bic hete rotrophic bac teria .

Thus, from a comparisonofII media at pH 6.5-9 .5 , inc uba tio n temperatures of 5-40°C and statistical analysis of the data by me an s of the stude nt's t-tcst, the highest num berof'aerobic heteotroph ic bacte ria was co nsistently recover ed o n med ium A3, which com prised 2.4% (WIV) sod ium chloride , 0.7% (WIV ) magne sium sulphate, 0.075% (WIV ) pot assium ch lori de, 0.1% (WIV) bac te rio logical pe pto ne (Oxoid ) a nd 1.5% (WI V) agar (Oxoid No .

I) at pH 7.

2-7.8 with incu bation at 20-25°C for 14 da ys.

Usin g thi s regim e .

the aerobic het e rot rophic ba cterial popula tio ns on th e gills of S.

rivulat us a nd from th e surroundings wat er (fish cages a nd open sea) were est imated at 6 x 10Slg.

3.3 x 104/ml and 6.6 x 102/ml, respectivel y.

The pre se nce of higher qua nt ities o f a diver se ran ge of organic nu trients ( inclu ding bacteriological peptone.

yeas t extract, be er extrac t and case in) led to the recover y of reduced number s of bacteri a from bot h gill and water samples .