Effect of Temperature , pH and Media on the Recovery of Aerobic Heterotrophic Bacteria from the Rabbitfish

IK A U:Mar.Sci..vol.8, pp.169-175 (14 17 A.H. 11997A.D.)

Effect of Temperature , pH and Media on the Recovery of Aerobic Heterotrophic Bacteria from the Rabbitfish

Siganus rivulatus

M.S.A.MU DAR RI S

Marine Biolog y Dept. , Faculty of Marine Sciences , Kin g A bdu laziz Unive rsity, Jeddah , Saudi A rabia

ABSTRACf . Aspart of ongoin g stu d ieson themicro b iology ofthe ra bbitfi sh Siganus rivulatus,farmedinsea cage sitesat Je dd ah ,method shavebeen de- visedfor the enume ra tionand re covery of dominant aero bic heterotrophic bacteria.Thus, from a compariso nof II me d ia atpH6.5-9.5 ,inc uba tio n tempe raturesof 5-40°C and statistical ana lysisof thedataby mean sof the stude nt's t-tcst,thehigh estnumber of'aerob ic hete rot roph icbact e ria was consiste n tly re co ver ed on med ium A3, which comp rise d 2.4% (WIV ) sod ium chloride , 0.7% (WIV ) magne siumsulphate , 0.075% (WIV )potas- siu mchlori de,0.1%(WIV) bacte rio logica lpep to ne (O xoi d ) and 1.5%(WI V) agar(OxoidNo.I) at pH 7.2-7 .8with incubation at 20-25°Cfor 14 days. Usin gthisre gim e .the aerobichet e rot roph ic bacterialpopula tio nson the gillsofS. rivulat us andfro m the surrou ndings water (fishcagesand open sea) wereestim a te d at6 x 10Slg.3.3 x 104/m land6.6 x 10^2/ml,resp ec- tivel y.The prese nce of high er qua nt ities of adiver serange oforganicnut- rients (inclu d ing bacteriolo gicalpeptone. yeas textra ct, beer extrac tand ca- sein) ledto the re co ver y ofreduced number s ofbacteri a fro m bot h gilland water sa m p les .

Introduction

Methods of bacterial e numeration ha ve a direct influence on the result ant qu antita- tive data. However , the most comm only used and widel y accepted methods for enume rating aerobic heterotrophs from wat er and soil s involve plate counts (Buck a nd Cleve rdo n, 1960; Jann asch a nd Jones, 1959) . Th e main problem o f pour plate methods is that many marine bacteria are heat sensitive. Consequentl y, damage to ami eve n death of th e cells may occur after expos ure to the temperatures of molten

169