Identifikasi Isolat Bakteri Pereduksi Cr(VI) (Identification of Cr(VI)-Reducing Bacteria)

Abstract

Previous studies had successfully obtained nine isolates of Cr(VI) tolerant bacteria from the rhizosphere of Acalypha indicacultivated in a soil medium contaning a mixture of textile waste water and tannery waste water (Meitiniarti et al.2012) and two isolates from a tannery waste water treatment plants (Natasia 2012). All of the eleven isolates were also recognized as Cr(VI)-reducing bacteria, yet these isolates have not yet been identified. Furthermore, one isolate encoded as SpR3 showed a high Cr(VI) reduction ability and is therefore potential for further bioremediation of Cr-contaminated environments. This study aims to identify these Cr(VI)-reducing isolates using morphological and physiological approaches. As one isolates could hardly be grown in Luria Agar medium, there were only ten isolates proceeded in the series of identification study. There was only one gram-positive bacteria that was identified as Streptococcus sp. The remaining nine isolates were all gram negative bacteria, where six isolates belong to the genus Moraxella, and three isolates belong to the genus Acinetobacter. Isolate SpR3 which showed high ability of Cr(VI) reduction in LB medium contaning 100 ug ml-1Cr(VI) belong to the genusAcinetobacterand were further identified up to species level on the basis of colony growth at high temperature, nitrate reduction, gelatine hydrolysis, acid formation from D-glucose, utilization of organic acids (citrate, malonate, lactic acids) and etanol, and utilization of selected amino acids. The colony growth at high temperature as well as physiological properties that are regarded as specific to differentiate the eight known species within the genus Acinetobacter (Henayl 2000) showed that isolate SpR3 was very close identical to Acinetobacter lwoffii.