<strong>Isolation and Identification of Heavy Metals Tolerant Bacteria from Mangrove Sediment in Pengudang and Tanjung Uban, Bintan Island, Indonesia</strong>. Bacterial searches for remediation of heavy metal pollutants continue to be carried out due to the increasing pollution in the ecosystem as a result of industrialization. This research aims to identification bacteria strains that are tolerant of heavy metals from mangrove sediments in the Pengudang and Tanjung Uban, Bintan Island in 2018. Bacterial isolation was carried out by pour plate method and purified using marine agar (MA) medium. Screening of bacterial isolates was carried out by growing isolates on MA medium with the addition of 100 ppm Pb. In addition, the determination of minimum inhibitory concentration (MIC) was performed on the isolates were tolerant to Pb, Cu, and Cd by addition of heavy metals in 50-1000 ppm concentrations. Identification of heavy metal tolerant isolates was carried out by sequencing the 16S rRNA gene. The results of bacterial isolation from mangrove sediments obtained 48 isolates used for testing the ability of heavy metals tolerant. Screening tests showed that PGD1A, PGD5A, PGD22A, PGD1B, PGD9B, PGD5C, PGD6C, TJU1, TJU5, and TJU7 isolates were heavy metal resistant. The results showed that bacterial isolated from mangrove sediments had MIC values of 800-900 ppm for Pb, 100-800 ppm for Cu and 100-200 ppm for Cd. There are 3 isolates that have high resistance to three kinds of heavy metals such as Bacillus oceanisediminis PGD1A, Vibrio alginolyticus PGD5A, and Halobacillus kuroshimensis PGD9B. This indicates that the isolate can be used efficiently for removal of heavy metals from the ecosystem.

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Twenty six isolates of Streptomyces spp. obtained from Cyperus rotundus L. rhizosphere were tested for ability to produce indole-3-acetic acid (IAA) in yeast malt extract (YM) medium containing 2 mg/mL tryptophan. Screening of the isolates for ability to produce IAA was carried out by adding Salkowski reagent in bacteria culture and was measured quantitatively by spectrophotometer at λ 530 nm. Thin Layer Chromatography (TLC) method was used to determine IAA. To ensure the IAA production in Streptomyces isolates, gene involved in IAA biosynthesis was detected by amplifying Tryptophan Monooxigenase (iaaM) gene. The study of the effect of tryptophan on the production of IAA was measured at different concentrations of tryptophan (0, 1, 2, 3, 4, 5 mg/mL) in the bacterial culture. The result showed that there were two Streptomyces spp. isolates which could produce IAA, namely the isolates of Streptomyces sp. MS1 (125.48 μg/mL) and Streptomyces sp. BR27 (104.13 μg/mL). The TLC result showed that the compound in both isolates was identifi ed to be IAA. The amplifi cation results showed that iaaM gene was detected in both isolates. This results indicated that the IAM pathway is predicted involved in the biosynthesis of IAA in the selected isolates. Both of the isolates were able to produce IAA after 24 h incubation and the highest production was at 120 h incubation with the concentration of tryptophan was 2 mg/mL dan 1 mg/mL, respectively. Therefore, it is concluded that Streptomyces spp. isolates are able to produce IAA and potentially to be utilized as biostimulat agent.

This study aims to isolate endophytic bacteria of sweet sorghum plants and characterize their ability as plant growth promoting. The characters tested in this study were the ability of endophytic bacteria in N fixation, phosphate dissolving, and IAA production to be developed as biological fertilizer agents. Twenty-four isolates were isolated from the roots, stems and shoots of sweet sorghum. The results of bacterial DNA fingerprint screening showed that 11 groups of endophytic bacteria had different fingerprints. Isolates capable of N fixation were grown on LGI media and showed a change in the color of the medium. The nifH gene detection is also carried out to determine endophytic diazotrophic bacteria. Isolate bacteria that can dissolve inorganic phosphate were tested using Pikovskaya media. Testing the ability of isolates to produce IAA was carried out by adding Salkowski's reagent to the bacterial culture and measured quantitatively with a λ 530 nm spectrophotometer. The results showed that two endophytic bacterial isolates proved to be diazotrophic and three isolates were able to dissolve phosphate, while one isolate was able to produce IAA. PA2 isolate showed ability in all the characters tested, namely N fixation, phosphate solvent and IAA producer.

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