Journal of Microbiology

Research Support, Non-U.S. Gov'ts

Role of Heavy Metal Resistant Ochrobactrum sp. and Bacillus spp. Strains in Bioremediation of a Rice Cultivar and Their PGPR Like Activities: Sanjeev Pandey , Pallab Kumar Ghosh , Sisir Ghosh , Tarun Kumar De , Tushar Kanti Maiti; J. Microbiol. 2013;51(1):11-17. Published online March 2, 2013; DOI: https://doi.org/10.1007/s12275-013-2330-7

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Abstract: The present study demonstrates the metal toxicity ameliorating and growth promoting abilities of three different bacterial isolates when applied to rice as host plant. The three bacterial strains included a cadmium resistant Ochrobactrum sp., a lead resistant Bacillus sp. and an arsenic resistant Bacillus sp. designated as CdSP9, PbSP6, and AsSP9, respectively. When these isolates were used as inocula applied to metaltreated rice plants of variety Satabdi, the germination percentage, relative root elongation (RRE), amylase and protease activities were increased. The toxic effect of metal was reduced in presence of these bacteria. The overall biomass and root/shoot ratio were also enhanced by bacterial inoculation. Hydroponic studies showed that the superoxide dismutase (SOD) activity and malondialdehyde (MDA) level, which had been increased in the presence of metal stress in rice roots, were lowered by the bacterial inoculation. In addition, all three strains were 1-aminocyclopropane-1-carboxylate (ACC) deaminase and catalase positive, whereas siderophore producing ability was lacking in PbSP6. However, both PbSP6 and AsSP9 were protease positive and could hydrolyse starch. The data indicate that these bacteria have promise for bioremediation as well as for plant growth promotion.

Dark Septate Endophyte (DSE) Fungi Isolated from Metal Polluted Soils: Their Taxonomic Position, Tolerance, and Accumulation of Heavy Metals In Vitro: Yujie Zhang , Yan Zhang , Maojun Liu , Xiaodong Shi , Zhiwei Zhao; J. Microbiol. 2008;46(6):624-632. Published online December 24, 2008; DOI: https://doi.org/10.1007/s12275-008-0163-6

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Abstract: To understand the possible role of the plant root associated fungi on metal tolerance, their role in the uptake of heavy metals and the potential transfer of these metal ions to the plant, three strains of dark septate endophytic (DSE) fungi were isolated from a waste smelter site in southwest China, and one strain was isolated from a non-contaminated site. According to molecular phylogenetic analysis of the ITS 1-5.8S rDNA-ITS 2 gene regions and morphological characteristics, one is identified as Exophiala pisciphila, and the other three are non-sporulating fungi under the experiment condition with the nearest phylogenetic affinities to the Thysanorea papuana strain EU041814. Tolerance and accumulation abilities of the three DSE strains for metals were investigated in liquid culture. Minimum inhibitory concentrations (MIC) of Pb, Zn, and Cd were determined. It was demonstrated that the tolerance of the DSE strains varied between metal species and strains. The E. pisciphila strain is able to accumulate lead and cadmium over 20% and 5% of dry weight of biomass, respectively. Partial of the sequestrated metals can be washed with CaCl2. Morphological and enzyme activity changes taking place in the presence of excessive Pb, Cd, and/or Zn also indicate that the mechanism of heavy metal tolerance and accumulation of the DSE strains would be a complex process. The findings indicated promising tolerance and accumulation of the DSE strains with potential values in metal cycling and restoration of soil and water system.

Diversity and Metal Tolerance of Nematode-Trapping Fungi in Pb-Polluted Soils: Ming-He Mo , Wei-Min Chen , Hao-Ran Yang , Ke-Qin Zhang; J. Microbiol. 2008;46(1):16-22.; DOI: https://doi.org/10.1007/s12275-007-0174-8

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Abstract: The diversity of nematode-trapping fungi (NTF) in two lead (Pb) mines in Yunnan Province, China was investigated in 2004. In total, 20 species belonging to five genera were identified from 500 samples collected at the Lanping and the Huize mines. Pb concentrations ranged from 216~7,150 mg/kg for the former and 132~13,380 mg/kg for the latter, respectively. The fungi were divided into five groups based on different trapping mechanisms. The trapping-net producer group contained the largest number of species, with nine. Two predators, Dactylellina ellipsosporum and Arthrobotrys oligospora, were found at frequencies of 32.85% and 15.41%, respectively. The diversity indexes of NTF were positively correlated with Pb pollution levels in both the Lanping Mine (r=0.66) and the Huize Mine (r=0.72), suggesting that the distribution of NTF was not negatively affected by Pb contamination. For most strains of a given species, there was no significant difference (P>0.01) in the Pb tolerance between the strains isolated from habitats with low or high Pb concentrations. However, Pb toxicity exerted adverse effects on trap formation and predacious capability of fungi. We discuss the possible metal tolerance mechanisms and their relationships to the survival strategy of NTF in Pb-polluted environments.

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