Isolation and characterization of an acid and metal tolerant Enterobacter cloacae NZS strain from former mining lake in Selangor, Malaysia

Abstract

Background: Metal polluted environments have been found to harbor acid and metal tolerant bacterial communities. Metal oxidizing bacteria in particular are industrially important microorganisms that can be utilized for potential applications in biomining and bioremediation. However, some well-characterized strains are not readily culturable as they are obligate and fastidious chemolithotrophs requiring special techniques for their cultivation. Hence, this study was aimed at isolating, identifying, and characterizing indigenous metal tolerant heterotroph(s) from abandoned mines that can potentially be used for biomining or bioremediation processes in the future. Results: Seventeen bacteria from former mining lakes were isolated and identified using 16S rRNA. Minimal inhibition concentration (MIC) and growth study of isolated bacteria carried out in Luria-Bertani media containing three different metals ions, zinc (II), copper (II), and iron (II), showed that a particular isolate termed Enterobacter cloacae NZS was found to exhibit better growth and tolerance for copper (up to 90 mM), zinc (up to 200 mM), and iron (up to 170 mM). Growth of the strain was notably well in the presence of iron (II). Compared to all the isolates, only E. cloacae NZS was able to be enumerated at pH lower than 5 while other strains were culturable only at pH 7. Its capability in iron (II) oxidation was preliminary assessed based on the pH, cell count, glucose consumption, and amount of iron oxidized throughout incubation in 9K media. E. cloacae NZS strain was found to be capable of oxidizing iron (II) supplied in 9K media to iron (III). Conclusion: As preliminary investigation showed that E. cloacae NZS was able to oxidize iron (II) in 9K media at pH2, further optimization on the strain, medium, and culture conditions in future may be able to provide a better insight on this strain to be possibly used as an iron oxidizer for various applications.

Indigenous multiresistant bacteria of Cupriavidus pauculus IrC4 isolated from Indonesia as a heavy metal bioremediation agent

“…Several studies also reported that Pseudomonas syringe, Burkholderia sp, Alcaligenes sp, Methylobacterium sp, and Acinetobacter sp performed a resistance mechanism by accumulating copper in the outer membrane and periplasm causing the colony color to turn blue or green (Cha and Cooksey 1991;Kunito et al 1997). A similar resistance mechanism was also observed in C. gilardii through copper bioaccumulation and biosorption (Mazalan et al 2020).…”

“…Exposure to copper at a concentration exceeding the optimum is toxic and inhibits bacterial growth. (Mazalan et al 2020). Perez et al (2015) reported that some heavy metals at low concentrations are important for the growth and development of microorganisms, but other heavy metals are toxic even in low concentrations.…”

Isolation and Characterization of Euglena gracilis-Associated Bacteria, Enterobacter sp. CA3 and Emticicia sp. CN5, Capable of Promoting the Growth and Paramylon Production of E. gracilis under Mixotrophic Cultivation

“…Some Enterobacter spp. are acidophilic [ 36 , 37 ] and can grow over a wide range of pH conditions (pH 2–9) [ 38 ]. Although CA3 was isolated from E. gracilis grown at pH 4.5, it exhibited viability across a wide range of pH values and showed growth- and paramylon-promoting activities at both pH 4.5 and 7.5 ( Figure 1 , Figure 2 and Figure 3 ).…”

Pantoea agglomerans, Klebsiella pneumoniae, and Shigella flexneri isolated from the Cisadane River as multiresistant bacteria to copper and dyes

“…Copper resistance tests need to be performed on isolate bacteria that are successfully isolated to find out the maxi mum resistance of bacteria to heavy metals such as copper (Mazalan et al 2020). Resistance tests on bacteria isolated from the Cisadane River were carried out in several stages.…”