Physicochemical and molecular characterization of heavy metal–tolerant bacteria isolated from soil of mining sites in Nigeria

Background Mining for precious metals is detrimental to the composition of soil structure and microbial diversity distribution and is a health risk to human communities around the affected communities. This study was aimed at determining the physical and chemical characteristics and diversity of bacteria in the soil of local mining sites for biosorption of heavy metals. Results Results of physical and chemical characteristics showed mean pH values and percentage organic carbon to range from 7.1 to 8.2 and 0.18 to 1.12% respectively with statistical significance between sampling sites (P ≤ 0.05). Similarly, cation exchange capacity, electrical conductivity, moisture, total nitrogen, and carbon/nitrogen ratio (C:N) in the soil ranged between 1.52 to 3.57 cmol/kg, 0.15 to 0.32 ds/m, 0.14 to 0.82%, 0.10 to 0.28%, and 1.7 to 4.8 respectively. The highest heavy metal concentration of 59.01 ppm was recorded in soils obtained from site 3. The enumeration of viable aerobic bacteria recorded the highest mean count of 4.5 × 106 cfu/g observed at site 2 with statistical significance (P ≤ 0.05) between the sampled soils. Alcaligenes faecalis strain UBI, Aeromonas sp. strain UBI, Aeromonas sobria, and Leptothrix ginsengisoli that make up 11.2% of total identified bacteria were able to grow in higher amended concentrations of heavy metals. The evolutionary relationship showed the four heavy metal–tolerant bacteria identified belonged to the phylum Proteobacteria of class Betaproteobacteria in the order Burkholderiales. Heavy metal biosorption by the bacteria showed Alcaligenes faecalis strain UBI having the highest uptake capacity of 73.5% for Cu. Conclusion In conclusion, Alcaligenes faecalis strain UBI (MT107249) and Aeromonas sp. strain UBI (MT126242) identified in this study showed promising capability to withstand heavy metals and are good candidates in genetic modification for bioremediation.

Phenotype Switching in Metal-Tolerant Bacteria Isolated from a Hyperaccumulator Plant

As an adaptation to unfavorable conditions, microorganisms may represent different phenotypes. Azolla filiculoides L. is a hyperaccumulator of pollutants, but the functions of its microbiome have not been well recognized to date. We aimed to reveal the potential of the microbiome for degradation of organic compounds, as well as its potential to promote plant growth in the presence of heavy metals. We applied the BiologTM Phenotypic Microarrays platform to study the potential of the microbiome for the degradation of 96 carbon compounds and stress factors and assayed the hydrolytic potential and auxin production by the microorganisms in the presence of Pb, Cd, Cr (VI), Ni, Ag, and Au. We found various phenotype changes depending on the stress factor, suggesting a possible dual function of the studied microorganisms, i.e., in bioremediation and as a biofertilizer for plant growth promotion. Delftia sp., Staphylococcus sp. and Microbacterium sp. exhibited high efficacy in metabolizing organic compounds. Delftia sp., Achromobacter sp. and Agrobacterium sp. were efficient in enzymatic responses and were characterized by metal tolerant. Since each strain exhibited individual phenotype changes due to the studied stresses, they may all be beneficial as both biofertilizers and bioremediation agents, especially when combined in one biopreparation.

Biosurfactants produced by metal-resistant Pseudomonas aeruginosa isolated from Zea mays rhizosphere and compost

Contextualization: Pseudomonas aeruginosa is capable of producing biosurfactants which have many uses in bioremediation and the production of antiviral, antibacterial, antiparasitic, sporicidal and antifungal agents, among others. Knowledge gap: This study describes the production of mono and di-rhamnolipid biosurfactants by P. aeruginosa strains isolated from Zea mays rhizosphere and composts in the state of Guerrero, Mexico. Purpose: The overall aims were to investigate biosurfactant, pyocyanin production, and tolerance to heavy metals and antimicrobial activity capacity than biosurfactants produced from P. aeruginosa strains from corn rhizosphere and compost in Mexico. Methodology: Biosurfactant production was determined based hemolysis on blood agar, blue halos in CTAB-Methylene blue agar, drop collapse test and production of foam on PPGAS broth, the emulsion index (IE24) and antibacterial capacity. The strains were identified by sequence of the 16S rDNA gene and their resistance to heavy metals were also evaluated. Results and conclusions: Two strains isolated from Zea mays rhizosphere (PAM8, PAM9) were the best biosurfactant producers and their extracts showed antimicrobial activity against Grampositive and Gramnegative bacteria. PAM8 and PAM9 showed >30% of cellular hydrophobicity to hydrocarbons, and were capable of emulsifying toluene, cyclohexane, petroleum, diesel and oils. All strains showed the same profile of heavy metal tolerance (As5+ >As3+ >Zn2+ >Pb2+ >Fe3+ >Cd2+ >Cu2+ >Cr6+ in concentrations of 20, 10, 10, 6, 4, 4, 2 and 2 mM., respectively). The isolation of biosurfactant-producing and heavy-metal tolerant bacteria from Zea mays rhizosphere and compost in Guerrero demonstrates the capacity for this region to harbor potentially important microbial strains for industrial or bioremediation applications.

Physicochemical properties, heavy metals, and metal-tolerant bacteria profiles of abandoned gold mine tailings in Krugersdorp, South Africa

Mine tailings are a potential source of heavy metals (HM) that can be toxic to microbes, plants, and animals in aquatic and terrestrial ecosystems. Bacteria have evolved several mechanisms to tolerate the uptake of HM ions. This study aimed to assess the physicochemical properties, concentrations of selected HM and metalloids [arsenic (As), nickel (Ni), lead (Pb), zinc (Zn), cadmium (Cd), and cobalt (Co)], and isolate potential metal-tolerant bacteria present at three abandoned gold mining sites with a view of understanding how tailings characteristics vary and the implications on microbial activities in tailings dumps. Heavy-metal-tolerant bacteria were isolated from the samples using minimum inhibitory and maximum tolerable concentrations of the Ni, Pb, Zn, Cd, and Co. The substrates of the studied sites were acidic and deficient in nutrients. High metals and metalloid concentrations in the order Zn > Ni > Co > As > Pb > Cd were recorded in some of the studied sites and its adjacent soil which exceeded South African recommended values for soil and sediments. Heavy-metal-tolerant bacteria that showed multiple tolerances to Ni, Pb, and Zn were isolated and putatively identified using biochemical tests as belonging to the phyla Proteobacteria, Actinobacteria, and Firmicutes. Gold mine tailings enriched the soil with HM and also affect soil physicochemical properties. Proper management of mine wastes must be ensured to prevent their adverse effects on the diversity, composition, and activity of soil microorganisms that help in maintenance of the ecosystem.

HEAVY METAL TOLERANT BACTERIA ISOLATED AND DETECTED FROM THE EFFLUENT OF HAZARIBAGH TANNERY INDUSTRY IN DHAKA CITY

The tanning industry is held to be an activity with the high budding for environmental pollution all over the world. Many Bacterial strains isolated from natural resources have been found to possess unique properties which make them useful for environmental cleans ups. So it is very important to find out an alternative ecofriendly way for the treatment of contaminated effluent. The objective of this study was to isolate, explore and pick out natural occurring bacteria capable of reducing heavy metals from tannery effluent collected from the Hazaribagh tannery industry of Dhaka. The pH value of all the effluents samples were ranged from 7.12 to 7.91. Five bacterial strains were confirmed as Bacillus bataviensis, Bacillus aryabhattai, Micrococcus antarcticus, Bacillus proteolyticus and Bacillus paranthracis on the basis of their morphological, cultural, biochemical, and 16S rRNA gene sequencing. Among these five strains, Bacillus bataviensisD1 exhibited higher resistance to cadmium (Cd), chromium (Cr), copper (Cu), lead (Pb) and arsenic (As) up to the amount of 550 µg/mL, 500 µg/mL, 500 µg/mL, 1050 µg/mL and 1100µg/mL respectively. Bacillus aryabhattai D2 and Micrococcus antarcticus D3 showed similar result to chromium (Cr) and Lead (Pb), but Bacillus proteolyticus B1 showed higher resistance to nickel (Ni) that is up to 250 µg/mL. From these results, it can be suggested that the identified heavy metal-adapted bacteria could be useful for the biosorption of heavy metal contaminated effluent.

Bioremediation of Cadmium Contaminated Effluent by Sporosarcina luteola: A Bacterium Isolated from Soil near Wazirpur Industrial Area, New Delhi, India

Heavy metals pollution is emerging as a threat to ecological systems causing various problems to mankind, plants and animals. Aim of the present study was to isolate and identify cadmium tolerant bacteria from the soil of Wazirpur industrial area of New Delhi (India). The study involved physico-chemical characterization of the polluted soil which was found to contain high concentration of iron, manganese and cadmium at 352, 15.3 g/kg soil and 3.16 ppm, respectively. One bacterial strain was identified as Sporosarcina luteola on the basis of morphological, biochemical and phylogeny analysis. Strain Sporosarcina luteola was highly resistant to Cd up to 5mM (mM= millimolar) when cultured in solidified nutrient agar plates and 7.2 mM in nutrient broth. Sporosarcina luteola has also showed substantial growth in presence of Co, Pb, Fe and Mn upto 2.0, 2.0, 3.5 and 4.0 mM, respectively in liquid medium. Optimum growth of identified bacteria was shown at 37 ºC, 7.0 pH and it tolerated up to 3 % sodium chloride (w/v). This is reported for the first time that Sporosarcina luteola (metal-tolerant bacteria) has potential of removal of cadmium from industrially contaminated soil.