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

U.B Ibrahim,A.H Kawo,I Yusuf,S Yahaya

doi:10.1186/s43141-021-00251-x

U.B Ibrahim, A.H Kawo + Show 2 more

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https://doi.org/10.1186/s43141-021-00251-x

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Abstract

BackgroundMining 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. ResultsResults 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. ConclusionIn 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.

Highlights

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
Biological, and chemical processes promote the movement of these chemicals across the soil horizon [1], the effect these movements have on the food chain was due to the passive nature of the soil, which hinder smooth interaction between soil humus and other fertility molecules [6]
Several studies [8, 9] have highlighted the importance of soil parameters such as organic matter (OM), particle size distribution, clay content, redox potential, electrical conductivity (EC), moisture content, cation exchange capacity (CEC), and pH on heavy metal behavior in soils

Summary

Introduction

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. The use of simple instruments and manual labor to extract precious metals is widespread nowadays This activity has increased the risk of degradation of soil biota and the displacement of microorganisms and microbial structure, likewise destruction of soil texture and arrangement [1]. Ibrahim et al Journal of Genetic Engineering and Biotechnology (2021) 19:152 organic matter, and can eventually reduce biological activity and decrease soil productivity This can lead to the soil environment being disrupted by modifying the physical and chemical contents and processes that might in one way or the other affect both living and non-living subject hosts in the affected environment [4]. Adewole and Adesina [7] posited that mining activities and mine waste generation, in addition to enriching soils with heavy metal (HM), could affect nutrient dynamics in soils because of dynamic and interaction changes in physical, chemical, and microbiological processes. Changes in the structure and activities of soil microbial communities because of mining-related changes in soil physicochemistry could have an impact on key ecosystem processes like soil organic matter turnover, resulting in a decline in overall ecosystem functioning, as well as indirect cascading effects on metal mobility [9]

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