Isolation and identification of metal-tolerant and antibiotic-resistant bacteria from soil samples of Cachar district of Assam, India

Abstract

The present study aims to assess the physicochemical properties and prevalence of microbial communities in soils samples collected from different locations of Cachar district, Assam, India. Bacterial communities in the soil were screened by morphological, biochemical and 16S rDNA sequence analysis and were identified as Bacillus megaterium, Bacillus cereus, Pseudomonas aeruginosa and Chromobacterium pseudoviolaceum. High concentrations of toxic metals negatively affect bacterial growth, and therefore, the minimum inhibitory concentration of isolated bacteria was determined against Cd, Pb, Fe and Cu by agar dilution technique. Co-resistance of antibiotic was also determined, which demonstrated that most of the metal-tolerant isolates were resistant to Methicillin and Penicillin. However, P. aeruginosa showed resistance to other antibiotics such as Cefdinir, Ampicillin, Kanamycin, Rifampicin and Vancomycin. The development and evolution of antibiotic resistance in soil bacteria occurs very likely naturally as a result of unethical and non-scientific disposal of toxic substances and industrial discharge, which also includes heavy-metal effluents and other clinical by-products. Therefore, pragmatic measures must be taken to limit the spread of antimicrobial resistance across the environment and to reduce the incidence of healthcare-associated infections.

Biosorption of heavy metal polluted soil using bacteria and fungi isolated from soil

“…Heavy metals are natural elements with atomic number greater than 20, characterized by a relatively high density (at least 5 g cm −3 ), and are toxic even at low concentrations [1][2][3]. They are characteristically existing components found in changing variation in the environments and are part of human daily activities, they are also found in important structures and in a range of other artificial mixes [4].…”

“…Besides the fact that they are non-biodegradable, they may also undergo microbial or chemical transformation [8,9,11,12]. Recently, Hasani et al [13] and Nath et al [3] reported that heavy metal polluted environments activate co-selection process and cause a decrease in microbial tolerance to antibiotics due to their ability to co-regulate genes responsible for antibiotic resistance.…”

Prevalence of antibiotic-resistant, toxic metal-tolerant and biofilm-forming bacteria in hospital surroundings

“…The physical linkage of antibiotic resistance and metal resistance is encoded on the plasmid that confers resistance to the bacteria even when only one co-selecting agent (either antibiotics or heavy metals) is present [ 78 – 80 ]. Co-selection of antibiotic resistance and heavy metal tolerance by P. aeruginosa is well documented in many studies [ 81 , 82 , 41 , 83 ]. Bacillus sp.…”

“…The initial concentration of these metal salts in nutrient plates was 100 μg/mL, and bacterial growth was observed by streaking on respective plates. Metal concentration was progressively increased by 50–100 μg/mL on a fresh agar plate, and the minimum inhibitory concentration (MIC) was noted when the isolates failed to grow on respective plates [ 41 ]. The experiment was conducted separately for Cd, Cu, Fe, Pb and Zn taking five replicates at each concentration.…”

Changes in growth responses in rice plants grown in the arsenic affected area: implication of As resistant microbes in mineral content and translocation

“…During the biogeochemical cycle of As a huge number of microbes are involved. There are various types of mechanism are occurred such as redox reaction, methylation, precipitation, biosorption by cell biomass, entrapments through cellular capsule and production of induced proteins, active cell transport, in the bacteria, fungi, algae, mosses, higher plants and macrophytes for the removal or mitigation of heavy metals including As [7,23,27,35,38].…”