Cadmium Pollution Impact on the Bacterial Community of Haplic Cambisols in Northeast China and Inference of Resistant Genera

Abstract

Modern industry and agriculture has aggravated heavy metal pollution of soils, of which cadmium (Cd) is among the common most toxic and widely distributed pollutants. Bacteria are a major group of microorganisms and the most abundantly occurring in soils. In Northeastern China, many mining sites occur whose soils need reclamation and Cd pollution has commonly existed. Haplic Cambisols is the zonal forest soil here. Yet, how Cd contamination may affect the bacterial characteristics and chemical properties of Haplic Cambisols is still unknown. Here, we applied different concentrations of Cd contamination to Haplic Cambisols and monitored the resulting changes to bacterial community structure and diversity, as well as the general soil environments; we then inferred Cd-resistant bacteria to provide theoretical support for microbial remediation of Cdcontaminated Haplic Cambisols in Northeast China. Haplic Cambisols were treated with different concentrations of CdCl 2 solutions (0 [CK], 1, 5, 25, 50, 75, 100 mg kg −1 , respectively expressed as T1, T2, T3, T4, T5, and T6) and incubated for 50 days, and then bacterial community composition was identified, and the pH, organic matter, hydrolytic nitrogen, available phosphorus, potassium, and cadmium contents of the soils were measured. Adding higher concentrations of Cd usually significantly increased the richness and diversity of the bacterial community in Haplic Cambisols in terms of both species and abundance with the effects of some treatments being not significant, and this effect varied with Cd concentration. Applying Cd significantly influenced the bacterial community's structure and its metabolic functioning. Cd also influenced bacterial diversity via several key soil environmental factors, namely the pH, organic matter, and hydrolytic nitrogen contents. Pseudolabrys, Ralstonia, Reyranella, Afipia, Pelomonas, Rhizomicrobium, and Bradyrhizobium within Proteobacteria; Rhodanobacter from Bacteroidetes; and Nitrobacter within Nitrospirae were the main resistant bacteria. Higher concentrations of Cd increased the bacterial community richness and diversity of Haplic Cambisols, as well as the relative abundance of their main bacterial populations. The Cd-resistant genera were inferred, and relative abundances of Ralstonia, Bradyrhizobium, Rhizomicrobium, and Afipia were the highest.

Cadmium Pollution Impact on the Bacterial Community Structure of Arable Soil and the Isolation of the Cadmium Resistant Bacteria

“…Previous study reports that Cd addition (>1 mg kg −1 ) of red paddy soil can inhibit soil microbial biomass (Guo et al, 2018). However, as to yellow cinnamon soils under Xanthoceras sorbifolium Bunge and forest soils of Haplic Cambisols in Northeast China, the opposite result was found (Jiang et al, 2018;Duan et al, 2020). Hence, the effects of Cd on microorganism are closely related to the concentrations of Cd and soil type.…”

“…Previous studies have reported that the presence of heavy metals can influence the microbial diversity and also change the community structure and function (Luo et al, 2019;Duan et al, 2020). Wang et al (2006) found that low contend of heavy metals can stimulate the growth of microorganisms, while at greater concentrations, an inhibitory effect becomes more prominent, which often leads negatively correlated outcomes.…”

“…These approaches, however, only provide limited insights into the bacterial profiles. Recently, the application of high-throughput sequencing based rRNA for evaluating microbial communities is widely used (Luo et al, 2019;Duan et al, 2020).…”

Theobroma cacao L. agricultural soils with natural low and high cadmium (Cd) in Santander (Colombia), contain a persistent shared bacterial composition shaped by multiple soil variables and bacterial isolates highly resistant to Cd concentrations

“…Bacteria genus with relative abundance (>0.5%) were identified: Nitrospira , candidatus Udaeobacter, Haliangium, Cupriavidus , MND1, Bacillus, Kitasatospora, Niveibacterium, Acidothermus, Burkholderia, Acidibacter, Terrimonas, Gaiella , ADurb.Bin063–1, candidatus Solibacter, Kitasatospora, Sphingomonas , and Streptomyces ; these genera have been related to Cd tolerance processes, for example, Feng et al., (2018) , reported the following genera from Cd contaminated soils: Nitrospira, Bacillus, Burkholderia , candidatus Solibacter; Cupriavidus ; as for endophytic genera of Cd-tolerant transgenic tobacco: MND1, Ralstonia, Sphingomonas, Streptomyces ( Wang et al., 2021 ), Lazzaro et al., (2006) identified the genera Streptomyces and Kitasatospora in forest soils with Cd; candidatus genera Solibacter , ADurb.Bin063–1 and Acidibacter present in soils with the presence of heavy metals (As, Pb, Cd, Zn) around an abandoned copper mine ( Chun et al., 2021 ); Ma et al., (2020) reported Burkholderia and Gaiella in soils near Sb mines; as for the candidatus genus Udaeobacter it was reported as the most abundant genus in soils with the presence of Zn, Cd, Ni and Cu adjacent to an abandoned copper mine ( Böhmer et al., 2020 ); genera such as Nitrospira and Haliangium were identified in soils with wheat crop contaminated with Cd ( Song et al., 2020 ); Duan et al., (2020) monitored changes in soil bacterial communities in the presence of different Cd concentrations and reported the presence of Acidothermus and Terrimonas ; the genus Kitasatospora has tolerance to heavy metals (Ni, Zn, and Cu) as published by Yun et al., (2020) .…”

Effects and Mechanism of Continuous Liming on Cadmium Immobilization and Uptake by Rice Grown on Acid Paddy Soils

“…These results should be useful for farmers worldwide as they will help to reduce the cost of lime application. Furthermore, the effect of lime application on soil pH depends to a great extent on some soil physical and chemical properties that affect soil buffering capacity such as cation exchange capacity, soil dehydrogenase activity, soil texture, and soil bacterial diversity (Bolan et al 2003;Duan et al 2020;Filipović et al 2020). The application of lime to the acid Cd-contaminated paddy soils greatly improved soil pH, and it peaked at the application of 3750 kg ha −1 of lime (Fig.…”