Bioremediation Potential of Native Bacillus sp. Strains as a Sustainable Strategy for Cadmium Accumulation of Theobroma cacao in Amazonas Region

Abstract

Cacao plant cadmium accumulation has become a major concern, especially for small Amazonian producers. A sustainable alternative to address its toxicity is the use of cadmium removal bacteria. In this regard, 138 rhizosphere isolates from cacao were examined. Supported by their phenotypic characterization and in vitro cadmium tolerance, three hypertolerant bacteria were selected and identified as members of the Bacillus (S1C2, R1C2) and Pseudomonas (V3C3) genera. They were able to grow normally and reduce the cadmium content under in vitro conditions. However, only S1C2 and R1C2 evidenced to employ intracellular Cd2+ accumulation, suggesting the variability of bacterial detoxification mechanisms. Their bioremediation capacity for Theobroma cacao CCN51 was also analyzed. Surprisingly, we found high detectable levels of Cd2+ in the non-cadmium supplemented control, suggesting an extra source of cadmium in the pot. Moreover, despite their cadmium reduction performance under in vitro conditions, they exerted highly variable outcomes on stem cadmium accumulation. While S1C2 and R1C2 showed a considerable reduction of Cd content in cacao stems, the strain V3C3 did not show any effect on Cd content. This highlights the complexity of the plant–bacteria interactions and the importance of the in vivo test for the selection of promising PGPR bacteria. Overall, our results suggest the cadmium alleviation potential and promising prospects of native Bacillus strains associated with Amazonian cacao.

Diversity and functional assessment of indigenous culturable bacteria inhabiting fine-flavor cacao rhizosphere: Uncovering antagonistic potential against Moniliophthora roreri

“…Several isolates of Bacillus , Paenibacillus , Fictibacillus , Peribacillus , and Neobacillus genera were also found. This agrees with previous reports, which have shown the association of Bacillus with Theobroma cacao [ 14 , 23 , [45] , [46] , [47] ]. Moreover, the involvement of Bacillus in the rhizosphere has been demonstrated through plant growth-promotion attributes such as indole-3-acetic acid (IAA) production, phosphate solubilization, and biofilm development [ 48 ].…”

“…In support of our findings, Pseudomonas , Burkholderia , Cupriavidus , and Enterobacter bacteria can also be found living in association with cacao roots [ 14 , 26 , [50] , [51] , [52] , [53] ]. P revious reports were not found about the isolates of Agrobacterium , Sinorhizobium , Sphingobium , Isoptericola , Celulosimicrobium , Sporosarcina , Paenarthrobacter , Arthrobacter , and Lysobacter genera.…”

“…Cadmium, a toxic heavy metal, can be naturally present in the soil or result from anthropogenic activities. It is introduced into the food chain through plant uptake, and its concentration depends on its bioavailability in the soil [ 13 , 14 ]. Due to the risks of cadmium to human health, regulatory agencies have adopted several actions to protect consumers from cadmium-contaminated products (European Food Safety Authority Commission Regulation, 2011; MERCOSUR, 2011; USDA, 2018).…”

Isolation and phylogenetic characterization of cultivable native bacteria from abandoned mines in Tacna, Peru.

“…En el caso del género Bacillus, se han realizado investigaciones en biotecnología, considerándolos agentes potencialmente activos y eficaces para la eliminación de diversos metales tóxicos presentes en el ambiente (Alotaibi et al, 2021;Arce-Inga et al, 2022). Las investigaciones realizadas por Zahoor y Rehman (2009), Guo et al (2010), Gupta et al (2010) así como Ayangbenro y Babalola (2020), aislaron Bacillus sp., Bacillus cereus, B.…”

Prevention of Cadmium Contamination by Microbial Inoculant and Its Potential Mechanism

“…In recent years, an increasing number of scholars have centered their research on enhancing crop quality [8] and mitigating Cd pollution [9,10] in farmland soil. Researchers have developed relevant technical methods, including physical [11][12][13], chemical [14], and biological [15][16][17] approaches, to reduce soil Cd pollution, increase crop yields, and improve quality. For example, a remediation device was designed for heavy metal-contaminated soil based on electrodynamic remediation technology [18].…”