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The Golden Activity of Lysinibacillus sphaericus: New Insights on Gold Accumulation and Possible Nanoparticles Biosynthesis.

ABSTRACT: Power struggles surrounding the increasing economic development of gold mining give rise to severe environmental and social problems. Two new strains of Lysinibacillus sphaericus were isolated from an area of active alluvial gold mining exploitation at El Bagre, Antioquia. The absorption capacity of these strains and some of the L. sphaericus Microbiological Research Center (CIMIC) collection (CBAM5, OT4b.31, III(3)7) were evaluated by spectrophotometry according to a calibration gold curve of HAuCl?- with concentrations between 0 µg/mL and 100 µg/mL. Bioassays with living biomass were carried out with an initial gold concentration of 60 µg/mL. Their sorption capacity was evident, reaching percentages of gold removal between 25% and 85% in the first 2 h and 75% to 95% after 48 h. Biosynthesis of possible gold nanoparticles (AuNPs) in assays with living biomass was also observed. Metal sorption was evaluated using scanning electron microscopy and energy-dispersive X-ray spectroscopy (EDS) analysis. The sorption and fabrication capacity exhibited by the evaluated strains of L. sphaericus converts this microorganism into a potential alternative for biomining processes, especially those related to gold extraction.

SUBMITTER: Bustos MC

PROVIDER: S-EPMC6163967 | biostudies-literature | 2018 Sep

REPOSITORIES: biostudies-literature

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The Golden Activity of Lysinibacillus sphaericus: New Insights on Gold Accumulation and Possible Nanoparticles Biosynthesis.

Bustos María Camila MC Ibarra Humberto H Dussán Jenny J

Materials (Basel, Switzerland) 20180902 9

Power struggles surrounding the increasing economic development of gold mining give rise to severe environmental and social problems. Two new strains of <i>Lysinibacillus sphaericus</i> were isolated from an area of active alluvial gold mining exploitation at El Bagre, Antioquia. The absorption capacity of these strains and some of the <i>L. sphaericus</i> Microbiological Research Center (CIMIC) collection (CBAM5, OT4b.31, III(3)7) were evaluated by spectrophotometry according to a calibration g ...[more]

PMID: 30200519

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Project description:BackgroundEarly in the 1990s, it was recognized that Lysinibacillus sphaericus, one of the most popular and effective entomopathogenic bacteria, was a highly heterogeneous group. Many authors have even proposed it comprises more than one species, but the lack of phenotypic traits that guarantee an accurate differentiation has not allowed this issue to be clarified. Now that genomic technologies are rapidly advancing, it is possible to address the problem from a whole genome perspective, getting insights into the phylogeny, evolutive history and biology itself.ResultsThe genome of the Colombian strain L. sphaericus OT4b.49 was sequenced, assembled and annotated, obtaining 3 chromosomal contigs and no evidence of plasmids. Using these sequences and the 13 other L. sphaericus genomes available on the NCBI database, we carried out comparative genomic analyses that included whole genome alignments, searching for mobile elements, phylogenomic metrics (TETRA, ANI and in-silico DDH) and pan-genome assessments. The results support the hypothesis about this species as a very heterogeneous group. The entomopathogenic lineage is actually a single and independent species with 3728 core genes and 2153 accessory genes, whereas each non-toxic strain seems to be a separate species, though without a clear circumscription. Toxin-encoding genes, binA, B and mtx1, 2, 3 could be acquired via horizontal gene transfer in a single evolutionary event. The non-toxic strain OT4b.31 is the most related with the type strain KCTC 3346.ConclusionsThe current L. sphaericus is actually a sensu lato due to a sub-estimation of diversity accrued using traditional non-genomics based classification strategies. The toxic lineage is the most studied with regards to its larvicidal activity, which is a greatly conserved trait among these strains and thus, their differentiating feature. Further studies are needed in order to establish a univocal classification of the non-toxic strains that, according to our results, seem to be a paraphyletic group.

Project description:The Cqm1 ?-glucosidase of Culex quinquefasciatus larvae acts as the midgut receptor for the binary toxin of the biolarvicide Lysinibacillus sphaericus. Mutations within the cqm1 gene can code for aberrant polypeptides that can no longer be properly expressed or bind to the toxin, leading to insect resistance. The cqm1 REC and cqm1 REC-2 alleles were identified in a laboratory selected colony and both displayed mutations that lead to equivalent phenotypes of refractoriness to L. sphaericus. cqm1 REC was first identified as the major resistance allele in this colony but it was subsequently replaced by cqm1 REC-2 , suggesting the better adaptive features of the second allele. The major aim of this study was to evaluate the occurrence of cqm1 REC-2 and track its origin in field populations where cqm1 REC was previously identified.The screening of the cqm1 REC-2 allele was based on more than 2000 C. quinquefasciatus larvae from five localities in the city of Recife, Brazil and used a multiplex PCR assay that is also able to identify cqm1 REC . Full-length sequencing of the cqm1 REC-2 and selected cqm1 samples was performed to identify further polymorphisms between these alleles.The cqm1 REC-2 allele was found in field samples, specifically in two heterozygous individuals from a single locality with an overall frequency and distribution much lower than that observed for cqm1 REC . The full-length sequences from these two cqm1 REC-2 copies were almost identical to the cqm1 REC-2 derived from the resistant colony but displayed more than 30 SNPs when compared with cqm1 and cqm1 REC . The cqm1 REC and cqm1 REC-2 resistant alleles were found to be associated with two distinct sets of wild-type cqm1 variants found in field populations.The cqm1 REC-2 allele occurs in populations in Recife and was probably already present in the samples used to establish the laboratory resistant colony. The data generated indicates that cqm1 REC-2 can be selected in field populations, although its low frequency and distribution in Recife suggest that cqm1 REC-2 presents a lower risk of selection compared to cqm1 REC .

Dataset Information

The Golden Activity of Lysinibacillus sphaericus: New Insights on Gold Accumulation and Possible Nanoparticles Biosynthesis.

Publications

The Golden Activity of Lysinibacillus sphaericus: New Insights on Gold Accumulation and Possible Nanoparticles Biosynthesis.

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