A genome-scale metabolic reconstruction of Lysinibacillus sphaericus unveils unexploited biotechnological potentials.

The toxic lineage (TL) of Lysinibacillus sphaericus has been extensively studied because of its potential biotechnological applications in biocontrol of mosquitoes and bioremediation of toxic metals. We previously proposed that L. sphaericus TL should be considered as a novel species based on a comparative genomic analysis. In the current work, we constructed the first manually curated metabolic reconstruction for this species on the basis of the available genomes. We elucidated the central metabolism of the proposed species and, beyond confirming the reported experimental evidence with genomic a support, we found insights to propose novel applications and traits to be considered in further studies. The strains belonging to this lineage exhibit a broad repertory of genes encoding insecticidal factors, some of them remain uncharacterized. These strains exhibit other unexploited biotechnological important traits, such as lactonases (quorum quenching), toxic metal resistance, and potential for aromatic compound degradation. In summary, this study provides a guideline for further research aimed to implement this organism in biocontrol and bioremediation. Similarly, we highlighted the unanswered questions to be responded in order to gain a deeper understanding of the L. sphaericus TL biology.

Evidence-based validation of quorum quenching from Lysinibacillus sphaericus and Geobacillus sp. in bioremediation of oil sludge.

Many studies on quorum quenching focus on the discovery and characterization of novel acyl-homoserine lactonases (AHL-lactonases) because these enzymes could be used in the control of diseases caused by Gram-negative bacteria. The effects of quorum quenching are also remarkable in the performance of bacterial consortia in applications such as bioremediation. In the current work, we demonstrated the presence of a potential novel AHL-lactonase-encoding locus (Bsph_3377) from Lysinibacillus sphaericus and Geobacillus sp. The deduced amino acid sequences for this enzyme possess the characteristic domains and motifs involved in Zn-binding from AHL lactonases and were grouped into 1 clade within the phylogeny of the lactonases from firmicutes, showing 70% of identity with the lactonase AhlS from Solibacillus silvestris. We demonstrated the locus transcription by RT-qPCR and its relationship with the suppression of the pathogenicity of Pectobacterium carotovorum. Additionally, we analyzed the interaction of these bacilli with a commercial consortium in the bioremediation of a hydrocarbon-contaminated soil, showing inhibitory effects on its establishment. These results represent a new contribution in the understanding of the potential biotechnological applications of L. sphaericus and Geobacillus sp. as well as in the research on antibacterial techniques based on quorum-sensing disruption.

Comparative genomics reveals Lysinibacillus sphaericus group comprises a novel species.

BACKGROUND: Early 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. RESULTS: The 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. CONCLUSIONS: The 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.

Complete Genome Sequence of Lysinibacillus sphaericus WHO Reference Strain 2362.

Lysinibacillus sphaericus is a species that contains strains widely used in the biological control of mosquitoes. Here, we present the complete 4.67-Mb genome of the WHO entomopathogenic reference strain L. sphaericus 2362, which is probably one of the most commercialized and studied strains. Genes coding for mosquitocidal toxin proteins were detected.