Investigation of a quorum sensing peptide in bacillus licheniformis and its novel antifungal property

Quorum sensing molecules (QSMs) are involved in the regulation of complicated processes helping bacterial population benefit from their cell-density. This phenomenon has been recently studied in some fungal populations. Prokaryotes and Eukaryotes’ co-evolution raises the prospect of the existence of inter-kingdom signalling pathways. The involvement of hormone-like molecules such as QSMs in microbial cells communication promise potential role of QS process in inter-kingdom cross-talk. Bacterial antagonistic activity against fungi is considered as an important bio-control opportunity to control fungal invasion of plants. Several bacterial species such as Bacillus spp. have shown the ability to inhibit fungal growth. During the screening of antagonistic bacteria against Aspergillus flavus (A. flavus), Bacillus subtilis (B. subtilis) was identified as having high antifungal activity. The bacterium, Bacillus licheniformis (B. licheniformis) is related to B. subtilis genetically and is used at industrial-scale for production of the antimicrobial compound bacitracin. Although the comQXPA cluster involved in QS development has been identified in the genome sequence of B. subtilis and different B. licheniformis strains, the QS system in B. licheniformis was not previously investigated in detail, and its QSM (ComX pheromone) was not identified. In this context, and given the importance of this antagonistic bacterium as an industrial workhorse, this study was aimed to use B. licheniformis NCIMB-8874 as a model antagonistic bacterium to investigate its effect, and the effect of its ComX pheromone on potential inhibition of fungal growth. The results obtained from bioinformatics studies on B. licheniformis NCIMB 8874 genome sequence presented in this project confirmed the presence of essential quorum sensing-related genes, such as the comQXPA gene cluster. The cell-cell communication of B. licheniformis NCIMB-8874 was investigated through further elucidation of QS process in this bacterium. The detection of the QSM, ComX pheromone, was achieved through molecular biology and biochemical studies including over-production, purification and partial identification. Subsequently, the potential influence of ComX pheromone and Bacillus cells on the growth of A. flavus was examined and concluded that the QSM could cause a significant reduction in the growth of A. flavus strains (NRRL 3357 and ESP 15). This work reports for the first time the amino acid sequence of the purified ComX pheromone and its novel antifungal property. Pheromone as a QSM is a potential signal for communication of cells between kingdoms and could be applied for bio-control purposes. Identification of new antifungal peptides against A. flavus could lead to the development of biotechnological strategies which facilitate control of aflatoxin contamination

Genomic and molecular characterization of a novel quorum sensing molecule in Bacillus licheniformis

Quorum sensing molecules (QSMs) are involved in the regulation of complicated processes helping bacterial populations respond to changes in their cell-density. Although the QS gene cluster (comQXPA) has been identified in the genome sequence of some bacilli, the QS system B. licheniformis has not been investigated in detail, and its QSM (ComX pheromone) has not been identified. Given the importance of this antagonistic bacterium as an industrial workhorse, this study was aimed to elucidate B. licheniformis NCIMB-8874 QS. The results obtained from bioinformatics studies on the whole genome sequence of this strain confirmed the presence of essential quorum sensing-related genes. Although polymorphism was verified in three proteins of this cluster, ComQ, precursor-ComX and ComP, the transcription factor ComA was confirmed as the most conserved protein. The cell–cell communication of B. licheniformis NCIMB-8874 was investigated through further elucidation of the ComX pheromone as 13-amino acid peptide. The peptide sequence of the pheromone has been described through biochemical characterisation

Microbial adaptation to venom is common in snakes and spiders

Animal venoms are considered sterile sources of antimicrobial compounds with strong membrane disrupting activity against multi-drug resistant bacteria. However, bite wound infections are common in developing nations. Investigating the oral and venom microbiome of five snake and two spider species, we evidence viable microorganisms potentially unique to venom for black-necked spitting cobras (Naja nigricollis). Among these are two novel sequence types of Enterococcus faecalis misidentified by commonly used clinical biochemistry procedures as Staphylococcus; the genome sequence data of venom-specific isolates feature an additional 45 genes, at least 11 of which improve membrane integrity. Our findings challenge the dogma of venom sterility and indicate an increased primary infection risk in the clinical management of venomous animal bite wounds

Landscapes of cellular phenotypic diversity in breast cancer xenografts and their impact on drug response

Funder: Cancer Research UK (CRUK); doi: https://doi.org/10.13039/501100000289Funder: AstraZeneca; doi: https://doi.org/10.13039/100004325Abstract: The heterogeneity of breast cancer plays a major role in drug response and resistance and has been extensively characterized at the genomic level. Here, a single-cell breast cancer mass cytometry (BCMC) panel is optimized to identify cell phenotypes and their oncogenic signalling states in a biobank of patient-derived tumour xenograft (PDTX) models representing the diversity of human breast cancer. The BCMC panel identifies 13 cellular phenotypes (11 human and 2 murine), associated with both breast cancer subtypes and specific genomic features. Pre-treatment cellular phenotypic composition is a determinant of response to anticancer therapies. Single-cell profiling also reveals drug-induced cellular phenotypic dynamics, unravelling previously unnoticed intra-tumour response diversity. The comprehensive view of the landscapes of cellular phenotypic heterogeneity in PDTXs uncovered by the BCMC panel, which is mirrored in primary human tumours, has profound implications for understanding and predicting therapy response and resistance

Inter-kingdom cross-talk and its bio-control applications

Quorum sensing (QS) molecules are involved in the regulation of complicated processes helping bacterial population benefit from their cell-density. The co-evolution of prokaryotes and eukaryotes raises the prospect of the existence of inter-kingdom signalling pathways, promoting parasitic/symbiotic relationships. While the members of each kingdom possess hormone-like molecules for cell–cell communication, the members of any given kingdom also respond to the signals produced by another. So, QS plays a major role in this cross-talk. Bacterial antagonistic activity against fungi is considered as an inter-kingdom communication. Interestingly, several bacteria like Bacillus, Lactobacillus and Pseudomonas have shown in laboratory experiments the ability to inhibit fungal growth and production of aflatoxins by Aspergillus. During the screening of antagonistic bacteria against Aspergillus flavus (causes pre-/post-harvest diseases in seed-crops) in vitro, Bacillus subtilis was identified having high antifungal activity. Bacillus licheniformis has industrial application due to its production of antimicrobial compounds. B. licheniformis is related to B. subtilis genetically, whose control of competence-sporulation is regulated by a QS mechanism (comQXPA operon). QS process in B. subtilis are regulated by a specific molecule, ComX pheromone. Pheromone encoding genes have been identified in B. licheniformis NCIMB-8874. To further investigate cell-cell communication, we designed a primer pair to amplify the QSM encoding genes. The comQX locus was sub-cloned into a shuttle vector under the control of an inducible promoter. The shuttle vector was expressed in E. coli and pheromone was isolated by reverse phase chromatography. Pheromone as a QSM is potential signal for communicating between kingdoms and could be applied for biocontrol purposes. Identification of new antifungal peptides against A. flavus could lead to the development of biotechnological strategies which facilitate control of aflatoxin contamination and genetic engineering of plant resistance to fungi through the exploitation of genes related to the bacterial antifungal peptide molecules