Phage Transduction is Involved in the Intergeneric Spread of Antibiotic Resistance-Associated blaCTX-M, mel, and tetM Loci in Natural Populations of Some Human and Animal Bacterial Pathogens.

The horizontal genetic transfer (HGT) of antibiotic resistance genes (ARGs) mediated by species-specific bacteriophages contributes to the emergence of antibiotic-resistant strains in natural populations of human and animal bacterial pathogens posing a significant threat to global public health. However, it is unclear and needs to be determined whether polyvalent bacteriophages play any role in the intergeneric transmission of ARGs. In this study, we examined the genome sequences of 2239 bacteriophages from different sources for the presence of ARGs. The identified ARG-carrying bacteriophages were then analyzed by PHACTS, PHAST, and HostPhinder programs to determine their lifestyles, genes coding for bacterial cell lysis, recombinases, and a spectrum of their potential host species, respectively. We employed the SplitsTree, RDP4 and SimPlot software packages in recombination tests to identify HGT events of ARGs between these bacteriophages and bacteria. In our analyses, some ARG-carrying bacteriophages exhibited temperate and/or polyvalent patterns. The bootstrap values (97-100) for the SplitsTree-generated parallelograms, fit values (97-100) for splits networks, Phi P values (< 10-17 to 3.9 × 10-16), RDP4 P values (≤ 7.8 × 10-03), and the SimPlot results, provided strong statistical evidence for the phage transduction events of blaCTX-M, mel, and tetM loci on inter-species level. These events involved several host species such as Escherichia coli, Salmonella enterica, Shigella sonnei, Streptococcus pneumoniae and Bacillus coagulans. HGT of mel loci between Erysipelothrix and Streptococcus phages were also detected. These results firmly suggest that certain bacteriophages possibly with temperate properties induce the intergeneric dissemination of blaCTX-M, mel and tetM in the above species.

PCMD-1 Organizes Centrosome Matrix Assembly in C. elegans.

Centrosomes, the major microtubule-organizing centers of animal cells, are essential for the assembly of a bipolar spindle during mitosis. Spindle defective-5 (SPD-5), the main scaffold protein of the centrosome matrix in Caenorhabditis elegans, forms a thin core around non-mitotic centrioles. Upon mitotic entry, the SPD-5-containing centrosome matrix expands in a Polo-like-kinase 1 (PLK-1)-dependent manner and this enables an enhanced microtubule nucleation activity during mitosis. How the non-mitotic centrosome core is formed and how this core facilitates robust SPD-5 expansion at mitotic entry remains unknown. Here, we present evidence that the coiled-coil protein pericentriolar matrix deficient-1 (PCMD-1) is necessary for the efficient loading of SPD-5, SPD-2, and PLK-1 to the non-mitotic centrosome core. Furthermore, we demonstrate that the absence of PCMD-1 disrupts pericentriolar material (PCM) recruitment and integrity. The expansion of centrosomes into spherical structures at the mitotic entry is compromised. We propose that PCMD-1 acts as a molecular platform for mitotic regulators and for components of the PCM, thereby allowing functional interactions between them, which in turn is necessary for the organization of the mitotic centrosome and, hence, spindle bipolarity.