RESUMEN
Stenotrophomonas maltophilia (S. maltophilia) is an emerging opportunistic pathogen that exhibits resistant to a majority of commonly used antibiotics. Phages have the potential to serve as an alternative treatment for S. maltophilia infections. In this study, a lytic phage, A1432, infecting S. maltophilia YCR3A-1, was isolated and characterized from a karst cave. Transmission electron microscopy revealed that phage A1432 possesses an icosahedral head and a shorter tail. Phage A1432 demonstrated a narrow host range, with an optimal multiplicity of infection of 0.1. The one-step growth curve indicated a latent time of 10 min, a lysis period of 90 min, a burst size of 43.2 plaque-forming units per cell. In vitro bacteriolytic activity test showed that phage A1432 was capable to inhibit the growth of S. maltophilia YCR3A-1 in an MOI-dependent manner after 2 h of co-culture. BLASTn analysis showed that phage A1432 genome shares the highest similarity (81.46%) with Xanthomonas phage Xoo-sp2 in the NCBI database, while the query coverage was only 37%. The phage contains double-stranded DNA with a genome length of 61,660 bp and a GC content of 61.92%. It is predicted to have 79 open reading frames and one tRNA, with no virulence or antibiotic resistance genes. Phylogenetic analysis using terminase large subunit and DNA polymerase indicated that phage A1432 clustered with members of the Bradleyvirinae subfamily but diverged into a distinct branch. Further phylogenetic comparison analysis using Average Nucleotide Identity, proteomic phylogenetic analysis, genomic network analysis confirmed that phage A1432 belongs to a novel genus within the Bradleyvirinae subfamily, Mesyanzhinovviridae family. Additionally, phylogenetic analysis of the so far isolated S. maltophilia phages revealed significant genetic diversity among these phages. The results of this research will contribute valuable information for further studies on their morphological and genetic diversity, will aid in elucidating the evolutionary mechanisms that give rise to them.
RESUMEN
Hydrogels have been widely used to mimic the biochemical and mechanical environments of native extracellular matrices for cell culture and tissue engineering. Among them, self-assembling peptide hydrogels are of special interest thanks to their great biocompatibility, designability and convenient preparation procedures. In pioneering studies, self-assembling peptide hydrogels have been used for the culture of bone marrow cells. However, the low mechanical stability of peptide hydrogels seems to be a drawback for these applications, as bone marrow cells prefer hard substrates for osteogenic differentiation. In this work, we explored the use of hydroxyapatite (HAP)-peptide hybrid hydrogels for three-dimensional (3D) culture and differentiation of osteogenic MC3T3-E1 cells. We used HAP nanoparticles as crosslinkers to increase the mechanical stability of peptide hydrogels. Meanwhile, HAP provided unique chemical cues to promote the differentiation of osteoblasts. A phosphate group was introduced to the self-assembling peptide so that the peptide fibers could bind to HAP nanoparticles specifically and strongly. Rheological characterization indicated that the hybrid hydrogels were mechanically more stable than the hydrogels containing only peptides and can be used for long term cell culture. Moreover, the hydrogels were biocompatible and showed very low cytotoxicity. The favorable mechanical properties of the hybrid hydrogels and the chemical properties of HAP synergistically supported the differentiation of MC3T3-E1 cells. Based on these characterizations, we believe that these hybrid hydrogels can potentially be used as scaffolds for cartilage and bone regeneration in the future.