Laterosporulin10 (LS10) is a defensin like peptide fromBrevibacillussp. strain SKDU10 that inhibited microbial pathogens. However, in this study, anticancer activity of LS10 was examined against different cancer cell lines and compared with normal cells. LS10 displayed cytotoxicity against cancer cells like MCF-7, HEK293T, HT1080, HeLa and H1299 at below 10 μM concentration, but not against prostate epithelium cells RWPE-1. Additionally, no hemolysis was observed at significantly higher concentration compared to IC₅₀values observed for different cancer cell lines. Release of lactate dehydrogenase from cancer cell lines at 15 μM concentration upon 120 min treatment indicated the lytic ability of LS10. Accordingly, electron microscopy experiments also confirmed the necrotic effect of LS10 at 15 μM concentration against cancer cells. Furthermore, flow cytometry analysis of treated cancer cell lines revealed that LS10 induce apoptosis even at 2.5 μM concentration. Nevertheless, RWPE-1 cells remained viable even at 20 μM concentration. These results provide evidence that LS10 is an anticancer bacteriocin, which causes apoptotic and necrotic death of cancer cells at lower and higher concentrations, respectively. Taken all results together, the present study signifies that LS10 is an anticancer peptide that could be further developed for therapeutic applications.

Attempts to isolate novel antimicrobial peptides from microbial sources have been on the rise recently, despite their low efficacy in therapeutic applications. Here, we report identification and characterization of a new efficient antimicrobial peptide from a bacterial strain designated A3 that exhibited highest identity with Paenibacillus ehimensis . Upon purification and subsequent molecular characterization of the antimicrobial peptide, referred to as penisin, we found the peptide to be a bacteriocin-like peptide. Consistent with these results, RAST analysis of the entire genome sequence revealed the presence of a lantibiotic gene cluster containing genes necessary for synthesis and maturation of a lantibiotic. While circular dichroism and one-dimension nuclear magnetic resonance experiments confirmed a random coil structure of the peptide, similar to other known lantibiotics, additional biochemical evidence suggests posttranslational modifications of the core peptide yield six thioether cross-links. The deduced amino acid sequence of the putative biosynthetic gene penA showed approximately 74% similarity with elgicin A and 50% similarity with the lantibiotic paenicidin A. Penisin effectively killed methicillin-resistant Staphylococcus aureus (MRSA) and did not exhibit hemolysis activity. Unlike other lantibiotics, it effectively inhibited the growth of Gram-negative bacteria. Furthermore, 80 mg/kg of body weight of penisin significantly reduced bacterial burden in a mouse thigh infection model and protected BALB/c mice in a bacteremia model entailing infection with Staphylococcus aureus MTCC 96, suggesting that it could be a promising new antimicrobial peptide.

Secondary bacterial infections are commonly associated with prior or concomitant respiratory viral infections. Viral infections damage respiratory airways and simultaneously defects both innate and acquired immune response that provides a favorable environment for bacterial growth, adherence, and facilitates invasion into healthy sites of the respiratory tract. Understanding the molecular mechanism of viral-induced secondary bacterial infections will provide us a chance to develop novel and effective therapeutic approaches for disease prevention. The present study describes details about the secondary bacterial infection during viral infections and their immunological changes.The outcome of discussion avails an opportunity to understand possible secondary bacterial infections associated with novel SARS-CoV-2, presently causing pandemic outbreak COVID-19.

Bacteriocins are antimicrobial peptides (AMPs) produced by bacteria to acquire survival benefits during competitive interactions between inter and intra species in complex ecosystems. In this study, an AMP producing soil bacterial strain designated as SKDU10 was isolated and identified as a member of the genus Brevibacillus. The AMP produced by strain SKDU10 was identified as a class IId bacteriocin with 57.6% homology to laterosporulin, a defensin like class IId bacteriocin. However, substantial differences were observed in antimicrobial activity spectrum of this bacteriocin named as laterosporulin10 when compared to laterosporulin. Laterosporulin10 effectively inhibited the growth of Staphylococcus aureus and Mycobacterium tuberculosis (Mtb H37Rv) with LD50 values of 4.0 µM and 0.5 µM, respectively. Further, laterosporulin10 inhibited the growth of Mtb H37Rv strain at about 20 times lesser MIC value compared to S. aureus MTCC 1430 or M. smegmatis mc2155 in vitro and ex vivo. Electron micrographic studies along with membrane potential analysis using FACS analyses revealed that the laterosporulin10 is a membrane permeabilizing peptide. Interestingly, laterosporulin10 was able to efficiently kill Mtb H37Rv strain residing inside the macrophages and did not show haemolysis up to 40 µM concentration.