Editorial [Hot Topic: Antimicrobial Substances Produced by Bacteria, Marine Sponges, and Tropical Plants (Guest Editor: Maria do Carmo de Freire Bastos)]

The spread of microbial resistance leads to a growing demand for novel antimicrobial drugs. However, despite the significant efforts in academia and the pharmaceutical industry, no genuinely new class of antimicrobial compounds has reached the market in the last years. However, a large variety of substances with potential antimicrobial activity is widely distributed in nature being produced by both prokaryotes and eukaryotes. Therefore, in this special issue of Current Pharmaceutical Biotechnology, we attempt to provide the reader with an overview on antimicrobial substances produced by bacteria, marine sponges, and tropical plants. Concerning prokaryotes, the reviews will focus on bacteriocins, antimicrobial peptides produced by bacteria. Bierbaum and co-workers focus their review on the current developments in the lantibiotic (class I bacteriocins) field and on recent findings concerning mode of action, biosynthesis and engineering of lantibiotics produced by Gram-positive bacteria, while the review written by Nissen-Meyer and co-workers focuses on the structure and mode of action of class II bacteriocins. Structure-function analysis of bacteriocins is particularly relevant for illuminating how these potent bactericidal agents function at a molecular level. Such knowledge is fundamental when considering the rational design of new bacteriocin variants with improved properties that make them especially useful for medical and biotechnological applications. Bastos and co-workers describe the relevant features of staphylococcins, bacteriocins produced by staphylococci, discussing examples of their potential biotechnological applications mainly as antibacterial agents. Diep and co-workers discuss some well-characterised quorum sensing networks involved in regulation of bacteriocin production in lactobacilli, with special focus on the use of the regulatory components in gene expression and on lactobacilli as potential delivery vehicle for therapeutic and vaccine purposes. The review of Lagos and co-workers is focused on microcin E492 features, a bacteriocin that, besides an antimicrobial activity, also displays a cytotoxic effect on tumor cell lines involving apoptosis induction. This trait makes this bacteriocin also suitable for cancer treatment. Laport and co-workers describe an overwhelming number of bioactive substances that have been discovered in sponges and their associated microorganisms. Sponges are considered the most prolific marine producers of novel substances exhibiting antimicrobial activity with a variety of biotechnologically relevant properties.