Dear Colleagues,

Many bacteria produce toxins of considerable medical importance. Vaccines have been developed for some of the toxin-mediated diseases (e.g., tetanus, diphtheria) and continue to be important in the prevention of disease. Over the past few decades, great strides have been made in our understanding of the structure and function of bacterial toxins and their role in disease.  These advances reflect the productive interactions of disciplines such as protein chemistry and crystallography, molecular genetics, molecular biology, genomics, immunology, neurobiology, pharmacology, and biophysics.  Remarkable progress has been made in the elucidation of the molecular mechanisms of a wide range of toxins with increasing numbers found to have enzymatic activities, including those that ADP-ribosylate (e.g., diphtheria toxin) and glycosylate novel targets, and Zn-proteinases with exquisite specificities (e.g., botulinum A neurotoxin and SNAP-25).    The host immune system is not only the primary defense against colonization and sometimes invasion by toxigenic bacteria, but it also constitutes a major target for bacterial toxins that can act either directly by cytotoxicity towards immune effector cells, or indirectly by deregulation of cytokine production. 

Toxin genes and other virulence determinants are frequently encoded by mobile genetic elements, which are located on pathogenicity islands and/or on mobilizable genetic elements such as plasmids, transposons, and bacteriophages.  These genetic elements with the capacity to be spread by horizontal gene transfer contribute to the rapid evolution of bacterial pathogens as the rearrangement, excision and acquisition of large genomic regions creates new pathogenic variants.  The occurrence of toxin-encoding genes on various interdepending genetic elements, their ability to delete from and integrate into chromosomal DNA and the existence of toxin families among a wide variety of bacterial species demonstrate that toxigenic pathogen evolution is connected to the transfer of foreign DNA harboring toxin determinants. 

The aim of this issue is to provide a collection of articles that highlights research on bacterial toxins.  The editors chose to focus this issue on Gram positive bacterial toxins.  Submissions reflecting all aspects of toxin research are welcome from applied (novel diagnostics, countermeasures, vaccines) to more basic areas related to the biology of the toxin, genomics, and pathogenesis.  Gram positive toxins include, but are not limited to, tetanus toxin, botulinum toxins, staphylococcal toxins, diphtheria toxin, streptococcal toxins, Listeria toxin, anthrax toxins, Bacillus cereus toxins, pneumolysin, enterococcal toxins, and other clostridial toxins (e.g., perfringolysin O).  Each of these toxins has a unique story to tell but needs a storyteller.  We hope you will be able to contribute to this special issue on Gram positive toxins. 

Dr. Shashi Sharma
Dr. Stephen A. Morse
Dr. Sabine Pellett
Guest Editors

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