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Author(s): Nicola J. Nadeau (corresponding author) [1, 2]; Carolina Pardo-Diaz [3]; Annabel Whibley [4, 5]; Megan A. Supple [2, 6]; Suzanne V. Saenko [4]; Richard W. R. Wallbank [2, 7]; [...]

The toxin complex (Tc) genes were first identified in the insect pathogen Photorhabdus luminescens and encode ~1 MDa protein complexes which are toxic to insect pests. Subsequent genome sequencing projects have revealed the presence of tc orthologues in a range of bacterial pathogens known to be associated with insects. Interestingly, members of the mammalian-pathogenic yersiniae have also been shown to encode Tc orthologues. Studies in Yersinia enterocolitica have shown that divergent tc loci either encode insect-active toxins or play a role in colonization of the gut in gastroenteritis models of rats. So far little is known about the activity of the Tc proteins in the other mammalian-pathogenic yersiniae. Here we present work to suggest that Tc proteins in Yersinia pseudotuberculosis and Yersinia pestis are not insecticidal toxins but have evolved for mammalian pathogenicity. We show that Tc is secreted by Y. pseudotuberculosis strain IP32953 during growth in media at 28[degrees]C and 37[degrees]C. We also demonstrate that oral toxicity of strain IP32953 to Manduca sexta larvae is not due to Tc expression and that lysates of Escherichia coil BL21 expressing the Yersinia Tc proteins are not toxic to Sf9 insect cells but are toxic to cultured mammalian cell lines. Cell lysates of E. coil BL21 expressing the Y. pseudotuberculosis Tc proteins caused actin ruffles, vacuoles and multinucleation in cultured human gut cells (Caco-2); similar morphology was observed after application of a lysate of E. coil BL21 expressing the Y. pestis Tc proteins to mouse fibroblast NIH3T3 ceils, but not Caco-2 cells. Finally, transient expression of the individual Tc proteins in Caco-2 and NIH3T3 cell lines reproduced the actin and nuclear rearrangement observed with the topical applications. Together these results add weight to the growing hypothesis that the Tc proteins in Y. pseudotuberculosis and Y. pestis have been adapted for mammalian pathogenicity. We further conclude that Tc proteins from Y. pseudotuberculosis and Y. pestis display differential mammalian cell specificity in their toxicity.

Climate change, changing farming practices, social and demographic changes and rising levels of antibiotic resistance are likely to lead to future increases in opportunistic bacterial infections that are more difficult to treat. Uncovering the prevalence and identity of pathogenic bacteria in the environment is key to assessing transmission risks. We describe the first use of the Wax moth larva Galleria mellonella, a well-established model for the mammalian innate immune system, to selectively enrich and characterize pathogens from coastal environments in the South West of the UK. Whole-genome sequencing of highly virulent isolates revealed amongst others a Proteus mirabilis strain carrying the Salmonella SGI1 genomic island not reported from the UK before and the recently described species Vibrio injenensis hitherto only reported from human patients in Korea. Our novel method has the power to detect bacterial pathogens in the environment that potentially pose a serious risk to public health. [ABSTRACT FROM AUTHOR]

The last 10 years has seen an explosion in our knowledge of the diversity of toxins produced by the insect pathogenic bacteria Photorhabdus and Xenorhabdus. Here we review new data on the structure, mode of action and biophysics of Photorhabdus toxins and place them into context with similar toxins made in other bacteria such as those of the genus Yersinia and Serratia. We look in detail at structure-function studies of the Toxin complexes or 'Tcs' and suggest that these might constitute a new mode of bacterial secretion, here termed the Toxin complex secretion system or 'TC-SS'. We examine current data on the Makes Caterpillars Floppy or 'Mcf' toxins both from insect pathogenic bacteria and also the related Mcf-like Fit toxin from Pseudomonas. We also review data on the Photorhabdus Virulence Cassettes or 'PVC's' and their equivalent phage-like secretion systems in other bacteria. Again these appear to be a totally novel secretion system, termed PVC-SS, derived from tailed myophages. Finally, we review the sheer diversity of other candidate toxins identified from Photorhabdus and Xenorhabdus genomes, such as PaTox and Photox, and from simple gain-of-function screens devised to identify novel effectors when expressed in recombinant Escherichia coli, termed 'Rapid Virulence Annotation' or 'RVA'. Taken together, available data support the early contention that Photorhabdus genomes do indeed encode more candidate toxins than those of other bacteria and suggest that this unique genus demands more time from serious toxinologists than has been devoted to date. [ABSTRACT FROM AUTHOR]

We present a novel method implementing unbiased high-content morphometric cell analysis to classify bacterial effector phenotypes. This clustering methodology represents a significant advance over more qualitative visual approaches and can also be used to classify, and therefore predict the likely function of, unknown effector genes from any microbial genome. As a proof of concept, we use this approach to investigate 23 genetic regions predicted to encode antimacrophage effectors located across the genome of the insect and human pathogen Photorhabdus asymbiotica. Statistical cluster analysis using multiple cellular measures categorized treated macrophage phenotypes into three major groups relating to their putative functionality: (i) adhesins, (ii) cytolethal toxins, and (iii) cytomodulating toxins. Further investigation into their effects on phagocytosis revealed that several effectors also modulate this function and that the nature of this modulation (increased or decreased phagocytosis) is linked to the phenotype cluster group. Categorizing potential functionalities in this way allows rapid functional follow-up of key candidates for more-directed cell biological or biochemical investigation. Such an unbiased approach to the classification of candidate effectors will be useful for describing virulence-related regions in a wide range of genomes and will be useful in assigning putative functions to the growing number of microbial genes whose function remains unclear from homology searching. [ABSTRACT FROM AUTHOR]

In this communication we describe the synthesis, characterisation and plasma deposition of a novel organo-silver compound for the prevention of the growth of Pseudomonas aeruginosaon both polystyrene surfaces and polypropylene non-woven fabrics. [ABSTRACT FROM AUTHOR]