Characterization and induction of prophages in human gut-associated Bifidobacterium hosts.

In the current report, we describe the identification of three genetically distinct groups of prophages integrated into three different chromosomal sites of human gut-associated Bifidobacterium breve and Bifidobacterium longum strains. These bifidobacterial prophages are distantly related to temperate actinobacteriophages of several hosts. Some prophages, integrated within the dnaJ2 gene, are competent for induction, excision, replication, assembly and lysis, suggesting that they are fully functional and can generate infectious particles, even though permissive hosts have not yet been identified. Interestingly, several of these phages harbor a putative phase variation shufflon (the Rin system) that generates variation of the tail-associated receptor binding protein (RBP). Unlike the analogous coliphage-associated shufflon Min, or simpler Cin and Gin inversion systems, Rin is predicted to use a tyrosine recombinase to promote inversion, the first reported phage-encoded tyrosine-family DNA invertase. The identification of bifidobacterial prophages with RBP diversification systems that are competent for assembly and lysis, yet fail to propagate lytically under laboratory conditions, suggests dynamic evolution of bifidobacteria and their phages in the human gut.

Milk digesta and milk protein fractions influence the adherence of Lactobacillus gasseri R and Lactobacillus casei FMP to human cultured cells.

Adhesion to the intestinal epithelium is considered an important feature of probiotic bacteria, which may increase their persistence in the intestine, allowing them to exert their beneficial health effect or promote the colonisation process. However, this feature might be largely dependent on the host specificity or diet. In the present study, we investigated the effect of selected milks and milk protein fractions on the ability of selected lactobacilli to adhere to the cells of an intestinal model based on co-culture Caco-2/HT29-MTX cell lines. Most milk digesta did not significantly affect bacterial adhesion except for UHT-treated milk and sheep milk. The presence of UHT-treated milk digesta reduced the adhesion of Lactobacillus gasseri R by 61% but not that of Lactobacillus casei FMP. However, sheep milk significantly increased the adherence of L. casei FMP (P < 0.05) but not of L. gasseri R. Among the protein fractions, rennet casein (RCN) and bovine serum albumin (BSA) showed reproducible patterns and strain-specific effects on bacterial adherence. While RCN reduced the adherence of L. gasseri R to <50% compared to the control, it did not have a significant effect on L. casei FMP. In contrast, BSA reduced L. casei FMP adherence to a higher extent than that of L. gasseri R. Whey protein (WH) tended to increase the adherence of both strains by 130%-180%. Recently, interactions between the host diet and its microbiota have attracted considerable interest. Our results may explain one of the aspects of the role of milk in the development of microbiota or support of probiotic supplements. Based on our data, we conclude that the persistence of probiotic strains supplemented as part of dairy food or constitutional microbiota in the gut might be affected negatively or positively by the food matrix through complex strain or concentration dependent effects.

Jasmonate- and salicylate-induced defenses in wheat affect host preference and probing behavior but not performance of the grain aphid, Sitobion avenae.

Jasmonate- and salicylate-mediated signaling pathways play significant roles in induced plant defenses, but there is no sufficient evidence for their roles in monocots against aphids. We exogenously applied methyl jasmonate (MeJA) and salicylic acid (SA) on wheat seedlings and examined biochemical responses in wheat and effects on the grain aphid, Sitobion avenae (Fab.). Application of MeJA significantly increased levels of wheat's polyphenol oxidase, peroxidase and proteinase inhibitor 1, 2 and 6 days after treatment. In two-choice tests, adult aphids preferred control wheat leaves to MeJA- or SA-treated leaves. Electrical penetration graph (EPG) recordings of aphid probing behavior revealed that on MeJA-treated plants, the duration of aphid's first probe was significantly shorter and number of probes was significantly higher than those on control plants. Also total duration of probing on MeJA-treated plants was significantly shorter than on control plants. Total duration of salivation period on SA-treated plants was significantly longer, while mean phloem ingestion period was significantly shorter than on control plants. However, no significant difference in total duration of phloem sap ingestion period was observed among treatments. The EPG data suggest that MeJA-dependent resistance factors might be due to feeding deterrents in mesophyll, whereas the SA-mediated resistance may be phloem-based. We did not observe any significant difference of MeJA and SA application on aphid development, daily fecundity, intrinsic growth rate and population growth. The results indicate that both MeJA- and SA-induced defenses in wheat deterred S. avenae colonization processes and feeding behavior, but had no significant effects on its performance.

The host range of gammaretroviruses and gammaretroviral vectors includes post-mitotic neural cells.

BACKGROUND: Gammaretroviruses and gammaretroviral vectors, in contrast to lentiviruses and lentiviral vectors, are reported to be restricted in their ability to infect growth-arrested cells. The block to this restriction has never been clearly defined. The original assessment of the inability of gammaretroviruses and gammaretroviral vectors to infect growth-arrested cells was carried out using established cell lines that had been growth-arrested by chemical means, and has been generalized to neurons, which are post-mitotic. We re-examined the capability of gammaretroviruses and their derived vectors to efficiently infect terminally differentiated neuroendocrine cells and primary cortical neurons, a target of both experimental and therapeutic interest. METHODOLOGY/PRINCIPAL FINDINGS: Using GFP expression as a marker for infection, we determined that both growth-arrested (NGF-differentiated) rat pheochromocytoma cells (PC12 cells) and primary rat cortical neurons could be efficiently transduced, and maintained long-term protein expression, after exposure to murine leukemia virus (MLV) and MLV-based retroviral vectors. Terminally differentiated PC12 cells transduced with a gammaretroviral vector encoding the anti-apoptotic protein Bcl-xL were protected from cell death induced by withdrawal of nerve growth factor (NGF), demonstrating gammaretroviral vector-mediated delivery and expression of genes at levels sufficient for therapeutic effect in non-dividing cells. Post-mitotic rat cortical neurons were also shown to be susceptible to transduction by murine replication-competent gammaretroviruses and gammaretroviral vectors. CONCLUSIONS/SIGNIFICANCE: These findings suggest that the host range of gammaretroviruses includes post-mitotic and other growth-arrested cells in mammals, and have implications for re-direction of gammaretroviral gene therapy to neurological disease.