Isolation and partial characterization of bacteriophages infecting Pseudomonas syringae pv. actinidiae, causal agent of kiwifruit bacterial canker.

The phytopathogen Pseudomonas syringae pv. actinidiae (Psa) is the causal agent of bacterial canker of kiwifruit. In the last years, it has caused severe economic losses to Actinidia spp. cultivations, mainly in Italy and New Zealand. Conventional strategies adopted did not provide adequate control of infection. Phage therapy may be a realistic and safe answer to the urgent need for novel antibacterial agents aiming to control this bacterial pathogen. In this study, we described the isolation and characterization of two bacteriophages able to specifically infect Psa. φPSA1, a member of the Siphoviridae family, is a temperate phage with a narrow host range, a long latency, and a burst size of 178; φPSA2 is a lytic phage of Podoviridae family with a broader host range, a short latency, a burst size of 92 and a higher bactericidal activity as determined by the TOD value. The genomic sequence of φPSA1 has a length of 51,090 bp and a low sequence homology with the other siphophages, whereas φPSA2 has a length of 40 472 bp with a 98% homology with Pseudomonas putida bacteriophage gh-1. Of the two phages examined, φPSA2 may be considered as a candidate for phage therapy of kiwifruit disease, while φPSA1 seems specific toward the recent outbreak's isolates and could be useful for Psa typing.

Assay of vtg, ERs and PPARs as endpoint for the rapid in vitro screening of the harmful effect of Di-(2-ethylhexyl)-phthalate (DEHP) and phthalic acid (PA) in zebrafish primary hepatocyte cultures.

In the last years the concern about the negative effects of phthalates on reproduction significantly increased. Considering that, at date data available dealing with the adverse outcome of Di-(2-ethylhexyl)-phthalate (DEHP) on the reproduction of several species are still contrasting, in this study, the effects induced by DEHP (0.05, 0.1, 1, 10 and 100 nM) and its active metabolite, phthalic acid (PA) (0.01, 0.1, 1 and 10 µM), were analyzed in zebrafish, Danio rerio, primary hepatocyte cultures, using target molecules involved in fish reproduction (vitellogenin--vtg and estrogen receptors--ERα, ß1 and ß2) and metabolism (peroxisome proliferators activated receptors--PPAR α, ß, γ). The use of in vitro culture, in fact, has the potential to significantly reduce the number of animals sacrificed for research allowing a precise control of the physical and chemical parameters that is often not possible in vivo. Moreover, since many toxicological studies revealed a sex specific response to toxicants, male and female primary hepatocyte cultures were set up to elucidate the possible gender specific effects of two common environmental phthalates. The increase of vtg levels observed in the culture media of male or female hepatocytes strongly evidenced the phthalates E2-like action. Moreover, the data obtained suggested that the observed different ERs isoforms modulation is otherwise associated with the vtg increase, depending on fish gender. Regarding PPARs, a similar trend of expression was found in both males and females. In conclusion, this study enforces the role of vtg as biomarker for evaluate the presence of environmental doses of DEHP and PA. Considering the similar gender modulation observed for vtg and PPARs, these molecules could be used for the rapid screening of the presence of DEHP and PA. Noteworthy the gender specific modulation observed for ERs opens a debate on the estrogenic mechanism of action of DEHP and PA and their role on vtg induction.