Draft Genome Sequence of Erwinia toletana, a Bacterium Associated with Olive Knots Caused by Pseudomonas savastanoi pv. Savastanoi.

Erwinia toletana was first reported in 2004 as a bacterial species isolated from olive knots caused by the plant bacterium Pseudomonas savastanoi pv. savastanoi. Recent studies have shown that the presence of this bacterium in the olive knot environment increases the virulence of the disease, indicating possible interspecies interactions with P. savastanoi pv. savastanoi. Here, we report the first draft genome sequence of an E. toletana strain.D.P.D.S. was the beneficiary of an ICGEB fellowship. The laboratory of V.V. was financed by Progetto AGER and ICGEB core funding

Synergistic interaction between the type III secretion system of the endophytic bacterium <i>Pantoea agglomerans</i> DAPP-PG 734 and the virulence of the causal agent of olive knot <i>Pseudomonas savastanoi pv. savastanoi</i> DAPP-PG 722

The endophytic bacterium Pantoea agglomerans DAPP-PG 734 was previously isolated from olive knots caused by infection with Pseudomonas savastanoi pv. savastanoi DAPP-PG 722. Whole-genome analysis of this P. agglomerans strain revealed the presence of a Hypersensitive response and pathogenicity (Hrp) type III secretion system (T3SS). To assess the role of the P. agglomerans T3SS in the interaction with P. savastanoi pv. savastanoi, we generated independent knockout mutants in three Hrp genes of the P. agglomerans DAPP-PG 734 T3SS (hrpJ, hrpN, and hrpY). In contrast to the wildtype control, all three mutants failed to cause a hypersensitive response when infiltrated in tobacco leaves, suggesting that P. agglomerans T3SS is functional and injects effector proteins in plant cells. In contrast to P. savastanoi pv. savastanoi DAPP-PG 722, the wildtype strain P. agglomerans DAPP-PG 734 and its Hrp T3SS mutants did not cause olive knot disease in 1-year-old olive plants. Coinoculation of P. savastanoi pv. savastanoi with P. agglomerans wildtype strains did not significantly change the knot size, while the DAPP-PG 734 hrpY mutant induced a significant decrease in knot size, which could be complemented by providing hrpY on a plasmid. By epifluorescence microscopy and confocal laser scanning microscopy, we found that the localization patterns in knots were nonoverlapping for P. savastanoi pv. savastanoi and P. agglomerans when coinoculated. Our results suggest that suppression of olive plant defences mediated by the Hrp T3SS of P. agglomerans DAPP-PG 734 positively impacts the virulence of P. savastanoi pv. savastanoi DAPP-PG 722

<i>Calendula officinalis</i>: A New Natural Host of <i>Pseudomonas viridiflava</i> in Italy

In November 2010, small necrotic spots surrounded by chlorotic halos, which sometimes enlarged and coalesced to form large dead areas, were observed on leaves of marigold (Calendula officinalis L.) plants grown in the Medieval Garden at the Agricultural Faculty of Perugia (central Italy). Cream-colored bacterial colonies were consistently isolated on nutrient agar (NA) from the diseased leaf tissues. Four representative selected strains, which were gram negative, fluorescent on King's medium B, and had oxidative but not fermentative metabolism, were subjected to a pathogenicity test by inoculating 1-month-old marigold plants. To prepare the inoculum, the bacterial strains were grown on NA at 27°C for 24 h, suspended in sterile deionized water, and adjusted to 1 × 106 CFU/ml. Sterile water was used for control plants. Marigold leaves were infiltrated with a glass atomizer at high pressure, and plants were kept in a growth chamber at 22 to 24°C, 70 μE·m–2·s–1 illumination and 12-h light period, and 80% relative humidity. Small, water-soaked necrotic spots were observed 10 days after inoculation, and the bacterium with the same cultural features of the original strains was reisolated from inoculated plants. For bacterial identification, the four original strains and two reisolates were subjected to LOPAT tests. They were levan negative, oxidase negative, potato rot positive, arginine dihydrolase negative, and tobacco hypersensitive response positive. These results were similar to those obtained with the type strain LMG 2352T of Pseudomonas viridiflava (Burkholder) Dowson. When 16S rDNA was amplified with the universal primers, P0 (6-27f Escherichia coli) and P6 (1515-1495r E. coli), and digested with the endonucleases, SacI and HinfI as previously reported (2), an identical restriction profile was obtained for marigold strains and reisolates and P. viridiflava strains, LMG 2352T, LMG 2353, LMG 5397, and NCPPB 1382. A completely different profile was obtained for P. syringae pv. syringae LMG 1247T. The 16S rDNA (1,364 bp) and the gyrB (570 bp) sequences of two selected marigold strains (GenBank Accession Nos. JN406504 and JN406505; JN406506 and JN406507), amplified by using universal and previously reported PCR primers (3), respectively, shared 100% sequence identity with P. viridiflava (GenBank Accession Nos. HM190229 and AY606763) for 16S rDNA and gyrB gene, respectively. On the basis of biochemical, physiological, molecular, and pathogenicity tests, it was concluded that the bacteria isolated from marigold leaves are P. viridiflava. To our knowledge, this is the first report of C. officinalis as a natural host of P. viridiflava. The plant was previously reported as a host of the bacterium by artificial inoculation (1). References: (1) J. F. Bradbury. Guide to Plant Pathogenic Bacteria. CAB International, Egham, UK, 1986. (2) A. J. González et al. Appl. Environ. Microbiol. 69:2936, 2003. (3) E. M. Goss et al. Genetics 169:21, 2005. </jats:p

Gravi attacchi di Septoria lavandulae su lavanda in Umbria

Descrizione di una malattia grave della lavanda in Umbri