Tracking the dissemination of Erwinia amylovora in the Eurasian continent using a PCR targeted on the duplication of a single CRISPR spacer

Fire blight is the most devastating disease affecting pome fruit production globally. The pathogen is native to North America and was imported to western Europe in the 1950s, progressively spreading over the continent in the ensuing decades. Previous phylogenetic studies have revealed the extreme genetic homogeneity of the pathogen outside its center of origin, which makes epidemiological studies difficult. These are generally only possible using hypervariable regions of the genome such as those represented by CRISPRs (Clustered Regularly Interspaced Short Palindromic Repeats), which are, however, not practical to sequence due to their size and variability. Here, we present a simple PCR assay targeting the duplication of a single CRISPR spacer in Erwinia amylovora that was found to be an important marker to discriminate between two main European populations of the pathogen. We implemented the assay on a total of 582 isolates to follow the spread of fire blight across the continent over several decades and, wherever possible, within single countries. The results obtained point to the occurrence of two major separate introduction events for E. amylovora in Europe that occurred approximately 20 years apart, and confirmed the existence of two principal distribution areas located in Northeastern Europe and the Eastern Mediterranean Basin from which the pathogen moved on to colonize the Eurasian continent

RESISTANCE OF FRUIT CROPS VARIETIES TO PHYTOPATHOGENIC
 BACTERIA PSEUDOMONAS SYRINGAE PV. SYRINGAE

The resistance of cherry, sweet cherry and pear varieties to bacterial canker was analyzed by using the method of arti-&#x0D; ficial contamination of unripe fruits. Two resistance groups were highlighted among the six analyzed cherry varieties:&#x0D; Uyfehertosh Fürthosh variety exercised the highest degree of resistance and Turgenevka exercised the lowest degree. Three&#x0D; groups of resistance were identified among the ten studied varieties of sweet cherries; the cultivar Lyubava Donetskaya turned out to be the most resistant, Gascinets proved to be the most affected. Four groups of resistance were distinguished among analyzed 14 pear varieties. The most resistant was Vilia variety and Kudesnitsa variety turned out to be the most affected.&#x0D; None of the examined crops varieties appears to be immune to bacterial canker. After artificial contamination of apples fruits&#x0D; (Belorusskoe sladkoe, Kovalenkovskoe and Nadzejny varieties) symptoms of the disease did not appear.</jats:p

PLEIOTROPIC EFFECT OF MUTATION IN THE GENES INVOLVED&#x0D; IN THE BIOSYNTHESIS OF LIPOPOLYSACCHARIDES OF ERWINIA&#x0D; AMYLOVORA PHYTOPATHOGENIC BACTERIA

In this study, we constructed Erwinia amylovora deletion mutant by waaC, waaD, waaF, waaL, wabK and wabM genes, coding enzymes involved in the synthesis of lipopolysaccharides of the bacteria outer membrane, and investigated the phenotypic manifestation of the resulting mutation. It was demonstrated that the resulting mutant has an increased ability to autoaggregation and biofilms formation, but is characterized by the reduced mobility and levan exopolysaccharide production. In addition, the deletion of genes of lipopolysaccharides biosynthesis led to the loss of the mutant strain virulence. The data obtained indicate the most important role the lipopolysaccharide layer plays in the virulence of E. amylovora bacteria.</jats:p

Quorum Sensing and Metabolic State of the Host Control Lysogeny-Lysis Switch of Bacteriophage T1

The dynamics of microbial communities are heavily shaped by bacterium-bacteriophage interactions. But despite the apparent importance of bacteriophages, our understanding of the mechanisms controlling phage dynamics in bacterial populations, and particularly of the differences between the decisions that are made in the dormant lysogenic and active lytic states, remains limited. In this report, we show that enterobacterial phage T1, previously described as a lytic phage, is able to undergo lysogeny. We further demonstrate that the lysogeny-to-lysis decision occurs in response to changes in the density of the bacterial population, mediated by interspecies quorum-sensing signal AI-2, and in the metabolic state of the cell, mediated by cAMP receptor protein. We hypothesize that this strategy enables the phage to maximize its chances of self-amplification and spreading in bacterial population upon induction of the lytic cycle and that it might be common in phage-host interactions.</jats:p

Quorum Sensing and Metabolic State of the Host Control Lysogeny-Lysis Switch of Bacteriophage T1

The dynamics of microbial communities are heavily shaped by bacterium-bacteriophage interactions. But despite the apparent importance of bacteriophages, our understanding of the mechanisms controlling phage dynamics in bacterial populations, and particularly of the differences between the decisions that are made in the dormant lysogenic and active lytic states, remains limited. In this report, we show that enterobacterial phage T1, previously described as a lytic phage, is able to undergo lysogeny. We further demonstrate that the lysogeny-to-lysis decision occurs in response to changes in the density of the bacterial population, mediated by interspecies quorum-sensing signal AI-2, and in the metabolic state of the cell, mediated by cAMP receptor protein. We hypothesize that this strategy enables the phage to maximize its chances of self-amplification and spreading in bacterial population upon induction of the lytic cycle and that it might be common in phage-host interactions.Bacterial viruses, or bacteriophages, are highly abundant in the biosphere and have a major impact on microbial populations. Many examples of phage interactions with their hosts, including establishment of dormant lysogenic and active lytic states, have been characterized at the level of the individual cell. However, much less is known about the dependence of these interactions on host metabolism and signal exchange within bacterial communities. In this report, we describe a lysogenic state of the enterobacterial phage T1, previously known as a classical lytic phage, and characterize the underlying regulatory circuitry. We show that the transition from lysogeny to lysis depends on bacterial population density, perceived via interspecies autoinducer 2. Lysis is further controlled by the metabolic state of the cell, mediated by the cyclic-3′,5′-AMP (cAMP) receptor protein (CRP) of the host. We hypothesize that such combinations of cell density and metabolic sensing may be common in phage-host interactions