SummaryFor possible control of fire blight affecting apple and pear trees, we characterized Erwinia amylovora phages from North America and Germany. The genome size determined by electron microscopy (EM) was confirmed by sequence data and major coat proteins were identified from gel bands by mass spectroscopy. By their morphology from EM data, φEa1h and φEa100 were assigned to the Podoviridae and φEa104 and φEa116 to the Myoviridae. Host ranges were essentially confined to E. amylovora, strains of the species Erwinia pyrifoliae, E. billingiae and even Pantoea stewartii were partially sensitive. The phages φEa1h and φEa100 were dependent on the amylovoran capsule of E. amylovora, φEa104 and φEa116 were not. The Myoviridae efficiently lysed their hosts and protected apple flowers significantly better than the Podoviridae against E. amylovora and should be preferred in biocontrol experiments. We have also isolated and partially characterized E. amylovora phages from apple orchards in Germany. They belong to the Podoviridae or Myoviridae with a host range similar to the phages isolated in North America. In EM measurements, the genome sizes of the Podoviridae were smaller than the genomes of the Myoviridae from North America and from Germany, which differed from each other in corresponding nucleotide sequences.

Fire blight, a plant disease of economic importance caused by Erwinia amylovora, may be controlled by the application of bacteriophages. Here, we provide the complete genome sequences and the annotation of three E. amylovora-specific phages isolated in North America and genomic information about a bacteriophage induced by mitomycin C treatment of an Erwinia tasmaniensis strain that is antagonistic for E. amylovora. The American phages resemble two already-described viral genomes, whereas the E. tasmaniensis phage displays a singular genomic sequence in BLAST searches.Several Erwinia amylovora phages from North America have been partially characterized before by restriction digests and proposed for control of fire blight (5). We determined the genomes of Ea1h, Ea100, and Ea104 by shotgun sequencing on ABI3730XL capillary sequencers (3) and by primer walking. The shotgun sequences were assembled with PHRAP and edited with Consed, GAP4, and Clonemanager 5. Open reading frames (ORFs) were predicted with GLIMMER3. Partial sequences were aligned with the sequence of phage Era103 (GenBank/EMBL/DDB accession number EF160123) for Ea1h and Ea100 and the sequence of phage Ea21-4 (accession number EU710883) for Ea104, and gaps were filled by sequencing PCR fragments.The genomes of Ea1h and Ea100, members of the Podoviridae, have almost identical sizes of 45,522 bp and 45,554 bp, respectively, and average GC contents of 49.7%. They differed in six base pairs and a 32-bp repeat for Ea100.Annotation revealed 50 major ORFs and a putative function for 27 genes, including genes coding for an extracellular polysaccharide (EPS) depolymerase and HNH endonucleases and genes associated with DNA replication, but no tRNA genes.The highly related genomes of Ea1h/Ea100 and Era103 diverged in 10 genes and a degenerated terminal repeat of 277 bp. Another peculiarity is a split gene for DNA polymerase and the associated 5Ј-3Ј exonuclease.The phages Ea1h and Ea100 may use direct repeats in their genomes for replication as concatemers, similar to E. coli phage T7 (2). A 54-mer is repeated twice and is present in both genomes.Phage Ea104 belongs to the Myoviridae and has a genome length of 84,565 bp with 43.9% GC content. One hundred eighteen ORFs were identified with similarity to ORFs in Ea21-4. Morphogenesis-related proteins were predicted for 10 genes, and an endolysin and a holin gene were identified. Ea104 carries genes involved in nucleotide metabolism but no EPS depolymerase. A cluster of 24 tRNAs was detected for Ea104, similar to phage Ea21-4 (4), with 23 genes coding for standard tRNAs without pseudogenes. For Ea104, a circularly permutated linear genome is assumed.Comparison of Ea104 with Ea21-4 revealed 98% identity for their genomes of 84,565 and 84,576 bp, respectively. Regions with high levels of mismatch but Ͼ97% protein identity were noted for genes encoding RIIA, a hypothetical protein, and DNA polymerase. BLAST search revealed

The harlequin ladybird Harmonia axyridis (Coleoptera: Coccinellidae) is a polyphagous predatory beetle native to Central and Eastern Asia. Since 2007 it has established all over Central Europe. In order to elucidate which defense strategy is responsible for its high resistance to diseases, we tested hemolymph as well as eleven main components of the headspace of H. axyridis for antimicrobial activity against Gram-positive (Bacillus subtilis, B. thuringiensis ssp. tenebrionis, Micrococcus luteus) and Gram-negative bacteria (Escherichia coli) and yeast (Saccharomyces cerevisiae). While three of the volatile compounds weakly reduced the growth of microorganisms, hemolymph of adults and larvae of H. axyridis strongly inhibited the growth of Gram-positive and Gram-negative bacteria as well as yeast. Furthermore, we compared the antimicrobial activity in the hemolymph of H. axyridis and Coccinella septempunctata. Antimicrobial activity in H. axyridis was about a thousand times higher compared to hemolymph from C. septempunctata. In contrast to C. septempunctata, the antimicrobial activity in H. axyridis was present without prior challenge. Minimal inhibitory concentration (MIC) of the hemolymph of H. axyridis was lowest against E. coli and yeast followed by B. subtilis, and was highest against entomopathogenic B. thuringiensis ssp. tenebrionidae. Furthermore, MIC values of the hemolymph obtained from live beetles were significantly lower than from frozen insects. This suggests that the active antimicrobial compound is affected by freezing and subsequent thawing of the beetles. Potential implications of our findings for the competitive advantages of H. axyridis over C. septempunctata are discussed.

No abstract

No abstract