Olive fruit fly rearing procedures affect the vertical transmission of the bacterial symbiont Candidatus Erwinia dacicola

BACKGROUND

The symbiosis between the olive fruit fly, Bactrocera oleae, and Candidatus Erwinia dacicola has been demonstrated as essential for the fly's larval development and adult physiology. The mass rearing of the olive fruit fly has been hindered by several issues, including problems which could be related to the lack of the symbiont, presumably due to preservatives and antibiotics currently used during rearing under laboratory conditions. To better understand the mechanisms underlying symbiont removal or loss during the rearing of lab colonies of the olive fruit fly, we performed experiments that focused on bacterial transfer from wild female flies to their eggs. In this research, eggs laid by wild females were treated with propionic acid solution, which is often used as an antifungal agent, a mixture of sodium hypochlorite and Triton X, or water (as a control). The presence of the bacterial symbiont on eggs was evaluated by real-time PCR and scanning electron microscopy.

RESULTS

DGGE analysis showed a clear band with the same migration behavior present in all DGGE profiles but with a decreasing intensity. Molecular analyses performed by real-time PCR showed a significant reduction in Ca. E. dacicola abundance in eggs treated with propionic acid solution or a mixture of sodium hypochlorite and Triton X compared to those treated with water. In addition, the removal of bacteria from the surfaces of treated eggs was highlighted by scanning electron microscopy.

CONCLUSIONS

The results clearly indicate how the first phases of the colony-establishment process are important in maintaining the symbiont load in laboratory populations and suggest that the use of products with antimicrobial activity should be avoided. The results also suggest that alternative rearing procedures for the olive fruit fly should be investigated.

Horizontal transfer and finalization of a reliable detection method for the olive fruit fly endosymbiont, Candidatus Erwinia dacicola

BACKGROUND

The olive fly, Bactrocera oleae, is the most important insect pest in olive production, causing economic damage to olive crops worldwide. In addition to extensive research on B. oleae control methods, scientists have devoted much effort in the last century to understanding olive fly endosymbiosis with a bacterium eventually identified as Candidatus Erwinia dacicola. This bacterium plays a relevant role in olive fly fitness. It is vertically transmitted, and it benefits both larvae and adults in wild populations; however, the endosymbiont is not present in lab colonies, probably due to the antibiotics and preservatives required for the preparation of artificial diets. Endosymbiont transfer from wild B. oleae populations to laboratory-reared ones allows olive fly mass-rearing, thus producing more competitive flies for future Sterile Insect Technique (SIT) applications.

RESULTS

We tested the hypothesis that Ca. E. dacicola might be transmitted from wild, naturally symbiotic adults to laboratory-reared flies. Several trials have been performed with different contamination sources of Ca. E. dacicola, such as ripe olives and gelled water contaminated by wild flies, wax domes containing eggs laid by wild females, cages dirtied by faeces dropped by wild flies and matings between lab and wild adults. PCR-DGGE, performed with the primer set 63F-GC/518R, demonstrated that the transfer of the endosymbiont from wild flies to lab-reared ones occurred only in the case of cohabitation.

CONCLUSIONS

Cohabitation of symbiotic wild flies and non-symbiotic lab flies allows the transfer of Ca. E. dacicola through adults. Moreover, PCR-DGGE performed with the primer set 63F-GC/518R was shown to be a consistent method for screening Ca. E. dacicola, also showing the potential to distinguish between the two haplotypes (htA and htB). This study represents the first successful attempt at horizontal transfer of Ca. E. dacicola and the first step in acquiring a better understanding of the endosymbiont physiology and its relationship with the olive fly. Our research also represents a starting point for the development of a laboratory symbiotic olive fly colony, improving perspectives for future applications of the Sterile Insect Technique.

Erwinia billingiae as Unusual Cause of Septic Arthritis, France, 2017

In 2017 in France, we treated a patient with knee septic arthritis caused by Erwinia billingiae after trauma involving a palm tree. This rare pathogen could only be identified through 16S rRNA gene sequencing. For bacterial infections after injuries with plants, 16S rRNA gene sequencing might be required for species identification.

Development of a real-time PCR method for the specific detection of the novel pear pathogen Erwinia uzenensis

Erwinia uzenensis is a plant-pathogenic bacterium, recently described in Japan, which infects pear trees, causing the ‘bacterial black shoot disease of European pear’ (BBSDP). Like other Erwinia pear pathogens, E. uzenensis causes damp, black lesions on young shoots resembling those of E. amylovora, but not blossom blight, fruitlet blight or wilting of the shoot tip. The distribution of E. uzenensis seems restricted to the country where it was reported up to now, but it may spread to other countries and affect new hosts, as is the current situation with E. piriflorinigrans and E. pyrifoliae. Fast and accurate detection systems for this new pathogen are needed to study its biology and to identify it on pear or other hosts. We report here the development of a specific and sensitive detection protocol based on a real-time PCR with a TaqMan probe for E. uzenensis, and its evaluation. In sensitivity assays, the detection threshold of this protocol was 10¹ cfu ml^-1 on pure bacterial cultures and 10²–10³ cfu ml^-1 on spiked plant material. The specificity of the protocol was evaluated against E. uzenensis and 46 strains of pear-associated Erwinia species different to E. uzenensis. No cross-reaction with the non-target bacterial species or the loss of sensitivity were observed. This specific and sensitive diagnostic tool may reveal a wider distribution and host range of E. uzenensis initially considered restricted to a region and will expand our knowledge of the life cycle and environmental preferences of this pathogen.

An Introduced Crop Plant Is Driving Diversification of the Virulent Bacterial Pathogen Erwinia tracheiphila

Erwinia tracheiphila is the causal agent of bacterial wilt of cucurbits, an economically important phytopathogen affecting an economically important phytopathogen affecting few cultivated Cucurbitaceae few cultivated Cucurbitaceae host plant species in temperate eastern North America. However, essentially nothing is known about E. tracheiphila population structure or genetic diversity. To address this shortcoming, a representative collection of 88 E. tracheiphila isolates was gathered from throughout its geographic range, and their genomes were sequenced. Phylogenomic analysis revealed three genetic clusters with distinct hrpT3SS virulence gene repertoires, host plant association patterns, and geographic distributions. Low genetic heterogeneity within each cluster suggests a recent population bottleneck followed by population expansion. We showed that in the field and greenhouse, cucumber (Cucumis sativus), which was introduced to North America by early Spanish conquistadors, is the most susceptible host plant species and the only species susceptible to isolates from all three lineages. The establishment of large agricultural populations of highly susceptible C. sativus in temperate eastern North America may have facilitated the original emergence of E. tracheiphila into cucurbit agroecosystems, and this introduced plant species may now be acting as a highly susceptible reservoir host. Our findings have broad implications for agricultural sustainability by drawing attention to how worldwide crop plant movement, agricultural intensification, and locally unique environments may affect the emergence, evolution, and epidemic persistence of virulent microbial pathogens.IMPORTANCEErwinia tracheiphila is a virulent phytopathogen that infects two genera of cucurbit crop plants, Cucurbita spp. (pumpkin and squash) and Cucumis spp. (muskmelon and cucumber). One of the unusual ecological traits of this pathogen is that it is limited to temperate eastern North America. Here, we complete the first large-scale sequencing of an E. tracheiphila isolate collection. From phylogenomic, comparative genomic, and empirical analyses, we find that introduced Cucumis spp. crop plants are driving the diversification of E. tracheiphila into multiple lineages. Together, the results from this study show that locally unique biotic (plant population) and abiotic (climate) conditions can drive the evolutionary trajectories of locally endemic pathogens in unexpected ways.

A High Salt Diet Modulates the Gut Microbiota and Short Chain Fatty Acids Production in a Salt-Sensitive Hypertension Rat Model

Emerging data indicate a correlation between gut microbial composition and cardiovascular disease including hypertension. The host's diet greatly affects microbial composition and metabolite production. Short chain fatty acids (SCFAs) are products of microbial fermentation, which can be utilized by the host. It has been suggested that SCFAs play a pivotal role as mediators in a microbiome host: microbial interactions occur in health and disease. The aim of this study was to evaluate the effect of a high salt diet (HSD) on microbial variation and to determine whether this effect is accompanied by an alteration in fecal SCFAs. To this end, Dahl salt-sensitive rats were divided into two groups (n = 10 each): (A) Control: fed regular chow; and (B) Fed HSD. High-throughput pyrosequencing of the 16S rRNA amplicon sequencing was used for microbiome characterizing. Chromatography-mass spectrometry was used to measure the levels of SCFAs: acetic acid, propionic acid, butyric acid, and isobutyric acid in fecal samples. Differences in microbial composition were noted between groups. Principal Coordinate Analysis (PCoA) principal coordinate 1 (PC1) primarily separated controls from the HSD. Four taxa displayed significant differences between HSD and controls. Taxa from the Erwinia genus, the Christensenellaceae and Corynebacteriaceae families, displayed an increased abundance in HSD versus control. In contrast, taxa from the Anaerostipes genus displayed a decreased abundance in HSD. We were able to identify seven unique taxa that were significantly associated with blood pressure. There was a significant difference in fecal acetic acid, as well as propionic and isobutyric acid, but not in the butyric acid composition between groups. Adding salt to a diet impacts the gut's microbial composition, which may alter fecal SCFA production.

Erwinia teleogrylli sp. nov., a Bacterial Isolate Associated with a Chinese Cricket

A bacterial isolate (SCU-B244^T) was obtained in China from crickets (Teleogryllus occipitalis) living in cropland deserted for approximately 10 years. The isolated bacteria were Gram-negative, facultatively anaerobic, oxidase-negative rods. A preliminary analysis of the 16S rRNA gene sequence indicated that the strain belongs to either the genus Erwinia or Pantoea. Analysis of multilocus sequence typing based on concatenated partial atpD, gyrB and infB gene sequences and physiological and biochemical characteristics indicated that the strain belonged to the genus Erwinia, as member of a new species as it was distinct from other known Erwinia species. Further analysis of the 16S rRNA gene showed SCU-B244^T to have 94.71% identity to the closest species of that genus, Erwinia oleae (DSM 23398^T), which is below the threshold of 97% used to discriminate bacterial species. DNA-DNA hybridization results (5.78±2.52%) between SCU-B244^T and Erwinia oleae (DSM 23398^T) confirmed that SCU-B244^T and Erwinia oleae (DSM 23398^T) represent different species combined with average nucleotide identity values which range from 72.42% to 74.41. The DNA G+C content of SCU-B244^T was 55.32 mol%, which also differs from that of Erwinia oleae (54.7 to 54.9 mol%). The polyphasic taxonomic approach used here confirmed that the strain belongs to the Erwinia group and represents a novel species. The name Erwinia teleogrylli sp. nov. is proposed for this novel taxon, for which the type strain is SCU-B244^T (= CGMCC 1.12772^T = DSM 28222^T = KCTC 42022^T).

Bacterial communities associated with host-adapted populations of pea aphids revealed by deep sequencing of 16S ribosomal DNA

Associations between microbes and animals are ubiquitous and hosts may benefit from harbouring microbial communities through improved resource exploitation or resistance to environmental stress. The pea aphid, Acyrthosiphon pisum, is the host of heritable bacterial symbionts, including the obligate endosymbiont Buchnera aphidicola and several facultative symbionts. While obligate symbionts supply aphids with key nutrients, facultative symbionts influence their hosts in many ways such as protection against natural enemies, heat tolerance, color change and reproduction alteration. The pea aphid also encompasses multiple plant-specialized biotypes, each adapted to one or a few legume species. Facultative symbiont communities differ strongly between biotypes, although bacterial involvement in plant specialization is uncertain. Here, we analyse the diversity of bacterial communities associated with nine biotypes of the pea aphid complex using amplicon pyrosequencing of 16S rRNA genes. Combined clustering and phylogenetic analyses of 16S sequences allowed identifying 21 bacterial OTUs (Operational Taxonomic Unit). More than 98% of the sequencing reads were assigned to known pea aphid symbionts. The presence of Wolbachia was confirmed in A. pisum while Erwinia and Pantoea, two gut associates, were detected in multiple samples. The diversity of bacterial communities harboured by pea aphid biotypes was very low, ranging from 3 to 11 OTUs across samples. Bacterial communities differed more between than within biotypes but this difference did not correlate with the genetic divergence between biotypes. Altogether, these results confirm that the aphid microbiota is dominated by a few heritable symbionts and that plant specialization is an important structuring factor of bacterial communities associated with the pea aphid complex. However, since we examined the microbiota of aphid samples kept a few generations in controlled conditions, it may be that bacterial diversity was underestimated due to the possible loss of environmental or transient taxa.

Surface survival and internalization of salmonella through natural cracks on developing cantaloupe fruits, alone or in the presence of the melon wilt pathogen Erwinia tracheiphila

Outbreaks of foodborne illness attributed to the consumption of Salmonella-tainted cantaloupe have occurred repeatedly, but understanding of the ecology of Salmonella on cantaloupe fruit surfaces is limited. We investigated the interactions between Salmonella enterica Poona, the plant pathogenic bacterium Erwinia tracheiphila, and cantaloupe fruit. Fruit surfaces were inoculated at the natural cracking stage by spreading S. enterica and E. tracheiphila, 20 µl at 107 cfu/ml, independently or together, over a 2×2 cm rind area containing a crack. Microbial and microscopic analyses were performed at 0, 9 and 24 days post inoculation (DPI). Even at 24 DPI (fruit maturity) S. enterica was detected on 14% and 40% of the fruit inoculated with S. enterica alone and the two-pathogen mixture, respectively. However, the population of S. enterica declined gradually after initial inoculation. E. tracheiphila, inoculated alone or together with Salmonella, caused watersoaked lesions on cantaloupe fruit; but we could not conclude in this study that S. enterica survival on the fruit surface was enhanced by the presence of those lesions. Of fruit inoculated with E. tracheiphila alone and sampled at 24 DPI, 61% had watersoaked lesions on the surface. In nearly half of those symptomatic fruits the watersoaking extended into the sub-rind mesocarp, and E. tracheiphila was recovered from that tissue in 50% of the symptomatic fruit. In this work, E. tracheiphila internalized through natural cracks on developing fruits. S. enterica was never detected in the fruit interior (ca. 2-3 mm below rind surface) under the limited conditions of our experiments, but the possibility that it, or other human pathogens that contaminate fresh produce, might also do so should be investigated under a wider range of conditions and produce types.

Dynamics of short- and long-term association between a bacterial plant pathogen and its arthropod vector

The dynamics of association between pathogens and vectors can strongly influence epidemiology. It has been proposed that wilt disease epidemics in cucurbit populations are sustained by persistent colonization of beetle vectors (Acalymma vittatum) by the bacterial phytopathogen Erwinia tracheiphila. We developed a qPCR method to quantify E. tracheiphila in whole beetles and frass and used it to assess pathogen acquisition and retention following variable exposure to infected plants. We found that (i) E. tracheiphila is present in frass in as little as three hours after feeding on infected plants and can be transmitted with no incubation period by vectors given brief exposure to infected plants, but also by persistently colonized vectors several weeks following exposure; (ii) duration of exposure influences rates of long-term colonization; (iii) frass infectivity (assessed via inoculation experiments) reflects bacterial levels in frass samples across time; and (iv) vectors rarely clear E. tracheiphila infections, but suffer no apparent loss of fitness. These results describe a pattern conducive to the effective maintenance of E. tracheiphila within cucurbit populations.

Genetic and virulence variability among Erwinia tracheiphila strains recovered from different cucurbit hosts

The causal agent of cucurbit bacterial wilt, Erwinia tracheiphila, has a wide host range in the family Cucurbitaceae, including economically important crops such as muskmelon (Cucumis melo), cucumber (C. sativus), and squash (Cucurbita spp.). Genetic variability of 69 E. tracheiphila strains was investigated by repetitive-element polymerase chain reaction (rep-PCR) using BOXA1R and ERIC1-2 primers. Fingerprint profiles revealed significant variability associated with crop host; strains isolated from Cucumis spp. were clearly distinguishable from Cucurbita spp.-isolated strains regardless of geographic origin. Twelve E. tracheiphila strains isolated from muskmelon, cucumber, or summer squash were inoculated onto muskmelon and summer squash seedlings, followed by incubation in a growth chamber. Wilt symptoms were assessed over 3 weeks, strains were reisolated, and rep-PCR profiles were compared with the inoculated strains. Wilting occurred significantly faster when seedlings were inoculated with strains that originated from the same crop host genus (P<0.001). In the first run of the experiment, cucumber and muskmelon strains caused wilting on muskmelon seedlings at a median of 7.8 and 5.6 days after inoculation (dai), respectively. Summer squash seedlings wilted 18.0, 15.7, and 5.7 dai when inoculated with muskmelon-, cucumber-, and squash-origin strains, respectively. In a second run of the experiment, cucumber and muskmelon strains caused wilting on muskmelon at 7.0 and 6.9 dai, respectively, whereas summer squash seedlings wilted at 23.6, 29.0 and 9.0 dai when inoculated with muskmelon-, cucumber-, and squash-origin strains, respectively. Our results provide the first evidence of genetic diversity within E. tracheiphila and suggest that strain specificity is associated with plant host. This advance is a first step toward understanding the genetic and population structure of E. tracheiphila.

Arsenic mobilization by epilithic bacterial communities associated with volcanic rocks from Camarones River, Atacama Desert, northern Chile

The arsenic biogeochemical cycle is greatly dependent on microbial transformations that affect both the distribution and mobility of arsenic species in the environment. In this study, a microbial biofilm from volcanic rocks was characterized on the basis of its bacterial composition and ability to mobilize arsenic under circumneutral pH. Biofilm microstructure was analyzed by scanning electron microscopy (SEM)-energy-dispersive spectroscopy (EDS). Strains were isolated from biofilms and identified by 16S rDNA sequences analysis. Arsenic oxidation and reduction capacity was assayed with high-performance liquid chromatography coupled to gaseous formation performing the detection by atomic absortion in a quartz bucket (HPLC/HG/QAAS), and polymerase chain reaction was used to detect aox and ars genes. Bacterial communities associated with volcanic rocks were studied by denaturing gradient gel electrophoresis (DGGE). The SEM-EDS studies showed the presence of biofilm after 45 days of incubation. The relative closest GenBank matches of the DNA sequences, of isolated arsenic-resistant strains, showed the existence of four different genus: Burkholderia, Pseudomonas, Erwinia, and Pantoea. Four arsenite-resistant strains were isolates, and only three strains were able to oxidize >97% of the As(III) present (500 uM). All arsenate-resistant isolates were able to reduce between 69 and 86% of total As(V) (1000 uM). Analysis of 16S rDNA sequences obtained by DGGE showed the presence of four bacterial groups (∝-proteobacteria, γ-proteobacteria, Firmicutes, and Actinobacteria). Experiments demonstrate that epilithic bacterial communities play a key role in the mobilization of arsenic and metalloids speciation.

[Differential medium for selection of bacterial L-asparaginase producer strains]

A specific, fast, and easy method for revelation of active plate producers of L-asparaginase using differential medium on the basis of LB or M9 with 1.5% agar was developed. Each 100 ml of LB or M9 medium additionally contained 6-7 ml ofglycerol, 4 g of L-asparagine, 0.2 g of CaCO3, and diagnostic components: 3 ml of 0.2 M CuSO4 x 5H2O and 2.5 ml of 0.1 M K3Fe(CN)6, pH 7.6-7.8. The results were counted 12-20 or 24-48 h after strain growth at 37 degrees C in corresponding mediums. Red color of colonies and colored zone around them showed the ability of the strain under study to destroy asparaginic complexes. The recommended method allows revealing bacterial strains producing L-asparaginase with specific activity of not less than 0.1-3.0 MU/mg of protein.

Erwinia mallotivora sp., a new pathogen of papaya (Carica papaya) in Peninsular Malaysia

Erwinia mallotivora was isolated from papaya infected with dieback disease showing the typical symptoms of greasy, water-soaked lesions and spots on leaves. Phylogenetic analysis of 16S rRNA gene sequences showed that the strain belonged to the genus Erwinia and was united in a monophyletic group with E. mallotivora DSM 4565 (AJ233414). Earlier studies had indicated that the causal agent for this disease was E. papayae. However, our current studies, through Koch’s postulate, have confirmed that papaya dieback disease is caused by E. mallotivora. To our knowledge, this is the first new discovery of E. mallotivora as a causal agent of papaya dieback disease in Peninsular Malaysia. Previous reports have suggested that E. mallotivora causes leaf spot in Mallotus japonicus. However, this research confirms it also to be pathogenic to Carica papaya.

Insect frass as a pathway for transmission of bacterial wilt of cucurbits

Insects that vector diseases of plants are of critical concern to agriculture, but relationships between the vectors and pathogens often are poorly understood. In this study, we present research on vector relationships between the striped cucumber beetle, Acalymma vittatum (F.) (Coleoptera: Chrysomelidae), and the pathogen that causes bacterial wilt of cucurbits, Erwinia tracheiphila (Smith) (Enterobacteriales: Enterobacteriaceae). We studied how the bacteria were retained in the gut of the beetle by developing a polymerase chain reaction (PCR)-based technique for extracting and identifying bacterial DNA in the frass. Bacterial DNA usually was present in the frass for 24 h after beetles had consumed inoculum but diminished quickly and was undetectable within 96 h. The amount of time that bacterial DNA could be detected in frass increased with the amount of inoculum and the length of time that beetles were exposed to inoculum and also varied with the strain of bacterium. Frass that tested positive for bacterial DNA also was infective to cucumber plants, confirming that DNA was indicative of viable bacteria and that frass could be a pathway for transmission of the pathogen. This research suggests that few cucumber beetles serve as long-term vectors of the pathogen and that aggregation of the beetle on host plants may be critical for initiating plant infections in spring.

Hypersensitive response and acyl-homoserine lactone production of the fire blight antagonists Erwinia tasmaniensis and Erwinia billingiae

Fire blight caused by the Gram-negative bacterium Erwinia amylovora can be controlled by antagonistic microorganisms. We characterized epiphytic bacteria isolated from healthy apple and pear trees in Australia, named Erwinia tasmaniensis, and the epiphytic bacterium Erwinia billingiae from England for physiological properties, interaction with plants and interference with growth of E. amylovora. They reduced symptom formation by the fire blight pathogen on immature pears and the colonization of apple flowers. In contrast to E. billingiae, E. tasmaniensis strains induced a hypersensitive response in tobacco leaves and synthesized levan in the presence of sucrose. With consensus primers deduced from lsc as well as hrpL, hrcC and hrcR of the hrp region of E. amylovora and of related bacteria, these genes were successfully amplified from E. tasmaniensis DNA and alignment of the encoded proteins to other Erwinia species supported a role for environmental fitness of the epiphytic bacterium. Unlike E. tasmaniensis, the epiphytic bacterium E. billingiae produced an acyl-homoserine lactone for bacterial cell-to-cell communication. Their competition with the growth of E. amylovora may be involved in controlling fire blight.

[Isolation and identification of a novel phosphate-dissolving strain P21]

Phosphate-dissolving microorganisms can be applied for better use of insoluble phosphorus as fertilizer., A phosphate-dissolving strain P21 was isolated from soil samples in China. The isolate was identified as Erwinia herbicola var. ananas, based on its 16Sr DNA sequence and physiological characteristics. Its activity was measured in solid media as well as liquid media using different phosphate sources including tricalium phosphate, hydroxyapatite, ferric phosphate, aluminium phosphate, zinc phosphate, and rock phosphates. E. herbicola could strongly dissolve 1206.20 mg tricalium phosphate and 529.67 mg hydroxyapatite in per liter liquid media. The strain showed high phosphate-dissolving ability for rock phosphates from Jinning and Kunyang in Yunnan province, Yaan in Sichuan province and Jinping in Jiangsu province with the capacity of 6.64 mg, 78.46 mg, 67.07 mg and 65.24 mg soluble phosphate respectively per liter medium, whereas the phosphate-dissolving ability to the rest of the eight rock phosphates was weak. According to the experiments, the phosphate-dissolving ability of E. herbicola was specific to different rock phosphates, and phosphate-dissolving ability of E. herbicola was not directly related to pH reduction of liquid media.

Evaluation of two surface sampling methods for detection of Erwinia herbicola on a variety of materials by culture and quantitative PCR

This research was designed to evaluate surface sampling protocols for use with culture and quantitative PCR (QPCR) amplification assay for detection of the gram-negative bacterial biothreat simulant Erwinia herbicola on a variety of surface materials. Surfaces selected for evaluation were wood laminate, glass and computer monitor screens, metal file cabinets, plastic arena seats, nylon seat cushions, finished concrete flooring, and vinyl tile flooring. Laboratory and test chamber studies were performed to evaluate two sampling methods, a sponge and a macrofoam swab, for detection of E. herbicola on surface materials. In laboratory trials, seven materials were inoculated with a known concentration of E. herbicola cells and samples were collected from the surfaces of the materials to determine sampling efficiencies. Culture analysis was ineffective for assessing E. herbicola collection efficiency because very few culturable cells were obtained from surface samples. QPCR demonstrated that E. herbicola DNA was present in high concentrations on all of the surface samples, and sampling efficiencies ranged from 0.7 to 52.2%, depending on the sampling method and the surface material. The swab was generally more efficient than the sponge for collection of E. herbicola from surfaces. Test chamber trials were also performed in which E. herbicola was aerosolized into the chamber and allowed to settle onto test materials. Surface sampling results supported those obtained in laboratory trials. The results of this study demonstrate the capabilities of QPCR to enhance the detection and enumeration of biocontaminants on surface materials and provide information on the comparability of sampling methods.

Erwinia tasmaniensis sp. nov., a non-phytopathogenic bacterium from apple and pear trees

Bacteria were isolated from flowers and bark of apple and pear trees at three places in Australia. In Victoria, Tasmania and Queensland, strains with white colonies on nutrient agar were screened for dome-shaped colony morphology on agar with sucrose and were found to be closely related by several criteria. The isolates were not pathogenic on apples or pears. They were characterized by a polyphasic approach including microbiological and API assays as well as fatty acid methyl ester analysis, DNA-DNA hybridization and DNA sequencing. For molecular classification, the 16S rRNA cistron and the conserved genes gpd and recA of these bacteria were investigated. Together with other taxonomic criteria, the results of these studies indicate that the bacteria belong to a novel separate species, which we propose to name Erwinia tasmaniensis sp. nov., with the type strain Et1/99(T) (=DSM 17950(T)=NCPPB 4357(T)). From DNA-DNA hybridization kinetics, microbiological characteristics and nucleotide sequence analyses, this species is related to pathogenic Erwinia species, but also to the epiphytic species Erwinia billingiae.

[Molecular identification and genetic diversity in Konnyaku's soft rot bacteria]

The soft rot bacteria Erwinia are an important pathogens of konnyaku and other ornamental plants. Thirty-three strains were isolated from soft-rotted konnyaku and other ornamental plants. According to the characteristics of pathogenicity and culture character on semi selective medium (crystal violet pectate, CVP), most of strains tested caused rotten symptom in tubers and stems of konnyaku, and characteristic deep cavities were formed on CVP. To amplify 16S-23S rDNA intergenic transcribed spacer( ITS) by PCR and electrophorese through agarose gel, most strains are clustered into two heterogeneous populations of Erwinia carotovora subsp. carotovora, E.c.c. and Erwinia chrysanthemi, E. ch.. Besides, several other strains could not be identified into species by ITS-PCR. The characteristic band patterns of E.c.c. and E.ch. could be clearly distinguished by repetitive element-polymerase chain reaction (rep-PCR,BOX and J3 primers). And the fingerprinting of E.c.c. stains were also different from each other. Dendrogram was generated from the data of primer BOX by using UPGMA analysis because the primer BOX was higher resolution than other primers (such as prime J3) for identifying the same intraspecies strains. Strains of E.c.c. were divided into five groups on the 0.1 level of linkage distance.

Erwinia toletana sp. nov., associated with Pseudomonas savastanoi-induced tree knots

Gram-negative bacteria were isolated from knots induced by Pseudomonas savastanoi in olive trees (Olea europaea L.). A total of nine endophytic bacterial strains were isolated, each from inside a different tree knot. Biochemical characterization indicated that all the strains belong to the family Enterobacteriaceae. Phylogenetic analyses of the 16S rRNA genes of these novel isolates revealed that they formed a homogeneous cluster within Erwinia species. DNA signatures of these isolates were identical to those described for the genus Erwinia. The strains formed a homogeneous group as shown by DNA-DNA hybridization analysis and numerical analysis of phenotypic data, clearly differentiated from all species of Erwinia with validly published names. The data provide strong evidence of the differentiation of these strains from the most closely related species. Therefore, these isolates represent a novel species, for which the name Erwinia toletana sp. nov. is proposed. The isolates are available at CFBP, CECT and ATCC. The G+C content is 52+/-0.5 mol%. The type strain is CFBP 6631(T) (=A37(T)=ATCC 700880(T)=CECT 5263(T)).

Erwinia papayae sp. nov., a pathogen of papaya (Carica papaya)

Bacterial canker of papaya (Carica papaya) emerged during the 1980s in different islands of the Caribbean. Nineteen strains of Gram-negative, rod-shaped, non-spore-forming bacteria isolated from papaya were compared to 38 reference and type strains of phytopathogenic Enterobacteriaceae and related bacteria. Phylogenetic analysis of 16S rRNA gene sequences showed that the papaya strains belonged to the genus Erwinia. The DNA G+C content of strain CFBP 5189T, 52·5 mol%, is in the range of the genus Erwinia. The 19 papaya strains were all pathogenic to papaya and were differentiated clearly from type or reference strains of phytopathogenic enterobacteria and related bacteria by phenotypic tests. The papaya strains constituted a discrete DNA hybridization group, indicating that they belonged to a unique genomic species. Thus, strains pathogenic to papaya belong to a novel species for which the name Erwinia papayae sp. nov. is proposed, with the type strain CFBP 5189T (=NCPPB 4294T).

Genus- and Isolate-Specific Real-Time PCR Quantification of Erwinia on Leaf Surfaces of English Oaks ( Quercus robur L.)

In order to quantify pathogenic epiphytic bacteria on leaf surfaces of the important European forest tree Quercus robur without time-intensive cultivation and separation of microorganisms, methods were developed to selectively quantify DNA copy numbers of the genus Erwinia in DNA isolated from the leaf surface. By using the combination of the two different real-time PCR techniques SYBR-Green and TaqMan, methods were developed not only to allow quantification of the total DNA copy number of Erwinia on the oak leaf surface, but also to distinguish between two significantly different groups of Erwinia strains. In the present work, these techniques were successfully applied to quantify the copy number of the genus Erwinia and its subgroups compared with the total bacteria number in DNA samples extracted from the upper leaf surface of English oaks collected on the 4th of June 2001 (Julian day 155).

A handheld real time thermal cycler for bacterial pathogen detection

The handheld advanced nucleic acid analyzer (HANAA) is a portable real time thermal cycler unit that weighs under 1 kg and uses silicon and platinum-based thermalcycler units to conduct rapid heating and cooling of plastic reaction tubes. Two light emitting diodes (LED) provide greater than 1 mW of electrical power at wavelengths of 490 nm (blue) and 525 nm (green), allowing detection of the dyes FAM and JOE/TAMRA. Results are displayed in real time as bar graphs, and up to three, 4-sample assays can be run on the charge of the 12 V portable battery pack. The HANAA was evaluated for detection of defined Escherichia coli strains, and wild-type colonies isolated from stream water, using PCR for the lac Z and Tir genes. PCR reactions using SYBR Green dye allowed detection of E. coli ATCC 11775 and E. coli O157:H7 cells in under 30 min of assay time; however, background fluorescence associated with dye binding to nonspecific PCR products was present. DNA extracted from three isolates of Bacillus anthracis Ames, linked to a bioterrorism incident in Washington DC in October 2001, were also successfully tested on the HANAA using primers for the vrrA and capA genes. Positive results were observed at 32 and 22 min of assay time, respectively. A TaqMan probe specific to the aroQ gene of Erwinia herbicola was tested on the HANAA and when 500 cells were used as template, positive results were observed after only 7 min of assay time. Background fluorescence associated with the use of the probe was negligible. The HANAA is unique in offering real time PCR in a handheld format suitable for field use; a commercial version of the instrument, offering six reaction chambers, is available as of Fall 2002.

Instability of short-sequence DNA repeats of pear pathogenic Erwinia strains from Japan and Erwinia amylovora fruit tree and raspberry strains

An array of short-sequence DNA repeats (SSRs) occurs in the plasmid pEA29 of the fire blight pathogen Erwinia amylovora. A large number of "fruit tree" strains, mainly from Central and Western Europe, were screened for their SSR numbers, and the analyses were extended to five raspberry strains from North America and six pear pathogenic Erwinia strains from Japan. The repeat ATTACAGA present in all E. amylovorastrains was found to be reiterated 3 to 15 times. The Japanese strains contained the major repeat sequence GGATTCTG, which was reiterated 16 to 24 times. ATTACAGG, which resembles the SSR of E. amylovora, was reiterated two or three times. In a novel approach, sequencing gels were used to visualize the rare occurrence of shorter arrays (down to three repeats) in E. amylovoraand the Japanese Erwinia strains. Changes in the repeat numbers in E. amylovora were observed repeatedly when the bacteria had been exposed to stress conditions. The repeat structures of homo- and heteroduplices of PCR-amplified repeats were also analyzed by cleavage of annealed molecules with the single-strand-specific endonuclease from bacteriophage T4. Not only heteroduplexes, but also homoduplexes showed non-matching regions in the SSRs, which could arise from transient formation of loops due to strand slippage during the assays.

[Isolation of endophytic bacteria in potato and test of antagonistic action to bacterial ring rot of potato]

In this study, two hundred and forty bacterial strains were isolated from inner tissue of potato tubers collected from DaTong, TaiYuan and Inner Mongolia Autonomous regions. On the basis of antagonistic examination in vitro, fifty and five bacteria strains were characterized for antagonistic bacteria to ring rot of potato. It was 22.9 percentage of all bacteria strains. The biggest radius of suppression circle was 13 mm. Nine strains were chosen for their suppression of bacterial ring rot, blackleg and dry rot of potato. These strains were bacteriologically ideatified. Strain 118 was Pseudomonas fluorescens biovar V. Strain 110 was Bacillus pumilus. Strain 085 was Bacillus stearothermophilus. Strain 069 was Erwinia herbicola. Strain 043 was Xanthomomas fragariae. Strain 116 was Curtobacterium. Strains A-10' and T3 were Bacillus. Strain H1-6 was Pseudomonas fluorescens.

[Isolation and screening of beneficial endophytic bacteria to control bacterial ring rot of potato]

One hundred and thirty-three bacterial strains were isolated from inner tissue of potato tubers collected from Datong, Taiyuan and Inner Mongolia Autonomous regions. On the basis of antagonistic examination in vitro, greenhouse and field tests, five strains named as 069, 085, 110, 116 and 118 were chosen for their suppression of bacterial ring rot or their growth promotion. Strain 118 is an endophytic bacterium with three effects of colonization, growth promotion and suppression of the pathogenic bacteria, showing good prospects for commercial use.

Molecular comparison of pathogenic bacteria from pear trees in Japan and the fire blight pathogen Erwinia amylovora

Several strains of the genus Erwinia, which were isolated in Japan from pear trees with necrotic symptoms that resembled fire blight, and tentatively identified as Erwinia amylovora, were reinvestigated for their relationship to the fire blight pathogen. These isolates produced ooze on slices of immature pears and were mucoid on MM2Cu agar plates, but did not synthesize levan and did not give the expected PCR signals with several primer pairs specific for Erwinia amylovora. The isolates tested positive with PCR primers designed to detect the novel pear pathogen Erwinia pyrifoliae, which was isolated from Nashi pear trees in South Korea. The nucleotide sequence analysis of a DNA fragment preceding the gene cluster for exopolysaccharide synthesis revealed a closer relationship to Erwinia pyrifoliae than to Erwinia amylovora. Plasmid profiles, protein patterns and genomic DNA analysed by PFGE after XbaI and SpeI digestion were different than Erwinia amylovora. Experiments with strains of Erwinia amylovora isolated from raspberry (Rubus sp.), Erwinia mallotivora and Enterobacter pyrinus also did not reveal a relationship between these bacteria and the Japanese Erwinia strains. The latter are not identical to Erwinia pyrifoliae, but possess many similar features to this pathogen that causes Asian pear blight. It is concluded that pathogenic bacteria isolated in Japan from pear trees with symptoms resembling fire blight are possibly different from Erwinia amylovora.

[Epiphytic phase of Erwinia amylovora and Pseudomonas syringae pv. syringae on orchard weeds]

Epiphyte phase of phytopathogenic bacteria Erwinia amylovora and Pseudomonas syringae pv. syringae on the fruit garden weeds has been studied. It has been shown that healthy weeds of the fruit-tree stands can be an ecologic niche for Erwinia amylovora and Pseudomonas syringae pv. syringae which gives them an opportunity to survive as epiphytes. Strains of Pseudomonas syringae pv. syringae were isolated from seven studied weeds (47-49%) during the whole vegetation period (March-October). Strains of Erwinia amylovora distributed on the leaves of Arctium lappa L., Amarantus reflexus L. and Tripleurospermum inodorum (L) Sch. Vir. in the period of the disease intensive development on the pear-tree (June-August). Cells of Erwinia amylovora were isolated from 12-14% of selected weeds.

Microbiological and biochemical study of coffee fermentation

The coffee fermentation microflora were rich and mainly constituted of aerobic Gram-negative bacilli, with Erwinia and Klebsiella genuses at the highest frequencies. The best population increase was observed with lactic acid bacteria and yeasts, whereas those microorganisms that counted on a pectin medium remained constant during the fermentation step. Qualitatively, lactic acid bacteria belonged mainly to Leuconostoc mesenteroides species but the others microflora were relatively heterogeneous. The microorganisms isolated on pectin medium were Enterobacteriaceae, identified as Erwinia herbicola and Klebsiella pneumoniae, not reported as strong pectolytic strains. Throughout coffee fermentation, 60% of the simple sugars were degraded by the total microflora and not specifically by pectolytic microorganisms.

Hospital infestation by the cluster fly, Pollenia rudis sensu stricto Fabricius 1794 (Diptera: Calliphoridae), and its possible role in transmission of bacterial pathogens in Germany

The potential of the cluster fly, Pollenia rudis sensu stricto, to transmit bacterial pathogens was investigated during a mass infestation that took place in a German hospital. Cluster flies were individually examined for mesophilic bacteria carried on the exoskeleton. Bacterial growth could only be detected by using the enrichment culture technique to increase sensitivity, but not by direct intoculation of fly samples to agar plates. All 50 cluster fly samples that were tested carried opportunistic aerobic mesophilic Bacillus spp., whereas 41 fly samples were positive for Erwinia spp., 16 samples for Erwinia amylovara, 24 samples for Stenotrophomonas maltophilia, and 4 samples for Flavobacterium odoratum. Staphylococcus lugdunensis and Pseudomonas aeruginosa were found in 5 samples. No bacteriologically sterile cluster fly samples were obtained. The whole bacterial pattern found on P. rudis s. s. is known for its potential to cause opportunistic and/or nosocomial infections in humans. The results obtained led to the assumption that mass infestations of cluster flies occurring in sensitive areas, especially in hospitals, may cause a low, but not neglectable health threat due to mechanical transmission of bacterial pathogens.

The use of 16S and 16S-23S rDNA to easily detect and differentiate common Gram-negative orchard epiphytes

The identification of Gram-negative pathogenic and non-pathogenic bacteria commonly isolated from an orchard phylloplane may result in a time consuming and tedious process for the plant pathologist. The paper provides a simple "one-step" protocol that uses the polymerase chain reaction (PCR) to amplify intergenic spacer regions between 16S and 23S genes and a portion of 16S gene in the prokaryotic rRNA genetic loci. Amplified 16S rDNA, and restriction fragment length polymorphisms (RFLP) following EcoRI digestion produced band patterns that readily distinguished between the plant pathogen Erwinia amylovora (causal agent of fire blight in pear and apple) and the orchard epiphyte Pantoea agglomerans (formerly E. herbicola). The amplified DNA patterns of 16S-23S spacer regions may be used to differentiate E. amylovora at the intraspecies level. Isolates of E. amylovora obtained from raspberries exhibited two major fragments while those obtained from apples showed three distinct amplified DNA bands. In addition, the size of the 16S-23S spacer region differs between Pseudomonas syringae and Pseudomonas fluorescens. The RFLP pattern generated by HaeIII digestion may be used to provide a rapid and accurate identification of these two common orchard epiphytes.

The association of Western flower thrips, Frankliniella occidentalis, with a near Erwinia species gut bacteria: transient or permanent?

Associations between insects and gut bacteria are ubiquitous. It is possible to make a distinction between permanent associations (called symbiosis), in which the same type of bacteria is present in more than one generation of the insect, and transient associations. Transient bacteria are ingested together with food but do not settle in the insect gut in such a way that they will be passed on to the next generation. In this study, we describe the permanent association between Western flower thrips (Frankliniella occidentalis), a polyphagous insect species that is a major pest worldwide, and one type of gut bacteria. On the basis of direct microscopic observations and counts of bacteria, it was found that thrips from the populations studied contained large numbers of bacteria in their hindgut. Bacteria were isolated from their host and grown on 10 different agar media. The number of bacteria isolated on agar media equaled the number of direct counts. All isolates had the same colony morphology. On the basis of their 16S rDNA sequence these bacteria were identified as Enterobacteriaceae, closely related to Escherichia coli. Isolates tested with API 20E biochemical tests were Erwinia species. This was the only type of bacteria found in all thrips individuals on any of the 10 different agar media. Universal primers, which would potentially pick up DNA from any bacterium present in the insect, were applied on crude DNA extracts from thrips with bacteria. We only found 16S rDNA sequences similar to those of the isolated thrips gut bacteria. The same type of bacteria was present in all life stages of the thrips and was found to persist in the thrips populations for at least 2 years (more than 50 generations).

Continuous concentration of bacteria in a microfluidic flow cell using electrokinetic techniques

A novel method for the concentration of bacterial solutions is presented that implements electrokinetic techniques, zone electrophoresis (ZE) and isoelectric focusing (IEF), in a microfluidic device. The method requires low power (< 3e-5 W) and can be performed continuously on a flowing stream. The device consists of two palladium electrodes held in a flow cell constructed from layers of polymeric film held together by a pressure-sensitive adhesive. Both ZE and IEF are performed with carrier-free solutions in devices in which the electrodes are in intimate contact with the sample fluid. IEF experiments were performed using natural pH gradients; no carrier ampholyte solution was required. Experiments performed in buffer alone resulted in significant electroosmotic flow. Pretreatment of the sample chamber with bleach followed by a concentrated solution of cationic detergent effectively suppressed electroosmotic flow.

Continuous concentration of bacteria in a microfluidic flow cell using electrokinetic techniques

A novel method for the concentration of bacterial solutions is presented that implements electrokinetic techniques, zone electrophoresis (ZE) and isoelectric focusing (IEF), in a microfluidic device. The method requires low power (< 3e-5 W) and can be performed continuously on a flowing stream. The device consists of two palladium electrodes held in a flow cell constructed from layers of polymeric film held together by a pressure-sensitive adhesive. Both ZE and IEF are performed with carrier-free solutions in devices in which the electrodes are in intimate contact with the sample fluid. IEF experiments were performed using natural pH gradients; no carrier ampholyte solution was required. Experiments performed in buffer alone resulted in significant electroosmotic flow. Pretreatment of the sample chamber with bleach followed by a concentrated solution of cationic detergent effectively suppressed electroosmotic flow.

Development of a highly sensitive nested-PCR procedure using a single closed tube for detection of Erwinia amylovora in asymptomatic plant material

A novel method, which involves a nested PCR in a single closed tube, was developed for the sensitive detection of Erwinia amylovora in plant material. The external and internal primer pairs used had different annealing temperatures and directed the amplification of a specific DNA fragment from plasmid pEA29. The procedure involved two consecutive PCRs, the first of which was performed at a higher annealing temperature that allowed amplification only by the external primer pair. Using pure cultures of E. amylovora, the sensitivity of the nested PCR in one tube was similar to that of a standard nested PCR in two tubes. The specificity and sensitivity were greater than those of standard PCR procedures that used a single primer pair. The presence of inhibitors in plant material, very common in E. amylovora hosts, is overcome with this system in combination with a simple DNA extraction protocol because it eliminates many of the inhibitory compounds. In addition, it needs a very small sample volume (1 microl of DNA extracted). With 83 samples of naturally infected material, this method achieved better results than any other PCR technique: standard PCR detected 55% of positive samples, two-tube nested PCR detected 71% of positive samples, and nested PCR in a single closed tube detected 78% of positive samples. When analyzing asymptomatic plant material, the number of positive samples detected by the developed nested PCR was also the highest, compared with the PCR protocols indicated previously (17, 20, and 25% of 251 samples analyzed, respectively). This method is proposed for the detection of endophytic and epiphytic populations of E. amylovora in epidemiological studies and for routine use in quarantine surveys, due to its high sensitivity, specificity, speed, and simplicity.

Erwinia pyrifoliae sp. nov., a novel pathogen that affects Asian pear trees (Pyrus pyrifolia Nakai)

A novel pathogen from Asian pears (Pyrus pyrifolia Nakai) was analysed by sequencing the 16S rDNA and the adjacent intergenic region, and the data were compared to related Enterobacteriaceae. The 16S rDNA of the Asian pear pathogen was almost identical with the sequence of Erwinia amylovora, in contrast to the 16S-23S rRNA intergenic transcribed spacer region of both species. A dendrogram was deduced from determined sequences of the spacer regions including those of several related species such as Erwinia amylovora, Enterobacter pyrinus, Pantoea stewartii subsp. stewartii and Escherichia coli. Dendrograms derived from 121 biochemical characteristics including Biotype 100 data placed the Asian pear pathogen close to Erwinia amylovora and more distantly to other members of the species Erwinia and to the species Pantoea and Enterobacter. Another DNA relatedness study was performed by DNA hybridizations and estimation of delta Tm values. The Asian pear strains constituted a tight DNA hybridization group (89-100%) and were barely related to strains of Erwinia amylovora (40-50%) with a delta Tm in the range of 5.2-6.8. The G + C content of DNA from the novel pathogen is 52 mol%. Therefore, it is proposed that strains isolated from Asian pears constitute a new species and the name Erwinia pyrifoliae is suggested; the type strain is strain Ep 16/96T (= CFBP 4172T = DSM 12163T).

Characterization and plasmid profile of an inhibitory strain of Erwinia herbicola isolated from Phaseolous vulgaris in Egypt

Erwinia herbicola strain 48 was isolated from diseased phaseolous seedlings and characterized by biochemical properties, cellular fatty acid analysis and SDS-PAGE of the soluble cell protein. Although cellular fatty acid profile and the soluble cellular protein pattern showed high degree of similarity in comparison to those from E. herbicola strain 347417, obtained from the International Mycological Institute U.K., plasmid profiles were different. Both strains harbor a 23.1 kb plasmid, in addition, E. herbicola 48 contains 2 more plasmids (26.8 and 32.5 kb). The antagonism of E. herbicola 48 against a number of Gram-negative and Gram-positive bacteria was tested in vitro. Only Gram-negative bacteria were inhibited, suggesting that the inhibitory factor is likely to be bacteriocin.

Phenotypic and phylogenetic characterization of ruminal tannin-tolerant bacteria

The 16S rRNA sequences and selected phenotypic characteristics were determined for six recently isolated bacteria that can tolerate high levels of hydrolyzable and condensed tannins. Bacteria were isolated from the ruminal contents of animals in different geographic locations, including Sardinian sheep (Ovis aries), Honduran and Colombian goats (Capra hircus), white-tail deer (Odocoileus virginianus) from upstate New York, and Rocky Mountain elk (Cervus elaphus nelsoni) from Oregon. Nearly complete sequences of the small-subunit rRNA genes, which were obtained by PCR amplification, cloning, and sequencing, were used for phylogenetic characterization. Comparisons of the 16S rRNA of the six isolates showed that four of the isolates were members of the genus Streptococcus and were most closely related to ruminal strains of Streptococcus bovis and the recently described organism Streptococcus gallolyticus. One of the other isolates, a gram-positive rod, clustered with the clostridia in the low-G+C-content group of gram-positive bacteria. The sixth isolate, a gram-negative rod, was a member of the family Enterobacteriaceae in the gamma subdivision of the class Proteobacteria. None of the 16S rRNA sequences of the tannin-tolerant bacteria examined was identical to the sequence of any previously described microorganism or to the sequence of any of the other organisms examined in this study. Three phylogenetically distinct groups of ruminal bacteria were isolated from four species of ruminants in Europe, North America, and South America. The presence of tannin-tolerant bacteria is not restricted by climate, geography, or host animal, although attempts to isolate tannin-tolerant bacteria from cows on low-tannin diets failed.

First report of a human isolate of Erwinia persicinus

Erwinia persicinus was first described in 1990 after being isolated from a variety of fruits and vegetables, including bananas, cucumbers, and tomatoes. In 1994, it was shown to be the causative agent of necrosis of bean pods. We now report the first human isolate of E. persicinus. The strain was isolated from the urine of an 88-year-old woman who presented with a urinary tract infection. By the hydroxyapatite method, DNA from this strain was shown to be 94.5% related at 60 degrees C and 86% related at 75 degrees C to the type strain of E. persicinus. The biochemical profile of E. persicinus is most similar to those of Erwinia rhapontici, Pantoea agglomerans, and Enterobacter species. It is negative in tests for lysine, arginine, ornithine, dulcitol, and urea. It is motile and positive in tests for D-sorbitol and sucrose. It is susceptible to the expanded-spectrum cephalosporins, aminoglycosides, and fluoroquinolones, but it is resistant to ampicillin, ticarcillin, and cefazolin.

Characterization of Erwinia amylovora strains using random amplified polymorphic DNA fragments (RAPDs)

The genetic diversity among 16 strains of Erwinia amylovora, chosen to represent different host plant origins and geographical regions, was investigated by RAPD analysis. One strain of Erwinia herbicola and one of Agrobacterium vitis were used as outgroups. Ninety-eight different RAPD fragments were produced by polymerase chain reaction amplification with six different 10-mer primers. RAPD banding profiles were found that enabled the Erw. amylovora strains to be distinguished from one another. Cluster analysis based on the number of RAPD fragments shared between strains showed that strains of Erw. amylovora isolated from subfamily Pomoideae formed a single group, whereas two strains from Rubus (subfamily Rosoideae) formed a second group. Two strains isolated from Asian pear on Hokkaido, Japan, formed a third group. Sets of RAPD fragments were identified that enabled each of the two host-range groups and one geographical region (Hokkaido) of Erw. amylovora strains to be unambiguously distinguished from one another and from the outgroups. This study shows that strains of Erw. amylovora exhibit genetic diversity detectable by RAPD analysis, and that molecular and statistical analysis of RAPD fragments can be used both to distinguish between strains and to determine relatedness between them.

Characterization of two epiphytic bacteria from soybean leaves with antagonistic activities against Pseudomonas syringae pv. glycinea

The strains 48b/90 and 22d/93 are naturally occurring ephiphytes which were isolated from soybean leaves. On the basis of pheno- and genotypic characteristics 48b/90 was identified as Erwinia herbicola and 22d/93 as Pseudomonas syringae. These two isolates produced biological active substances against different indicator organisms. The E. herbicola strain showed clear antagonistic properties against Escherichia coli and Pseudomonas syringae pv. glycinea, but not against Geotrichum candidum. 22d/93 was active against P. glycinea and G. candidum, but not against E. coli. Strain 48b/90 produced at least two different inhibitors: an antibiotic substance and an inhibitor of the alginate synthesis. Strain 22d/93 produced at least three different compounds inhibitory to P. glycinea and one to G. candidum. Their activities against the bacterial blight pathogen, P. glycinea, can be observed in planta, too. Under the influences of the antagonists the pathogen multiplied at lower rates and to lower stationary phase population levels. The development of bacterial blight symptoms was suppressed.

Identification of the fire blight pathogen, Erwinia amylovora, by PCR assays with chromosomal DNA

Erwinia amylovora, the causative agent of fire blight, was identified independently from the common plasmid pEA29 by three different PCR assays with chromosomal DNA. PCR with two primers was performed with isolated DNA and with whole cells, which were directly added to the assay mixture. The oligonucleotide primers were derived from the ams region, and the PCR product comprised the amsB gene, which is involved in exopolysaccharide synthesis. The amplified fragment of 1.6 kb was analyzed, and the sequence was found to be identical for two E. amylovora strains. The identity of the PCR products was further confirmed by restriction analysis. The 1.6-kb signal was also used for detection of the fire blight pathogen in the presence of other plant-associated bacteria and in infected plant tissue. For further identification of isolated strains, the 16S rRNA gene of E. amylovora and other plant-associated bacteria was amplified and the products were digested with the restriction enzyme HaeIII. The pattern obtained for E. amylovora was different from that of other bacteria. The sequence of the 16S rRNA gene was determined from a cloned fragment and was found to be closely related to the sequences of Escherichia coli and other Erwinia species. Finally, arbitrarily primed PCR with a 17-mer oligonucleotide derived from the sequence of transposon Tn5 produced a unique banding pattern for all E. amylovora strains investigated. These methods expand identification methods for E. amylovora, which include DNA hybridization and a PCR technique based on plasmid pEA29.

Identification of Erwinia stewartii by a ligase chain reaction assay

A PCR-coupled ligase chain reaction (LCR) assay was developed to distinguish the plant pathogenic bacterium Erwinia stewartii from other erwiniae. This new technique allows discrimination to the species level on the basis of a single-base-pair difference in the 16S rRNA gene which is unique to E. stewartii. Portions of the 16S rRNA genes of E. stewartii and the closely related Erwinia herbicola were sequenced. From comparison of the two 16S rRNA gene regions, two primer pairs were constructed such that only E. stewartii DNA gave a product in the LCR assay. The ligated product was separated from the radioactively labelled primers by denaturing polyacrylamide gel electrophoresis and visualized by autoradiography. Twenty-four different Erwinia species and strains were tested by PCR-coupled LCR to verify the specificity of the assay, and only E. stewartii strains gave a positive reaction. In addition, infected and healthy plant material was also assayed. E. stewartii was detected in infected plant material, even when large populations of epiphytic bacteria were present. No enrichment was necessary for detection of the pathogen in corn leaves. This assay has potential as a diagnostic technique for the detection of E. stewartii in infected plant and vector material.

Isolation by genomic subtraction of DNA probes specific for Erwinia carotovora subsp. atroseptica

Erwinia carotovora subsp. atroseptica is a pathogen of potatoes in Europe because of its ability to induce blackleg symptoms early in the growing season. However, E. carotovora subsp. carotovora is not able to produce such severe symptoms under the same conditions. On the basis of the technique described by Straus and Ausubel (Proc. Natl. Acad. Sci. USA 87:1889-1893, 1990), we isolated DNA sequences of E. carotovora subsp. atroseptica 86.20 that were absent from the genomic DNA of E. carotovora subsp. carotovora CH26. Six DNA fragments ranging from ca. 180 to 400 bp were isolated, cloned, and sequenced. Each fragment was further hybridized with 130 microorganisms including 87 E. carotovora strains. One probe was specific for typical E. carotovora subsp. atroseptica strains, two probes hybridized with all E. carotovora subsp. atroseptica strains and with a few E. carotovora subsp. carotovora strains, and two probes recognized only a subset of E. carotovora subsp. atroseptica strains. The last probe was absent from the genomic DNA of E. carotovora subsp. carotovora CH26 but was present in the genomes of many strains, including those of other species and genera. This probe is homologous to the putP gene of Escherichia coli, which encodes a proline carrier. Further use of the probes is discussed.

Sensitive and species-specific detection of Erwinia amylovora by polymerase chain reaction analysis

Detection and identification of the fire blight pathogen, Erwinia amylovora, can be accurately done by polymerase chain reaction (PCR) analysis in less than 6 h. Two oligomers derived from a 29-kb plasmid which is common to all strains of E. amylovora were used to amplify a 0.9-kb fragment of the plasmid. By separation of the PCR products on agarose gel, this fragment wa specifically detected when E. amylovora DNA was present in the amplification assay. It was not found when DNA from other plant-pathogenic bacteria was used for the assay. A visible band specific to the 0.9-kb fragment was produced with DNA from fewer than 100 E. amylovora cells. A signal of similar strength was also obtained from E. amylovora cell lysates in the presence of the mild detergent Tween 20. Signals were weaker when bacteria were added to the PCR mixture without the detergent. As with results obtained from hybridization experiments using pEA29 DNA< the PCR signal was obtained with E. amylovora isolates from various geographic regions. This technique could also be used for detection of the fire blight pathogen in extracts of tissue obtained from infected plant material.

Pantoea punctata sp. nov., Pantoea citrea sp. nov., and Pantoea terrea sp. nov. isolated from fruit and soil samples

A total of 37 bacterial strains with the general characteristics of the family Enterobacteriaceae were isolated from fruit and soil samples in Japan as producers of 2,5-diketo-D-gluconic acid from D-glucose. These organisms were phenotypically most closely related to the genus Pantoea (F. Gavini, J. Mergaert, A. Beji, C. Mielearek, D. Izard, K. Kersters, and J. De Ley, Int. J. Syst. Bacteriol. 39:337-345, 1989) and were divided into three phenotypic groups. We selected nine representative strains from the three groups for an examination of DNA relatedness, as determined by the S1 nuclease method at 60 degrees C. Strain SHS 2003T (T = type strain) exhibited 30 to 41 and 28 to 33% DNA relatedness to the strains belonging to the strain SHS 2006T group (strains SHS 2004, SHS 2005, SHS 2006T, and SHS 2007) and to the strains belonging to the strain SHS 2008T group (strains SHS 2008T, SHS 2009, SHS 2010, and SHS 2011), respectively. Strain SHS 2006T exhibited 38 to 46% DNA relatedness to the strains belonging to the strain SHS 2008T group. The levels of DNA relatedness within the strain SHS 2006T group and within the strain SHS 2008T group were more than 85 and 71%, respectively. Strain SHS 2003T, SHS 2006T, and SHS 2008T DNAs exhibited less than 18% binding to Pantoea dispersa ATCC 14589T and Pantoea agglomerans ATCC 27155T DNAs.(ABSTRACT TRUNCATED AT 250 WORDS)