Effect of bacterial symbionts Xenorhabdus on mortality of infective juveniles of two Steinernema species

Steinernema species are entomopathogenic nematodes associated with Xenorhabdus bacteria. The life cycle of these associations is composed of two stages: (1) a free stage in the soil, where infective juveniles (IJs), which carry bacteria in their guts, search for new insect hosts; and (2) a parasitic stage, where the IJs infect insects, release their Xenorhabdus symbionts and reproduce in order to produce new IJs. Previous studies clearly showed benefits to the association for several Steinernema species during the parasitic stage. Nevertheless, no study has so far explored, during the free stage, the existence of costs or benefits to the association for different Steinernema. Here, we compared the survival of both symbiotic and aposymbiotic IJs in two nematode species: (1) Steinernema carpocapsae-exhibiting IJs that carry a high number of Xenorhabdus cells in their guts; and (2) its closely relative species, S. scapterisci-exhibiting IJs, that carry very few Xenorhabdus cells in their guts. We showed that the bacterial symbionts were costly for S. carpocapsae by increasing IJs' mortality but not for S. scapterisci. This difference in cost induced by bacteria to IJs during the free stage could be correlated with the difference in the numbers of bacteria carried by IJs of each nematode species.

F supergroup Wolbachia in bush crickets: what do patterns of sequence variation reveal about this supergroup and horizontal transfer between nematodes and arthropods?

Wolbachia pipientis, an intracellular, alpha-proteobacterium, is commonly found in arthropods and filarial nematodes. Most infected insects are known to harbor strains of Wolbachia from supergroups A or B, whereas supergroups C and D occur only in filarial nematodes. Here, we present molecular evidence from two genes (ftsZ and 16S rDNA) that 2 Orthopterans (the bush cricket species Orocharis saltator and Hapithus agitator; Gryllidae: Eneopterinae) are infected with Wolbachia from the F supergroup. Additionally, a series of PCR tests revealed that these bush cricket specimens did not harbor nematodes, thus indicating that our positive results were not a by-product of nematodes being present in these cricket samples. Patterns of molecular variation suggest that (1) strains of F supergroup Wolbachia exhibit less genetic variation than the nematode-specific C and D supergroups but more than the A and B supergroups found in arthropods and (2) that there is no evidence of recombination within F supergroup strains. The above data support previous findings that F supergroup Wolbachia is not only harbored in both nematodes and arthropods, but that horizontal transfer has likely occurred recently between these diverse taxonomic groups (although the exact details of such horizontal transmissions remain unclear). Moreover, the limited genetic variation and lack of recombination in the F supergroup suggest that this clade of Wolbachia has radiated relatively rapidly with either (1) little time for recombination to occur or (2) selection against recombination as occurs in the mutualistic C and D strains of Wolbachia - both of which remain to be explored further.

Cloning, expression and deletion of the cuticle-degrading protease BLG4 from nematophagous bacterium Brevibacillus laterosporus G4

Brevibacillus laterosporus G4, which was isolated from soil sample, kills free-living nematodes (Panagrellus redivius) and plant-parasite nematodes (Bursaphelenchus xylophilus) and degrades their cuticle in previous bioassay. Our works for B. laterosporus G4 had demonstrated that an extracellular alkaline protease BLG4 played a key role as a pathogenic factor in infection against nematode. In this study, the nematicidal activity of BLG4 was further verified by an in vitro assay with purified recombinant BLG4. The encoding gene of BLG4 was cloned and showed high degree of homology with the subtilisin subclass of serine protease gene and another reported cuticle-degrading protease gene from nematophagous bacterium Bacillus sp. B16. Deletion of BLG4 by homologous recombinant had a significant effect on the pathogenicity of B. laterosporus. In infection assays the BLG4-deficient strain (BLG4-6) lost about 50% of its nematocidal activity and in toxicity tests the mortality rate of nematodes decreased with approximately 56% in comparison to wild-type strain. This is the first report analyzing the function of a subtilisin enzyme involved in bacterium against nematode at the molecular level, and it is possible to use B. laterosporus as a model to study host-parasite interaction and to gain detailed knowledge of the infection process.

[Diversity of actinomycetes associated with root-knot nematode and their potential for nematode control]

Twenty actinomycetes were isolated from root-knot nematode eggs and females collected from 11 plant root samples infested by Meloidogyne spp.. The isolates were assigned to the genera Streptomyces, Nocardia and Pseudonocardia respectively, based on analysis of morphological characteristics, cell-wall DAPs and 16S rRNA gene sequences. 80% of them were streptomycetes. Biocontrol potential of the isolates against Meloidogyne hapla was evaluated in liquid culture in vitro. The average percentages of egg parasitism, egg hatching, and juvenile mortality were 54.1, 40.4 and 26.2, respectively. Three Streptomyces strains and one Nocardia strain with high pathogenicity in vitro were selected to determine their ability to reduce tomato root galls in greenhouse. The results demonstrated good biocontrol efficacy (31.4%-56.4%) of the strains.

Monoxenic liquid culture of the entomopathogenic nematode Steinernema carpocapsae using a culture medium containing whey

The submerged culture of the entomopathogenic nematode Steinernema carpocapsae and its symbiotic bacterium, Xenorhabdus nematophila, was carried out in orbitally agitated bottles using a culture medium containing whey (in grams per litre: 500 whey, 20 yeast extract, 10 dried egg yolk-food grade, 3 sodium chloride, 37 corn oil-food grade). Maximum total viable nematode concentrations of 198,333ml(-1) were achieved within fermentations of 24 days with 64% of the nematode population within the infective juvenile stage (IJ) (126,666ml(-1)) at the end. The kinetics of the bioprocess was well modelled using the four-parameter Sigmoidal model and the corresponding maximum specific rates of nematode production (0.47 day(-1)), carbohydrates consumption (0.0008g(carbohydrates)g(nematodes)(-1)day(-1)) and nitrogen consumption (4.44g(nitrogen)g(nematodes)(-1)day(-1)) are first proposed. Besides, X. nematophila appears to have the capacity of lactose hydrolysis.

Purification and characterization of an extracellular serine protease from the nematode-trapping fungus Dactylella shizishanna

AIMS

To evaluate the production of an extracellular serine protease by Dactylella shizishanna and its potential as a pathogenesis factor.

METHODS AND RESULTS

An extracellular alkaline serine protease (Ds1) was purified and characterized from the nematode-trapping fungus D. shizishanna using cation-exchange chromatography and hydrophobic interaction chromatography. The molecular mass of the protease was approximately 35 kDa estimated by SDS-PAGE. The optimum activity of Ds1 was at pH 10 and 55 degrees C (over 30 min). The purified protease could degrade purified cuticle of Penagrellus redivivus and a broad range of protein substrates. The purified protease was highly sensitive to phenylmethyl sulfonyl fluoride (PMSF) (0.1 mmol l(-1)), indicating it belonged to the serine protease family. The N-terminal amino acid residues of Ds1 are AEQTDSTWGL and showed a high homology with Aozl and PII, two serine proteases purified from the nematode-trapping fungus Arthrobotrys oligospora.

CONCLUSIONS

Nematicidal activity of D. shizishanna was partly related to its ability to produce extracellular serine protease.

SIGNIFICANCE AND IMPACT OF THE STUDY

In this report, we purified a new serine protease from D. shizishanna and provided a good foundation for future research on infection mechanism.

Phylogenetics and evolution of nematode-trapping fungi (Orbiliales) estimated from nuclear and protein coding genes

The systematic classification of nematode-trapping fungi is redefined based on phylogenies inferred from sequence analyses of 28S rDNA, 5.8S rDNA and beta-tubulin genes. Molecular data were analyzed with maximum parsimony, maximum likelihood and Bayesian analysis. An emended generic concept of nematode-trapping fungi is provided. Arthrobotrys is characterized by adhesive networks, Dactylellina by adhesive knobs, and Drechslerella by constricting-rings. Phylogenetic placement of taxa characterized by stalked adhesive knobs and non-constricting rings also is confirmed in Dactylellina. Species that produce unstalked adhesive knobs that grow out to form loops are transferred from Gamsylella to Dactylellina, and those that produce unstalked adhesive knobs that grow out to form networks are transferred from Gamsylella to Arthrobotrys. Gamsylella as currently circumscribed cannot be treated as a valid genus. A hypothesis for the evolution of trapping-devices is presented based on multiple gene data and morphological studies. Predatory and nonpredatory fungi appear to have been derived from nonpredatory members of Orbilia. The adhesive knob is considered to be the ancestral type of trapping device from which constricting rings and networks were derived via two pathways. In the first pathway adhesive knobs retained their adhesive material forming simple two-dimension networks, eventually forming complex three-dimension networks. In the second pathway adhesive knobs lost their adhesive materials, with their ends meeting to form nonconstricting rings and they in turn formed constricting rings with three inflated-cells.

A new C-type lectin similar to the human immunoreceptor DC-SIGN mediates symbiont acquisition by a marine nematode

Although thiotrophic symbioses have been intensively studied for the last three decades, nothing is known about the molecular mechanisms of symbiont acquisition. We used the symbiosis between the marine nematode Laxus oneistus and sulfur-oxidizing bacteria to study this process. In this association a monolayer of symbionts covers the whole cuticle of the nematode, except its anterior-most region. Here, we identify a novel Ca(2+)-dependent mannose-specific lectin that was exclusively secreted onto the posterior, bacterium-associated region of L. oneistus cuticle. A recombinant form of this lectin induced symbiont aggregation in seawater and was able to compete with the native lectin for symbiont binding in vivo. Surprisingly, the carbohydrate recognition domain of this mannose-binding protein was similar both structurally and functionally to a human dendritic cell-specific immunoreceptor. Our results provide a molecular link between bacterial symbionts and host-secreted mucus in a marine symbiosis and suggest conservation in the mechanisms of host-microbe interactions throughout the animal kingdom.

Molecular approach for assessing responses of microbial-feeding nematodes to burning and chronic nitrogen enrichment in a native grassland

A substantial proportion of the primary productivity in grassland ecosystems is allocated belowground, sustaining an abundant and diverse community of microbes and soil invertebrates. These belowground communities drive many important ecosystem functions and are responsive to a variety of environmental changes. Nematodes, an abundant and diverse component of grassland soil communities, are particularly responsive to altered environmental conditions, such as those associated with reduced fire frequency and nitrogen enrichment, with the most consistent responses displayed by microbial-feeding nematodes. However, much of the available research characterizing nematode responses to environmental change has been carried out at the taxonomic level of family or by broad trophic categories (e.g. fungivores, bacterivores). The extent to which differential responses to environmental change occurs at the genus level or below is unclear. Therefore, the objective of this study was to use molecular methods to quantify the response of microbial-feeding nematodes, at the lowest levels of taxonomic resolution, to nitrogen enrichment and changes in fire frequency. Using sequencing and quantitative polymerase chain reaction (PCR) probes for the 18S ribosomal RNA gene and the ITS1 region, we identified 19 microbial-feeding nematode taxa across four families. When nematodes were sampled across treatments, we found that some nematode taxa within a family responded similarly to nitrogen and burning treatments, while other taxa within the same family respond quite differently. Additionally, although nematodes from different families on average responded differently to nitrogen enrichment and burning, similar responses were seen in nematode taxa that span three taxonomic families. Thus, if nematodes are to be used as indicators of environmental change, care should be taken to assess the response at the lowest taxonomic level possible.

Mycobacterium avium ssp. paratuberculosis and its potential survival tactics

Mycobacterium avium ssp. paratuberculosis (Map) is an important animal pathogen with a potential, but as yet unproven, role in human disease. This review briefly describes the characteristics of Map that distinguish it from other Mycobacterium spp., presenting new information arising from completion of the sequencing of the Map genome. It then focuses on the potential mechanisms Map might employ to survive and disseminate in the environment, including interaction with protozoa and insects, dormancy, biofilm formation and aerosolization.

A neutral protease from Bacillus nematocida, another potential virulence factor in the infection against nematodes

A neutral protease (npr) (designated Bae16) toxic to nematodes was purified to homogeneity from the strain Bacillus nematocida. The purified protease showed a molecular mass of approximately 40 kDa and displayed optimal activity at 55 degrees C, pH 6.5. Bioassay experiments demonstrated that this purified protease could destroy the nematode cuticle and its hydrolytic substrates included gelatin and collagen. The gene encoding Bae16 was cloned, and the deduced amino acid sequence showed 94% sequence identity with npr gene from B. amyloliquefaciens, but had low similarity (13-43%) with the previously reported virulence serine proteases from fungi or bacteria, which reflected their differences. Recombinant mature Bae16 (rm-Bae16) was expressed in Escherichia coli BL21 using pET30 vector system, and its nematicidal activity confirmed that Bae16 could be involved in the infection process. Our present study revealed that the npr besides the known alkaline serine protease could serve as a potential virulence factor in the infection against nematodes, furthermore, the two proteases with different characteristics produced by the same strain co-ordinated efforts to kill nematodes. These data helped to understand the interaction between this bacterial pathogen and its host.

Ambient pH signaling regulates expression of the serine protease gene (spr1) in pine wilt nematode-trapping fungus, Monacrosporium megalosporum

We have cloned and characterized spr1, a putative serine protease gene, from a nematode-trapping fungus, Monacrosporium megalosporum. The gene was present as a single copy in the genome. The predicted protein sequence of spr1 is homologous to the putative cuticle-degrading serine proteases PII and Azo1 from the nematode-trapping fungus, Arthrobotrys oligospora. In the 5' untranslated region near the initiation codon, consensus sequences to an AreA binding site, a well-known mediator of nitrogen metabolite repression in the fungus Aspergillus nidulans, a CreA binding site, a carbon response regulator in A. nidulans, and a PacC binding site, a transcription factor that responds to ambient pH signals in A. nidulans were found. However, spr1 was not regulated by carbon or nitrogen source, and exogenous protein did not induce expression of spr1. The transcription of the spr1 gene of this fungus was significantly affected by ambient pH. Based on RT-PCR, the product of the spr1 gene was not transcribed at pH 4, whereas under alkaline conditions such as pH 8 and 9, the spr1 gene was transcribed well. These results indicate that the spr1 gene is controlled only by a PacC homologue. Moreover, the expression profile of the spr1 gene corresponded with the pH-dependent physiology of this fungus.

Biological control of nematode parasites in sheep1

In a world in which sheep producers are facing increasing problems due to the rapid spread of anthelmintic resistance, the battle against gastrointestinal parasitic nematodes is a difficult one. One of the potential new tools for integrated control strategies is biological control by means of the nematode-destroying microfungus Duddingtonia flagrans. This fungus forms sticky traps that catch developing larval stages of parasitic nematodes in the fecal environment. When resting spores (chlamydospores) of this fungus are fed daily to grazing animals for a period of time, the pasture infectivity and thus, the worm burden of grazing animals are lowered, especially in young lambs. Research has been conducted throughout the world covering many different climates and management systems. An Australian parasite model showed that if the fungus performs efficiently (> or =90% reduction in worm burden) for 2 or 3 mo, it should contribute significantly to a reduction in the number of dead lambs otherwise occurring when managed only by anthelmintic treatment and grazing management. Feeding or field trials have clearly demonstrated that dosing with a few hundred thousand spores per kilogram of live BW not only reduced the number of infective larvae but also increased the BW of the lambs compared with controls not given fungus. Initial Australian work with feeding spores by means of a block formulation or a slow-release device has shown some promise, but further work is needed to fully develop these delivery systems. In tropical Malaysia, small paddock trials and field studies resulted in significant improvements, in terms of lower worm burdens and increased live BW, when feeding half a million spores daily to grazing lambs. Additional benefits have been observed when the fungus is employed in combination with a fast rotational grazing system. Research has also demonstrated that spores can be delivered in slightly moist feed block material, but only if such blocks are consumed rapidly, because of their very short shelf life. In the northern, temperate Danish climate it has been demonstrated that daily feeding of half a million spores per kilogram of live BW can lead to significant production benefits, with increased live BW gain in fungus-exposed animals. Biological control of parasitic nematodes in sheep seems to hold promise for the future, but to be able to assist producers, the optimal delivery system needs to be refined and further developed. In addition, more work will be needed to define the best use of this technology in different geographic regions.

Analysis of the PixA inclusion body protein of Xenorhabdus nematophila

The symbiotic pathogenic bacterium Xenorhabdus nematophila produces two distinct intracellular inclusion bodies. The pixA gene, which encodes the 185-residue methionine-rich PixA inclusion body protein, was analyzed in the present study. The pixA gene was optimally expressed under stationary-phase conditions but its expression did not require RpoS. Analysis of a pixA mutant strain showed that PixA was not required for virulence towards the insect host or for colonization of or survival within the nematode host, and was not essential for nematode reproduction. The pixA gene was not present in the genome of Xenorhabdus bovienii, which also produces proteinaceous inclusions, indicating that PixA is specifically produced in X. nematophila.

Providencia vermicola sp. nov., isolated from infective juveniles of the entomopathogenic nematode Steinernema thermophilum

In the course of isolating bacteria from infective juveniles of the entomopathogenic nematodeSteinernema thermophilumGanguly & Singh, 2000, three isolates were obtained (OP1T, OP29 and VS3). On the basis of 16S rRNA gene sequence analysis and riboprint patterns, these three strains were identical to each other but distinct from the type strains of the five recognized species of the genusProvidencia. Based on biochemical and genomic analysis and supported by the low (<35 %) DNA–DNA relatedness between strain OP1Tand the type strain of its phylogenetically closest relative,Providencia rettgeri(99·5 % 16S rRNA gene sequence similarity), strain OP1Twas considered to be sufficiently distinct from recognizedProvidenciaspecies to warrant the description of a novel species. The nameProvidencia vermicolasp. nov. is proposed, with OP1T(=DSM 17385T=CIP 108829T) as the type strain.

Whole-genome comparison between Photorhabdus strains to identify genomic regions involved in the specificity of nematode interaction

The bacterium Photorhabdus establishes a highly specific association with Heterorhabditis, its nematode host. Photorhabdus strains associated with Heterorhabditis bacteriophora or Heterorhabditis megidis were compared using a Photorhabdus DNA microarray. We describe 31 regions belonging to the Photorhabdus flexible gene pool. Distribution analysis of regions among the Photorhabdus genus identified loci possibly involved in nematode specificity.

A novel species of Xenorhabdus, family Enterobacteriaceae: Xenorhabdus indica sp. nov., symbiotically associated with entomopathogenic nematode Steinernema thermophilum Ganguly and Singh, 2000

In the search for novel Xenorhabdus strains in a recently described nematode species, Steinernema thermophilum, three strains (strain 28(T) = DSM 17382(T), strain 42 = DSM 17383 and strain 43 = DSM 17384) were isolated from three independent isolation approaches from crushed mixture of infective juveniles. 16S rRNA gene sequence comparison of strains 28(T) and DSM 17383 indicated identity and the phylogenetic position pointed towards an individual taxon within the phylogenetic dendrogram of Xenorhabdus type strains. The nearest phylogenetic relatives of strain 28(T) were Xenorhabdus poinarii and Xenorhabdus szentirmaii (97.7% each). The three isolates were almost identical in reaction towards the API and BIOLOG substrate panels but differed in their reactions from those of the established type strains of the genus Xenorhabdus. These clear genomic and metabolic differences let us propose a new species, Xenorhabdus indica sp. nov. for the three clones. The type strain is strain 28(T), DSM 17382(T), CIP 108830(T).

Characterization of an extracellular protease and its cDNA from the nematode-trapping fungus Monacrosporium microscaphoides

To better exploit the biocontrol potential of nematophagous fungi, it is important to fully understand the molecular background of the infection process. In this paper, several nematode-trapping fungi were surveyed for nematocidal activity. From the culture filtrate of Monacrosporium microscaphoides, a neutral serine protease (designated Mlx) was purified by chromatography. This protease could immobilize the nematode Penagrellus redivivus in vitro and degrade its purified cuticle, suggesting that Mlx could serve as a virulence factor during infection. Characterization of the purified protease revealed a molecular mass of approximately 39 kDa, an isoelectric point of 6.8, and optimum activity at pH 9 at 65 °C. Mlx has broad substrate specificity, and it hydrolyzes protein substrates, including casein, skimmed milk, collagen, and bovine serum albumin. The gene encoding Mlx was also cloned and the nucleotide sequence was determined. The deduced amino acid sequence contained the conserved catalytic triad of aspartic acid – histidine – serine and showed high similarity with two cuticle-degrading proteases (PII and Aoz1), which were purified from the nematode-trapping fungus Arthrobotrys oligospora. Research on infection mechanisms of nematode-trapping fungi has thus far only focused on A. oligospora. However, little is known about other nematode-trapping fungi. Our report is among the first to describe the purification and cloning of an infectious protease from a different nematode-trapping fungus.Key words: extracellular serine protease, Monacrosporium microscaphoides, nematode-trapping fungus, nematocidal activity.

The Steinernema carpocapsae intestinal vesicle contains a subcellular structure with which Xenorhabdus nematophila associates during colonization initiation

Steinernema carpocapsae infective juvenile (IJ) nematodes are intestinally colonized by mutualistic Xenorhabdus nematophila bacteria. During IJ development, a small number of ingested X. nematophila cells initiate colonization in an anterior region of the intestine termed the vesicle and subsequently multiply within this host niche. We hypothesize that efficient colonization of a high percentage of S. carpocapsae individuals (typically>85%) is facilitated by bacterial adherence to a site(s) in the nematode intestine. We provide evidence that the adherence site is a structure in the lumen of the IJ vesicle that we have termed the intravesicular structure (IVS). The IVS is an untethered cluster of anucleate spherical bodies that co-localizes with colonizing X. nematophila cells, but does not require X. nematophila for its formation. Colocalization with the IVS is readily apparent in IJs colonized by X. nematophila mutants that initiate intestinal colonization but fail to proliferate normally, suggesting that bacterial-IVS interaction occurs early in the colonization process. Treatment with insect haemolymph induces anal release of X. nematophila from colonized IJs and induces release of the IVS from uncolonized S. carpocapsae IJs. Released IVS were probed with several carbohydrate-specific lectins. One lectin, wheat-germ agglutinin, reacts strongly with a mucus-like substance that is present around individual spheres in the aggregate IVS. Potential roles for the IVS in mediating X. nematophila colonization of the nematode intestine are discussed.

The use of real-time PCR and species-specific primers for the identification and monitoring of Paecilomyces lilacinus

The Paecilomyces lilacinus is the most widely tested fungus for the control of root-knot and cyst nematodes. The fungus has also been implicated in a number of human and animal infections, difficulties in diagnosis often result in misdiagnosis or delays in identification leading to a delay in treatment. Here, we report the development of species-specific primers for the identification of P. lilacinus based on sequence information from the ITS gene, and their use in identifying P. lilacinus isolates, including clinical isolates of the fungus. The primer set generated a single PCR fragment of 130 bp in length that was specific to P. lilacinus and was also used to detect the presence of P. lilacinus from soil, roots and nematode eggs. Real-time PCR primers and a TaqMan probe were also developed and provided quantitative data on the population size of the fungus in two field sites. PCR, bait and culture methods were combined to investigate the presence and abundance of the fungus from two field sites in the United Kingdom where potato cyst nematode populations were naturally declining, and results demonstrated the importance of using a combination of methods to investigate population size and activity of fungi.

Comparative efficacy of the nematode-trapping fungus Duddingtonia flagrans against Haemonchus contortus, Teladorsagia circumcincta and Trichostrongylus colubriformis in goat faeces: influence of the duration and of the temperature of coproculture

Amongst the alternative strategies to the use of anthelmintics, the administration of Duddingtonia flagrans spores has already proved its efficacy in reducing the number of developing larvae of several nematode species in goat faeces. In this trial, the efficacy of this fungus against the larvae of the three major nematode species of goats was compared in various conditions of coproculture. Twelve strongyle free goats were experimentally infected with either Trichostrongylus colubriformis, Teladorsagia circumcincta or Haemonchus contortus larvae. Half of the animals received an oral dose of 5x10(5) Duddingtonia chlamydospores/kg BW daily for 27 days, whereas the remaining was kept as control goats. From the 7th day of administration onwards, individual coproscopical examinations as well as coprocultures, which were incubated 4, 7, 10 or 14 days at 21 or 28 degrees C, were performed. The reduction in developing larvae due to the activity of Duddingtonia ranged from 62.8 to 99.5% compared to control. The trapping efficacy depended on temperature (better activity of the fungus at 21 than at 28 degrees C) and on duration (larval reductions lower after 4 days than after 7, 10 and 14 days of coproculture). Teladorsagia larvae were the least trapped, and Haemonchus larvae were the most trapped.

[Effects of pine wood nematode on propagation of its carrying bacteria]

In this paper, the aseptic eggs of Bursaphelenchus xylophilus were obtained after treated with 30% H202, and cultured with Pinus thunbergii callus. Ten B. xylophilus-carrying bacterial strains directly isolated from diseased P. thugbergii and P. massoniana in six epidemic provinces i.e., GcM6-2A Pseudomonas putida, GcM6-1A P. putida, ZpB1-2A P. putida, HeM2A Pseudomonas sp., HeM1A Pseudomonas sp., HeM142B Pseudomonas sp., GcM1-3A P. cepacia and HM3 Pantoeu sp., ZpB4-2B Staphylococcus sciuri and ZpB2-3A Enterobacter amnigenus, were collected, and the effects of axenic B. xylophilus (ABx) on their propagation were studied. The results showed that pine wood nematode (PWN) promoted the propagation of 7 bacterial strains in Pseudomonas and 1 bacterial strain in Pantoeu sp., including Pseudomonas putida, P. putida, P. putida , Pseudomonas sp., Pseudomonas sp., Pseudomonas sp., P. cepacia and Pantoeu sp., but inhibited Staphylococcus sciuri and Enterobacter amnigenus, which could explain the phenomenon that Pseudomonas was the prevailing genus of the bacteria carried by PWN, and might provide essential nutrition to the bacteria. The close relationship between PWN and bacterial strains in Pseudomonas might account for the pine wood nematode disease.

Soil nematodes mediate positive interactions between legume plants and rhizobium bacteria

Symbiosis between legume species and rhizobia results in the sequestration of atmospheric nitrogen into ammonium, and the early mechanisms involved in this symbiosis have become a model for plant-microbe interactions and thus highly amenable for agricultural applications. The working model for this interaction states that the symbiosis is the outcome of a chemical/molecular dialogue initiated by flavonoids produced by the roots of legumes and released into the soil as exudates, which specifically induce the synthesis of nodulation factors in rhizobia that initiate the nodulation process. Here, we argue that other organisms, such as the soil nematode Caenorhabditis elegans, also mediate the interaction between roots and rhizobia in a positive way, leading to nodulation. We report that C. elegans transfers the rhizobium species Sinorhizobium meliloti to the roots of the legume Medicago truncatula in response to plant-released volatiles that attract the nematode. These findings reveal a biologically-relevant and largely unknown interaction in the rhizosphere that is multitrophic and may control the initiation of the symbiosis.

Pathogenicity of bacterium, Xenorhabdus nematophila isolated from entomopathogenic nematode (Steinernema carpocapsae) and its secretion against Galleria mellonella larvae

The entomopathogenic bacterium, Xenorhabdus nematophila was isolated from the hemolymph of Galleria mellonella infected with Steinernema carpocapsae. The bacterial cells and its metabolic secretions have been found lethal to the Galleria larvae. Toxic secretion in broth caused 95% mortality within 4 d of application whereas the bacterial cells caused 93% mortality after 6 d. When filter and sand substrates were compared, the later one was observed as appropriate. Similarly, bacterial cells and secretion in broth were more effective at 14% moisture and 25 degrees C temperature treatments. Maximum insect mortality (100%) was observed when bacterial concentration of 4x10(6) cells/ml was used. Similarly, maximum bacterial cells in broth (95%) were penetrated into the insect body within 2 h of their application. However, when stored bacterial toxic secretion was applied to the insects its efficacy declined. On the other hand, when the same toxic secretion was dried and then dissolved either in broth or water was proved to be effective. The present study showed that the bacterium, X. nematophila or its toxic secretion can be used as an important component of integrated pest management against Galleria.

Transformation and mutagenesis of the nematode-trapping fungus Monacrosporium sphaeroides by restriction enzyme-mediated integration (REMI)

In this study, the nematode-trapping fungus, Monacrosporium sphaeroides, was transformed with a plasmid harboring the hygromycin B phosphotransferase gene, via restriction enzyme-mediated integration (REMI). Frequencies of up to 94 transformants microg(-1) per linearized plasmid DNA were obtained by optimizing the PEG concentration, as well as the category and quantity of the added restriction enzyme. 90% of the transformants were determined to be stable for drug resistance when 20 randomly selected transformants were tested. Southern analyses revealed that the transforming DNA was integrated into the M. sphaeroides genome either with or without rearrangement. Five mitotic stable mutant strains were obtained using this approach, all of which had been altered with regard to sporulation capacity and pathogenicity toward nematodes. Southern blot analyses of the five mutants revealed that foreign plasmid DNA had integrated into the genome. Three of the mutants, Tms2316, Tms3583 and Tms1536, exhibited integration at a single location, whereas the remaining two, Tms32 and Tms1913, manifested integration at double or multiple locations. Our results suggest that the transformation of M. sphaeroides via REMI will facilitate insertional mutagenesis, the functional analysis of a variety of genes, and the tagging or cloning of genes of interest.

Emended description of Pasteuria nishizawae

The description of the Gram-positive, obligately parasitic, mycelial and endospore-forming bacterium, Pasteuria nishizawae, is emended to include additional observations on the life cycle, host specificity and endospore morphology. The nucleotide sequence of the 16S rRNA gene is also provided.

Survey of nematophagous fungi in South Africa : research communication

Three hundred and eighty-four samples of leaf litter, soil, faeces from domestic and game animals, compost and aqueous cultures of infective nematode larvae contaminated with unidentified fungi were plated out on water agar, baited with pure infective larvae of Haemonchus contortus, incubated and examined for the presence of nematophagous fungi. Duddingtonia flagrans was isolated from five samples, and 73 samples were positive for other nematophagous fungi.

Toxicity of Bacillus thuringiensis to parasitic and free-living life-stages of nematode parasites of livestock

A collection of Bacillus thuringiensis (Bt) strains (Bts) were screened for activity against the free-living larval stages of nematode parasites of livestock. Two strains were identified with significant activity in inhibiting larval development of Haemonchus contortus, Trichostrongylus colubriformis and Ostertagia circumcincta. These strains were also toxic to the adult parasitic stages of these nematode species in vitro. Adult H. contortus and O. circumcincta showed complete cessation of movement within 2 and 4 days, respectively. Trichostrongylus colubriformis adults were less affected, however, movement was still significantly reduced compared with controls. The in vitro activity against the larval stages was of a magnitude similar to or greater than that seen with the anthelmintic drugs thiabendazole and levamisole. N-terminal amino acid sequencing indicated that the two Bts contained either Cry5A and Cry5B proteins, or a Cry13 protein, and the presence of the corresponding cry5A, cry5B and cry13 genes was confirmed by PCR and sequencing. Bacillus thuringiensis spore-crystal suspensions exposed to acidic pH conditions (pH<or=3) showed greatly reduced toxicity in subsequent bioassays with nematode larvae, highlighting the need to protect the toxin from the acidic conditions of the sheep abomasum if it were to be administered per os as an anthelmintic. This study indicates that both the parasitic adult stages and the free-living larval stages of economically significant nematode parasites are susceptible to the effects of Bt, thus identifying this group of toxins as potential biocontrol agents.

Two groups of entomopathogenic bacteria, Photorhabdus and Xenorhabdus, share an inhibitory action against phospholipase A2 to induce host immunodepression

Photorhabdus and Xenorhabdus are two genera of entomopathogenic bacteria having a mutualistic relationship with their respective nematode hosts, Heterorhabditis and Steinernema. One of the pathogenic mechanisms of these bacteria includes host immunodepression, which leads to lethal septicemia. It has been known that X. nematophila inhibits phospholipase A2 (PLA2) to induce host immunodepression. Here, we tested the hypothesis of PLA2 inhibition using another bacterial species involved in other genera. P. temperata subsp. temperata is the intestinal symbiont of an entomopathogenic nematode, H. megidis. The bacteria caused potent pathogenicity in a dose-dependent manner against the fifth instar larvae of a test target insect, Spodoptera exigua, as early as 24 h after the intra-hemocoelic injection. In response to the live bacterial injection, hemocyte nodulation (a cellular immune response) and prophenoloxidase (pPO) activation were inhibited, while the injection of heat-killed bacteria significantly induced both immune reactions. The immunodepression induced by the live bacteria was reversed by the addition of arachidonic acid, the catalytic product of phospholipase A2. In contrast, the addition of dexamethasone, a specific PLA2 inhibitor to the heat-killed bacterial treatment, inhibited both immune capacities. In addition to a previously known PLA2 inhibitory action of X. nematophila, the inhibition of P. temperata temperata on PLA2 suggests that bacteria symbiotic to entomopathogenic nematodes share a common pathogenic target to result in an immunodepressive state of the infected insects. To prove this generalized hypothesis, we used other bacterial species (X. bovienni, X. poinarii, and P. luminescens) involved in these two genera. All our experiments clearly showed that these other bacteria also share their inhibitory action against PLA2 to induce host immunodepression.

Effect of phenotypic variation inXenorhabdus nematophilaon its mutualistic relationship with the entomopathogenic nematodeSteinernema carpocapsae

The entomopathogenic nematodeSteinernema carpocapsaeis mutualistically associated with the bacteriumXenorhabdus nematophila. Infective Juveniles (IJs) transportX. nematophilacells that provide them with good conditions to reproduce within the insect. In the laboratory, long term stationary-phase culture conditions sometimes leadX. nematophila's variant 1 cells, which were previously isolated from the worms, to spontaneously and irreversibly change into a new phenotypic variant (variant 2). In this paper, we tested the ability of each phenotypic variant to (i) be transmitted by IJs, (ii) to optimize the worm's fitness within the insect, and (iii) to counteract the effect of closely related antagonistic bacteria previously shown as being able to totally preventS. carpocapsae's reproduction within the insect. We found that IJs did associate with cells of both phenotypes but that the variant 2 cells were preferentially retained by the nematodes when both variants were present in the insect. Both phenotypic variants led to the same fitness ofS. carpocapsaein insects not infected by antagonistic bacteria. In insects infected by antagonistic bacteria, both variants were able to provide protection toS. carpocapsae. Nevertheless, this protection depended on the phenotypic variant and the antagonistic bacteria that were co-injected into the insect. Further analysis conducedin vitroshowed that this variability could be partly linked to the sensitivity of each antagonistic bacterium to xenorhabdicin, produced byX. nematophila.

An extracellular protease from Brevibacillus laterosporus G4 without parasporal crystals can serve as a pathogenic factor in infection of nematodes

Brevibacillus laterosporus is an aerobic spore-forming bacterium with the ability to produce canoe-shaped lamellar parasporal inclusions adjacent to spores. An isolate named G4 was identified as a B. laterosporus which does not produce parasporal crystals and shows significant toxic activity toward nematodes. Crude extracellular protein extract from culture supernatant of B. laterosporus G4 killed the nematodes within 12 h and finally destroyed the targets within 24 h, which suggested possible proteinaceous pathogeny. A homogeneous extracellular protease with nematicidal activities, purified by chromatography, confirmed the hypothesis that it might serve as a pathogenic factor during infection of the G4 strain. Characterization of the purified protease revealed a molecular mass of 30 kDa and optimum activity at pH 10 and 50 degrees C. The protease hydrolyzed relatively broad substrates including collagen and the cuticle of nematodes, and histopathological observations demonstrated the resulting destroyed nematode cuticle upon treatment by purified protease. Our present study reveals that extracellular protease, but not previously reported parasporal crystals, can be employed in infection against invertebrates by the B. laterosporus G4 strain.

Improvement on genetic transformation in the nematode-trapping fungus Arthrobotrys oligospora and its quantification on dung samples

An improved DNA-mediated transformation system for nematode-trapping fungus Arthrobotrys oligospora based on hygromycin B resistance was developed. The transformation frequency varied between 34 and 175 transformants per microg linearized DNA and 93% of the transformants were stable for drug resistance when tested 100 randomly selected transformants. More than 2000 transformants were obtained by transformation of the fungus with pBChygro in the presence of HindIII and among them, one, YMF1.00110, which lost its ability of forming predacious structure, was isolated. Southern analysis showed that the plasmid DNA had integrated into the genome of all tested transformants (including YMF 1.00110) except one. The transformant tagged with hph gene could be re-isolated and quantified from dung samples based on the resistance of hygromycin B. All the results suggested that the method of restriction enzyme mediated integration (REMI) should facilitate not only the insertional mutagenesis for tagging and analysis genes of interest but also the ecological investigation of tagged fungi in a given environment.

Potential role of Diploscapter sp. strain LKC25, a bacterivorous nematode from soil, as a vector of food-borne pathogenic bacteria to preharvest fruits and vegetables

Diploscapter, a thermotolerant, free-living soil bacterial-feeding nematode commonly found in compost, sewage, and agricultural soil in the United States, was studied to determine its potential role as a vehicle of Salmonella enterica serotype Poona, enterohemorrhagic Escherichia coli O157:H7, and Listeria monocytogenes in contaminating preharvest fruits and vegetables. The ability of Diploscapter sp. strain LKC25 to survive on agar media, in cow manure, and in composted turkey manure and to be attracted to, ingest, and disperse food-borne pathogens inoculated into soil or a mixture of soil and composted turkey manure was investigated. Diploscapter sp. strain LKC25 survived and reproduced in lawns of S. enterica serotype Poona, E. coli O157:H7, and L. monocytogenes on agar media and in cow manure and composted turkey manure. Attraction of Diploscapter sp. strain LKC25 to colonies of pathogenic bacteria on tryptic soy agar within 10, 20, 30, and 60 min and 24 h was determined. At least 85% of the worms initially placed 0.5 to 1 cm away from bacterial colonies migrated to the colonies within 1 h. Within 24 h, > or =90% of the worms were embedded in colonies. The potential of Diploscapter sp. strain LKC25 to shed pathogenic bacteria after exposure to bacteria inoculated into soil or a mixture of soil and composted turkey manure was investigated. Results indicate that Diploscapter sp. strain LKC25 can shed pathogenic bacteria after exposure to pathogens in these milieus. They also demonstrate its potential to serve as a vector of food-borne pathogenic bacteria in soil, with or without amendment with compost, to the surface of preharvest fruits and vegetables in contact with soil.

Orbilia quercisp. nov. and its knob-forming nematophagous anamorph

Orbilia querci, a new nematode-trapping fungus, was found on rotten wood of Quercus sp. in Huai-rou County, Beijing, China. It is characterized by having a tear-shaped spore body in the cylindrical ascospore. Pure culture was obtained from the ascospores. Conidiophores were simple or occasionally branched, bearing a single conidium on the tip. Conidia were spindle-shaped, mostly with 3-septa. Nematodes were captured by means of adhesive stalked knobs. The adhesive knobs were produced frequently on nutritional agar plates even in the absence of challenging nematodes. Its anamorph is placed in Dactylellina and named as D. querci. The sequence divergence of the ITS1 region between the fungus and the other knob-forming species tested was 23.8-33.4%, supporting O. querci as a distinct species. This is the first report of the connection between a knob-forming nematophagous hyphomycete and an Orbilia teleomorph.

Characterization of a lipoprotein, NilC, required by Xenorhabdus nematophila for mutualism with its nematode host

Xenorhabdus nematophila is a gamma-proteobacterial mutualist of an insect-pathogenic nematode, Steinernema carpocapsae. X. nematophila requires nilC, a gene predicted to encode an outer membrane lipoprotein of unknown function, for colonization of its nematode host. Characterization of NilC, described here, demonstrated it is a 28 kDa lipoprotein directed to the periplasm by an N-terminal signal sequence. Lipidation and processing of NilC occurs by a mechanism that is conserved in proteobacteria. This work also showed NilC is membrane associated and oriented towards the periplasm of X. nematophila and is produced as an outer membrane-associated protein when expressed in Escherichia coli. Expression analyses revealed that nilC transcription is directly or indirectly repressed by Lrp, and this regulatory link may explain the nematode mutualism defect of a previously identified lrp::Tn5 mutant. An lrp::Tn5 mutant produces an additional nilC transcript, not observed in wild-type cells growing in vitro, and produces approximately 75-fold more nilC than wild-type cells in late stationary phase. These fundamental characterizations of nilC expression and nilC localization and processing events have provided firm bases for understanding the role of this colonization factor in the X. nematophila/S. carpocapsae microbe-host interaction.

The genus Podocrella and its nematode-killing anamorph Harposporium

Several genera are described in the literature as having morphology similar to the clavicipitaceous genus Podocrella, viz. Atricordyceps, Ophiocordyceps, Wakefieldiomyces and "Cordyceps" peltata. These genera have capitate-stipitate stromata that gradually expand into a horizontally flattened fertile head that is dark, has strongly protruding perithecia and asci containing eight multiseptate filiform ascospores. These ascospores disarticulate at the middle septum to form two lanceolate multiseptate part-as-cospores. In this study several specimens of the above-mentioned genera, including the types, were examined to determine whether they are congeneric with Podocrella. This study also reveals the connection of Podocrella to its anamorph genus, Harposporium, and its relationship to several other clavicipitaceous genera, based on cultural data and large subunit nuclear ribosomal DNA (LSU) sequences. Nematode predation of the Harposporium anamorph of P. peltata is demonstrated. The results show Podocrella and selected Harposporium LSU sequences form a monophyletic group and that this clade is closely related to Aschersonia. A new species of Podocrella from Costa Rica, P fusca, is described, new combinations made for P. peltata and P. harposporifera, and a key to the known species is presented.

Taxonomy of Australian clinical isolates of the genus Photorhabdus and proposal of Photorhabdus asymbiotica subsp. asymbiotica subsp. nov. and P. asymbiotica subsp. australis subsp. nov

The relationship of Photorhabdus isolates that were cultured from human clinical specimens in Australia to Photorhabdus asymbiotica isolates from human clinical specimens in the USA and to species of the genus Photorhabdus that are associated symbiotically with entomopathogenic nematodes was evaluated. A polyphasic approach that involved DNA-DNA hybridization, phylogenetic analyses of 16S rRNA and gyrB gene sequences and phenotypic characterization was adopted. These investigations showed that gyrB gene sequence data correlated well with DNA-DNA hybridization and phenotypic data, but that 16S rRNA gene sequence data were not suitable for defining species within the genus Photorhabdus. Australian clinical isolates proved to be related most closely to clinical isolates from the USA, but the two groups were distinct. A novel subspecies, Photorhabdus asymbiotica subsp. australis subsp. nov. (type strain, 9802892T=CIP 108025T=ACM 5210T), is proposed, with the concomitant creation of Photorhabdus asymbiotica subsp. asymbiotica subsp. nov. Analysis of gyrB sequences, coupled with previously published data on DNA-DNA hybridization and PCR-RFLP analysis of the 16S rRNA gene, indicated that there are more than the three subspecies of Photorhabdus luminescens that have been described and confirmed the validity of the previously proposed subdivision of Photorhabdus temperata. Although a non-luminescent, symbiotic isolate clustered consistently with P. asymbiotica in gyrB phylogenetic analyses, DNA-DNA hybridization indicated that this isolate does not belong to the species P. asymbiotica and that there is a clear distinction between symbiotic and clinical species of Photorhabdus.

Extracellular enzymes serving as virulence factors in nematophagous fungi involved in infection of the host

Extracellular enzymes, including serine protease, chitinase and collagenase, corresponding to the main chemical constituents of the nematode cuticle and eggshell, have been reported to be involved in the infectious process as virulence factors. This review will focus on the categories, characterization, purification, cloning and potential function of these virulence enzymes and will attempt to provide new insights into the mechanisms of fungal pathogenesis in nematodes.

The pbgPE operon in Photorhabdus luminescens is required for pathogenicity and symbiosis

Photorhabdus is a genus of gram-negative Enterobacteriaceae that is pathogenic to insect larvae while also maintaining a mutualistic relationship with nematodes from the family Heterorhabditis, where the bacteria occupy the gut of the infective juvenile (IJ) stage of the nematode. In this study we describe the identification and characterization of a mutation in the pbgE1 gene of Photorhabdus luminescens TT01, predicted to be the fifth gene in the pbgPE operon. We show that this mutant, BMM305, is strongly attenuated in virulence against larvae of the greater wax moth, Galleria mellonella, and we report that BMM305 is more sensitive to the cationic antimicrobial peptide, polymyxin B, and growth in mildly acidic pH than the parental strain of P. luminescens. Moreover, we also show that the lipopolysaccharide (LPS) present on the surface of BMM305 does not appear to contain any O antigen. Complementation studies reveal that the increased sensitivity to polymyxin B and growth in mildly acidic pH can be rescued by the in trans expression of pbgE1, while the defects in O-antigen assembly and pathogenicity require the in trans expression of pbgE1 and the downstream genes pbgE2 and pbgE3. Finally, we show that BMM305 is defective in symbiosis as this mutant is unable to colonize the gut of the IJ stage of the nematode. Therefore, we conclude that the pbgPE operon is required for both pathogenicity and symbiosis in P. luminescens.

Wolbachia.Bacterial Endosymbionts of Filarial Nematodes

Filarial nematodes are important helminth parasites of the tropics and a leading cause of global disability. They include species responsible for onchocerciasis, lymphatic filariasis and dirofilariasis. A unique feature of these nematodes is their dependency upon a symbiotic intracellular bacterium, Wolbachia, which is essential for normal development and fertility. Advances in our understanding of the symbiosis of Wolbachia bacteria with filarial nematodes have made rapid progress in recent years. Here we summarise our current understanding of the evolution of the symbiotic association together with insights into the functional basis of the interaction derived from genomic analysis. Also we discuss the contribution of Wolbachia to inflammatory-mediated pathogenesis and adverse reactions to anti-filarial drugs and describe the outcome of recent field trials using antibiotics as a promising new tool for the treatment of filarial infection and disease.

High society (of nematologists)

A report on the 43rd annual meeting of the Society of Nematologists (SON), Estes Park, USA, 7-11 August 2004.

A report on the 43rd annual meeting of the Society of Nematologists (SON), Estes Park, USA, 7-11 August 2004.

Microbial control of diamondback moth, Plutella xylostella L. (Lepidoptera: Yponomeutidae) using bacteria (Xenorhabdus nematophila) and its metabolites from the entomopathogenic nematode Steinernema carpocapsae

Cells and cell-free solutions of the culture filtrate of the bacterial symbiont, Xenorhabdus nematophila taken from the entomopathogenic nematode Steinernema carpocapsae in aqueous broth suspensions were lethal to larvae of the diamondback moth Plutella xylostella. Their application on leaves of Chinese cabbage indicated that the cells can penetrate into the insects in the absence of the nematode vector. Cell-free solutions containing metabolites were also proved as effective as bacterial cells suspension. The application of aqueous suspensions of cells of X. nematophila or solutions containing its toxic metabolites to the leaves represents a possible new strategy for controlling insect pests on foliage.

sp. nov., an anamorphic ascomycetous yeast associated with nematodes in poplar slime flux

A new species of Botryozyma, Botryozyma mucatilis, was isolated from the surface of free-living nematodes, Panagrellus dubius, inhabiting slime flux from hybrid poplars, Populus deltoidesxtrichocarpa, in Oregon, USA. This species was discovered in relatively close proximity to the teleomorphic species Ascobotryozyma americana and Ascobotryozyma cognata, both collected from P. dubius nematodes inhabiting beetle galleries in Populus spp. and Populus and Salix spp., respectively. B. mucatilis is recognized as a distinct species based on molecular and morphological data. Sequence divergence in both the D1/D2 domain of the nuclear large-subunit rDNA and internal transcribed spacer region rDNA, low DNA reassociation values, notably different amplified fragment-length polymorphic fingerprints, and significantly longer cells all support the designation of a novel species.

AstR-AstS, a new two-component signal transduction system, mediates swarming, adaptation to stationary phase and phenotypic variation in Photorhabdus luminescens

Photorhabdus luminescens is an insect-pathogenic bacterium that forms a symbiosis with specific entomopathogenic nematodes. In this bacterium, a symbiosis-'deficient' phenotypic variant (known as the secondary variant or form II) arises at a low frequency during prolonged incubation. A knock-out mutant was generated of the regulator of a newly identified two-component regulatory system, designated AstR-AstS. Interestingly, this mutation altered the timing of phenotypic switching. Variant cells arose in the mutant strain several days before they did in the wild-type population, suggesting that AstRS is directly or indirectly involved in the genetic mechanism underlying variant cell formation. This mutation also affected motility and antibiotic synthesis. To identify AstRS-regulated genes, a comparative analysis using two-dimensional gel electrophoresis was performed. Seventeen proteins with modified synthesis in stationary phase were identified by mass spectrometry and shown to be involved in electron-transport systems, energy metabolism, iron acquisition and stress responses. The results imply that AstRS is involved in the adaptation of cells to the stationary phase, whilst negatively affecting the competitive advantage of form I cells. The link between AstRS-dependent stationary-phase adaptation and phenotypic variation is discussed.

Dense molecular marking reveals genetic diversity in morphologically similar isolates of the nematophagous fungus Duddingtonia flagrans

Three morphologically similar isolates of Duddingtonia flagrans [(Duddington) R. C. Cooke] viz., Df-2550, Df-2507 and Df-BJ were subjected to RAPD (Randomly Amplified Polymorphic DNA) and SRFA (Selective Fragment Length Amplification) mode of DNA fingerprinting analysis to generate 233 different anonymous DNA markers. Mean number of alleles per primer/primer pair for RAPD and SRFA primers was 13.75 and 29.66 respectively. Phylogenetic analysis through bootstrapping of 1000 simulated replicates of the data set demonstrated that Df-2550 was ancestral in the group of three and did not align with Df-2507 and Df-BJ, which appeared to diversify recently and therefore remained at the end of the phylogenetic tree. Genomic islands were also identified by three SRFA primer pairs, where Df-2550 aligned with Df-BJ, which is reverse to the master consensus-grouping pattern. Scanning image of the amplicon profiles when represented graphically generated unique molecular signature for the isolates.

Implications of Fungicidal Effects of Benzimidazole Compounds on Duddingtonia flagrans in Integrated Nematode Parasite Management in Livestock

An in vitro trial with carbendazim fungicide on the growth profile of the predatory fungus Duddingtonia flagrans was undertaken and in vivo trials in sheep and buffaloes, fed on chlamydospores of D. flagrans and administered albendazole anthelmintic, were conducted. Although no growth inhibition was detected at a carbendazim concentration of 0.05 ppm, growth inhibition was recorded of 50% and above at concentrations of 0.25 and 1.00 ppm (p < 0.001) and of around 90% at concentrations of 2.00 to 5.00 ppm (p <0.0001). Scanty recovery of the fungus was made from faecal culture 48 h following a single dose of albendazole both in sheep and buffaloes. However, profuse fungal recovery was made from 96 h post dosing onwards. When the drug was used as an intraruminal slow-release capsule, no faecal fungal recovery could be made from day 3 after administration of the capsule, when the albendazole sulphoxide concentration was around 1.0 microg/ml. However, profuse and scanty fungal recovery could be made on days 1 and 2, respectively, after administration of the capsule, when the plasma albendazole sulphoxide concentration was around 0.4 and 0.9 microg/ml, respectively. The implications for use of a combination of anthelmintics and biological control in sustainable parasite control programmes are discussed.

Interaction between lactic acid bacteria and gastrointestinal nematodes of caprine origin

To compare the level of parasitism with gastrointestinal nematodes in sheep and goats, several studies have been conducted. They have generally shown that goats were more infected than sheep, as they exhibited higher worm burdens and egg excretion. This difference between two host species has been attributed not only to a difference in feeding behavior, but also to a lesser ability of goats to develop resistance to trichostrongylate infection (In kids and lambs the greatest damage is observed from weaning until 1 yr of age; mature mothers, before and after parturition and during suckling, are affected). In the last few decades, the most common tool (and frequently the only one) used for controlling internal parasites in livestock was the anthelmintic drugs. The application of anthelmintic treatments; must be accompanied by epidemic data and determinations supporting the appropriate timing and frequency of animal treatment. This view has not always been respected. In our country, because of a decrease in price, the anthelmintic drugs were used indiscriminately, causing the resistance we see today. This serious problem, added to the objective of producing organic foods without drug residuals, calls for better use of the antiparasitic drugs and for the developmentment of alternative methods that are ecologically viable and without risks for human health.Little information is available on the interactions between bacteria and intestinal nematodes of caprine origin. Some reports note ovicidal activity of different strains of Bacillus thuringiensis on the eggs of zooparasitic nematodes. Recent work found inhibitory actions of lactic bacteria on gastrointestinal nematodes (both of caprine origin). In the present chapter we describe the methods used for the determination of interactions between lactic acid bacteria and nematodes.

Pathogenomics

The genomes described this month reflect the overall historical bias of microbial genomics towards pathogenic bacteria. Although the balance is now being redressed to some extent, especially through the study of extremophiles, it is still the case that the opportunities provided by genomic studies are primarily taken up by those who study bacterial pathogenicity. This part of the field is, however, being broadened by including the study of pathogens of animals, insects and plants alongside those that afflict humans.