Rhabditis Sp Research Articles

Pathogenicity of native Strains of Entomopathogenic Nematodes against Aphids and Pseudostem Weevil

The pathogenicity of three native strains of entomopathogenic nematodes isolated from different locations of Kerala were evaluated against aphids, Aphis craccivora Koch and 4th instar grubs of banana pseudostem weevil, Odoiporous longicollis Olivier under laboratory condition. Based on the morphological characters and morphometric measurements, they were identified as Steinernema sp., Metarhabditis sp. and Rhabditis sp. Metarhabditis sp. @ 100 IJs (infective juveniles) recorded 100% mortality of aphids at 48 HAT (hours after treatment) and it was statistically on par with dimethoate 30EC. Metarhabditis sp.@ 100 and 200 IJs/ insect showed 47.49 and 62.66% mortality of pseudostem weevil grubs at 72 HAT. Molecular characterization of the most potent isolate effective against both the pests was done and it was identified as Metarhabditis rainai.

An update of intestinal helminth infections among urban slum communities in Bangladesh

To assess the prevalence of intestinal helminth infections and associated risk factors among people living in urban slums in Bangladesh. A cross-sectional study was conducted across three clusters: Dhaka, Sylhet and Chattogram. In total, 360 individuals divided into two groups (school-aged children and adults) provided stool samples and completed a semi-structured questionnaire. Parasitological assessment was performed using the formol-ether concentration technique. Overall, 31.7% (114/360) of participants had helminthiasis, with 13.3% (48/360) having mixed infections. Among the infected participants, school-aged children had a higher rate of infection (41.7%, 75/180) compared with adults (21.7%, 39/180). Ascaris lumbricoides was the predominant parasite, followed by hookworms, Trichuris trichiura, Hymenolepis nana, Enterobius vermicularis and Rhabditis sp. Parasitic infections were significantly associated with type of latrine used, direct exposure to soil, open defaecation, and presence of free-roaming animals. Despite continuous efforts to control helminthiasis, a substantial proportion of the study participants were infected with intestinal helminths. Ignorance of the roles of the environment and animals was influential, and had a negative impact on existing control interventions. An integrated public health and veterinary public health approach is required for sustainable control of intestinal helminthiasis.

Discovery of Cinnamylidene Derivative of Rhodanine with High Anthelmintic Activity against Rhabditis sp.

The treatment of parasitic infections requires the application of chemotherapy. In view of increasing resistance to currently in-use drugs, there is a constant need to search for new compounds with anthelmintic activity. A series of 16 cinnamylidene derivatives of rhodanine, including newly synthesized methoxy derivatives (1–11) and previously obtained chloro, nitro, and diethylamine derivatives (12–16), was investigated towards anthelmintic activity. Compounds (1–16) were evaluated against free-living nematodes of the genus Rhabditis sp. In the tested group of rhodanine derivatives, only compound 2 shows very high biological activity (LC50 = 0.93 µg/µL), which is higher than the reference drug albendazole (LC50 = 19.24 µg/µL). Crystal structures of two compounds, active 2 and inactive 4, were determined by the X-ray diffraction method to compare molecular geometry and search for differences responsible for observed biological activity/inactivity. Molecular modelling and selected physicochemical properties prediction were performed to assess the potential mechanism of action and applied in the search for an explanation as to why amongst all similar compounds only one is active. We can conclude that the tested compound 2 can be further investigated as a potential anthelmintic drug.

PARASITOFAUNA OF GIANT AFRICAN SNAILS (Achatina achatina) COMMERCIALISED IN DALOA (CENTER-WESTERN IVORY COAST)

Snails of the Achatina achatina species were collected at the markets of Daloa. Specifically, it was about identifying the species of parasites encountered at each collection site and their prevalence, then informing the intensity of infestation of each specie of parasites from the freshly emitted faeces. The flotation method that was used yielded the following results: On all three sites, the results showed the presence of larvae and eggs of Strongyloides sp, larvae of Rhabditis sp, and larvae of Harpacticoida sp . The parasite prevalences recorded are respectively 48.9% of Strongyloides sp larvae, 20% for Rhabditis sp and 31.1% for Harpacticoida sp. These results showed that the identified parasites can be transmitted to humans through snails.

Nematicidal activity of naphthalimide-boron cluster conjugates.

This study presents the activity of a series of 1,8-naphthalimide-carborane/metallacarborane conjugates against Rhabditis sp. The carborane conjugates were the least active. Selected conjugates with cobaltacarborane (5 and 6) showed high activity. Their lethal concentration (LC50) values are substantially lower than that of the drug mebendazole.

Micro-food web interactions involving bacteria, nematodes, and mycorrhiza enhance tree P nutrition in a high P-sorbing soil amended with phytate

Phytate is considered a poorly available plant P source but proved to be useful for particular soil bacteria strains. In soil-free conditions, it has been shown that bacteria locked up the mineralized phosphorus from phytate whereas bacterial grazers like nematodes were able to deliver P to plants. Here, we aimed to determine if the interactions between phytate-mineralizing bacteria, bacterial grazer nematodes, and mycorrhizal fungi could increase plant P acquisition from phytate in high P-adsorbing soils. Pinus pinaster was grown in a Cambisol supplemented with phytate. Plants, whether associated or not associated with the ectomycorrhizal fungus Hebeloma cylindrosporum, were either inoculated or not inoculated with the phytase-releasing bacteria Bacillus subtilis and the bacterial-feeding nematode Rhabditis sp. After 100 days, the dual inoculation of bacteria and nematodes significantly increased net plant P accumulation. We observed that, on average, mycorrhizal plants accumulated more P in their shoots than non-mycorrhizal plants. However, the highest plant P acquisition efficiency was found when the three soil organisms were present in the P. pinaster rhizosphere. We conclude that, in a highly inorganic P-fixing soil, plant P acquisition from phytate strongly depends on the grazing of phytate-mineralizing bacteria. Our results confirm the importance of the soil microbial loop to improve plant P nutrition from phytate, which should be considered a route to improve the utilization of this source of poorly available P by plants.

Получение иммунореагентов для серологического определения возбудителей дитиленхозов сельскохозяйственных и декоративных культур

The purpose of the research is obtaining immuno reagents for determination of two types of parasitic nematodes Ditylenchus destructor and D. dipsaci (antigens and antiserums for them). Materials and methods. Three immunizations of laboratory animals (white scrub mice) have been carried out at a dose of 20 mcg of the target protein per animal at 7–10 day intervals. The efficient titer of the antiserums obtained was described by the Dot-ELISA method using secondary goat anti-mouse immunoglobulins conjugated with alkaline phosphatase. For measuring a specificity of the obtained immuno reagents, an ELISA plate in an indirect format was used. Results and discussion. The antiserums obtained have a specificity for two types of nematodes D. destructor and D. dipsaci, and for one non-parasitic nematode Rhabditis sp. The specificity of the obtained antiserums ranges from 82 to 97%. The sensitivity of antiserums to homogenates of stem nematodes D. destructor and D. dipsaci of plants at the antiserum dilution 1 : 3000 is 1 ng and 50 ng accordingly.

Germ cell cysts and simultaneous sperm and oocyte production in a hermaphroditic nematode

Studies of gamete development in the self-fertile hermaphrodites of Caenorhabditis elegans have significantly contributed to our understanding of fundamental developmental mechanisms. However, evolutionary transitions from outcrossing males and females to self-fertile hermaphrodites have convergently evolved within multiple nematode sub-lineages, and whether the C. elegans pattern of self-fertile hermaphroditism and gamete development is representative remains largely unexplored. Here we describe a pattern of sperm production in the trioecious (male/female/hermaphrodite) nematode Rhabditis sp. SB347 (recently named Auanema rhodensis) that differs from C. elegans in two striking ways. First, while C. elegans hermaphrodites make a one-time switch from sperm to oocyte production, R. sp. SB347 hermaphrodites continuously produce both sperm and oocytes. Secondly, while C. elegans germ cell proliferation is limited to germline stem cells (GSCs), sperm production in R. sp. SB347 includes an additional population of mitotically dividing cells that are a developmental intermediate between GSCs and fully differentiated spermatocytes. These cells are present in males and hermaphrodites but not females, and exhibit key characteristics of spermatogonia — the mitotic progenitors of spermatocytes in flies and vertebrates. Specifically, they exist outside the stem cell niche, increase germ cell numbers by transit-amplifying divisions, and synchronously proliferate within germ cell cysts. We also discovered spermatogonia in other trioecious Rhabditis species, but not in the male/female species Rhabditis axei or the more distant hermaphroditic Oscheius tipulae. The discovery of simultaneous hermaphroditism and spermatogonia in a lab-cultivatable nematode suggests R. sp. SB347 as a richly informative species for comparative studies of gametogenesis.

Cytoskeletal variations in an asymmetric cell division support diversity in nematode sperm size and sex ratios

Asymmetric partitioning is an essential component of many developmental processes. As spermatogenesis concludes, sperm are streamlined by discarding unnecessary cellular components into cellular wastebags called residual bodies (RBs). During nematode spermatogenesis, this asymmetric partitioning event occurs shortly after anaphase II, and both microtubules and actin partition into a central RB. Here, we use fluorescence and transmission electron microscopy to elucidate and compare the intermediate steps of RB formation in Caenorhabditis elegans, Rhabditis sp. SB347 (recently named Auanema rhodensis) and related nematodes. In all cases, intact microtubules reorganize and move from centrosomal to non-centrosomal sites at the RB-sperm boundary whereas actin reorganizes through cortical ring expansion and clearance from the poles. However, in species with tiny spermatocytes, these cytoskeletal changes are restricted to one pole. Consequently, partitioning yields one functional sperm with the X-bearing chromosome complement and an RB with the other chromosome set. Unipolar partitioning may not require an unpaired X, as it also occurs in XX spermatocytes. Instead, constraints related to spermatocyte downsizing may have contributed to the evolution of a sperm cell equivalent to female polar bodies.

Mating dynamics in a nematode with three sexes and its evolutionary implications

Nematodes have diverse reproductive strategies, which make them ideal subjects for comparative studies to address how mating systems evolve. Here we present the sex ratios and mating dynamics of the free-living nematode Rhabditis sp. SB347, in which males, females and hermaphrodites co-exist. The three sexes are produced by both selfing and outcrossing, and females tend to appear early in a mother’s progeny. Males prefer mating with females over hermaphrodites, which our results suggest is related to the female-specific production of the sex pheromones ascr#1 and ascr#9. We discuss the parallels between this system and that of parasitic nematodes that exhibit alternation between uniparental and biparental reproduction.

Purification and identification of an antibacterial protein from the symbiotic bacteria associated with novel entomopathogenic nematode, Rhabditis (Oscheius) sp.

Entomopathogenic nematodes (EPN) belonging to the families steinernematidae and heterorhabditidae and their symbiotic bacteria Xenorhabdus and Photorhabdus are well-known as biological control agents and are found to produce a wide range of bioactive secondary metabolites. Studies carried out at the Central Tuber Crops Research Institute (CTCRI) on entomopathogenic nematodes resulted in the identification of novel EPN belonging to the family Rhabditidae. This study reports the purification of a high molecular weight antibacterial protein from culture filtrates of a bacterium (Bacillus cereus) symbiotically associated with a novel entomopathogenic nematode Rhabditis (Oscheius) species, maintained at CTCRI laboratory. Fermentation conditions were standardized and optimum antibacterial activity was observed in tryptic soy broth after 48h incubation at 30°C. The aqueous extracts yielded antibacterial proteins which were purified by ammonium sulfate precipitation followed by ion exchange chromatography and size exclusion chromatography. Native gel electrophoresis indicated an active protein of molecular mass 220KDa which resolved into a major band of 90kDa and a minor band of about 40kDa on SDS-PAGE. The 90kDa protein showed antibacterial activity and was further analysed by MALDI TOF-MS/MS. The protein was identified as a TQXA (Threonine-glutamine dipeptide) domain containing protein from Bacillus cereus. The protein was found to be active against Bacillus subtilis MTCC2756, Staphylococus aureus MTCC902 and Escherichia coli MTCC 2622 and was thermally stable.

Outer Ear Canal Infection with Rhabditis sp. Nematodes in a Human

Here we report the first human case of an outer ear canal infection with a free-living nematode of the genus Rhabditis. Otomicroscopy revealed viable worms in the outer ear canal of a patient suffering from chronic otorrhea and hearing loss. The nematode was identified by microscopy and internal transcribed spacer (ITS)-PCR.

Evaluation of predation of the mite Lasioseius penicilliger (Aracnida: Mesostigmata) on Haemonchus contortus and bacteria-feeding nematodes

Predation by the mite Lasioseius penicilliger was studied on three nematode species, i.e. infective larval stages (L3) of Haemonchus contortus and adults of Panagrellus redivivus and Rhabditis sp. Experiments were carried out in 5.5-cm diameter Petri dishes containing 2% water-agar over a period of 5 days. Batches of up to 1500 third-stage larvae (L3) of H. contortus and 1000 adult nematodes of P. redivivus and Rhabditis sp. were exposed to five mites in separate Petri dishes. Upon contact, each mite used its pedipalp and legs to identify and hold its prey and then used its chelicerae to feed upon the prey. Predation by L. penicilliger was chance dependent but mites became aggregated around any injured/damaged prey, thereby suggesting some form of chemoperception. The rate of predation on the three species of nematodes was high but L3 of H. contortus and adult Rhabditis sp. were preferred.

Regulation of Sexual Plasticity in a Nematode that Produces Males, Females, and Hermaphrodites

The mechanisms by which new modes of reproduction evolve remain important unsolved puzzles in evolutionary biology. Nematode worms are ideal for studying the evolution of mating systems because the phylum includes both a large range of reproductive modes and large numbers of evolutionarily independent switches [1, 2]. Rhabditis sp. SB347, a nematode with sexual polymorphism, produces males, females, and hermaphrodites [3]. To understand how the transition between mating systems occurs, we characterized the mechanisms that regulate female versus hermaphrodite fate in Rhabditis sp. SB347. Hermaphrodites develop through an obligatory nonfeeding juvenile stage, the dauer larva. Here we show that by suppressing dauer formation, Rhabditis sp. SB347 develops into females. Conversely, larvae that under optimal growth conditions develop into females can be respecified toward hermaphroditic development if submitted to dauer-inducing conditions. These results are of significance to understanding the evolution of complex mating systems present in parasitic nematodes.

Asymmetric spermatocyte division as a mechanism for controlling sex ratios

Although Mendel's first law predicts that crosses between XY (or XO) males and XX females should yield equal numbers of males and females, individuals in a wide variety of metazoans transmit their sex chromosomes unequally and produce broods with highly skewed sex ratios. Here, we report two modifications to the cellular programme of spermatogenesis, which, in combination, help to explain why males of the free-living nematode species Rhabditis sp. SB347 sire <5% male progeny. First, the spermatogenesis programme involves a modified meiosis in which chromatids of the unpaired X chromosome separate prematurely, in meiosis I. Second, during anaphase II, cellular components essential for sperm motility are partitioned almost exclusively to the X-bearing sperm. Our studies reveal a novel cellular mechanism for the differential transmission of X-bearing sperm and suggest Rhabditis sp. SB347 as a useful model for studying sex chromosome drive and the evolution of new mating systems.

Mononchoides composticola n. sp. (Nematoda: Diplogastridae) associated with composting processes: morphological, molecular and autecological characterisation

Mononchoides composticola n. sp. was isolated from compost and is described based on light and scanning electron microscopy, supplemented with SSU rDNA sequence data. It is characterised by the following features: a denticulate ridge in addition to the dorsal claw-like tooth, a small tooth-like swelling at the stegostom base, ca 26 longitudinal ridges on the female body, a uterine sac associated with two dumb-bell-shaped pouches, relatively small spicules (30-38 µm long), a simple gubernaculum shorter than half the spicule length, the genital subventral papillae (v6) consisting of three very small papillae, and a long filiform tail (female: 391-550 µm, 18-26 anal body diam.; male: 304-548 µm, 19-30 anal body diam.). Phylogenetic analyses placed the new species together with M. striatus, sister to Tylopharynx foetida. Since the use of nematodes as functional indicators often relies on the allocation of nematodes to feeding groups, experiments were performed to elucidate the feeding strategy of the new species. Both its ability to move actively to bacterial food sources and to prey on other compost nematodes were tested. Mononchoides composticola n. sp. actively moved towards the compost bacterium Achromobacter, a taxis that was temperature dependent, and also preyed on other nematodes. Predation was selective, with a higher predation rate on the relatively small and slow-moving Rhabditella sp. than on the considerably larger and more motile Rhabditis (Poikilolaimus) sp. Adults of M. composticola n. sp. have a dual feeding behaviour and can apparently alternate between bacterial and nematode prey

Alternative morphs and plasticity of vulval development in a rhabditid nematode species

The nematode species Rhabditis sp. SB347 (Family Rhabditidae) in standard culture conditions displays two developmental morphs with distinct modes of sexual reproduction: (1). females and males that develop through four feeding juvenile ("larval") stages; (2). self-fertile protandric hermaphrodites that develop through an obligatory non-feeding third juvenile stage, the "dauer" larva. In females and males, somatic gonad development begins in the first larval stage, whereas in hermaphrodites it is delayed to the second larval stage. Vulval development also differs between females and hermaphrodites: (1). the P8.p cell divides in females but stays undivided in hermaphrodites; (2). the number, timing, and source of inductive signals from the gonad to the vulval precursor cells differ between the two morphs. These results show that discrete vulva developmental routes can be adopted by animals of the same genotype.

Um caso de parasitismo por Rhabditis sp em criança natural de Goiânia, Goiás, Brasil

We report a case of parasitism by Rhabditis sp in a five-month-old child, from Goiás State, Brazil. He had a history of diarrhea with liquid and green faeces which later became bloody. Parasitological examination revealed the presence of larvae and adult female of Rhabditis sp. We used thiabendazole in this case after which the child improved. The authors suggest a better differential diagnostic between Strongyloides and Rhabditis.

Effect of cold storage on survival and parasitic activity ofHetero Rhabditis SP.

Heterorhabditis sp. (HW79) was stored in its culture substrate in Erlenmeyer flasks at a temperature of 6,0±0,4°C. Surviving infective juveniles were counted after 1, 22, 42 and 63 days of storage respectively. No significant decrease in surviving juveniles was found even after 63 days, nor was there any increase in numbers of dead juveniles after this same time. No reduction in parasitic activity againstO. sulcatus-larvae could be observed of juveniles stored at 6°C for up to 66 days. These experiments demonstrate thatHeterorhabditis sp. survives well under the mentioned conditions and fully maintains its infectivity. This is an important aspect in planning mass production of nematodes for commercialization.

Mineralization of nitrogen and phosphorus by mixed cultures of the ciliate protozoan Colpoda steinii, the nematode Rhabditis SP. and the bacterium Pseudomonas fluorescens

Numbers of the ciliate protozoan Colpoda steinii Maupas were increased by the presence of a nematode (Rhabditis sp.), in soil and liquid culture. The development of nematode numbers was inhibited by the ciliate. Observations of hatching nematodes, together with counts of total and viable numbers of the bacterium Pseudomonas fluorescens, indicate that Rhabditis sp. increased bacterial productivity but that the activity of C. steinii inhibited feeding by the nematode. When the two bacterial grazers were present in combination C. steinii benefited from increased bacterial productivity induced by Rhabditis sp. Both grazers increased the mineralization of NH4+-N when added separately to soil, and this was further increased when nematodes and ciliates were present in combination. There was no effect of grazing on levels of bicarbonate-soluble phosphate (Pi), while nematodes had a variable effect on levels of soil NO3−-N.