Ultrastructure and localization of Neorickettsia in adult digenean trematodes provides novel insights into helminth-endobacteria interaction

Abstract

Background Neorickettsia are a group of intracellular α proteobacteria transmitted by digeneans (Platyhelminthes, Trematoda). These endobacteria can also infect vertebrate hosts of the helminths and cause serious diseases in animals and humans. Neorickettsia have been isolated from infected animals and maintained in cell cultures, and their morphology in mammalian cells has been described. However, limited information is available on the morphology and localization of Neorickettsia in the trematode host.MethodsWe used a Neorickettsia-infected strain of the model trematode Plagiorchis elegans to infect Syrian Golden hamsters to produce adult worms. Ultrastructure of Neorickettsia was assessed by transmission electron microscopy of high pressure freezing/freeze substitution fixed specimens. A Neorickettsia surface protein from P. elegans (PeNsp-3) was cloned and antibodies against the recombinant protein were used to localize Neorickettsia by immunohistochemistry.ResultsUltrastructural analysis revealed moderate numbers of pleomorphic endobacteria with a median size of 600 × 400 nm and characteristic double membranes in various tissue types. Endobacteria showed tubular membrane invaginations and secretion of polymorphic vesicles. Endobacteria were unevenly localized as single cells, or less frequently as small morula-like clusters in the ovary, Mehlis’ gland, vitelline follicles, uterus, intrauterine eggs, testis, cirrus-sac, tegument, intestine and the oral and ventral sucker. Examination of hamster small intestine infected with P. elegans showed many endobacteria at the host-parasite interface such as the oral and ventral sucker, the tegument and the excretory pore.ConclusionsWe conclude that adult P. elegans trematodes carry Neorickettsia endobacteria in varying numbers in many tissue types that support vertical transmission, trematode to trematode transmission via seminal fluid, and possibly horizontal transmission from trematodes to vertebrate hosts. These means appear to be novel mechanisms of pathogen transmission by endoparasitic worms.Electronic supplementary materialThe online version of this article (doi:10.1186/s13071-017-2123-7) contains supplementary material, which is available to authorized users.

Host phenotype and microbiome vary with infection status, parasite genotype, and parasite microbiome composition

“…solidus was dominated by Proteobacteria and Firmicutes, and to a lesser extent with Bacteroidetes, Actinobacteria and Chloroflexi. The microbiome of the trematodes Coitocaecum parvum , Philophthalmus attenuates , and Opisthorchis viverrini are also dominated by Firmicutes, Proteobacteria and Actinobacteria (Chng et al, 2016; Fischer et al, 2017; Itthitaetrakool et al, 2016; Jorge et al, 2021; Leggett et al, 2014; Ling et al, 2020). Together, these results strongly support the hypothesis that any parasitic flatworm may host a microbiome and encourage studies to investigate the structure and function of helminth microbiome.…”

“…Parasites can also host microbes and for some parasites, such as nematodes and some digenean trematodes, the role of bacterial symbionts in virulence and pathogenesis has been thoroughly investigated (Fischer et al, 2017; Lawrence & Poulin, 2016; Pusterla et al, 2003; Taylor et al, 2005; Vaughan et al, 2012). However, for most parasite taxa, their associated microbiota remains unknown, and in fact, the presence of other bacteria in trematodes and nematodes has not yet been thoroughly investigated (Hahn & Dheilly, 2016).…”

Characterization and localization of antigens for serodiagnosis of human paragonimiasis

“…Two blocks with three flukes per block were sectioned, stained, and analyzed. The alkaline phosphatase-anti-alkaline phosphatase (APAAP) technique was used as previously described for immunostaining (Fischer et al 2011a(Fischer et al , 2017. Briefly, the unstained tissue sections were rehydrated and incubated in 10% bovine serum albumin (Sigma) for 30 min to reduce background staining.…”

“…The slides were examined with an Olympus-BX40 microscope (Olympus, Tokyo, Japan) and photographed with an Olympus DP70 digital camera. For fluorescence microscopy, Alexa Fluor 488 anti-mouse IgG (Invitrogen, green fluorescence) was used as the secondary antibody, and wheat germ agglutinin 633 (200 μg/ml, Invitrogen, red fluorescence), and DAPI (Prolong Antifade with DAPI, Molecular Probes by Life Technologies, Carlsbad, CA, USA, blue fluorescence) were used to label membranes and double-stranded DNA, respectively (Fischer et al 2017;McNulty et al 2017). Sections were examined with a wide field fluorescence microscope (WFFM, Zeiss Axios Imager Upright Fluorescence Microscope) with planapochromat × 100 oil, × 63, or × 40 objectives.…”

The host phenotype and microbiome varies with infection status, parasite origin and parasite microbiome composition

“…Many nematodes depend on Wolbachia for normal development and fertility, and the bacteria also contributes to inflammation and adverse reaction to anti-filarial drugs [51]. Similarly, the bacteria Neorickettsia has high prevalence among digenean trematodes and is often transmitted to parasitized hosts causing associated diseases [52][53][54][55]. But, for most parasite taxa, their associated microbiota remains unknown, and in fact, the presence of other bacteria in trematodes and nematodes has not yet been thoroughly investigated [56].…”