Molecular diversity of bacterial endosymbionts associated with dagger nematodes of the genus Xiphinema (Nematoda: Longidoridae) reveals a high degree of phylogenetic congruence with their host

Abstract

Bacterial endosymbionts have been detected in some groups of plant-parasitic nematodes, but few cases have been reported compared to other groups in the phylum Nematoda, such as animal-parasitic or free-living nematodes. This study was performed on a wide variety of plant-parasitic nematode families and species from different host plants and nematode populations. A total of 124 nematode populations (previously identified morphologically and molecularly) were screened for the presence of potential bacterial endosymbionts using the partial 16S rRNA gene and fluorescence in situ hybridization (FISH) and confocal microscopy. Potential bacterial endosymbionts were only detected in nematode species belonging to the genus Xiphinema and specifically in the X. americanum group. Fifty-seven partial 16S rRNA sequences were obtained from bacterial endosymbionts in this study. One group of sequences was closely related to the genus 'Candidatus Xiphinematobacter' (19 bacterial endosymbiont sequences were associated with seven nematode host species, including two that have already been described and three unknown bacterial endosymbionts). The second bacterial endosymbiont group (38 bacterial endosymbiont sequences associated with six nematode species) was related to the family Burkholderiaceae, which includes fungal and soil-plant bacterial endosymbionts. These endosymbionts were reported for the first time in the phylum Nematoda. Our findings suggest that there is a highly specific symbiotic relationship between nematode host and bacterial endosymbionts. Overall, these results were corroborated by a phylogeny of nematode host and bacterial endosymbionts that suggested that there was a high degree of phylogenetic congruence and long-term evolutionary persistence between hosts and endosymbionts.

Remarkable Diversity and Prevalence of Dagger Nematodes of the Genus Xiphinema Cobb, 1913 (Nematoda: Longidoridae) in Olives Revealed by Integrative Approaches

“…pachtaicum may suggest also adaptability to a range of soil types, and reproduction sustained over a broad range of temperatures [112, 113]. Nevertheless, these wider ecological requirements are difficult to explain regarding their low genetic diversity [108] and could be more associated with the presence of specific ovarial-intestine endosymbionts [114], but some of the other species from the X . americanum -group also possesses ovarial-intestine endosymbionts and were more restricted to some areas ( viz .…”

“…plesiopachtaicum and X . rivesi ) [114]. Other species with a broad distribution were included in the X .…”

Comparative Genomics of Wolbachia–Cardinium Dual Endosymbiosis in a Plant-Parasitic Nematode

“…Belowground plant-feeding organisms can experience similar pressures due to plant-diet specialization. For example, the plant-parasitic nematode (PPN), Xiphinema americanum , has evolved one or more obligate endosymbionts with nutrient supplementation roles ( Brown et al, 2015 ; Palomares-Rius et al, 2016 ), whereas other PPNs appear to have evolved microbial partners to degrade plant compounds ( Cheng et al, 2013 ).…”

Metagenomics Analysis Reveals An Extraordinary Bacterial Diversity in Anisakids (Nematoda: Anisakidae) L3 Larvae

“…This association has been denominated metaorganism rst and holobiont afterwards [155] and has been considered as a "unit of natural selection" [156]. Following theses assumptions, [157] the rst systematic analysis of the native microbiome of Caenorhabditis elegans, which is mainly characterized by Proteobacteria including the genera Ochrobactrum, Pseudomonas, Stenotrophomonas and Sphingomonas was performed. In that study the native microbiome of wild type naturate C. elegans strains in comparison with the congeneric species C. briggsae and C. remanei was described.…”