Distribution and population structure of endobacteria in arbuscular mycorrhizal fungi at North Atlantic dunes

Abstract

Arbuscular mycorrhizal fungi (AMF, Glomeromycotina), in addition to forming symbioses with the majority of land plants, harbor vertically transmitted endosymbiotic bacteria 'Candidatus Glomeribacter gigasporarum' (CaGg) and 'Candidatus Moeniiplasma glomeromycotorum' (CaMg). CaGg is a nonessential mutualist of AMF, whereas the lifestyle of CaMg is unknown. To start unraveling the interactions between AMF and their endosymbionts in nature, we examined diversity and distribution of AMF-associated endobacteria in North Atlantic dunes at Cape Cod. Of nearly 500 foredune AMF isolates successfully genotyped during a systematic study, 94% were classified as Gigasporaceae. Two percent of all AMF spores harbored CaGg, and 88% contained CaMg. CaGg was found only in the Gigasporaceae, whereas CaMg was present in Gigasporaceae, Acaulosporaceae, and Diversisporaceae. Incidence of CaGg across AMF was not affected by any of the environmental parameters measured, whereas distribution of CaMg in one of the fungal hosts was impacted by plant density. CaMg populations associated with AMF individuals displayed high levels of genetic diversity but no evidence of gene flow, suggesting that host physical proximity is not sufficient to facilitate horizontal transmission of CaMg. Finally, in addition to a novel lineage of CaGg, we discovered that AMF likely harbor Burkholderia-related bacteria with close phylogenetic affinity to free-living Burkholderia and endobacteria of other Mucoromycota fungi.

Prevalence and Intra-Family Phylogenetic Divergence of <i>Burkholderiaceae</i>-Related Endobacteria Associated with Species of <i>Mortierella</i>

“…2 and Table 2). Furthermore, Lastovetsky et al (24) newly detected BRE in Acaulospora sp. ( Acaulosporaceae , Diversisporales , and Glomeromycotina) as a new fungal host group of BRE.…”

Conserved and reproducible bacterial communities associate with extraradical hyphae of arbuscular mycorrhizal fungi

“…The Betaproteobacteriales , formerly the Betaproteobacteria [ 52 ], are frequent and significant components of plant microbiomes [ 49 , 53 ] and our results add to previous reports of their interaction with AMF. Betaproteobacteriales interaction with AMF range from the vertically transmitted endosymbionts known as Burkholderia -like organisms ( Candidatus Glomeribacter gigasporarum ) [ 17 , 47 , 48 , 54 ] to more broad fungal-associated lifestyles. In vitro attachment of Betaproteobacteria to ERH was observed by Scheublin et al [ 32 ], who found Oxalobacteraceae were overrepresented in hyphal attached communities.…”

Genomic Analysis of Diverse Members of the Fungal Genus Monosporascus Reveals Novel Lineages, Unique Genome Content and a Potential Bacterial Associate

“…While preparing our assemblies for submission we noticed that three of the Monosporascus assemblies contained a substantial number of bacterial contigs that were classified as Ralstonia pickettii. The genus Ralstonia belongs to the Burkholderiaceae, a family that contains known fungal endosymbionts (Uehling et al 2017;Lastovetsky et al 2018;Bonfante and Lanfranco 2019). Previous studies have demonstrated that R. pickettii can exist as a bacterial endosymbiont in fungi and that it is capable of promoting fungal pathogenesis through this intimate relationship (Itabangi et al 2019).…”