Detection of a new bacterium of the family Holosporaceae (Alphaproteobacteria: Holosporales) associated with the oribatid mite Achipteria coleoptrata

Abstract

We detected an unknown bacterium in Achipteria coleoptrata (Acari: Oribatida). Its 16S rDNA gene sequence showed 89% identity to the endosymbiont BCandidatus Nucleicultrix amoebiphila^from amoebae and BCandidatus Gortzia sp.^from ciliates. Phylogenetic analysis revealed that the microorganism is a member of the family Holosporaceae, order Holosporales of Alphaproteobacteria. Its occurrence in Oribatida is enigmatic. It cannot be excluded that it is a symbiont of Oribatida as well as it is an endosymbiont of a smaller, even unicellular, organisms living inside the mite. The issue of the occurrence of this microorganism is interesting and further research is needed to gain the knowledge of its role and the nature of bacterium-host interaction.

‘Candidatus Gromoviella agglomerans’, a novel intracellular Holosporaceae parasite of the ciliate Paramecium showing marked genome reduction

“…Bealeia’). In any case, the present data indicate probable recurring host species shifts along the evolutionary history of Holosporaceae , involving several hosts, mostly protists, in particular ciliates, as well as arthropods (Jones et al ., 2008; Nunan et al ., 2013; Konecka and Olszanowski, 2019). Horizontal transfer abilities, even within the same hosts species, were experimentally observed for several of these bacteria, including many Holospora and HLB (Schrallhammer and Potekhin, 2020) as well as Gromoviella in this study, and are consistent with such reconstructions.…”

“…Holospora and HLB display a peculiar dimorphic infectious life cycle, along which they invade the host nuclear apparatus (Schrallhammer and Potekhin, 2020). Other Holosporaceae bacteria were retrieved in association with protists, including diverse ciliates (Eschbach et al ., 2009; Szokoli et al ., 2016; Takeshita et al ., 2019; Korotaev et al ., 2020) and diplonemids (Tashyreva et al ., 2018; George et al ., 2020), as well as with arthropods (Jones et al ., 2008; Nunan et al ., 2013; Konecka and Olszanowski, 2019). Some of them show peculiar localization, namely in proximity or even within host nuclei (Eschbach et al ., 2009; Szokoli et al ., 2016) or near mitochondria/hydrogenosomes (Tashyreva et al ., 2018; Takeshita et al ., 2019; Korotaev et al ., 2020).…”

Novel evolutionary insights on the interactions of the Holosporales (Alphaproteobacteria) with eukaryotic hosts from comparative genomics

“…Until now, due to the paucity of available genomic sequences, most phylogenetic studies on Holosporales relied only on 16S rRNA gene sequences (Konecka & Olszanowski, 2019; Korotaev et al, 2020; Szokoli et al, 2016; Takeshita et al, 2019; Tashyreva et al, 2018), which however could not resolve with high support multiple inner relationships. Here, the newly obtained Bealeia genome allowed us to get much more reliable reconstructions.…”

“…Paracaedibacteraceae’, form a monophylum (Muñoz‐Gómez et al, 2019; Szokoli et al, 2016). Holosporaceae are intracellularly associated with protists, such as ciliates and diplonemids (Boscaro et al, 2019; Castelli, Lanzoni, et al, 2022; George et al, 2020; Korotaev et al, 2020; Potekhin et al, 2021; Shiohama et al, 2022; Szokoli et al, 2016; Tashyreva et al, 2018), as well as with arthropods, such as crustaceans and arachnids (Konecka & Olszanowski, 2019; Nunan et al, 2013). According to the available genome sequences, a trend towards genome reduction was evidenced within this family, reaching much more extreme levels than other Holosporales and in general other professional symbionts (frequently below 1 Mb, down to ~600 Kb) (Castelli, Lanzoni, et al, 2022; George et al, 2020; Shiohama et al, 2022).…”

“Candidatus Intestinibacterium parameciiphilum”—member of the “Candidatus Paracaedibacteraceae” family (Alphaproteobacteria, Holosporales) inhabiting the ciliated protist Paramecium

“…Paracaedibacteraceae”, “ Caedimonadaceae ”, and Holosporaceae families (Fig. 1 ) were as well typically retrieved in association with freshwater protists, such as amoebozoans, ciliates, dinoflagellates, cercozoans, and euglenids (Horn et al 1999 ; Birtles et al 2000 ; Baker et al 2003 ; Kim et al 2010 ; Schulz et al 2014 ; Szokoli et al 2016a ; Hess et al 2016 ; Schrallhammer et al 2018 ; Potekhin et al 2018 ; Boscaro et al 2019 ; Takeshita et al 2019 ; Schrallhammer and Potekhin 2020 ), with only few exceptions, such as marine diplonemids (Tashyreva et al 2018 ), brackish water ciliates (Fokin et al 2019 ), and marine (Nunan et al 2013 ) and terrestrial arthropods (Konecka and Olszanowski 2019 ). Thus, these data allow us to speculate on whether even more ancient ancestors of Holosporales could have been preferentially associated with freshwater protists.…”