Bacterial Microbiota Associated with the Glacier Ice Worm Is Dominated by Both Worm-Specific and Glacier-Derived Facultative Lineages

Abstract

The community structure of bacteria associated with the glacier ice worm Mesenchytraeus solifugus was analyzed by amplicon sequencing of 16S rRNA genes and their transcripts. Ice worms were collected from two distinct glaciers in Alaska, Harding Icefield and Byron Glacier, and glacier surfaces were also sampled for comparison. Marked differences were observed in bacterial community structures between the ice worm and glacier surface samples. Several bacterial phylotypes were detected almost exclusively in the ice worms, and these bacteria were phylogenetically affiliated with either animal-associated lineages or, interestingly, clades mostly consisting of glacier-indigenous species. The former included bacteria that belong to Mollicutes, Chlamydiae, Rickettsiales, and Lachnospiraceae, while the latter included Arcicella and Herminiimonas phylotypes. Among these bacteria enriched in ice worm samples, Mollicutes, Arcicella, and Herminiimonas phylotypes were abundantly and consistently detected in the ice worm samples; these phylotypes constituted the core microbiota associated with the ice worm. A fluorescence in situ hybridization analysis showed that Arcicella cells specifically colonized the epidermis of the ice worms. Other bacterial phylotypes detected in the ice worm samples were also abundantly recovered from the respective habitat glaciers; these bacteria may be food for ice worms to digest or temporary residents. Nevertheless, some were overrepresented in the ice worm RNA samples; they may also function as facultative gut bacteria. Our results indicate that the community structure of bacteria associated with ice worms is distinct from that in the associated glacier and includes worm-specific and facultative, glacier-indigenous lineages.

Metagenomic analyses highlight the symbiotic association between the glacier stonefly Andiperla willinki and its bacterial gut community

“…DNA was extracted from the faecal and glacier surface samples using bead beating methods described previously by Murakami et al . () and Segawa et al . () respectively.…”

“…This implies that some glacier‐indigenous bacterial strains specifically proliferate and are enriched in the gut environment of the glacier stonefly nymph. Previous studies have also inferred a symbiotic association between Polaromonas species and snow algae (Gawor et al ., ; Terashima et al ., ), while a specific association was also suggested between glacier‐indigenous bacterial taxa and the glacier ice worm, Mesenchytraeus solifugus (Murakami et al ., ). Therefore, symbioses between glacier‐indigenous bacteria and eukaryotes, including invertebrates, may be a common phenomenon in glacier ecosystems.…”

“…DNA was extracted from the faecal and glacier surface samples using bead beating methods described previously by Murakami et al (2017) and Segawa et al (2014) respectively. The five surface samples per site were combined prior to DNA extraction.…”

“…16S rRNA gene amplicon libraries targeting the V3-V4 region were constructed as described previously (Murakami et al, 2017). Metagenomic libraries from the four faecal samples were constructed using a Nextera XT DNA Library Prep Kit (Illumina, San Diego, CA, USA) according to the manufacturer's instructions.…”

Outwitting planarian’s antibacterial defence mechanisms:Rickettsialesbacterial trans-infection fromParamecium multimicronucleatumto planarians

“…Such findings have clearly indicated the ability of those “aquatic” Rickettsiales to perform horizontal transmission including host species shift, although mostly from indirect evidence, i.e. closely related bacteria in hosts as different as ciliates, hydra [34], corals [35], ring worms [36], ascidians [37, 38], as well as incongruent host and symbionts phylogenies [3, 39, 40]. In few cases, direct evidence in experimental interspecific transfers between unicellular hosts was produced [19, 29].…”