Diversity of bacterial communities associated with Spongilla lacustris (Linnaeus, 1759) specimens inhabiting two different sub-Arctic freshwater environments

Description

The associations between microbial populations and porifera are the topic of several studies, driven by the interest of a better understanding of dynamics in these relationships. It has been proven that sponges tend to actively select the microbial components for a closer relationship, and that these microbial communities play pivotal roles in the wellbeing of their hosts. The knowledge of freshwater sponge microbiomes is still scantly explored, especially in the Arctic areas. Within the INTERACT projects BIP and CIRCE (Grant Agreement EU2020 no. 730938) sponge specimens of Spongilla lacustris (Linnaeus, 1759) were collected from the Pasvik River (Norway) and the Kevo Lake (Finland), both in the Northern Fennoscandia. Physical-chemical parameters were measured at sampling time. Here we aim at comparing the microbial communities associated with the two sponges, with the intention of highlighting differences between the microbial populations and relating them to the different environmental conditions. Microbial community diversity was investigated by next generation sequencing (NGS) after DNA extraction and amplification with standard universal primers. Analysis of biomass, live/dead cells, microbial enzymatic activities (leucine aminopeptidase, LAP, beta-glucosidase, GLU, alkaline phosphatase, AP) were additionally carried out. Proteobacteria (Alpha- and Gammaproteobacteria) predominated in both the sponge-associated microbial communities, but some differences at phylum and genus level occurred in the samples, probably related to the different origin of the sponges. The occurrence of high percentage of chloroplast was observed in both S. lacustris bacterial sequences. Data of diversity, enzymatic values, cellular abundance and morphology are discussed in relation to the physical-chemical parameters.

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