Showcasing the role of seawater in bacteria recruitment and microbiome stability in sponges

Abstract

We studied the core bacterial communities of 19 sponge species from Nha Trang Bay (Central Vietnam), with particular emphasis on the contribution of planktonic seawater bacteria to the sponge core microbiomes. To ensure consistent sponge-microbe associations and accurate identification of planktonic bacteria transmitted from seawater, we were very restrictive with the definition of the sponge core microbiomes (present in all the replicates), and with the identification of valid biological 16S rRNA gene sequences (100% sequence identity) that belonged to potentially different bacterial taxa. We found a high overlap (>50% relative abundance) between the sponge species core microbiome and the seawater bacterial core in ca. a half of the studied species, including representatives of both, HMA and LMA sponges. From our restrictive analysis, we point to horizontal transmission as a relevant way of symbiont acquisition in sponges. Some species-specific recognition mechanisms may act in sponges to enrich specific seawater bacteria in their tissues. These mechanisms would allow the maintenance of bacterial communities in a species across geographical ranges. Moreover, besides contrasting preferences in bacteria selection from seawater, divergent physiological traits may also account for the different microbiomes in species of HMA and LMA sponges.

Host genetics and geography influence microbiome composition in the spongeIrcinia campana

“…Therefore, our results show that while genotype exerts an effect on non‐core microbiome taxa, it does not drive abundances of core taxa. This lends support to the theory that horizontal transmission has an important role in forming the core microbiome (Turon et al, ), as we may expect vertical transmission to produce significant genotype–core microbiome relationships. However, some refinement of the core microbiome concept and, in particular, the associated methodologies to define and identify ‘core’ taxa may be required to further our understanding of their significance, role and transmission.…”

“…At the 99% OTU level, the core microbiome in our study was comprised of two OTUs, which made up 1.2% and 1.3% of the total microbiome in Long Key and Kemp Channel, respectively. This core community appears small compared with results reported in some previous studies on sponges (Marino et al, ; Turon et al, ). Marino et al () found 119 core OTUs among 18 I. campana individuals, comprising 79.2%–87.0% of the total microbiome.…”

“…The core microbial genera in our study formed 63% and 69% of the total microbiome in Long Key and Kemp Channel, respectively, suggesting that the differences observed relative to previous work primarily reflect methodical differences (Astudillo‐García et al, ). Furthermore, the higher the number of replicates, the smaller the apparent ‘core’ microbiome appears (Turon et al, ), and in this study, the number of within‐species replicates we used ( n = 33) was substantially larger than in many previous studies.…”

“…Sponge microbiome composition is predominantly host-driven, with only a small degree of overlap with seawater microbial communities (Hentschel et al, 2002;Schmitt et al, 2012). Similarly, relatively few microbial taxa are shared across the phylum, and host species is a key determinant of microbiome composition (Blanquer, Uriz, & Galand, 2013;Pita, Turon, López-Legentil, & Erwin, 2013;Schmitt et al, 2012;Thomas et al, 2016;Turon, Cáliz, Garate, Casamayor, & Uriz, 2018). This strong association is thought to be driven by a combination of vertical transmission of microbial associates (i.e., parent to offspring transmission) and horizontal transmission of seawater microbes to highly selective host environments (Fieth, Gauthier, Bayes, Green, & Degnan, 2016;Thacker & Freeman, 2012;Turon et al, 2018).…”

“…Despite the strong effect of host species identity, significant variation in microbiome composition is still present within host sponge species (Thomas et al, 2016;Turon et al, 2018). Intraspecific microbiome variation has been associated with environmental variation, such as geographic location (Fiore, Jarett, & Lesser, 2013;Luter et al, 2015;Swierts, Cleary, & de Voogd, 2018), depth (Morrow, Fiore, & Lesser, 2016), habitat (Cleary et al, 2013;Weigel & Erwin, 2017) and water quality (Luter et al, 2015).…”