Diversity of Epiphytic Bacterial Communities Associated with Adriatic Fucacean Species Phycosphere

Abstract

The aim of the study was to explore the relationship between membrane-regulating functional lipids of three fucacean species and their associated epiphytic bacterial communities. The analyzed algae Treptacantha barbata, Carpodesmia crinita and Cystoseira compressa, formerly classified under the Cystoseira genus, are indigenous to the Adriatic Sea. The thalli of sampled Fucales species were divided into perennial and annual parts. T. barbata and C. crinita show high contents of mono- and polyunsaturated fatty acids but, however, show a clear distinction between branches, cauloids and apical parts. Along with the highest unsaturation degree (4.32), the C. crinita branches and apical parts demonstrated high proportion of both C18 and C20 polyunsaturated fatty acids, with eicosapentaenoic (C20:5 n-3) and arachidonic (C20:4 n-6) fatty acids up to 5.46% and 13.82%, respectively. The highest proportion of saturated fatty acids was found in thalli of C. compressa, particularly on cauloids and old branches (≥90%). The similarity profile routine analysis of fatty acids and microbial community structure has shown clear separation of the cauloids and apical parts from the branches of C. crinita and T. barbata. Based on the nonmetric multidimensional scaling analysis several representatives of the Gammaproteobacteria class, identified as Vibrionales (Vibrio), Cellvibrionales and Xanthomonadales, which contributed strongly to the separation of T. barbata apical parts and branches, C. compressa receptacles and C. crinita branches from the T. barbata cauloids and C. crinita apical parts and cauloids. The highest richness in polyunsaturated fatty acids, in particular C18:3(n-3), C20:4(n-6) and C20:5(n-3), was observed on branches, accompanied by a distinctive epiphytic microbial structure dominated by numerous representatives with potentially beneficial biological activity. The results showed a strong relationship between fatty acid profiles of the analyzed species and phycosphere community structure, underlining the host physiological condition in shaping the biological interactions and maintaining a healthy microbiome, as well as compiling the ecophysiological and molecular research in order to better assess the resilience of the ecosystem.

Keywords

• fucacean species
• fatty acids
• epiphytic bacteria
• Adriatic Sea