Rich microbial and depolymerising diversity in Antarctic krill gut

• Published in: Microbiology Spectrum
• Main Authors: Möller, Lars, Vainshtein, Yevhen, Meyer, Bettina, Neidhardt, John, Eren, A. Murat, Sohn, Kai, Rabus, Ralf
• Other Authors: Kormas, Konstantinos Aristomenis, Bundesministerium für Bildung und Forschung
• Format: Article in Journal/Newspaper
• Language: English
• Published: American Society for Microbiology 2024
• Subjects: Infectious Diseases; Cell Biology; Microbiology (medical); Genetics; General Immunology and Microbiology; Ecology; Physiology; Antarc*; Antarctic; Antarctic Krill; Euphausia superba
• Online Access: http://dx.doi.org/10.1128/spectrum.04035-23; https://journals.asm.org/doi/pdf/10.1128/spectrum.04035-23

ABSTRACT With almost a quadrillion individuals, the Antarctic krill processes five million tons of organic carbon every day during austral summer. This high carbon flux requires a broad range of hydrolytic enzymes to decompose the diverse food-derived biopolymers. While krill itself possesses numerous such enzymes, it is unclear, to what extent the endogenous microbiota contribute to the hydrolytic potential of the gut environment. Here we applied amplicon sequencing, shotgun metagenomics, cultivation, and physiological assays to characterize the krill gut microbiota. The broad bacterial diversity (273 families, 919 genera, and 2,309 species) also included a complex potentially anaerobic sub-community. Plate-based assays with 198 isolated pure cultures revealed widespread capacities to utilize lipids (e.g., tributyrin), followed by proteins (casein) and to a lesser extent by polysaccharides (e.g., alginate and chitin). While most isolates affiliated with the genera Pseudoalteromonas and Psychrobacter , also Rubritalea spp. (Verrucomicrobia) were observed. The krill gut microbiota growing on marine broth agar plates possess 13,012 predicted hydrolyses; 15-fold more than previously predicted from a transcriptome-proteome compendium of krill. Cultivation-independent and -dependent approaches indicated members of the families Flavobacteriaceae and Pseudoalteromonadaceae to dominate the capacities for lipid/protein hydrolysis and to provide a plethora of carbohydrate-active enzymes, sulfatases, and laminarin- or porphyrin-depolymerizing hydrolases. Notably, also the potential to hydrolyze plastics such as polyethylene terephthalate and polylactatide was observed, affiliating mostly with Moraxellaceae. Overall, this study shows extensive microbial diversity in the krill gut, and suggests that the microbiota likely play a significant role in the nutrient acquisition of the krill by enriching its hydrolytic enzyme repertoire. IMPORTANCE The Antarctic krill ( Euphausia superba ) is a keystone species of the Antarctic ...