Bacteria associated with marine benthic invertebrates from Polar environments: unexplored frontiers for biodiscovery?

The ecological function of bacteria-invertebrate interactions in Polar areas remains poorly
understood, despite increasing evidence that microbial metabolites may play pivotal roles in
host-associated chemical defense and in shaping the symbiotic community structure. The metabolic
and physiological changes that these organisms undergo in response to adapting to extreme
conditions result in the production of structurally and functionally novel biologically active molecules.
Deepening our knowledge on the interactions between bacteria and their invertebrate host would
be highly helpful in providing the rationale for why (e.g., competition or cooperative purpose) and
which (whether secondary metabolites, enzymes, or proteins) bioactive compounds are produced.
To date, cold-adapted bacteria associated with marine invertebrates from the Arctic and Antarctica
have not been given the attention they deserve and the versatility of their natural products remains
virtually unexplored, even if they could represent a new attractive frontier in the search for novel
natural compounds. This review is aimed at showcasing the diversity of cold-adapted bacteria
associated with benthic invertebrates from Polar marine areas, highlighting the yet unexplored
treasure they represent for biodiscovery.