Marine Invertebrates: Underexplored Sources of Bacteria Producing Biologically Active Molecules

Abstract

The marine bioprospecting could be considered as a new phenomenon, and already potentially more promising than terrestrial one in terms of possible discovery of new compounds. The secondary metabolites produced by associated-bacteria are actually studied for their remarkable role in several fields, including agricultural, industrial, medical, and bioremediation strategies against different contaminants. The use of such renewable sources could be helpful in the streamlining of the patenting process for natural compounds of good quality, produced with lower energy costs and less impact on the environment. Anyway, more improvements in the research and application of bioactive compounds as alternative to the synthetic counterparts have to be carried out for the costs reduction and the large-scale production upgrading. The use of marine invertebrates could help to overcome these difficulties, as hotspots of microbial diversity and favorable matrix for the development of conditions stimulating the production of substances with special activities. This review will deal with the current accepted definitions and recent advances concerning: (i) the marine symbiotic relationships in which microorganisms and invertebrates are involved; (ii) the principal taxa of marine invertebrates that establish interactions with microorganisms, the biodiversity of these latter, and their role in the symbiosis; (iii) we address the state of current literature and knowledge about the bacterial associated communities specialized in biosurfactants (BSs) and extracellular polymeric substances (EPSs) production; and, (iv) their potential biotechnological applications reported still now.

Biosurfactants from Marine Microorganisms

“…According to Ref. [6], the producer isolation and detection are crucial phases in the research for new BSs, which have to be strongly related to the aim of the investigation. While the terrestrial sources have been extensively explored, the marine environments have been focused as potential optimal source only in recent decades.…”

“…Only recently, innovative marine sources of isolation has been proposed, and researchers have focused their studies on biological matrices, that is, filter-feeding organisms as host of microbial communities specialized in the production of secondary metabolites with functional roles. As reviewed in [6], BS producers with optimal potentialities have been isolated from polychaetes [19,20], sponges [21][22][23][24][25], sea pens [26], cnidarians [27,28], and fish [29]. A common characteristic of BSs is to relax or decrease surface tension and this increases solubility so that BSs may interact with the interfaces and affect the adhesion and the detachment of bacteria [4].…”

“…Furthermore, some BSs play an essential role for the survival of microbial producers against other competing or dangerous microorganisms by acting as biocide agents [4], and some others have shown the ability to stimulate plant and animal defense responses against microbes [5]. By considering that, these aspects have been explored especially for terrestrial bacteria, in the light of the above said characteristics, BSs from marine bacteria have been getting attention more and more as new suitable alternatives to chemical surfactants of petroleum origin in the food, cosmetic, health care industries [6], synthetic medicines and can be safe and effective therapeutic agents in medicine.…”

Bacteria Associated with Marine Benthic Invertebrates from Polar Environments: Unexplored Frontiers for Biodiscovery?

“…In this latter case, EPS production by cold-adapted bacteria also represents a survival strategy to thrive in low temperatures, avoiding cell damage and the attenuation of cell viability in environments such as cold Polar regions, where freeze-thaw cycles are frequent, by maintaining a protective microhabitat around microorganisms. To date, biological matrices have rarely been employed for bacterial extracellular polymer production, even if they may play a key role in bacterial adhesion to living surfaces [8], and a single report on EPS-producing bacteria isolated from Antarctic sponges exists [104]. The production of EPSs by Winogradskyella spp.…”

“…Bacterial epi-and endobiotic associations play an important role in the development and evolution of an organism. These associations can be positive or negative, depending on the benefits or damage incurred by one of the organisms during association (reviewed in [8,9]). This is particularly true in extreme and isolated environments, such as Antarctica and, at a lesser extent, the Arctic, where the host and the symbionts often evolve together, establishing peculiar and strict interactions.…”