Abstract
Bacteria growing inside biofilms are more resistant to hostile environments, conventional antibiotics, and mechanical stresses than their planktonic counterparts. It is estimated that more than 80% of microbial infections in human patients are biofilm-based, and biofouling induced by the biofilms of some bacteria causes serious ecological and economic problems throughout the world. Therefore, exploring highly effective anti-biofilm compounds has become an urgent demand for the medical and marine industries. Marine microorganisms, a well-documented and prolific source of natural products, provide an array of structurally distinct secondary metabolites with diverse biological activities. However, up to date, only a handful of anti-biofilm natural products derived from marine microorganisms have been reported. Meanwhile, it is worth noting that some promising antifouling (AF) compounds from marine microbes, particularly those that inhibit settlement of fouling invertebrate larvae and algal spores, can be considered as potential anti-biofilm agents owing to the well-known knowledge of the correlations between biofilm formation and the biofouling process of fouling organisms. In this review, a total of 112 anti-biofilm, anti-larval, and anti-algal natural products from marine microbes and 26 of their synthetic analogues are highlighted from 2000 to 2021. These compounds are introduced based on their microbial origins, and then categorized into the following different structural groups: fatty acids, butenolides, terpenoids, steroids, phenols, phenyl ethers, polyketides, alkaloids, flavonoids, amines, nucleosides, and peptides. The preliminary structure-activity relationships (SAR) of some important compounds are also briefly discussed. Finally, current challenges and future research perspectives are proposed based on opinions from many previous reviews.
Highlights
In the past two decades, marine microorganisms have provided a large number of potential AF natural products, some of which can be considered a promising source for the further exploration of potent anti-biofilm agents according to some previous reviews [5,7,16,17,18,19,20]
This review focuses on the anti-biofilm, anti-larval, and anti-algal secondary metabolites of marine microorganisms from 2000 up to the end of 2021
Polyketides, as one of the largest families of natural products from marine microorganisms, have provided many anti-biofilm and AF compounds with structural diversity, including benzylazaphilones, dihydroisocoumarins, anthraquinones, xanthones, and 14-membered resorcylic acid lactones (RALs) (Figures 14–16)
Summary
It should be noted that biofouling based on the biofilm formation of fouling microbes causes enormous economic losses annually to the maritime and medical industries [2,5,6,7,8,9,10,11]. In the past two decades, marine microorganisms have provided a large number of potential AF natural products, some of which can be considered a promising source for the further exploration of potent anti-biofilm agents according to some previous reviews [5,7,16,17,18,19,20]. The further direction in the search for anti-biofilm/AF natural products from marine microbes is prosed in the concluding remarks
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