Lichen-Derived Actinomycetota: Novel Taxa and Bioactive Metabolites

Abstract

Actinomycetes are essential sources of numerous bioactive secondary metabolites with diverse chemical and bioactive properties. Lichen ecosystems have piqued the interest of the research community due to their distinct characteristics. Lichen is a symbiont of fungi and algae or cyanobacteria. This review focuses on the novel taxa and diverse bioactive secondary metabolites identified between 1995 and 2022 from cultivable actinomycetota associated with lichens. A total of 25 novel actinomycetota species were reported following studies of lichens. The chemical structures and biological activities of 114 compounds derived from the lichen-associated actinomycetota are also summarized. These secondary metabolites were classified into aromatic amides and amines, diketopiperazines, furanones, indole, isoflavonoids, linear esters and macrolides, peptides, phenolic derivatives, pyridine derivatives, pyrrole derivatives, quinones, and sterols. Their biological activities included anti-inflammatory, antimicrobial, anticancer, cytotoxic, and enzyme-inhibitory actions. In addition, the biosynthetic pathways of several potent bioactive compounds are summarized. Thus, lichen actinomycetes demonstrate exceptional abilities in the discovery of new drug candidates.

Keywords: actinomycetes; antimicrobial; bioactive secondary metabolites; biosynthetic pathways; diversity; lichen.

Figure 1

Collection points for lichen samples (the red dots represent the sampling sites).

Figure 2

The proportions of novel actinomycete species belonging to different families.

Figure 3

Chemical structures of compounds 1–13 from lichen-associated actinomycetota.

Figure 4

Chemical structures of compounds 14–25 from lichen-associated actinomycetota.

Figure 5

Chemical structures of compounds 26–40 from lichen-associated actinomycetota.

Figure 6

Chemical structures of compounds 41–44 from lichen-associated actinomycetota.

Figure 7

Chemical structures of compounds 45–51 from lichen-associated actinomycetota.

Figure 8

Chemical structures of compounds 52–64 from lichen-associated actinomycetota.

Figure 9

Chemical structures of compounds 65–76 from lichen-associated actinomycetota.

Figure 10

Chemical structures of compounds 77–93 from lichen-associated actinomycetota.

Figure 11

Chemical structures of compounds 94–100 from lichen-associated actinomycetota.

Figure 12

Chemical structures of compounds 101–108 from lichen-associated actinomycetota.

Figure 13

Chemical structures of compounds 109–113 from lichen-associated actinomycetota.

Figure 14

Chemical structure of compound 114 from lichen-associated actinomycetota.

Figure 15

(A) The gene clusters of Streptomyces sp. YIM130001. (B) The biosynthetic pathway of geninthiocin B [28].

Figure 16

(A) The gene clusters of cladoniamides. (B) The biosynthetic pathway of cladoniamides A–C [74].