Phylogenetic Analysis and Screening of Antimicrobial and Antiproliferative Activities of Culturable Bacteria Associated with the AscidianStyela clavafrom the Yellow Sea, China

Abstract

Over 1,000 compounds, including ecteinascidin-743 and didemnin B, have been isolated from ascidians, with most having bioactive properties such as antimicrobial, antitumor, and enzyme-inhibiting activities. In recent years, direct and indirect evidence has shown that some bioactive compounds isolated from ascidians are not produced by ascidians themselves but by their symbiotic microorganisms. Isolated culturable bacteria associated with ascidians and investigating their potential bioactivity are an important approach for discovering novel compounds. In this study, a total of 269 bacteria were isolated from the ascidian Styela clava collected from the coast of Weihai in the north of the Yellow Sea, China. Phylogenetic relationships among 183 isolates were determined using their 16S rRNA gene sequences. Isolates were tested for antimicrobial activity against seven indicator strains, and an antiproliferative activity assay was performed to test for inhibition of human hepatocellular carcinoma Bel 7402 and human cervical carcinoma HeLa cell proliferation. Our results showed that the isolates belonged to 26 genera from 18 families in four phyla (Firmicutes, Actinobacteria, Proteobacteria, and Bacteroidetes). Bacillus and Streptomyces were the most dominant genera; 146 strains had potent antimicrobial activities and inhibited at least one of the indicator strains. Crude extracts from 29 strains showed antiproliferative activity against Bel 7402 cells with IC50 values below 500 μg·mL−1, and 53 strains showed antiproliferative activity against HeLa cells, with IC50 values less than 500 μg·mL−1. Our results suggest that culturable bacteria associated with the ascidian Styela clava may be a promising source of novel bioactive compounds.

Culture-Dependent Microbiome of the Ciona intestinalis Tunic: Isolation, Bioactivity Profiling and Untargeted Metabolomics

“…This contrasts with a recent review that analyzed bioactive ascidian-derived microbial compounds that showed higher rates of cytotoxicity (47%) than antimicrobial activity (31%) [16]. However, the vast potential of marine-derived microorganisms for discovery of novel antibiotics from ascidians and other marine invertebrates is known [69][70][71]. The fact that pathogenic Gram-negative bacteria were not inhibited by any of our tunic-associated microorganisms is in line with their general lesser susceptibility towards antibiotics due to their additional outer membrane [70,72].…”

“…The P. destructans isolate cultivated on medium CAG (CHT56-CAG) produced compounds of polyketide (55,(60)(61)(62) and terpenoid (56,65,67,70) origin (Figure 6 and Figure S6, Table S7). Accordingly, the two largest clusters in the FBMN, which consisted in total of 78 nodes, were putatively assigned to benzofuran-type polyketides and sesquiterpenoids.…”

Diversity, Bioactivity Profiling and Untargeted Metabolomics of the Cultivable Gut Microbiota of Ciona intestinalis

“…The antimicrobial assays included the so-called ESKAPE panel, drug-resistant bacterial pathogens that were categorized by the WHO as priority level 1 and 2 for the discovery of new antimicrobial agents [ 43 ]. Most extracts ( n = 65) exhibited activity against MRSA and/or E. faecium , but also anticancer ( n = 23) and antifungal ( n = 11) activities were observed ( Figure 3 , Table S2 ), exceeding bioactivity levels previously reported for cultivable bacteria associated with solitary ascidians [ 44 , 45 ]. The high rate of bioactivity observed in this study is in line with the excellent biodiscovery potential reported for tunicates and their microbial associates [ 11 , 13 , 42 ].…”

Bioprospecting Antiproliferative Marine Microbiota From Submarine Volcano Tagoro

“…For example, Davies-Bolorunduro et al ( 2019) evaluated the anticancer activity of 32 actinomycetes strains against a panel of cancer cell lines and the isolates of genera Micromonospora and Streptomyces exhibited cytotoxicity with IC 50 values ranging from 0.03 to 4.4 mg/mL. Among other Phyla, some extracts of Halomonas and Bacillus have showed cytotoxicity with IC 50 < 50 µg/mL (Aboul-Ela et al, 2012;Sagar et al, 2013;Chen et al, 2019). It is noticeable that many secondary metabolites have been isolated from Bacillus, including peptides, terpenoids, polyketides, and isocumarins, however, a few marine Bacillus strains have been examined for pharmaceutical activities (Chen et al, 2019).…”