Actinobacteria Community and Their Antibacterial and Cytotoxic Activity on the Weizhou and Xieyang Volcanic Islands in the Beibu Gulf of China

Abstract

Weizhou Island and Xieyang Island are two large and young volcanic sea islands in the northern part of the South China Sea. In this study, high-throughput sequencing (HTS) of 16S rRNA genes was used to explore the diversity of Actinobacteria in the Weizhou and Xieyang Islands. Moreover, a traditional culture-dependent method was utilized to isolate Actinobacteria, and their antibacterial and cytotoxic activities were detected. The alpha diversity indices (ACE metric) of the overall bacterial communities for the larger island (Weizhou) were higher than those for the smaller island (Xieyang). A beta diversity analysis showed a more dispersive pattern of overall bacterial and actinobacterial communities on a larger island (Weizhou). At the order level, Frankiales, Propionibacteriales, Streptomycetales, Micrococcales, Pseudonocardiales, Micromonosporales, Glycomycetales, Corynebacteriales, and Streptosporangiales were the predominant Actinobacteria. A total of 22.7% of the OTUs shared 88%–95% similarity with some known groups. More interestingly, 15 OTUs formed a distinct and most predominant clade, and shared identities of less than 95% with any known families. This is the first report about this unknown group and their 16S rRNA sequences obtained from volcanic soils. A total of 268 actinobacterial strains were isolated by the culture-dependent method. Among them, 55 Streptomyces species were isolated, representing that 76.6% of the total. S. variabilis and S. flavogriseus were the most abundant. Moreover, some rare Actinobacteria were isolated. These included Micromonospora spp., Nocardia spp., Amycolatopsis spp., Tsukamurella spp., Mycobacterium spp., and Nonomuraea spp. Among them, eight Streptomyces spp. exhibited antibacterial activity against Bacillus cereus. Only three strains inhibited the growth of Escherichia coli. Four strains showed good activity against aquatic pathogenic bacterial strains of Streptococcus iniae. The cytotoxicity assay results showed that 27 strains (10.07%) exhibited cytotoxic activity against HeLa and A549 cell lines. Many actinobacterial strains with cytotoxic activity were identified as rare Actinobacteria, which illustrated that volcanic islands are vast reservoirs for Actinobacteria with promising antibacterial and cytotoxic activity. This study may significantly improve our understanding of actinobacterial communities on volcanic islands. The isolated Actinobacteria showed promising prospects for future use.

Diversity and Functionality of Bacteria Associated with Different Tissues of Spider Heteropoda venatoria Revealed through Integration of High-Throughput Sequencing and Culturomics Approaches

“…In recent years, there has been a growing interest in identifying and characterizing symbiotic bacteria from various environments, such as marine environments and invertebrates, because of their potential to produce compounds with significant anticancer activity [ 18 ]. Previous studies have shown that Actinobacteria isolated from volcanic sea islands exhibited cytotoxic activity against Hela and A549 cell lines [ 33 ]. Additionally, an endophytic bacterium isolated from the medicinal plant Ophiopogon japonicas , identified as Bacillus amyloliquefaciens , also demonstrated antitumoral activity [ 74 ].…”

“…The cytotoxic effects of the crude extract from the fermentation broth were tested using the 3-[4,5-Dimethylthiazol-2-yl] -2,5-diphenyl tetrazolium bromide (MTT) assay [ 33 ]. The human gastric cancer cell line MGC-803 was inoculated into 96-well plates and divided into the control group and the experimental group.…”

Diversity and Functionality of Bacterial Symbionts in Different Tissues of Spider Heteropoda venatoria Revealed through Integration of High-throughput Sequencing and Culturomic Approaches

“…In recent years, there has been a growing interest in the identi cation and characterization of symbiotic bacteria from various environments, including marine environments and invertebrates, due to their potential for producing compounds with signi cant anticancer activity [18]. Previous studies have shown that Actionbacteria isolated from volcanic sea islands exhibited cytotoxic activity against Hela and A549 cell lines [75], while an endophytic bacterium isolated from the medicinal plant Ophiopogon japonicas, identi ed as the Bacillus amyloliquefaciens, also demonstrated antitumoral activity [76]. In this study, three symbiotic strains, namely GL312, PL211, and PL316 isolated from the gut and venom gland, were identi ed to the genus Bacillus (PL211 and PL316) and Priestia (GL312), and were found to exhibit cytotoxic activity against cancer cells.…”