Uncovering the biotechnological capacity of marine and brackish water Planctomycetota

Abstract

An appealing strategy for finding novel bioactive molecules in Nature consists in exploring underrepresented and -studied microorganisms. Here, we investigated the antimicrobial and tumoral anti-proliferative bioactivities of twenty-three marine and estuarine bacteria of the fascinating phylum Planctomycetota. This was achieved through extraction of compounds produced by the Planctomycetota cultured in oligotrophic medium followed by an antimicrobial screening against ten relevant human pathogens including Gram-positive and Gram-negative bacteria, and fungi. Cytotoxic effects of the extracts were also evaluated against five tumoral cell lines. Moderate to potent activities were obtained against Enterococcus faecalis, methicillin-sensitive and methicillin-resistant Staphylococcus aureus and vancomycin-sensitive and vancomycin-resistant Enterococcus faecium. Anti-fungal effects were observed against Trichophyton rubrum, Candida albicans and Aspergillus fumigatus. The highest cytotoxic effects were observed against human breast, pancreas and melanoma tumoral cell lines. Novipirellula caenicola and Rhodopirellula spp. strains displayed the widest spectrum of bioactivities while Rubinisphaera margarita ICM_H10T affected all Gram-positive bacteria tested. LC-HRMS analysis of the extracts did not reveal the presence of any known bioactive natural product, suggesting that the observed activities are most likely caused by novel molecules, that need identification. In summary, we expanded the scope of planctomycetal species investigated for bioactivities and demonstrated that various strains are promising sources of novel bioactive compounds, which reenforces the potential biotechnological prospects offered by Planctomycetota.

Specificities and commonalities of the Planctomycetes plasmidome

“…But beyond their distinctive cell attributes, Planctomycetes are recognized as pivotal contributors to global carbon and nitrogen cycles, owing to their metabolic proficiency in the degradation of complex carbon substrates (Jeske et al, 2013;Wiegand et al, 2018), and their unique ability to combine ammonium and nitrite or nitrate to form nitrogen gas (Kuenen, 2008;Strous et al, 1999). Moreover, their genomic repertoire encompasses genes associated with secondary metabolite pathways, which are implicated in the production of bioactive compounds, including antimicrobial and algicidal agents (Graça et al, 2016;Jeske et al, 2013Jeske et al, , 2016Vitorino et al, 2024).…”