Cellulamides: A New Family of Marine-Sourced Linear Peptides from the Underexplored Cellulosimicrobium Genus

Bioprospecting the secondary metabolism of underexplored Actinomycetota taxa is a prolific route to uncover novel chemistry. In this work, we report the isolation, structure elucidation, and bioactivity screening of cellulamides A and B (1 and 2), two novel linear peptides obtained from the culture of the macroalga-associated Cellulosimicrobium funkei CT-R177. The host of this microorganism, the Chlorophyta Codium tomentosum, was collected in the northern Portuguese coast and, in the scope of a bioprospecting study focused on its associated actinobacterial community, strain CT-R177 was isolated, taxonomically identified, and screened for the production of antimicrobial and anticancer compounds. Dereplication of a crude extract of this strain using LC-HRMS(/MS) analysis unveiled a putative novel natural product, cellulamide A (1), that was isolated following mass spectrometry-guided fractionation. An additional analog, cellulamide B (2) was obtained during the chromatographic process and chemically characterized. The chemical structures of the novel linear peptides, including their absolute configurations, were elucidated using a combination of HRMS, 1D/2D NMR spectroscopy, and Marfey's analysis. Cellulamide A (1) was subjected to a set of bioactivity screenings, but no significant biological activity was observed. The cellulamides represent the first family of natural products reported from the Actinomycetota genus Cellulosimicrobium, showcasing not only the potential of less-explored taxa but also of host-associated marine strains for novel chemistry discovery.

Bioinformatic Approach to Investigate Larvae Gut Microbiota Cellulosimicrobium protaetiae via Whole-Genome Analysis

The insect larvae Protaetia brevitarsis seulensis have recently been researched as a nutritious food source and concentrated on their environmental impacts. Therefore, their gut microbiota has been studied to elucidate their effects and roles on the environment. Of the abundance of bacterial genus identified based on the 16S rRNA genes from isolates of the gut of insect larva Protaetia brevitarsis seulensis, six of the prominent genus were identified as Bacillus (40.2%), Cellulosimicrobium (33.5%), Microbacterium (2.8%), Streptomyces (3%), Krasilnikoviella (17.5%), and Isoptericola (3%) and their similarity of 16S rRNA blast changed from 99 to 100%. Cellulosimicrobium protaetiae BI34T showed strong denitrification and cellulose degradation activity. The newly complete genome sequence of BI34T and the genomes of five species was published in the genus Cellulosimicrobium with emphasis on the denitrification and secondary metabolite genes. In order to elucidate the relationship between the strain BI34T and the host insect larva, the whole-genome sequence was analyzed and compared with the genomes of five strains in the same genus, Cellulosimicrobium, loaded from GenBank. Our results revealed the composition of the gut microbiota of the insect larvae and analyzed the genomic data for the new strain to predict its characteristics and to understand the nitrogen metabolism pathway.

Bacterial community and culturable actinomycetes of Phyllostachys viridiglaucescens rhizosphere

During the course of development plants form tight interactions with microorganisms inhabiting their root zone. In turn, rhizosphere bacteria, in particular members of the phylum Actinomycetota, positively influence the host plant by increasing access to essential nutrients and controlling the pathogenic microorganism's population. Herein, we report the characterisation of the rhizosphere associated actinobacteria community of Phyllostachys viridiglaucescens growing in the Nikitsky Botanical Garden (Crimean Peninsula, Ukraine). The overall composition of the bacterial community was elucidated by 16S rRNA gene amplicon sequencing followed by isolation of culturable microorganisms with the focus on actinomycetes. The metagenomic approach revealed that the representatives of phylum Actinomycetota (57.1%), Pseudomonadota (20.0%), and Acidobacteriota (12.2%) were dominating in the studied microbiome with Ilumatobacter (phylum Actinomycetota) (13.1%) being the dominant genus. Furthermore, a total of 159 actinomycete isolates, belonging to eight genera of Streptomyces, Micromonospora, Nonomuraea, Arthrobacter, Actinomadura, Kribbella, Cellulosimicrobium, and Mumia, were recovered from P. viridiglaucescens rhizosphere. The isolated species were tested for antimicrobial activity. 64% of isolates were active against at least one bacterial test-culture and 7.5% against fungal test culture. In overall, the rhizosphere bacterial communities act as a great source of actinobacterial diversity with the high potential for production of new bioactive compounds.

Isolation of Spirosoma foliorum sp. nov. from the fallen leaf of Acer palmatum by a novel cultivation technique

In the effort of isolating novel microbial species, the strain PL0132T was isolated from a fallen leaf under fresh water at a stream, which glided when grown on a tap water medium (without nutrients). The strain was determined to be Gram-negative, strictly aerobic, and rod-shaped, which grew optimally at 25 °C, pH 6-7, and the strain tolerates 1% (w/v) NaCl concentration. The complete genome of strain PL0132T comprises one contig with a sequencing depth of 76×, consisting of 8,853,064 base pairs and the genomic DNA G + C content was 46.7% (genome). 16S rRNA gene sequence analysis revealed that strain PL0132T represents a member of the phylum Bacteroidetes and is affiliated with the genus Spirosoma. Based on genomic, phenotypic, and chemotaxonomic characteristics, the strain PL0132T represents a novel species of the genus Spirosoma, for which the name Spirosoma foliorum sp. nov. is proposed (= KCTC 72228 T = InaCC B1447T).