Pelagibacterium xiamenense sp. nov., isolated from intertidal sediment

Microbial diversity in intertidal zones remains underexplored despite their ecological significance. Prior research has shown that these zones host unique bacterial communities adapted to fluctuating environmental conditions. However, the taxonomic classification of newly discovered isolates often remains incomplete. This gap motivated researchers to investigate the genetic and phenotypic traits of a newly isolated strain from the Haicang Coast. While existing studies describe general characteristics of marine bacteria, few focus on species within the genus Pelagibacterium. No prior work had resolved the taxonomic status of this specific isolate. The intertidal sediment environment presents a unique niche for bacterial adaptation. Understanding such adaptations requires detailed genomic and biochemical analyses. This paper's contribution lies in identifying a novel species within a well-defined taxonomic framework.

The aim of this study was to characterize a newly isolated bacterial strain from intertidal sediment. The specific problem addressed was the lack of a taxonomic classification for this organism. Researchers sought to determine whether the isolate represented a novel species within the genus Pelagibacterium. The motivation stemmed from the ecological importance of intertidal zones and the need to expand microbial databases. By combining genomic, phylogenetic, and biochemical data, the authors aimed to establish a robust taxonomic framework. This approach allows for accurate species delineation in complex environments. The study also aimed to provide a reference for future microbial diversity assessments. The findings contribute to the broader understanding of marine bacterial ecology.

The study employed a multi-omics approach to characterize the isolate. Researchers first conducted Gram staining and physiological tests to assess basic cell traits. They then determined growth conditions, including temperature, pH, and salt tolerance ranges. Phylogenetic analysis was based on 16S rRNA gene sequencing. Digital DNA-DNA hybridization and average nucleotide identity were calculated to compare genomic similarity. Fatty acid profiling was performed using gas chromatography. Respiratory quinone and polar lipid compositions were analyzed chemically. The G+C content of chromosomal DNA was measured to support taxonomic placement. These methods collectively enabled a comprehensive assessment of the isolate's identity.

The isolate, HS1C4-1T, exhibited Gram-negative morphology and aerobic respiration. It grew optimally at 37 °C and pH 7.0-9.0. Salt tolerance was highest at 1 % NaCl. Phylogenetic analysis placed it within the genus Pelagibacterium. The highest 16S rRNA similarity was with Pelagibacterium luteolum at 97.6 %. Digital DNA-DNA hybridization values ranged from 18.7 % to 20.2 %. Average nucleotide identity was 77.3 % to 78.4 %. Fatty acid C19:0 cyclo ω8c was dominant at 50.5 %. Q-10 was the sole respiratory quinone. Polar lipids included diphosphatidylglycerol and phosphatidylglycerol. The G+C content was 62.9 %. These findings confirmed the isolate's novelty within the genus.

Based on phylogenetic, phenotypic, and genomic data, the authors propose HS1C4-1T as a novel species. The isolate's distinct fatty acid profile and genomic divergence support this claim. The respiratory quinone and polar lipid composition further distinguish it from related species. The optimal growth conditions align with intertidal zone characteristics. This study expands the known diversity of Pelagibacterium. The taxonomic framework provided aids future microbial identification. The findings emphasize the importance of integrating multiple data types in species delineation. The proposed name, Pelagibacterium xiamenense, reflects the geographic origin of the isolate.