Newly Identified Bacteria Found in Intestines

Greg Howard
11th February, 2025

Newly Identified Bacteria Found in Intestines

Red Swamp Crayfish (Procambarus clarkii), one of the species mentioned.

Photo adapted from: Nico Hernandez / CC BY (Source)

Key Findings

  • Researchers from Hohai University discovered a new bacterial species, Comamonas squillarum, in the intestine of the red swamp crayfish
  • Genomic and biochemical analyses confirmed that this bacterium is distinct from closely related species, justifying its classification as a novel species
  • The discovery highlights the unique microbiota of crayfish and its potential ecological and biotechnological significance
The genus Comamonas comprises a group of Gram-negative bacteria commonly found in diverse environments, including soil, water, and even animal hosts. These bacteria are of interest due to their metabolic diversity and potential applications in biotechnology, environmental remediation, and microbiology. Recent research conducted by Hohai University has identified a new member of this genus, designated strain PR12T, isolated from the intestine of the red swamp crayfish (Procambarus clarkii)[1]. This study expands our understanding of the genus Comamonas and highlights the potential ecological and functional roles of this novel species. Strain PR12T was found to form creamy white colonies on tryptic soy agar (TSA) plates. Its growth was observed across a range of conditions, with optimal temperatures of 28-30°C, pH of 7.0-8.5, and salinity levels of 0-1.5% NaCl. The bacterium is rod-shaped, non-motile, and aerobic, with positive oxidase and catalase activity. These characteristics align with other members of the Comamonas genus, but further analyses were necessary to confirm its novelty. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain PR12T is closely related to Comamonas koreensis (99.0% similarity)[2], Comamonas sediminis (98.8%), and Comamonas piscis (98.0%)[3]. However, genomic comparisons, including digital DNA-DNA hybridization and average nucleotide identity (ANI), demonstrated that PR12T is distinct from these species. Its genome size is 5.11 Mb, with a G+C content of 63.5%, slightly lower than the 65.5% G+C content reported for C. piscis[3]. These genomic differences, combined with phenotypic and biochemical data, support the classification of PR12T as a new species. The cellular fatty acid profile of PR12T is consistent with other Comamonas species, with major components including C16:0, C17:0 cyclo, and summed features 3 (C16:1ω6c and/or C16:1ω7c) and 8 (C18:1ω6c and/or C18:1ω7c). Its respiratory quinone is ubiquinone Q-8, and its polar lipids include diphosphatidylglycerol (DPG), phosphatidylglycerol (PG), and phosphatidylethanolamine (PE). These chemotaxonomic features further confirm its placement within the genus. The discovery of PR12T builds on earlier studies that have expanded the taxonomy of Comamonas. For example, the identification of C. koreensis as a novel species relied on a combination of 16S rRNA gene analysis and phenotypic differentiation, including motility and chemotaxonomic markers[2]. Similarly, C. piscis was distinguished from closely related species through genomic and biochemical analyses[3]. These approaches were also applied to PR12T, demonstrating its distinctiveness and justifying its classification as Comamonas squillarum sp. nov.. The study also draws parallels with earlier taxonomic revisions within the genus, such as the reclassification of Comamonas terrigena into multiple species based on DNA-DNA hybridization and phenotypic differences[4]. These foundational studies established the importance of combining genetic, biochemical, and phenotypic data to delineate species boundaries within Comamonas. The current research continues this tradition by employing modern genomic tools alongside traditional microbiological methods. The identification of Comamonas squillarum contributes to our understanding of microbial diversity in aquatic environments and host-associated microbiomes. The red swamp crayfish, an invasive species in many regions, harbors a unique intestinal microbiota that may influence its adaptability and ecological impact. Understanding the role of C. squillarum within this microbiome could provide insights into host-microbe interactions and the potential applications of this bacterium in biotechnology or aquaculture. In conclusion, the discovery of Comamonas squillarum by Hohai University researchers underscores the importance of integrative approaches in microbial taxonomy. By combining genomic, phenotypic, and chemotaxonomic analyses, the study not only expands the taxonomy of Comamonas but also highlights the ecological and functional significance of these bacteria. As more novel species are identified, our understanding of microbial diversity and its implications for various ecosystems will continue to grow.

Animal ScienceMarine Biology

References

Main Study

1) Comamonas squillarum sp. nov., Isolated from Intestine of Red Swamp Crayfish (Procambarus clarkii).

Published 10th February, 2025

https://doi.org/10.1007/s00284-025-04093-5

Related Studies

2) Comamonas koreensis sp. nov., a non-motile species from wetland in Woopo, Korea.

Journal: International journal of systematic and evolutionary microbiology, Issue: Vol 52, Issue Pt 2, Mar 2002

3) Comamonas piscis sp. nov., isolated from the intestine of a Korean rockfish, Sebastes schlegelii.

https://doi.org/10.1099/ijsem.0.000790

4) Description of Comamonas aquatica comb. nov. and Comamonas kerstersii sp. nov. for two subgroups of Comamonas terrigena and emended description of Comamonas terrigena.

https://doi.org/10.1099/ijs.0.02450-0


Related Articles

An unhandled error has occurred. Reload 🗙