Multifaceted Community Analyses Uncover Novel Bacterial Species in the Colorectal Tumor Niche

The tumor-associated microbiota is an inherent component of the tumor microenvironment across various human cancer types1. Although members of tumor-associated microbiomes can be identified through 16S rRNA analysis, physical access to bacterial isolates facilitates functional and mechanistic studies to determine the role of these bacterial species in cancer initiation, progression, and patient response to treatment. Here, through complimentary application of large-scale culturing techniques and bacterial single-cell whole genome sequencing approaches, we isolated three novel bacterial species across four tumor tissue samples from patients with colorectal cancer, including a novel Fusobacterium species2. Utilizing PacBio Single Molecule Real Time (SMRT) sequencing we obtained complete genomes for all three novel bacterial species, which facilitated comparative genomics to identify the nearest species neighbors and bioinformatic analyses to distinguish genetic factors that are uniquely present in these tumor isolates. These analyses will inform future mechanistic studies to understand the capabilities and roles of these novel bacterial species.

Learning Objectives:

1. Describe the advantages and disadvantages of various techniques and technologies to identify and culture bacterial species from a tissue-associated microbial community.

2. Explain why physical access to bacterial isolates can be a powerful advantage to microbiologists.

3. Discuss at least two approaches by which the novelty of a bacterial species can be confirmed.