In bacteria, essential genes are typically located on the chromosome, whereas plasmids usually carry accessory genes - such as those
conferring antibiotic resistance - that provide advantages under specific conditions but are not indispensable for survival.
We have been studying bacteria that defy this conventional genome organization, in which ribosomal RNA genes are located exclusively
on small plasmids. Initially regarded as rare exceptions, these bacteria were later found, through exploration of genomic databases, to be
phylogenetically diverse while sharing a similar genome organization. We also discovered that this seemingly unstable genome
organization has been stably maintained for hundreds of millions of years.
However, the mechanisms underlying this long-term stability, and the biological significance of this genome organization, remain largely
unknown. This research unit will address these fundamental questions by investigating newly uncovered exceptions and testing whether
they reflect broader principles, thereby generating new insights and perspectives in microbial genomics.
