Allison G

Out now in @natcomms.nature.com: We found a plasmid in a preterm infant’s gut microbiome that’s 1.58 million base pairs long, about 30X the size of a typical E. coli plasmid. Then we found its relatives in hundreds of microbiomes worldwide. Read on to learn more about the elusive pMEGAs! 🧵

I'm excited to continue learning more about pMEGAs! These discoveries would not be possible without research participants, so I’m very grateful to the families in the NANO trial and to all families who enroll in gut microbiome research. 💜 #gutmicrobiome

Out now in @natcomms.nature.com: We found a plasmid in a preterm infant’s gut microbiome that’s 1.58 million base pairs long, about 30X the size of a typical E. coli plasmid. Then we found its relatives in hundreds of microbiomes worldwide. Read on to learn more about the elusive pMEGAs! 🧵

Beyond showing that pMEGAs are maintained in the gut microbiome over time, we also found metatranscriptomic datasets confirming that plasmid genes are expressed in the gut microbiome. Related elements also turned up in dozens of bacterial isolates of E. coli, Salmonella, and Shigella. #megaplasmids

Out now in @natcomms.nature.com: We found a plasmid in a preterm infant’s gut microbiome that’s 1.58 million base pairs long, about 30X the size of a typical E. coli plasmid. Then we found its relatives in hundreds of microbiomes worldwide. Read on to learn more about the elusive pMEGAs! 🧵

It started with an odd, long contig: its sequence did not suggest a fragmented bacterial chromosome or a virus, but it contained many genes with unknown functions. Extensive annotation and structure prediction helped us classify this element as a plasmid, most likely a conjugative one! #plasmids

A great review in @cp-trendsgenetics.bsky.social by Kiguchi and Suzuki on recently discovered large mobile elements, including our description of megabase-scale plasmids in Enterobacteriaceae www.cell.com/trends/genet...

The authors highlight how emerging long-read technology has helped to uncover the diversity of previously uncharacterized large extrachromosomal elements and that much more likely remains to be discovered: "The few currently characterized examples likely represent only the tip of the iceberg [...]".

Most plasmids described in E. coli are small compared to the megaplasmids we identified here! Check out the preprint if you want to learn about these mysterious large elements and their potential functions 🧬. I’m very grateful to have had the opportunity to work on this in @banfieldlab.bsky.social

Almost 80% of the predicted proteins on the plasmids have hypothetical or unknown annotations by various tools. We used structural predictions to help elucidate some of the major functions including potential virulence, antibiotic resistance, and strategies to overcome bacterial host defences.

Most plasmids described in E. coli are small compared to the megaplasmids we identified here! Check out the preprint if you want to learn about these mysterious large elements and their potential functions 🧬. I’m very grateful to have had the opportunity to work on this in @banfieldlab.bsky.social

Here are a few highlights: We first identified a 1.58 Mbp plasmid in an infant gut metagenome thanks to @pacbio.bsky.social sequencing. The average bacterial genome size in these communities is usually less than 5 Mbp so this was curious to us. We then found similar elements in other infants.