Despite the seemingly limitless knowledge mankind possesses nowadays, it is surprising how relatively little we know about the estimated 100 trillion bacterial cells that reside on and inside us (~10 times as many cells as the human body). Just like fingerprints, the microbial composition of each microbiome is individual to each human being. The love-hate relationship we have with these bugs can either benefit or hinder us (relationship status: ‘it’s complicated’). Just like every other couple, sometimes communication is the best answer, or in our case- understanding which microbial combination benefits our body most.
This microbial community acts as an organ for all intents and purposes. As such, it is the most dynamic one- ever pulsating, changing and developing to adapt to various environments in the most extreme manner. Like some organs, it may be transplanted, which can be as challenging as any other organ transplant. While recent studies have unearthed much regarding these microbes, the complexity of this environment reminds us that this is just the tip of the iceberg.
Zooming in to the microbial world shows an intriguing phenomenon, where tiny circular fragments of DNA -named plasmids- encoding different genes, are passed around between bacterial cells of the same and even of different species. This process is termed HGT (Horizontal Gene Transfer).
Studies show that for these plasmids- geography is not a barrier[i]. In other words, the same plasmid can be found in different guts across different countries and even continents, although it will differ in its abundance based on various factors. In fact, plasmid composition may vary based on almost anything and everything- from diet to religious practices, travel tendencies and even hygiene and beauty product usage.
The thought that these miniscule mobile DNA strands have such a tremendous impact on the microbial population as well as the human host -even leading to death in extreme cases- is inconceivable. Thank god for Marvel comics, that have taught us, time and again, not to underestimate based on size.
In fact, plasmids are becoming one of modern medicine’s worst nightmares. The problem dates to the 1940s, when antibiotics were introduced to the medical world and have since dramatically reduced death rates from bacterial infections. Mainly due to overuse and misuse of these medications, bacterial infections are making a major comeback lately. The culprits? You’ve guessed it- mobile plasmids. These plasmids convey antibiotic resistance to their bacterial hosts, allowing them to live and prosper through treatment- even cleaning out the rest of the bacterial cells that don’t have antibiotic resistant plasmids – therefore clearing the field of competition.
While the plasmidome (meaning all plasmids in a bacterial population) is known to take part in designing and influencing our everyday lives in body and mind alike, in sickness and in health, the exact mechanisms of some aspects remain unknown. Though the importance of plasmids has been established, the scope of their influence has not yet been determined and many questions remain unanswered: Which other genes do these plasmids harbor? Do the bacterial cells benefit from them? Do we? Is this process more frequent under certain conditions or in certain environments?
To try and answer these questions, these tiny evasive DNA strands need to be captured and further investigated. My research deals with methods of capturing them from different environments to compare their abundance and understand the mechanisms that drive their transfer and transfer rate between bacteria.
These mysterious and intriguing plasmids brought me, the lab newbie, now in my first year of my master’s degree, to join the poop-collecting-hard-working-cow-loving-Mizrahi-lab!
[i] Mobile genes in the human microbiome are structured from global to individual scales, I. L. Brito et al.