foreign [Music] there are trillions of microbes in this Auditorium many of them are the bacteria that live on and in our bodies the vast majority of these microbes however are the ones that live in almost each and every one of our cells the microbes that I'm referring to are mitochondria for those of you who remember your high school textbooks you're probably thinking wait a minute mitochondria are not microbes they're small things that perform important functions in ourselves you're absolutely right but today I want to share with you why we should instead think of mitochondria as
microbes and how viewing them from this microbial lens can help us discover new ways to combat infectious disease mitochondria have a dirty little secret their ancestors were bacteria although the idea that mitochondria were derived from bacteria was considered ridiculous when it was first proposed in the 1960s We Now understand that about 1.5 billion years ago a bacterium found its way into a larger cell and stayed thanks to this event we now have mitochondria which have retained some of their bacterial traits traits that render them susceptible to the antibiotics that we all take and traits like
their DNA and given that Mother's Day is approaching I have to remind you all that all of our mitochondrial DNA comes from our mother sorry Papa 1.5 billion years later we cannot live without our mitochondria if our mitochondria are not happy we are not healthy there's an avalanche of studies that shows that unhealthy mitochondria are linked to all sorts of illnesses including neurodegenerative cardiac diseases and age-related diseases so what makes mitochondria so important well we know they perform several important functions for example they help us produce hormones like testosterone estrogen and cortisol hormones that help
our bodies develop and respond to stress but probably their most vital function is that they are the powerhouses of ourselves they produce the chemical energy that is required for Life known as ATP your mitochondria are making about 65 kilos of ATP per day that helps power your bodies to do so mitochondria use about 90 of the oxygen that we breathe and the nutrients that we consume this same nutrients that are pilfered and consumed by bacteria viruses and parasites when they invade ourselves this brings me to the question that has fascinated me for over 10 years
how do our mitochondria respond when there's another microbe in their territory just imagine the scene mitochondria are in peace in their cell making ATP and then all of a sudden out of the blue there's an intruder an intruder who's making a mess in their cellular home and who's competing for the same nutrients you might think I'm about to tell you about how mitochondria Seek and Destroy these Intruders but the reality is we actually know very little about what mitochondria do to microbial Invaders and that's because our mitochondria which have the power of life and death
over ourselves are considered to be simply targets during infection this is surprising no maybe this makes sense if we only consider mitochondria as powerhouses invading microbes could steal their ATP or energy or prevent them from making energy to power cellular defenses but if we think of them as intracellular bacteria guarding their home the idea that they don't do anything in the event of an intruder doesn't make much sense so in my lab we try and understand how mitochondria can defend us against microbial Invaders we think that the answers to this question can help us discover
new ways to combat microbes in order to tackle this question we ask how and why mitochondria change their behavior during infection and as our mitochondrial Challenger we use the human parasite Toxoplasma gondi this parasite infects about one-third of the human population so that's about 500 of us in this room you may have heard of Toxoplasma in the same sentence as cats or poop and that's because cats are the definitive hosts for this parasite if the cat is infected it can pass billions of parasites in its feces which makes its way to us through contaminated food
or the undercooked meat of animals that have been previously contaminated infected so what do mitochondria do when Toxoplasma enters their cell what I'm showing you here is a video that captures the encounter between parasite and mitochondria Toxoplasma in red invades a Cell full of mitochondria in green mitochondria surround this first parasite and seem to destroy it what we found is that some of the changes in mitochondrial Behavior are linked to changes in their metabolism or motive eating because during infection we have a sort of Hunger Game scenario both mitochondria and parasite need fats however our
mitochondria begin to take up more fats thereby diminishing the parasite access to the fats it needs to grow if we enhance the ability of mitochondria to take up fats the parasites take up less and grow slower if we however block the ability of mitochondria to use fats parasites take up more and grow faster so this tells us that mitochondria are not simply targets during infection but can defend our cells against microbes considering mitochondria as intracellular microbes guarding their home changes our fundamental perception of our cellular powerhouses and allows us to ask new and Powerful questions
like can we use what we've learned about these Hunger Games to develop novel antimicrobials can mitochondria deprive microbes from other nutrients are there other ways that mitochondria can defend ourselves from microbes apart from these Hunger Games we hope to have the answers to these questions in the coming years but in the meantime I'll leave you with a take-home message and a question the take-home message is our mitochondria are not simply powerhouses but also the Guardians of ourselves keep them happy with a healthy lifestyle the take-home message is or the question is mitochondria have had 1.5
billion years to evolve from bacteria so is it fair for me to still consider the microbes I think this becomes more of a philosophical question so naturally let's turn to the Greeks in his Masterpiece parallel lives the Greek philosopher Plutarch recounts the Paradox of Theseus the Greek Mythic hero who slayed the Minotaur that had Menace the Athenians and returned to Athens in a ship made of wood this wooden ship was considered sacred and so preserved over the centuries as the wooden planks deteriorated new ones took its place at a certain point all of the planks
used to build the original ship had been replaced even though the ship maintained its original form the question that arises and that is divided philosophers for centuries is has the ship of Theseus retained its identity is it still the same ship or is it only similar to the original I think that the ships are the same and that mitochondria are microbes what do you think thank you [Applause]
