The scoop: Long before passenger planes carried infectious diseases to far-flung parts of the globe, dust storms were doing the same thing. Ongoing research into what lives in airborne dust has revealed a thriving microbial source of disease that encircles the planet. Microbiologist Dale Griffin's job is to seek out the spores and other tiny life forms that are hitching rides on the transcontinental dust plumes. Among the weird and surprising discoveries: A lot of the particles you inhale in Florida are from Africa. Read on to find out...
dale.w.griffin: Hello Larry......you there?
larryo: Hello! Yep. Thanks for making time for this.
dale.w.griffin: Anytime
larryo: So let's start with where you are. USGS office or lab somewhere?
dale.w.griffin: Actually, I'm at the house. Gmail chat isn't permitted from office computers
larryo: Ah. Okay. Makes sense. Where's the office. I have no idea about your location.
dale.w.griffin: Our office is on North Monroe Street in Tallahassee, Florida
larryo: You are microbiologist. Is that correct?
dale.w.griffin: Correct, I'm an environmental/public health microbiologist
larryo: Not what most people associate with USGS. Right?
dale.w.griffin: Correct, I'm one of the few microbiologists in our Geological group but we have many other in our water and biological divisions
larryo: From what I've been told, you have worked on microbes and dust. Do you still work on this?
dale.w.griffin: Yes, I will be doing field work out in southern New Mexico and then later out in the Pacific looking at the dust/microbe issue
larryo: New Mexico too? (I live and work in Albuquerque). You have worked in the Caribbean as well, is that right.
dale.w.griffin: Yes, we have conducted a number of studies in the Caribbean looking at the types of microbes moving across the Atlantic in clouds of desert dust
larryo: When you got started in this work, what was the thinking about microbes carried by dust, and has that thinking changed?
dale.w.griffin: Originally it was thought that UV light sterilized these dust clouds as they moved across the oceans. What we know now is that many different genera of bacteria and fungi can survive the trip........about 20 to 30 percent of them are recognized pathogens to some type of plant or animal....very interesting stuff with global scale implications
larryo: Why did folks think UV killed them?
dale.w.griffin: Prolonged exposure to UV is lethal to cells...think sunburn.....it takes 3 to 5 days for a cloud of desert dust that blows off the west coast of N. Africa to cross the Atlantic and impact air quality in the Caribbean and SE US.....so that amounts to a lot of UV exposure.........I'd hate to see what I looked like after laying on the beach for 3 to 5 days with no sunscreen....ouch!
larryo: But no one had tested that idea, by trying to culture?
dale.w.griffin: No, which is amazing
larryo: Yeah! Just one of those things no one thought to try! Just love it when one of those things pops up in science. Always humbling. So was the African dust the first to be found with microbes -- and then connected to actual disease?
dale.w.griffin: On a long range study yes and the first connection was finding a pathogen that causes sea fan disease...a species of the fungi Aspergillus
larryo: Have there been other cases like that -- dust/pathogen/infections?
dale.w.griffin: Yes, one of the most well known is the fungus that causes Valley Fever in the SW United States. Outbreaks of this usually follow exposure to clouds of dust in our deserts
larryo: That's more of a regional problem, right? Or can wind subject folks belong the SW to the fungus too? That's more of a regional problem, right? Or can wind subject folks belong the SW to the fungus too?
dale.w.griffin: No, it is regional.......this pathogen, Coddidioides immitis is only found in the Americas
larryo: I'm curious about the role of inorganic dust in all this. Is it an actual carrier for the microbes or are they all just hitching rides on the same wind?
dale.w.griffin: In most cases microbes adhere to soil particles....we know that this relationship is beneficial to the longevity of the organisms
larryo: Are there any other human pathogens out there you have discovered in the dusty air?
dale.w.griffin: Yes, we have found a number of different species of fungi that are known pathogens..species of Aspergillus, Neotestudina, Phoma, Stemphylium, etc....bacteria also, Pseudomonas, Bacillus Staphylococcus, etc.....many, but most are opportunistic, meaning that the can only cause disease in an individual whose immune system is compromised.......but, keep in mind that we only identify a small fraction of what grows due to costs...and these are only the ones that would grow...we know that less than 1 percent of what is really there will grow on media....
larryo: Wow. So this is a major way that these microbes disperse? Does this make them ubiquitous?
dale.w.griffin: Yes, we think many are...at least in those environments that are downwind......dust blowing out of Asia can circumnavigate the globe so this is the primary means of global dispersion
larryo: Does this help explain any disease patterns seen in the past? Or help predict/avoid outbreaks in the future?
dale.w.griffin: We know certain types of pathogens move through the air, most over very short distances...like the cold and flu viruses....but can they or other pathogens move further......we think that given the diversity of microbes we've seen in these dust clouds and given the frequency of dust movement and its scale that outbreaks do occur in this manner......
larryo: I've heard of weird ways diseases can pop up within days in very different locations. So this would perhaps explain some cases like that?
dale.w.griffin: Yes, I believe so.......human movement via flight certainly facilitates rapid movement...huge numbers of microbes moving about the globe in clouds of desert dust is another
larryo: Ah. So our passenger planes did not invent this aerial dispersal after all. One last question: This work would seem to combine geology, meteorology, microbiology and epidemiology. How do you guys manage all that?
dale.w.griffin: Kind of goes back to your earlier note...and microbiologist in the USGS.......it was a senior USGS geologist (Eugene Shinn) that proposed the pathogens were moving about the planet in this manner...he happened to be on my Ph.D. committee......so there you have geology and microbiology, we add the meteorology and epidemiology via side investigations and through collaboration
larryo: If you don't mine one more: What will you be looking for in your next field work?
dale.w.griffin: we will be looking at Asian dust moving across the Pacific...using non-culture based approaches to help us define the entire microbial community, not just the ones that we can grow.....
larryo: Asian dust like the spring plumes that sometimes pour across the Pacific towards North America?
dale.w.griffin: Yes, so we will be venturing out in mid-April which is the peak of the Asian dust season...and yes, they move over the Pacific and impact our air quality.........we get Asian dust from one side and African dust from the other
larryo: I noticed that in reading up on this. Both corners of North America get it. So that keeps you busy.
dale.w.griffin: Yes, both sides...a bit of trivia.....in the summer in Florida when you take a breath....~50% of the particles you inhale come from Africa
larryo: Whoa! That's incredible. And the other 50% (I had to ask)?
dale.w.griffin: Local one would think .....of course what is local given that these clouds have been moving soil and microbes around the planet for billions of years
larryo: Mars isn't the only dusty planet, I guess.
Perhaps that's where they should look for life there -- in the dust
dale.w.griffin: No, just a real good example of one.....yes, it may be the place to look
larryo: Well I won't keep you. Let me know if there is any way for us to reconnect after the Asian dust work. I'd love to hear about it.
dale.w.griffin: Sure will and bug me anytime
larryo: Thanks. Appreciate it. Good luck with the research.
dale.w.griffin: Thanks Larry....take care
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