Our Gut and Biosolids Microbial Communities

I have a tremendous idea for a new biosolids research project, but first….

It was no big surprise that one of my wife’s Christmas gifts to me was Gut: The Inside Story of our Body's Most Underrated Organ.  I have displayed at home, as well as in my biosolids commentaries, an abnormally high interest in the human gut microbiome.  To my delight, this book, translated from German and written by Giulia Enders, a young female, award-winning, Ted-talk-giving, science writer, is a breezy and comprehensive work. It is, as Amazon says, a “beguiling manifesto.”

Clearly, one of its main messages is that the health of the human gut microbiome effects the health and well-being of its host, that is you and me.  I checked with Amazon, and Ender’s “gut” book shares the virtual bookshelves with a whole host of similar titles, also drawing on the connection between happy microbes and happy people: The Microbiome Cookbook: 150 Delicious Recipes to Nourish your Microbiome and Restore your Gut HealthThe Mind-Gut Connection: How the Hidden Conversation Within Our Bodies Impacts Our Mood, Our Choices, and Our Overall Health,  The Good Gut: Taking Control of Your Weight, Your Mood, and Your Long-term Health

This flurry of book is all very new, each book printed in 2016.

Then the news services on January 3rd reported that a new organ had been uncovered in the human body, one connected to the intestines, and called the “mesentery.” Another young female science writer with Live Science, Sarah G. Miller, wrote the article Gut Decision: Scientists Identify New Organ in Humans:  “scientists can now focus on learning more about how the organ functions, Coffey said. In addition, they can also learn about diseases associated with the mesentery, he added.”

I can confidently assert that we will be hearing a lot about gut flora over the next decade, and we should take note of this for our work with biosolids, particularly for the positive connection between microbial communities and human health. A major research question was which gut microbes caused major gastrointestinal illnesses, such as Crohn’s Disease and ulcerative colitis, in hope of an easy path for medical control. But the nature of gut ecosystems was too complex for a simple answer. Instead researchers turned to the question how the gut ecosystem actively keeps us all healthy, particularly when so many species of gut microbes are known human pathogens.

Over the past several years, journal articles have addressed these questions:

Wow! Who would have guessed that our health and well-being is really the result of our wonderful gut flora?

I realized in reading these reports that I had only a foggy idea of what comprised the human gut flora.  We are all familiar with E coli as an important class of bacteria, but its distinction for us is not in its role in the human microbiome but its choice as an indicator of environmental contamination.  And, as it turns out, it is not a particularly good indicator at that.  Escherichia coli is just one species in a large class of protobacteriods, a group that together makes up perhaps a quarter of the 3 trillion microbes in the adult human gut. E coli’s role is relatively small in the gut, but its presence in activated sludge treatment works turns out to be very significant, which is one reason (along with its easy culturability in the laboratory) we know so much about it, why we track it, and why we regulate it.

But we are learning of far more important microbes.  One particularly interesting microbial group in the gut is called Lachnospiraceae.  Besides its very dominant role in the gut flora in a class of organisms called the Firmicutes, this group is interesting because it connects to my next topic, the sewerage system. One young, female professor in Wisconsin, Sandra L. McLellan, has emerged as a leader in researching the unique microbial ecosystem of sewers. She has identified the class of bacteria Lachnospiraceae as a robust indicator of human fecal waste, occurring in the human gut and in the sewer, and being distinct from microbes from other animal and environmental sources.  Check out her paper, Sewage reflects the distribution of human faecal Lachnospiraceae, showing that public sewers fed with human-sourced food are the habitat for unique microbial communities, and this one microbe class that can be readily tracked, the Lachnopriracea. You heard it here first.

Just as we are on the early part of the learning curve of the microbial communities of sewers, the same is true with biosolids itself.  This brings me to Kyle Bibby’s work while a PhD student at Yale University, where he characterized the biota of different biosolids products.  In his paper, Pyrosequencing of the 16S rRNA gene to reveal bacterial pathogen diversity in biosolids, his intention is to clarify the potential array of pathogenic organisms, viruses as well as bacteria, that may be present in biosolids. But his work necessarily included a broader survey of microbial.  He discovered that different processes, such as aerobic versus mesophilic anaerobic digestion vs composting, resulted in biosolids with microbial ecosystems common within processes but different between processes.  Wastewater plants grow out of the influent food and microbes different biosolids-based microbial communities, each characteristic of treatment facility processes.

In his presentation to the MABA Annual Symposium, The role of microbes on soil health and questions for biosolids research, Dr. Jeffrey Buyer had covered Bibby’s work, but then extended the conversation to the effects of biosolids on soil microbial communities. He summarized soils research that showed many soil communities are stable, just as in the human gut, and that additions of various organic feedstocks, biosolids along with manures, help to push around, but not to fundamentally change, those soil microbial communities.  Where we humans might eat a carton of Greek yogurt for our daily dose of probiotics, our annual application of biosolids may do the same for a healthy soil.  Biosolids microbial communities make soils happy.

Dr. Buyer’s presentation this past November reminded me that Dr. Xunzhong Zhang at Virginia Tech, made a presentation to the 2013 MABA Annual Symposium, “Biostimulants Released from Biosolids have impact on Crop Stress Tolerance and Yield.”  Dr. Zhang showed that biosolids release auxins and stimulate soil microbes to do the same, which together significantly increase crop growth. He shows that biosolids makes for happy soil microbes, in turn making plants happy.

So where have I gone with this? Our historical engagement with biosolids microbes has largely been in what goes wrong in controlling pathogen indicators in our treatment processes or where their presence in the environment is a marker for pollution. Instead, what we are learning, starting with the human microbiome, is how critical complex microbial communities are for health -- the health of our bodies, the health of transformative processes in sewers, the health of our activated sludge treatment systems, and in the health-giving properties of biosolids for plant growth.

The analytical tools are at hand and affordable, and only our imagination limits the questions we can ask. This is my research question.  What attributes of biosolids microbial communities contribute most to a positive growth response in plants, and how can we design our treatment plant equipment to optimize those attributes?  Instead of “high quality biosolids” research focusing mainly on attributes of odor, aesthetics, and handleability that influence human sensibilities, let’s look at biosolids from the viewpoint of the healthy plant.  That would be a worthy research project. At least, that is what my gut tells me!