DaveTheGardenGuy

Getting Dirty is Good For You!

    We know that productive garden soil contains between 100 million and 1 billion bacteria per gram (about a teaspoon full).  We also know that many of these bacteria have important roles to play in the Soil Food Web and are to a great degree orchestrated by plants through plant root exudates.  What we don't know is what roles many of the different bacteria play.  We know about a small fraction of them that help with nutrient cycling, disease suppression, and are important to water dynamics in the soil but the greater number by far and their related interaction with other organisms is currently beyond our understanding.  In 2007, Christopher Lowry, a neuroscientist now at the University of Colorado found that certain strains of soil-borne bacteria sharply stimulated the human immune system.  One bacteria, however, Mycobacterium vaccae, has been found to have amazing benefits to us directly.

    Mycobacterium vaccae, a bacteria that is common in soil, has been found to activate a specific group of neurons in our brains that produce serotonin.  Serotonin is found in the brain and the blood and is a very important neurotransmitter which helps regulate a whole host of functions including:

• metabolism
• appetite
• sleep
• aggression
• anger
• mood
• anxiety
• behavioral arousal
• motor activity
• coping responses to stress

    Many antidepressants work by serotonin pathways or serotonergic systems.  Antigens derived from the bacteria, which is non-pathogenic and saprophytic in nature, altered stress-related emotional behavior in mice.  The tests and results of studies in London and Bristol showed that the bacteria caused an increase in serotonin metabolism within the prefrontal cortex.  The conclusions from the 2007 studies included "a novel hypothetical framework for investigating the relationships among immune activation, serotonergic systems, and mental health."  This added to previous work showing "unexpected improvements in quality of life scores" to clinical cancer and inflammatory disorder trials.  Another trial using the soil bacteria to treat psoriasis showed Mycobacterium vaccae "gave long-lasting clinical benefit to most patients, with minimal side effects."

    Related to M. vaccae are two scary bacteria:  M. leprae and M. tuberculosis which cause leprosy and TB.  M. vaccae, named after the cow, however, because it was first isolated from cow manure, is ubiquitous in fertile soil and thrives anywhere soil is enriched with organic matter.  Christopher Lowry said that the effect of M. vaccae is "basically no different from all the SSRIs".  This is exciting:  SSRIs are antidepressants and include medicines such as Prozac, but whereas SSRI's are considered "blunt instruments" by many scientists for treating mood disorders, M. vaccae are selective and specific in their ability to excite certain neurons that produce serotonin and directly impact cognition and mood regulation as well as increase the ability to cope with stress and anxiety.

    In a 2008 article in Psychology Today, Daniel Marano explains that eating antioxidant-rich fruits and vegetables may only be half of a newly evolving story of health and that our society's displacement from the natural world has disrupted a deep and direct connection we have to the soil and it's resident organisms.  Indeed, the sharp rise in chronic asthma, inflammatory bowel disease, and other inflammatory, allergic, and immune disorders has resulted in "The Hygiene Hypothesis".  The bottom line is that we as a society have gotten too clean and the recent obsession with sanitation and anti-microbial products has caught up to us.  It's clear that we are a part of the Soil Food Web and removing us from the soil is to our detriment!

    Not only does M. vaccae promote the generation of serotonin in our brains, but also norepinephrine.
Perhaps more important, it induces the neurogenesis, or creation, of more neurons that produce these two amazing  compounds in our brains.  Norepinephrine is just as important as serotonin and affects the amygdala part of the brain where attention responses are controlled, including the "fight-or-flight response and related heart rate, glucose release, and blood pressure responses.  Norepinephrine plays a large role in attention and focus and may be used for indications of attention-deficit/hyperactivity disorder, depression, and hypotension.

    Similar to the striking rise in allergic and inflammatory disorders, the rise in ADHD and Depression and the related increase in the use (and abuse) of drugs such as the psychostimulants Ritalin or Concerta as well as tricyclic antidepressants or newer SNRI's such as Effexor and Cymbalta point towards a modern society who's young kids do not get to play in the soil enough and one who has abused the use of antibiotics.  It would seem that exposing ourselves and especially our children to the soil in the garden could be a good thing indeed.  The Hygiene Hypothesis page in Wikipedia now has 39 references as well as plenty of supporting articles for further reading and external links.  It "has become an important theoretical framework for the study of allergic disorders" and both their increase since industrialization as well as their higher incidence in more developed countries lends credence to the theory which was first given a scientific background by David Strachan in 1989 and later made popular in the 2005 book by Richard Louv called "Last Child in the Woods: Saving Our Children from Nature-Deficit Disorder."  This is now a movement called No Child Left Inside and a Federal bill introduced to the House of Representatives on April 22, 2009, Earth Day.  The bill is currently languishing in a subcommittee on early childhood education due to opposition from a conservative american "think tank" called The Heritage Foundation.

    It is now clear that exposure to bacteria, and especially during neo-natal development helps to adequately develop regulatory T cells.  In 2007, Keven Becker of the Gene Expression and Genomics Unit at the National Institute on Aging wrote an article that supports a link to Autism, also on the rise, to the hygiene hypothesis and shows etiological links between autism, asthma, and inflammation disorders.  He hypothesizes that "immune pathways altered by hygiene practices in western society may effect brain structure or function contributing to the development of autism."

    More recently, Dorothy Mathews and Susan Jenks of the Sage Colleges in New York tested live mice by feeding them live M. vaccae and found that they could "navigate a maze twice as fast and act with less demonstrated anxiety behaviors as control mice".  Mathews said in a May 25 2010 Science Daily article that "learning environments in schools that include time in the outdoors where M. vaccae is present may decrease anxiety and improve the ability to learn new tasks."  This is a pretty good reason to promote school gardens!

    So what then, do all these medical maladies have to do with gardening, horticulture, and landscaping?... the point here is that we as organisms co-evolved on this planet along with and as a part of the soil ecology over millions of years.  Over the past 100 years or so we have become increasingly detached from the soil that supports us and our efforts to further cut us off from bacteria and microbes by the use of antibiotics and antibacterial products has led to increases in diseases and disorders.  It's time we realize the health benefits of our natural connection to the Web of life and rejoice in the practice of getting dirty.  The next time you breath in the steamy aroma of fresh turned earth, compost, and manure, think of all the wonderful biology making it's way into your personal ecosystem.  Contemplate the increased biodiversity you now harbor and be glad.  While there are still valid concerns over other bacteria such as certain strains of Escherichia coli, for the most part, the little soil that sticks on the fresh veggies you eat may actually be covered in organisms that are very good for you.  -Yet another great reason to grow your own food and if you don't have one, start a garden today!

Plants are so cool!

 I have been pondering lately about just how cool plants are -again!  I've written about this in the past but was inspired to revisit the topic on this blog while listening to Glenn Keator, an engaging local author, educator, and plant enthusiast, discuss plant biology with the Marin Master Gardeners.  It dawned on me how fortunate we are to be able to be so intertwined in the lives of so many plants and to be privy to the growing information regarding plants and plant lore.  But it goes deeper than that.  Our day to day relationships with plants as gardeners make us appreciate plants for the beauty they provide and we go about our roles of propagating, pampering, growing, and combining them in artistic and useful ways.  But how often do we contemplate on how much we have in common and how much we owe it to plants for our very existence?

Vascular plants have been here on Earth, indeed, actually involved in the Earth’s evolution, for approximately 440 million years.  There are approximately 350 thousand species of plants.  We as gardeners know that many species are divided up into dozens of cultivars.  The diversity is astounding.  It’s cool to think that this many species have a whole energy system that is somewhat opposite that of ours:  Plants use carbon dioxide to synthesize glucose and give off oxygen as a waste product.  We use oxygen and glucose and give off carbon dioxide as a waste product.  What goes around comes around.

Plants have evolved to accept light at two specific wavelengths.  At these bluer and redder wavelengths, Chlorophyll molecules absorb light in the chloroplasts and we see them in the spectrum of what is not absorbed -green.  Humans have been on the earth about 200 million years -less than half as long as plants.  We are only now figuring out how to capture the energy of sunlight using photovoltaics.  Thank goodness plants have been at it for such a long time.  About 4.4 billion years ago our atmosphere was mostly carbon dioxide and water vapor -and almost no oxygen.  Although the cyanobacteria started producing oxygen about 3.5 billion years ago, when the photosynthesizing plants evolved, the atmosphere changed dramatically and eventually the carbon dioxide got locked up in limestone, shells, and fossil fuels.   This allowed oxygen breathing organisms to evolve.   Now that we’ve been using those fossil fuels for a short while we’ve had to acknowledge  the inconvenient truth that it creates more carbon dioxide in the atmosphere -and global warming.  All the oxygen in the atmosphere also allows the creation of a layer of a special allotrope of oxygen that protects us from much of the suns ultraviolet radiation -the  ozone layer.  Also inconvenient is how our recent use of chlorofluorocarbons has reduced the number of these special  types of oxygen and have allowed a growing amount of genetic damage to living organisms, including us.  As I said, what goes around comes around.

The oxygen put into the atmosphere by plants also reacted with the ammonia from all the early volcanos and formed the nitrogen that now makes up 75% of our atmosphere and is the basic building block of all living tissues and amino acids.  It’s the first number on any  bag of fertilizer.  What’s really amazing is that nitrogen can’t be used directly by plants or animals.  Plants are part of a network though.  Certain bacteria can use nitrogenase enzymes to “fix” ammonium into nitrites, which is then converted by other bacteria into nitrates, finally usable by plants to eventually form proteins, amino acids, and alkaloids.  Some plants have even assimilated the useful nitrogen fixing bacteria into a symbiotic relationship in their roots as in the case with legumes, which makes up a large part of our diet.  Most of our livestock feeds and  pasture forage plants are legumes.  Other plants do this too.  I was surprised to find out that one of my favorite plants, Gunnera, also has a symbiotic relationship with a nitrogen fixing bacteria.  So do Casuarinas, Myricas, and lichens.  The real wonder of nitrogen, however, is when you put four of them in a ring, as in Chlorophyll.

 Glenn brought up a fascinating bit of information to ponder: the similarities between chlorophyll and hemoglobin.  In mammals hemoglobin makes up 97% of red blood cells (dry weight) and is the carrier of oxygen from lungs (or gills) to the rest of the body.  It also is important in neurons and as an antioxidant in kidneys.  In Hemoglobin, an iron ion is surrounded by four nitrogen in a plane, the iron being able to bind with oxygen and translocate it.  In Chlorophyll, it's a magnesium ion that is similarly surrounded by four nitrogens.  These amazing molecules are both produced through the same metabolic pathways and are called Porphyrins;  coordinated with iron: you get the building blocks of our blood, coordinated with magnesium and you get the building blocks of our photosynthetic friends.  Interestingly, but not surprisingly, very similar structures also create bacteriochlorophylls, other photosynthetic pigments that various bacteria use to absorb other wavelengths of sunlight -even sulfur based bacteria.    These amazing similarities between the chemical workhorses of the biological world always inspires a sense of wonder in me, and at the same time a strong sense of oneness, -of connectedness; ourselves being so similar in basic structure to plants and even bacteria.  

Just to leave Nitrogen as a basic building block really doesn’t tell the whole story, though:  Nitrogen, along with a diverse group of bacteria and fungi, are also the basis for decomposition.  Where do you think we’d be without decomposition?  Talk about circular events.   As gardeners we all know the wonders of compost.  And what do we balance in the compost pile?  Moisture, oxygen, nitrogenous material, and carbonaceous material.  And where do you think the carbonaceous material came from?  Plants, of course!  The amazing evolutionary trick that plants pulled off was to develop cell walls.  Animal cells only have a plasma membrane.  Plants get a cell wall.  By combining Hydrogen from water with Carbon from carbon dioxide, again using the amazing chlorophyll in photosynthesis, they can make carbohydrate frameworks: cellulose, by far the most abundant form of living terrestrial biomass.   Plant cell walls consist of several layers of cellulose microfibrils held together with hydrogen bonds that allow high tensile strength and ... wood.  Now where would us landscapers be without wood?  Would our species have evolved at all?

So everything you breath, everything you eat, every hydrocarbon in your body -and every other body, big, small, human or otherwise- is the result of plants.  We may think we are higher on the “food chain”, but perhaps we should think of it more like a tall pyramid with us precariously balanced at the top.  The more solid foundation is made up of plants, bacteria, and minerals.  The “carbon cycle” trumps the “food chain” any day anyhow, and it’s based on plants.  When you think of all the bacteria and enzymes involved, then we’re looking at a Web.  And when you sit out this summer warming yourself in the sun, or find yourself in the hot sun working in a garden, think about all the plants around you using that energy, turning those photons into sugars, breaking the chemical bonds of water, and be jealous.  Be very jealous.  I wish I could do that!  Maybe I’d look good in green too.   Now that we are “building green”,  “voting green”, and “living green”, desperately trying to undue the mess our opposable thumbs and enlarged cerebral cortexes have gotten us into, it’s good to reflect on our fine photosynthetic friends and appreciate them not only for their beauty and usefulness, but for allowing us the ability to be here, use our senses, and appreciate anything in the first place.  It sure is nice to know we are a part of the “green industry” and that our species has now acknowledged the Web and the importance of green.  It's also really nice to know we're so closely related.

"All things share the same breath -the beast, the tree, the man... the air shares it's spirit with all the life it supports"   -Chief Seattle

(chemical structures from Wikipedia- I love the Web!)