Microbes, by latitudes and altitudes, shed new light on life's diversity

August 12, 2008

Microbial biologists, including the University of Oregon's Jessica L. Green, may not have Jimmy Buffett's music from 1977 in mind, but they are changing attitudes about evolutionary diversity on Earth, from oceanic latitudes to mountainous altitudes.

In two recent National Science Foundation-funded papers in the Proceedings of the National Academy of Sciences, Green and colleagues show that temperature, not productivity, primarily drives the richness of bacterial diversity in the oceans, and that life, both plant and microbial, by altitude in the Rocky Mountains may be close, but not exactly, to what biologists have theorized for years.

Swedish naturalist and botanist Carl Linnaeus, the father of taxonomy who died in 1778, proposed that the planet once was covered by oceans, except for Paradise Island on the equator, and that all organisms emerged from the island and migrated as waters receded. More than a century later, microbiologist Lourens G.M. Bass Becking in the 1930s wrote that "everything is everywhere, but the environment selects."

"What's interesting to me," said Green, a professor of biology and member of the UO Center for Ecology and Evolutionary Biology, "is that the founders of these disciplines envisioned the same thing: That you have this broad dispersal of all of the organisms that each happened to be studying, and that they would colonize the surface of the Earth depending on whether the environment was suitable for them."

In the last decade, microbial biology, using molecular techniques, has changed everything, Green said in an interview about the two PNAS papers and an extensive review of microbial biogeography in the May 23 issue of the journal Science. She was lead author on the Science paper.

"Before now, all biologists could do was look at the biodiversity of microbes that could be cultured in a petri dish. We now know that the vast majority of microbial life cannot be kept in captivity. Now we have the ability to grab DNA from the environment and try to characterize different species or taxonomic groups using genetic material, allowing our field to blast off."

Yet, she added: "We are just beginning to scratch the surface of what these patterns look like."

Green was among several co-authors on a project led by biologist Jed A. Fuhrman of the University of Southern California and published in PNAS in May.

Using samples of ocean-dwelling bacteria collected over 15 years from 57 locations around the world and sorting them into species or taxonomic units, researchers found twice as many microbes at the equator than at the poles. In particular, they found that samples from colder waters still contained many bacterial species, suggesting that productivity as generated by light through photosynthesis has little influence on diversity.

Warmth dictated such diversity, the seven co-authors concluded, but they left open the possibility that the kinetics of metabolism related to temperature is still linked with photosynthesis. "What we found," Green said, "was that the diversity gradient more correlated with temperature than primary productivity."

As for the mountains, traditional wisdom, beginning with Linnaeus, has said that diversity of animal and plant life is highest at the bottom and decreases as you climb. While that scenario has been observed, a second one is emerging, that of a hump shape, with diversity at its height just above the foothills.

In a paper published Aug. 12 in a PNAS special publication (the "Sackler Colloquium: In the Light of Evolution--Biodiversity and Extinction") , Green, as principal investigator, and five colleagues documented diversity patterns of a combination of plant and microbial life, focusing on flowering plants and soil-abundant Acidobacteria, in the Rocky Mountains in Colorado. They found significant differences, using a combination of classical taxonomic and phylogenetic approaches.

Plant communities became less phylogenetically clustered than did microbial life as they drew samples from five sites rising over 24 miles, from 8,071 feet to 11,089 feet. As they went higher, plant life saw a decline in species richness, but for microbes, researchers saw a hump shape in species richness as they went up the slopes.

Their conclusion: "From our study, we saw that environmental selection seemed to play a larger role and was more important for microbes than the plants," Green said.

The trick to the research, she said, involved the scale from which the samples were drawn. Plants were gathered from one-meter-square quadrants, while microbes were taken from soil cores. "You have to be careful about the conclusions that you make," Green said. "So on a 2,000-meter elevation gradient, for example, the spatial scale relative to the body size of a plant is much, much larger when you consider what the universe looks like to a microbe."

That spatial consideration, she said, led her team to narrowly focus on the diversity of Acidobacteria rather than a wide range of microbes present in each area. This allowed the researchers to focus on patterns within one microbial phylum.

"Diversity patterns on mountainsides have been studied mostly on plants and animals for hundreds of years," Green said. "Yet microbes are the most diverse set of organisms on Earth, and they are really important for how ecosystems work. Our study establishes the first elevation-gradient pattern for microbes. We found that, yes, microbes do have a diversity pattern that is similar to what has been studied for plants and animals, but the pattern is different than what you see for plants in the Rockies, and there is much to be done to understand why microbes might have a different biodiversity pattern."

It could boil down to finding a good comparative technique, she said. "I don't think that microbes are fundamentally different from a biological standpoint from plants and animals. I think that we haven't figured out how to study them in an analogous way."

University of Oregon

---

---

	Teaming with Microbes: The Organic Gardener's Guide to the Soil Food Web, Revised Edition by Jeff Lowenfels (Author), Wayne Lewis (Author) The 2011 Garden Writers of America Gold Award for Best Writing/Book proves soil is anything but an inert substance. Healthy soil is teeming with life -- not just earthworms and insects, but a staggering multitude of bacteria, fungi, and other microorganisms. When we use chemical fertilizers, we injure the microbial life that sustains healthy plants, and thus become increasingly dependent on an arsenal of artificial substances, many of them toxic to humans as well as other forms of life. But there is an alternative to this vicious circle: to garden in a way that strengthens, rather than destroys, the soil food web -- the complex world of soil-dwelling organisms whose interactions create a nurturing environment for plants. By eschewing jargon and overly technical language, the authors make...
	March of the Microbes: Sighting the Unseen by John L. Ingraham (Author), Roberto Kolter (Foreword) Though nothing in the natural world would be quite the same without them, microbes go mostly unnoticed. They are the tiny, mighty force behind the pop in Champagne and the holes in Swiss cheese, the granite walls of Yosemite and the white cliffs of Dover, the workings of snowmaking machines, Botox, and gunpowder; and yet we tend to regard them as peripheral, disease-causing, food-spoiling troublemakers. In this book renowned microbiologist John Ingraham rescues these supremely important and ubiquitous microorganisms from their unwonted obscurity by showing us how we can, in fact, see them—and appreciate their vast and varied role in nature and our lives. Though we might not be able to see microbes firsthand, the consequences of their activities are readily apparent to our unaided...
	Microbe by Moselio Schaechter (Author), John L. Ingraham (Author), Frederick C. Neidhardt (Author) "Microbe", a brand-new, general microbiology textbook intended for upper-division undergraduate and beginning graduate courses, is an exciting introduction to the world of microbes. With a distinct ecological and evolutionary orientation, "Microbe" invites readers to partake of the most current advances in the field. Written by prominent scientists with practical teaching, textbook writing, and research experience, this new textbook will engage students in the learning process with its clear, reader-friendly style and unique perspective of the field. This work: emphasizes the roles of microbes in sustaining all life on Earth; presents paradigm-driven material in a clear, reader-friendly style; deals with the complexities of medical microbiology from the standpoint of both the microbe and...
	Deadly Companions: How Microbes Shaped Our History by Dorothy H. Crawford (Author) Combining tales of devastating epidemics with accessible science and fascinating history, Deadly Companions reveals how closely microbes have evolved with us over the millennia, shaping human civilization through infection, disease, and deadly pandemic. Beginning with a dramatic account of the SARS pandemic at the start of the 21st century, Dorothy Crawford takes us back in time to follow the interlinked history of microbes and humanity, offering an up-to-date look at ancient plagues and epidemics, and identifying key changes in the way humans have lived--such as our move from hunter-gatherer to farmer to city-dweller--which made us ever more vulnerable to microbe attack. Showing that how we live our lives today--with increased crowding and air travel--puts us once again at risk, Crawford...
	The Invisible ABC's: Exploring the World of Microbes by Rodney P. Anderson (Author) This book offers a balanced presentation of the microbial world to children in the early school-age years. Using vivid micrographs that show microorganisms shaped as letters of the alphabet, this book teaches children that microorganisms are fascinating life forms that carry out essential activities in our ecosystems to sustain life on Earth. features over 100 superb illustrations of algae, molds, bacteria, and viruses emphasizes the beneficial roles of microorganisms children encounter in their daily activities, from eating bread and cheese to taking medicines presents scientifically accurate information in an age-appropriate format that is both colorful and captivating communicates the size of microorganisms by relating them to items children are familiar with from everyday experiences.
	The Invisible Kingdom: From the Tips of Our Fingers to the Tops of Our Trash, Inside the Curious World of Microbes by Idan Ben-Barak (Author) With the wit of Bill Bryson and the spirit of Natalie Angier, Idan Ben- Barak takes us on a fantastic voyage into the infinitesimal world of microbiology. In The Invisible Kingdom, he introduces us to the amazing lives and workings of genes, proteins, bacteria, and viruses, and the ways in which they interact to shape life on Earth. Exploring everything from radioactive waste and insect sex-change operations to the inner workings of antibiotics, Ben-Barak reveals how important these tiny critters are to all of us. He brings this largely unseen world to life with refreshing analogies and metaphors: cells “pop like bubbles” and bacteria “dream of rain.” On the journey, we learn about the teamwork required to rot human teeth, the origins of diseases, what really goes on inside cow...
	Microbe Hunters by Paul de Kruif (Author), F. Gonzalez-Crussi (Introduction) In this classic bestseller, Paul de Kruif dramatizes the pioneering bacteriological work of such scientists as Leeuwenhoek, Spallanzani, Koch, Pasteur, Reed, and Ehrlich. This seventieth anniversary edition features a new introduction by F. Gonzalez-Crussi. Index.
	The Good, the Bad, the Slimy: The Secret Life of Microbes (Prime) by Sara L. Latta (Author), Dennis Kunkel (Photographer)
	Alcamo's Microbes and Society, Third Edition (Jones & Bartlett Learning Topics in Biology Series) by Benjamin S. Weeks (Author) Revised and updated to reflected new information in the field, the Third Edition of Alcamo's Microbes and Society is intended for liberal arts students taking a foundation course in the life sciences. It discusses the role of microbes in our everyday lives, from food production to their roll in biotechnology and the numerous other ways that microbes contribute to our world. It goes on to explore such topics as the function of microbes in ecological systems and environmental systems. Coverage of bioterrorism, antibiotic resistance, and microbial disease offer students a broad and current perspective of the extensive impact of various microbes. Consistent with Edward Alcamo's student-friendly writing style, material is presented in a lively format that will engage students and highlight...
	Microbe by Bill Clem (Author) In 1947, the U.S. Army left behind a secret when they closed Ft. Miles, Delaware. A threat so deadly, they buried it 1000 feet down in the Atlantic Ocean. Now, sixty years later, an oil rig drilling off the coast of Delaware has hit something. Within hours, crew members are dying from a mysterious illness that kills unmercifully. On the opposite coast, Justin Flannigan, an estranged epidemiologist is visited by the director of the CDC who convinces him to come to Delaware to investigate the bizarre illness. But shortly after he begins his investigation, he gets another visit. This time from an eccentric old man who claims to know the origin of the deadly contagion, and soon, Justin begins to suspect there is more to it than what first appeared. It is evolving swiftly, becoming more...