Microbial Mysteries

Unraveling the mysteries of microbial life

Documenting the gigantic diversity of tiny life in the ocean

Although tiny in size, the vast quantity of marine microbes in the ocean comprise the largest reservoir of genetic diversity on Earth, yet they remain one of the least explored and understood groups of life. What is known, however, is amazing. Marine microbes have demonstrated astounding resilience, living in the harshest conditions on Earth – in boiling hydrothermal vents, in sediments deep below the seafloor, and in nutrient-depleted ocean gyres, to name a few. Marine microbes display an incredible ability to evolve, adapt, and impact the health and wellbeing of entire marine ecosystems. Bigelow Laboratory scientists are world experts in marine microbes, and they are leading efforts to understand the diverse makeup and interactions of the tiny giants of the sea.

The Single Cell Genomics Center (SCGC) at Bigelow Laboratory is at the scientific frontier, developing technological solutions that were not available even a few years ago and making them accessible to the broad research community. Single cell genomics has enabled scientists to analyze the physiology, viral infections, global distribution, and other features of marine microorganisms without having to culture them in a laboratory. As less than 1 percent of marine microorganisms have been successfully cultured in laboratories, this major breakthrough is providing a practical means of studying these organisms. There is great demand for this kind of technology and expertise, and the SCGC is currently collaborating with more than 100 universities, research institutions, and companies around the world.


Dr. Ramunas Stepanauskas,director of the SCGC, has used this technology to study bacteria in the dark ocean, beyond the reach of sunlight where 90 percent of the entire ocean’s volume is contained. He has discovered that bacteria in these waters consume carbon dioxide, which may have a significant impact on the global carbon cycle. More recently, Stepanauskas and his colleagues have been searching subsurface environments, as far as 2.5 miles underground in South Africa, to find and study microbes that have never been exposed to conditions on the planet’s surface. With the use of single cell genomics technology, Stepanauskas’ research program, supported and advanced by a team of postdoctoral researchers -Maria Pachiadaki, Jessica Labonté, and Eric Becraft -is expanding our knowledge of the early evolution of life on Earth, and of the biology and planetary impact of some of the most abundant and mysterious organisms in the world.

Dr. Mike Lomas has also been examining marine microbes—eukaryotic phytoplankton whose cells contain a distinct self-contained nucleus—to test a long-standing concept in ocean science known as the Redfield Ratio. The Redfield Ratio has traditionally described the proportion of carbon, nitrogen, and phosphorus in plankton throughout the ocean— a key aspect of marine phytoplankton biology. Researchers had believed that the Redfield Ratio was dependent on evolutionary lineage. Dr. Lomas and his colleagues, however, have found that the chemical composition of marine plankton communities is significantly influenced by latitude and temperature, and relates to changes in the abundance of different plankton groups. Using the outstanding taxonomic diversity held in the NCMA, Lomas has been able to study this idea in depth. He has observed that while some families of phytoplankton’s ‘Redfield Ratios’ seem to be impacted by lineage, the observation is by no means universal. Lomas’ research is enhanced by the work of his postdoctoral researchersSteven Baer and Leann Whitney,who also study phytoplankton diversity and ecology. Baer is researching how the Redfield Ratio varies in discrete natural phytoplankton populations. Whitney is studying the genetic response of phytoplankton to phosphorus stress and ocean acidification. Understanding the interplay between evolutionary diversity and the physiology of phytoplankton in controlling global processes like carbon sequestration is currently a ‘hot topic’ in oceanography and one that Bigelow Laboratory scientists are uniquely situated to study.

Dr. David Emerson is also advancing understanding of the diversity of marine microbes and their environmental implications. His investigations, and those of postdoctoral researcherJarrod Scott, have ranged from studying bacteria that derive energy from rusting iron to the microbial community that lives inside whale guts. Their whale gut research demonstrates how both diet and evolution play a role in the community of microbes living in whales, and how these microbes are uniquely adapted to provide nutrition to their host. While baleen whales are carnivores, the microbes found in their guts share characteristics with both plant-eating cows and meat-eating predators. This community of microbes helps whales extract the greatest level of nutrients from their food sources. This study opens the possibility of being able to track and investigate the microbiota of wild animal populations to understand more about the dynamics of their diet, and how these organisms impact animal health.

Dr. Beth Orcutt explores some of the most remote and inhospitable environments in the ocean to understand how microbes survive there. Last summer, Orcutt dove in the human submersible Alvin to collect microbes from below the seafloor, and in the fall, Orcutt again dove in Alvin to study life on a previously unexplored undersea mountain in the Pacific Ocean, which hosts a unique hydrothermal vent environment. Microbes in these environments are able to gain energy from “eating” chemicals in the rocks, and Orcutt is seeking to understand how they do this. Postdoctoral researchersStephanie Carr and Jessica Labonté support and advance this work in the laboratory. Orcutt also led two research cruises in the Gulf of Mexico this year to study the role that microbes play in degrading oil at the bottom of the ocean. Exploring the genetics of microbes from these “extreme” environments could lead to novel biotech applications.

Dr. Joaquín Martínez Martínez investigates marine viruses in extreme environments. Marine viruses are by far the most abundant life form in the ocean and the reservoir of most of the genetic diversity in the sea. Recent advances in genomic technology have made it possible to identify viruses, and Martínez Martínez is at the forefront of this work. He has identified viruses that are affecting the diversity and evolution of life in the ocean in deep subsurface hydrothermal fluid and vents. In the laboratory, Martínez Martínez is examining the interactions between viruses and their microalgae hosts, while also studying how viruses respond to increasing ocean acidity. Such knowledge will help us predict how viruses will continue to adapt, change, and affect all marine life as the ocean continues to change.

The variety of life in the ocean is not only astounding to behold, but, as scientists increase what is known about this vast reservoir of life, they are discovering life’s potential to adapt, evolve, and provide many valuable services.