Big or small it seems life’s creatures all display similar habits.
This week in Science, researchers from MIT and elsewhere report that planktonic microbes in the open ocean follow predictable patterns and behaviours with respect to their biological activity. The oceans are filled with armies of plankton working stiffs going about their day to day lives just like the rest of us.
What might be remarkable to many readers is that these plankton display a great variety of characteristics relating to simple behaviours such as eating, breathing, and growing. Some are early risers, with respiration, metabolism, and protein synthesis firing up in the morning hours, while others drag their asses into action later into the day or evening hours.
Ethnicity plays out with a bacterial division of roles similar to those we find in our own society “Italian-like” trench working plumbers consistently carry out tasks in very different forms and places from their “Mohawk sky-scraper” aerialists.
Ed DeLong, of MIT’s Department of Civil and Environmental Engineering, says this daily procession of bacterial work and life is surprisingly dependable and orderly. He’s created a wonderfully graphic view of his world of ocean plankton working stiffs. I sure hope he has the graphic novel underway! The anti-anthropomorphic stiffs will be going nuts right about now.
“This is the first observation for microbes, on a species by species basis, of this bucket brigade of activities that is happening, boom, every day like clockwork,” DeLong says. “You can imagine that these microorganisms sort of punch the time clock and engage in their daily activities at slightly different times, but in the same order each day, across the whole community.”
DeLong discovered the daily regularity and routine occurs among ranks and legions of microbes that are genetically quite different. The work clearly shows that any given working stiff bacteria’s behavior may not be based solely on that organism’s individual machinery. Rather the myriad plankton all somehow get it together to do their respective jobs by tuning into the timing, rhythm, and requirements of the workplace community at large. “It’s like an orchestra that’s finely tuned,” DeLong says. “Organisms are slightly staggered in terms of when they start to chime in, but they’re extremely tightly coupled.”
Punching the clock
DeLong and his colleagues deployed a free-drifting robotic sampler for three days in the North Pacific in 2011 to collect seawater. Every two hours the robot like a workplace security camera took a good look at and collected samples of the thriving community of bacterial plankton. (Note – what we used to call “blue green algae” we now call bacteria)
Back in the lab, the researchers used RNA sequencing techniques to identify the transcriptome profile of each sample—the genes that are turned on or off at any given moment across the whole community. Like a shift change bell these trigger activities such as respiration and metabolism (heavy breathing and piss breaks for you and I common working stiffs).
The researchers pieced together the genetic information to identify daily cycles—24-hour patterns of behavior—for a number of groups of bacteria. The majority of samples were dominated by Prochlorococcus, the most abundant photosynthetic organism on Earth. This productive plankton is known to have a very rigorous metabolic schedule, set to the sun.
In their genetic analyses, the researchers observed a similar trend: Prochlorococcus started exhibiting signs of metabolic activity at dawn, peaking around noon as it absorbed sunlight and produced carbon.
In addition to Prochlorococcus, the team analyzed five heterotrophic species—bacteria that consume organic carbon to make new cells. Among these populations, a group called Roseobacter was first to exhibit signs of activity after sunrise, with other bacteria soon following suit later in the day. “Early in the morning, one set of organisms got up first and turned on its genes for making proteins, and also for respiring, and those are proxies for subsequent activity and growth,” DeLong says.
He explains what happens is a “wave-like progression” of activity, set to the clock of Prochlorococcus: At dawn, the plankton begins to absorb sunlight, converting it into carbon for the rest of the ocean community. As more carbon becomes available, heterotrophic species like Roseobacter begin to take it up. As different species have different rates of metabolism, they may be more active at certain times of day. “What we’re seeing out in the ocean is telling us how complex assemblages of different microorganisms are basically working together and coordinating their daily activities,” DeLong says.
Last year the group conducted a parallel study, oogling plankton working stiffs activity in coastal waters, where they observed less regular metabolic patterns. DeLong suggests this may due to vastly more available nutrients. In rich coastal waters these plankton working stiffs can pick and choose from a large selection of food trucks that show up at the work site. Thus their characteristics are more varied as they feast on nutrients from a variety of more sporadic environmental sources, such as rivers and surrounding phytoplankton blooms.
The open ocean is more like a remote work site with very stable conditions, you eat at the project cookhouse and that’s it. In those far away open ocean locations the primary producers like Prochlorococcus, like domineering Bull Cooks become strong regulators of behaviour, driving much of an ocean community’s characteristic activities.
Andrew Allen, of the J. Craig Venter Institute, says: “To date, oceanographers have been generally blind to the occurrence of daily metabolic cycles in marine bacteria. This study represents application of state-of-the-art robotic and automatic sampling of marine microbial communities.
It is unique in terms of enabling highly standardized collection of samples from the same water mass at depth at short temporal intervals. The reported daily patterns will provide valuable new context for thinking about and modeling microbial processes and associated nutrient cycles and other food web dynamics in the ocean.”
Ed DeLong is enthused about future work and says, “Because of improvements in genome sequencing technologies, we can drill down and sequence a lot deeper into the microbial community’s gene transcripts at each time point. Microbes can turn on and off their gene expression on the order of minutes. So we’re getting closer to the resolution of where activities really matter.”
The most important thing to learn from Ed’s wonderful work is that ocean pasture ecology cannot be reduced to a bunch of simplified chemical and physical oceanography equations assuming it is just some simple beaker full of chemicals ruled by basic chemistry and physics.
It is life with more wonders and mysteries than we perhaps can even imagine. But at the same time it is life not so very different than we ourselves experience and understand.
The ocean pastures are in desperately poor condition compared with their state of health and abundance of decades ago. We can and are working to restore them back to historic conditions of abundance and it just works. Here’s a link to how we have nourished life in a vital ocean pasture which is bringing the fish back.
References: MIT News Office and The Journal Science