ocean microbe shift workers
July 12, 2014

Scientists Confirm Different Types Of Ocean Microbes Have Different Daily Life Cycles

redOrbit Staff & Wire Reports - Your Universe Online

Like humans, ocean microbes have their own daily life cycles, following predictable patterns of eating, breathing, growing and other biological activity, according to new research published in the July 11 edition of the journal Science.

As part of the study, scientists from MIT, the University of Hawaii, the University of Georgia, the Singapore Centre on Environmental Life Sciences Engineering at Nanyang Technological University and the Monterey Bay Aquarium Research Institute in California analyzed communities of microbial life living in the open ocean.

While conducting their research at Station ALOHA, a deep ocean facility located 100 kilometers north of Oahu, Hawaii, the study authors discovered that the creatures each possessed their own daily life cycles, similar to the people residing in a bustling city. Some species start their days early, showing signs of respiration, metabolism, and protein synthesis during the morning hours, while others tend to be more active later in the day.

“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,” research team member Edward DeLong, a biological oceanographer at the University of Hawaii at Manoa and a professor in environmental systems at MIT, explained in a statement Thursday.

“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,” he added, noting that the behavior of bacteria is based somewhat on the rhythm of the overall group. “It’s like an orchestra that’s finely tuned. Organisms are slightly staggered in terms of when they start to chime in, but they’re extremely tightly coupled.”

DeLong and his colleagues began their work in September 2011, using a free-drifting robot to collect seawater samples in the North Pacific over the course of three days. Samples were collected from the same community of bacteria every two hours, and then the investigative team used RNA sequencing techniques to identify which genes were turned on or off at any given time throughout the entire microbial community.

The study authors then took this information, also known as transcriptome profiles, and compiled them to complete diel cycles (patterns of behavior over a 24-hour period) for multiple different species of bacteria. They found that each species expressed different types of genes in cycles that were different from each other, but consistent.

The bulk of the samples were of Prochlorococcus – plankton described by the researchers as the most abundant photosynthetic organism in the world and a creature known to have a rigorous metabolic schedule linked to the sun. While genetically analyzing the Prochlorococcus, the researchers observed that the microbes began showing signs of metabolic activity at dawn, with the activity peaking around noon as it absorbed sunlight and produced carbon.

In addition, DeLong and his colleagues analyzed five heterotrophic bacteria species, or species that consume organic carbon in order to create new cells. In these populations, a type of microbe known as Roseobacter was first to exhibit signs of activity after sunrise, with the four other types of bacteria following suit shortly thereafter.

“It was almost like a shift of hourly workers punching in and out on a clock,” explained DeLong in a separate statement provided by the National Science Foundation. “For any given species, the gene transcripts for specific metabolic pathways turn on at the same time each day.”

Matt Kane of the National Science Foundation called the study “a major advance in understanding microbial communities through studies of gene expression in a dynamic environment,” and his NSF colleague Mike Sieracki said that the results confirm the decades-old theory that marine bacteria actively respond to day-night cycles.


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