Algae

Scientists discover first algae that can fix nitrogen — thanks to a tiny cell structure

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A newly discovered ‘organelle’ that converts nitrogen gas into a useful form could pave the way for engineered plants that require less fertilizer

1000x magnification micrograph of Braarudospharea bigelowii cell.
A Braarudosphaera bigelowii cell magnified 1,000-fold.

Researchers have discovered a type of organelle, a fundamental cellular structure, that can turn nitrogen gas into a form that is useful for cell growth.

The discovery of the structure, called a nitroplast, in algae could bolster efforts to genetically engineer plants to convert, or ‘fix’, their own nitrogen, which could boost crop yields and reduce the need for fertilizers. The work was published in Science on 11 April1.New cellular ‘organelle’ discovered inside fruit-fly intestines

“The textbooks say nitrogen fixation only occurs in bacteria and archaea,” says ocean ecologist Jonathan Zehr at the University of California, Santa Cruz, a co-author of the study. This species of algae is the “first nitrogen-fixing eukaryote”, he adds, referring to the group of organisms that includes plants and animals.

In 2012, Zehr and his colleagues reported that the marine algae Braarudosphaera bigelowii interacted closely with a bacterium called UCYN-A that seemed to live in, or on, the algal cells2. The researchers hypothesised that UCYN-A converts nitrogen gas into compounds that the algae use to grow, such as ammonia. In return, the bacteria were thought to gain a carbon-based energy source from the algae.

But in the latest study, Zehr and his colleagues conclude that UCYN-A should be classed as organelles inside the algae, rather than as a separate organism. According to genetic analysis from a previous study, ancestors of the algae and bacteria entered a symbiotic relationship around 100 million years ago, says Zehr. Eventually, this gave rise to the nitroplast organelle, now seen in B. bigelowii.

Defining organelles

Researchers use two key criteria to decide whether a bacterial cell has become an organelle in a host cell. First, the cell structure in question must be passed down through generations of the host cell. Second, the structure must be reliant on proteins provided by the host cell.

By imaging dozens of algae cells at various stages of cell division, the team found that the nitroplast splits in two just before the whole algae cell divides. In this way, one nitroplast is passed down from the parent cell to its offspring, as happens with other cell structures.A seagrass harbours a nitrogen-fixing bacterial partner

Next, the researchers found that the nitroplast gets the proteins it needs to grow from the wider algae cell. The nitroplast itself — which makes up more than 8% of the volume of each host cell — lacks key proteins required for photosynthesis and making genetic material, says Zehr. “A lot of these proteins [from the algae] are just filling those gaps in metabolism,” he says.

The discovery was made possible thanks to work by study author Kyoko Hagino at Kochi University in Japan, who spent around a decade fine-tuning a way to grow the algae in the lab — which allowed it to be studied in more detail, says Zehr.

“It’s quite remarkable,” says Siv Andersson, who studies how organelles evolve at Uppsala University in Sweden. “They really see all these hallmarks that we think are characteristic of organelles.”

Upgraded plants

Understanding how the nitroplast interacts with its host cell could support efforts to engineer crops that can fix their own nitrogen, says Zehr. This would reduce the need for nitrogen-based fertilizers and avoid some of the environmental damage they cause. “The tricks that are involved in making this system work could be used in engineering land plants,” he says.

“Crop yields are majorly limited by availability of nitrogen,” says Eva Nowack, who studies symbiotic bacteria at the Heinrich Heine University Düsseldorf in Germany. “Having a nitrogen-fixing organelle in a crop plant would be, of course, fantastic.” But introducing this ability into plants will be no easy feat, she warns. Plant cells containing the genetic code for the nitroplast would need to be engineered in such a way that the genes were transferred stably from generation to generation, for example. “That would be the most difficult thing to do,” she says.

“It’s both a pleasure and very impressive to see this work build up to what is certainly a major stepping stone in understanding,” says Jeffrey Elhai, a cell biologist at Virginia Commonwealth University in Richmond.

ESA Discovers an Organism That Can Survive 16 Months in Outer Space

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IN BRIEF
  • Algae has proven to be quite the formidable organism by being able to survive 16 months in space outside of the International Space Station.
  • The samples will now be sent back to Earth to test if there were any genetic changes in the specimens.

ALGAE IN SPACE

Fraunhofer scientists aboard the International Space Station (ISS) recently ran an experiment where they let algae loose into the vacuum of space for a full 16 months. And, surprisingly enough, the simple plants survived the harrowing journey. Despite extreme temperature variations, UV radiation, cosmic radiation, and incredible length of time, the algae were brought back aboard still alive.

These researchers aboard the ISS are currently running experiments as part of the Biology and Mars Experiment (BIOMEX) project. Within this experimental algae portion of the project, they tested the durability of algae species that are known to love freezing temperatures. Since the mixture of extreme conditions found in space is impossible to replicate in a laboratory environment exactly, the crew on the ISS used their location to put these cold-loving species to the test. However, despite knowing what these plants will endure on Earth, the scientists were astonished at how much they can really take.

Thomas Leya / Fraunhofer IZI-BB
Thomas Leya / Fraunhofer IZI-BB

COLD LOVING ALIENS

Post-experiment, the researchers aboard the ISS will send these algae samples back to Earth. There, they will be rigorously tested to see the actual extent that the temperatures and combined radiation impacted them. This information could be crucial to future human missions to Mars. It could help to ensure the safety of humans and any plant-based food to be consumed.

However, beyond the positive benefits that this research could have on future missions of humans in space, it could also potentially tell us a little bit more about alien life. According to many, including famed astrophysicist Neil Degrasse Tyson, thinking that we are somehow the only living creatures in the universe would be “inexcusably egocentric.” And, while previously, few would have thought that any plants could survive such an extended stay in space, we now know better. And so, while certain environments in space may seem inhospitable, we now know that life could exist in places we never before would have suspected.

Source:futurism.com/

Scientists have developed a power cell that harnesses electricity from algae

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Next week, international leaders and scientists are meeting in Paris to figure out how to lower the world’s reliance on fossil fuels – but one of the key challenges they’ll face is finding clean and highly efficient energy sources to take their place.

One candidate for the job? Green slime. Or, technically, blue-green slime. Scientists in Canada have used blue-green algae to energise a new kind of power cell that harnesses an electrical charge from the photosynthesis and respiration of cyanobacteria, which are the microorganisms that make up blue-green algae.

“Both photosynthesis and respiration, which take place in plant cells, involve electron transfer chains. By trapping the electrons released by blue-green algae during photosynthesis and respiration, we can harness the electrical energy they produce naturally,” said engineer Muthukumaran Packirisamy from Concordia University in Montreal.

The photosynthetic power cell consists of an anode, cathode, and proton exchange membrane. The blue-green algae are placed in the anode chamber, and as they undergo photosynthesis, they release electrons onto the electrode surface. With an external load attached to the cell, it’s possible to extract the electrons and harness power from the device.

From a natural resources point of view, blue-green algae are a fantastic choice to help take the burden off diminishing fossil fuels cyanobacteria are one of the most prosperous microorganisms on Earth. Plus, unlike other renewable energy sources like solar power and wind power, their efficiency doesn’t vary with changes in the weather.

“By taking advantage of a process that is constantly occurring all over the world, we’ve created a new and scalable technology that could lead to cheaper ways of generating carbon-free energy,” said Packirisamy.

It’s still early days for the technology, with the researchers noting that they have a lot of work to do in terms of scaling the power cell to make the concept commercially viable.

So far, they’ve measured open-circuit voltage as high as 993 millivolts and obtained a peak power of 175.37 microwatts, as detailed in their published findings in Technology. If they can expand on these initial achievements, the researchers hope the system will one day be powerful enough to run the electronic devices we use everyday – in addition to helping humanity cut down greenhouse gas emissions.

“In five years, this will be able to power your smart phone,” Packirisamy told Chris Arsenault at Reuters. Take that, lithium-ion.

Critical tool for brain research derived from ‘pond scum’.

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The poster child for basic research might well be a one-celled green algae found in ordinary lakes and ponds. Amazingly, this unassuming creature—called Chlamydomonas—is helping scientists solve one of the most complex and important mysteries of science: How billions of neurons in the brain interact with one another through electrochemical signals to produce thoughts, memories and behaviors, and how malfunctioning neurons may contribute to incurable brain diseases such as Parkinson’s disease and schizophrenia.

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It may seem counterintuitive that a tiny, relatively simple organism that doesn’t even have a brain could help scientists understand how the brain works. But this algae‘s value to brain scientists is not based on its intellect. Rather, it is based on its light-sensitivity, i.e., the fact that this organism’s movements are controlled by light.

 

Following the light

 

Chlamydomonas is light sensitive because it must detect and move towards light to feed itself through photosynthesis. You’ve seen this type of light sensitivity in action if you’ve ever noticed algae accumulate in a lake or pond on a sunny day.

 

The secret to the Chlamydomonas’s light-chasing success is a light-sensitive protein, known as a channelrhodopsin, which is located on the boundary of the algae’s eye-like structure, called an eyespot.

When hit by light, this light-sensitive protein—acting much like a solar panel—converts light into an electric current. It do so by changing its shape to form a channel through the boundary of the eyespot. This channel allows positively charged particles to cross the boundary and enter the eyespot region. The resulting flow of charged particles generates an electric current that, through a cascade of events, forces the algae’s two flagella—whip-like swimming structures—to steer the organism towards the light.

The light-sensing proteins of Chlamydomonas and their ability to generate electric currents for light chasing were discovered in 2002 by a research team at the University of Texas Health Science Center at Houston that was led by John Spudich and included Oleg SIneshchekov and Kwang-Hwan Jung; the team was funded by the National Science Foundation (NSF). This team’s discoveries about the algal proteins followed decades of research by Spudich, a biophysical chemist, and his collaborators on how light-sensing receptors control swimmingbehavior in many types of microorganisms.

 

“My interest in Chlamydomonas was derived from my interest in the basic principles of vision. That is, the molecular mechanisms by which organisms use light to obtain information about their environment,” says Spudich. “I have long been fascinated with how microorganisms ‘see’ the world and started with the simplest—bacteria with light-sensitive movements (phototaxis), followed by phototaxis in more complex algae. Our focus throughout has been on understanding the basic biology of these phenomena.”

 

Identifying the functions of neurons

Nevertheless, Spudich’s discovery of the light-sensitive algal proteins was a game-changer for an NSF-funded team of brain researchers at Stanford University that was comprised of Karl Deisseroth, Edward Boyden, and Feng Zhang. Working together in a uniquely interdisciplinary team during the early 2000s, these researchers collectively offered expertise in neuroscience, electrical engineering, physiology, chemistry, genetics, synthetic biology and psychiatry. (Boyden and Zhang are now at MIT.)

criticaltool

A primary goal of this team was to develop a new technology for selectively turning on and off target neurons and circuits of neurons in the brains of laboratory animals, so that resulting behavioral changes could be observed in real time; this information could be used to help identify the functions of targeted neurons and circuits.

The strategy behind this technology—eventually dubbed optogenetics—is analogous to that used by someone who, one by one, systemically turns on and off the fuses (or circuit breakers) in a house to identify the contribution of each fuse (or circuit breaker) to the house’s power output.

 

An on/off switch for neurons

But unlike household fuses and circuit breakers, neurons don’t have a user-friendly on/off switch. To develop a way to control neurons, the Stanford team had to create a new type of neuronal switch. With funding from NSF, the team developed a light-based switch that could be used to selectively turn on target neurons merely by exposing them to light.

Why did the team opt for a light-based strategy? Because light—an almost omnipresent force in nature—has the power to turn on and off many types of important electrical and chemical reactions that occur in nature including, for example, photosynthesis. The team therefore reasoned that light might, under certain conditions, also have the power to turn on and off electrochemical signaling from brain neurons.

But to create a light-based neuronal on/off switch, the team had to solve a big problem: Neurons are not naturally light sensitive. So the team had to find a way to impart target neurons with light sensitivity, so that they could be selectively activated by a light-based switch without altering non-target neurons. One potential strategy: to implant in target neurons some kind of light sensitive molecule that is not present elsewhere in the brain.

 

The team lacked the right type of light-sensitive molecule for the job until several important studies were announced. These studies included Spudich’s discovery of the light-sensitive algal proteins, as well as research led by microbial biophysicists Peter Hegemann, Georg Nagel and Ernst Bamberg in Germany, which showed that these proteins can generate electrical currents in animal cells, not just in algae.

 

Flicking the switch

These studies inspired the team to insert Spudich’s light-sensitive algal proteins into cultured neurons from rats and mice via a pioneering genetic engineering method that was developed by the team. When exposed to light in laboratory tests in 2004, these inserted proteins generated electric currents—just as they did in the light-sensitive algae from which they originated. But instead of turning on light-chasing behaviors as they did in the algae, these currents—when generated in target neurons—turned on the normal electrochemical signaling of the neurons, as desired.

In other words, the team showed that by selectively inserting light-sensitive proteins into target neurons, they could impart these neurons with light sensitivity so that they would be activated by light. The team thereby developed the basics of optogenetics—which is defined by Deisseroth as “the combination of genetics and optics to control well-defined events within specific cells of living tissue.”

The members of the team (either working together or in other teams) also developed tools to:

·         Turn off target neurons and stop their electrochemical signaling by manipulating light-sensing proteins.

·         Deliver light to target neurons in laboratory animals via a laser attached to a fiber cable implanted in the brain.

·         Insert light-sensitive proteins into various types of neurons so that their functions could be identified.

·         Control the functioning of any gene in the body. Such control supports studies of how gene expression in the brain may influence neurochemical signaling and how changes in key genes in neurons may influence factors such as learning and memory.

“The brain is a mystery, and in order to solve it, we need to develop a great variety of new technologies,” says Boyden. “In the case of optogenetics, we turned to the diversity of the natural world to find tools for activating and silencing neurons—and found, serendipitously, molecules that were ready to use.”

 

The power of optogenetics

 

Thousands of research groups around the world are currently incorporating increasingly advanced techniques in optogenetics into studies of the brains of laboratory animals. Such studies are designed to reveal how healthy brains learn and create memories and to identify the neuronal bases of brain diseases and disorders such as Parkinson’s disease, anxiety, schizophrenia, depression, strokes, pain, post-traumatic stress syndrome, drug addiction, obsessive-compulsive disease, aggression and some forms of blindness.

Deisseroth says, “What excites neuroscientists about optogenetics is control over defined events within defined cell types at defined times—a level of precision that is most crucial to biological understanding even beyond neuroscience. And milliscale-scale timing precision within behaving mammals has been essential for key insights into both normal brain function and into clinical problems, such as parkinsonism.”

Indeed, optogenetics is now so important to brain research that it is considered one of the critical tools for the Brain Research through Advancing Innovative Neurotechnologies through Advancing Innovative Neurotechnologies (BRAIN) Initiative, which was announced by President Obama in April 2013.

In addition, optogenetics is being applied to other organs besides the brain. For example, NSF-funded researchers are working to develop optogenetic techniques to treat cardiac arrhythmia.

 

The laws of unintended consequences.

 

As with many pivotal scientific advances, the development of optogenetics was built upon many basic-research studies that were inspired by the intellectual curiosity of researchers who could not possibly have foreseen the important practical applications of their work.

“The development of optogenetics is yet one more beautiful example of a revolutionary biotechnology growing out of purely basic research,” says Spudich.

What’s more, many of the varied disciplines that contributed to the invention of optogenetics—including electrical engineering, genetic engineering, physics and microbiology—may seem, on first blush, unrelated to one another and to brain science. But perhaps most surprising was the importance of basic research on algal proteins to the development of optogenetics.

Deisseroth said, “The story of optogenetics shows that hidden within the ground we have already traveled over or passed by, there may reside the essential tools, shouldered aside by modernity, that will allow us to map our way forward. Sometimes these neglected or archaic tools are those that are most needed—the old, the rare, the small and the weak.”

Food for thought for anyone tempted to dismiss algae in a murky body of water as worthless pond scum!