By TOM GERROW
BG Independent News
Cyanobacteria, sometimes called blue-green algae (even though they are bacteria, not algae), are a very common, very hardy organism found throughout the world. Often, they are harmless, and occasionally even useful as a source of nutrition for humans, but they can also produce toxins that adversely affect human health.
At this month’s Science Café, “What Lies Beneath – Toxins and Toxicants in Freshwaters,” associate professor Dr. James Metcalf, the Hollingsworth Smith Endowed Chair in Biological Sciences at BGSU, dove into the details of cyanobacteria and the toxins that some of them produce.
Assisting in the presentation at Ground for Thought was a panel of BGSU graduate students: Grant Hayden, Ashlynn Malloy, and Zachary Morris.
Metcalf noted that cyanobacteria are very ancient organisms, showing up in the fossil record about 3.5 billion years ago, and they can live in extreme environments, such as hot springs, that other organisms can’t tolerate. Cyanobacteria were one of the first organisms to appear on Earth, and they are most likely the source of the oxygen in our atmosphere.
And, Metcalf said, “They like to be fed. You give them the right nutrients, phosphorus, nitrogen, a bit of light, the right conditions … and they can potentially cause problems.”
Metcalf said there is evidence that humans have been aware of cyanobacteria since ancient times, but it wasn’t until the 1800s that people started exploring a possible connection between these organisms and illnesses, or even deaths. It became apparent that livestock that drank water contaminated with cyanobacteria’s characteristic green scum would perish.
But the golden age of toxin discovery was from the 1980s to the present, when scientists began to apply analytical chemistry to discover what exactly was in the harmful “algal” blooms that could kill. And they found a smorgasbord – cytotoxins that kill cells, and anatoxins and saxitoxins that affect the nervous system.
“These are extremely potent compounds that bind to your neurons and your muscles, either paralyzing them or stopping them from working,” Metcalf said. “Most of the time with this stuff, you die because you just can’t breathe. And unfortunately, there’s no solution to that problem.”
One slide during the presentation showed the relative potency of various toxins as they compared to cyanide, which was given a base value of 1. Strychnine, with a score of 20, is 20 times more toxic than cyanide. Cyanobacterial toxins can be from 13 to 1,100 times more toxic than cyanide.
“We have to know what’s in this stuff so that we can tell you what to do, what not to do, what to be careful of,” Metcalf said. “It’s a public health issue.”
Metcalf noted that there are multiple ways people can be exposed to these toxins – orally, though eating or drinking contaminated food or liquids; or through inhalation of toxic airborne particles; or recreationally, by playing on, in or under contaminated water. Metcalf has a particular interest in air sampling.
“So all these different routes can contribute to your own exposure, your own outcomes as well,” Metcalf said. “Inhalation has a lot more different routes potentially than drinking water in terms of the body and what it does. There’s also the issue of long-term exposure.”
“One thing I’ve been working on is this toxin called BMAA,” Metcalf said. “A number of people in my lab are also working on this as well. This is a toxin that is linked to Lou Gehrig’s disease, or ALS. The idea is that if you have a certain genetic trigger, maybe this could lead to things like Alzheimer’s and Parkinson’s.”
Metcalf said that research by a physician colleague showed that many ALS patients in New Hampshire lived in proximity to lakes with cyanobacteria, indicating a possible connection, if not necessarily a direct cause. BMAA has been found in Lake Erie, so it’s something that should be investigated further.
“But many of us in Bowling Green really are interested in Lake Erie,” Metcalf said. “And we all know it’s gone through cycles of good times and bad times, having lots of problems, trying to clean up those problems. And it’s important to deal with trying to get Lake Erie in a good place, because Lake Erie is very important for a whole host of things. Many organisms, species of animals, rely on it. Twelve million people drink its water. There’s a lot of commercial and recreational opportunities. There is tons and tons of money involved. This is a very, very big thing.”
Metcalf emphasized that BGSU students are at the forefront of the actual research that’s performed on Lake Erie. Of note is the Sandusky Bay research project, where students collect samples from various sites in the bay every week throughout the summer. The samples are then analyzed for toxins.
Exposure routes are the focus of graduate student Grant Hayden. “Given I’m on the Sandusky Bay crew, I’m more interested than anyone in knowing how exposed I’m getting,” Hayden said. The Sandusky Bay crew wears wristbands intended to measure the extent of their exposure while on the lake.
Graduate student Ashley Malloy focuses on plastic pellet leachates, the chemicals these plastics accumulate and release, and how they affect various organisms. Her work has shown that plastics of different colors actually have different chemical interactions in the environment.
As part of investigating the toxins present in the lake, graduate student Zachary Morris analyzed the number of peer-reviewed scientific papers published on the different toxins they were finding. He found an overwhelming focus on microcystin in the literature, while other toxic cyanobacterial peptides were relatively neglected, indicating a need for more research to understand the impacts of these other toxins on human health.
Morris responded to an audience question asking whether all cyanobacteria are harmful.
“The answer is no,” Morris said. “Some people actually consume them as a dietary supplement.”
Morris noted that Lake Chad, in Africa, is dominated by blooms of arthrospira platensis, a type of cyanobacteria.
“Arthrospira platensis is actually a great source of various amino acids, fatty acids, various vitamins and things like that,” Morris said. “What I’ve been doing in the lab lately is analyzing samples of Lake Chad Arthrospira for the presence of microcystins and various other peptides, and I have found absolutely nothing. So no, not all cyanobacteria are harmful, and that’s a great thing because they can be a very good food source.”
