Cyanobacterial cell lysis myths and what they get wrong
Cell lysis is often portrayed as an inevitable outcome of treating cyanobacterial blooms. The reality is more hopeful.
Cyanobacteria thrive in warm, nutrient-rich water. A bloom can quickly cover a lake or pond with a thick green layer containing millions of cyanobacteria. Many types of cyanobacteria produce potentially harmful substances known as cyanotoxins within their cells. These toxins can pose a serious health risk to humans and animals that are exposed.
Conventional wisdom suggests that it is better to hold off treating cyanobacterial blooms and let them run their natural course instead. The logic is that treated cells will lyse — break open — and release cyanotoxins into the water column. When catastrophic cell lysis occurs and cyanotoxins are abruptly released into the water, they become more difficult to manage.
Like most natural processes, however, cyanobacterial cell lysis does not always occur in a single, uniform way. While it almost always ends in cell death, it does not always end with the abrupt release of cyanotoxins into the water. There is another way.
With the right treatment and monitoring, it is possible to induce a more gradual form of cell lysis that can be your ally and not your enemy.
Total microcystin concentration (ppb) and cell density (cells/ml) after treatment versus no treatment. West M. Bishop, Brenda M. Johnson, John H. Rodgers, Jr., Clemson University, Clemson SC “Microcystin concentrations following treatments of harmful algal blooms.”
What is Cell Lysis?
Cyanobacterial cells are surrounded by a cell membrane and cell wall which contain the vital cytoplasmic materials that control metabolic functions. If the cell wall-membrane complex develops one or more weak points, the intracellular contents can be lost to the surrounding environment; this process is referred to as lysis.
Although most definitions do not indicate a specific timeframe for intracellular materials to be released, it is implicit that lysis is a rapid process occurring in less than a second to a few minutes, depending on the treatment or conditions used. A damaged cell membrane can allow some intracellular materials to slowly leak out of a cell, in the absence of a time limit, the result of lysis and leakage will be the same – loss of cell materials and viability.
In the scientific literature, cell lysis is often represented as a risky and unpredictable outcome of algaecide treatment. According to this argument, cell lysis increases water toxicity by causing a rapid release of cyanotoxins into the water column. This leads to the assumption that when more toxins are released there is a higher chance of potential poisoning in living organisms. It seems logical that adding more toxins to an already toxic environment is not a good idea.
But is this assumption true?
Hidden microscopic factors provide a more nuanced picture. Cell lysis should not be considered as synonymous with cell leakage. It is important to understand how treatments affect cyanobacterial cells, and more specifically how lysis or leakage occurs. Understanding treatment mode-of-action is essential to reducing toxic cyanobacteria blooms and the threat cyanotoxins pose to other organisms.
Here are five popular myths surrounding cyanobacterial cell lysis and what they get wrong:
Myth #1: Cyanotoxins are more dangerous when they are released from the cell.
Conventional wisdom says that free-floating cyanotoxins are more dangerous than those inside the cyanobacterial cell. In fact, the cell-free cyanotoxins are just more difficult to remove from the water. They are equally dangerous whether they are inside or away from the cell. When intact cyanobacterial cells are ingested by another organism, they can still emit toxins that pass into the organism’s blood stream and tissues. So, whether the cyanotoxin is free-floating or remains inside the cell, humans and animals may still become ill from exposure.
The World Health Organization (WHO) and the Environmental Protection Agency (EPA) have set limits for microcystin, a cyanotoxin, that do not distinguish whether the toxin is located inside or outside the cell — they’re equally toxic. The primary concern should be to disrupt the lifecycle of a toxic cyanobacterial bloom in such a way as to preserve the dead cells with their toxins largely intact. That way they are easier to remove using conventional or enhanced coagulation, flocculation and filtration methods.
Myth #2: Cell lysis caused by treating cyanobacterial blooms increases water toxicity.
Depending on the method or chemical compound used, treatment of toxic cyanobacterial blooms can cause catastrophic cell lysis and a spike in the concentration of free cyanotoxins in the water column. That much is true. But with the right testing and treatment strategy, you can reduce overall toxicity while preventing or minimizing spikes in cyanotoxin concentrations.
Cell lysis is a natural part of the cell cycle. All cells die at some point, either through apoptosis (programmed cell death) or an external factor such as consumption and digestion by other organisms or contact with a biocidal agent. Apoptosis is a normal process necessary to maintain balance within the cell’s environment, whereas external factors can be environmental or the result of human intervention.
Like all organisms, cyanobacterial cells naturally phase through the different stages of their lifecycle. They typically reach cell lysis and death at a pace that remains in balance with the surrounding environment. When cyanobacterial cells die at a steady rate, neighboring organisms consume the dead cells and any released cytoplasmic material. The potential negative impacts of cell lysis can be avoided when treatment mimics this natural process.
If a treatment is too harsh, cyanobacterial cells may die too quickly and release cyanotoxins into the water depending on what physical or chemical factor was responsible. When the rate of catastrophic cell death surpasses what can be consumed by other organisms, the concentration of cyanotoxins in the water column spikes. On the other hand, controlled treatment can chemically induce cell death without forcing catastrophic cell ruptures and radically destabilizing the aquatic ecosystem.
A well-designed treatment regimen can prevent cyanobacterial growth by inhibiting photosynthesis; this prevents further cell reproduction and cyanotoxin production. However, the treatment must not cause rapid cell lysis. It should stop growth but not cause lysis to avoid spikes in the concentration of toxins in the water column.
Myth #3 Cell lysis is necessary for cell death.
Cell death can result from various kinds of cellular malfunctions. Cell lysis is only one such malfunction. Some cells remain intact during cell death without releasing any cytoplasmic material. More often, cells die with only a small amount of membrane damage and cytoplasmic material leakage. Their metabolic functions simply fail, and they die before releasing the majority of their toxins.
Thus, cell lysis is not the only path to cell death. When cell lysis does occur, it has various degrees of severity. Proper treatment can minimize the severity of cell lysis and reduce the chance that cells will release high concentrations of hard-to-remove cyanotoxins into the water column. The preferred process is to allow slow leakage of intracellular materials while the cells die.
Myth #4 Cell lysis is risky and unpredictable.
Because some treatments cause aggressive and abrupt cell rupture (lysis), there is a misconception that all treatments target the cell in the same way. In fact, cell lysis can be stabilized so that cells break down slowly and consistently rather than rupturing abruptly and catastrophically.
With the right treatment, under controlled conditions, the rate of cell lysis is often compatible with the rate of bacterial decomposition of cyanobacterial cells and their cellular contents. This allows nature to work for you. Fast growing bacteria ingest the cyanobacterial cell contents and materials, including toxins, removing them from the water column before they enter your plant.
Myth #5 Beneficial microorganism are harmed by cyanotoxins released during cell lysis.
Cyanotoxins can be harmful to many species but a simple microscope offers a glimpse of the other side to this story, where cyanobacteria, and even their toxins, are a source of food for neighboring microorganisms.
Cyanobacteria are part of the primary producer community of aquatic systems and, as such, are at the base of the food chain. As primary producers, cyanobacteria create organic compounds from CO2 and sunlight. They serve as an excellent source of food and energy for other organisms (e.g., amoebae and ciliates).
Mixed species of microorganisms 48 hours after treatment with 60 ppb EarthTec.
Many species of aquatic bacteria have been shown to biodegrade cyanotoxins and other cellular materials produced by cyanobacteria. Far from being harmed by ingesting cyanotoxins, these organisms use cyanotoxins as fuel. Such short food chains or food webs are part of the many processes that help regulate the aquatic environment, stabilizing the structure and function of the indigenous biotic communities.
When treatment of cyanobacterial blooms is implemented correctly, the natural symbiotic-like relationships between microbes remain balanced. If the treatment happens to have any negative impact on non-target microorganisms, those organisms recover very quickly and continue to consume cellular and cytoplasmic materials released by cyanobacterial cells. Proper treatment of an aquatic system should inhibit nuisance species while allowing “non-target” organisms to restore the aquatic ecosystem to a healthier state.
Let nature fight for you, not against you.
Cell lysis can be an enemy in the fight against cyanobacteria, but cell leakage can be a hero. With the right treatment, controlled cell leakage and nature’s own army can help you reduce toxic cyanobacteria blooms without causing spikes in the concentration of hard-to-remove cyanotoxins in the water.
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