I recall it being the toughest of samples to find critters in. Each year I would order a variety of microorganisms from supply houses for my general biology classes. Many of the small plastic jars came with specified microbes that were easy to find and view under the microscope. But the trickiest of all to see were the amoebas, even though they were larger than many other specimens.
The main thing I remember teaching about amoebas was that they had no particular form. They just kind of crawled around like a blob, extending arm-like knobs in the direction they might be moving. We could see the protoplasm running into these extensions, as well as some large structures inside the amoebas called vacuoles. These were periodically expelled to get rid of water they took in before it would cause them to burst.
It has been many years since I viewed amoebas with my students, or even gave them much thought. That is until recently, when it appears Minnesota had its third death in five years from a particular species called the brain-eating amoeba. People are usually infected swimming in lakes when water carrying one of the amoebas goes up their nose. Within days, it follows nerve pathways into the brain where an almost-always fatal infection occurs.
What I have found most interesting in Googling amoebas is that the species responsible for this deadly infection is touted as liking warm water, and can even survive in water over 100 degrees. The fewer than 150 deaths in the U.S. over the past 50 years have mostly been in southern states. So, the recent deaths in Minnesota waters that freeze in winter have prompted many scientists to agree we really don't know much about these organisms.
However, it is agreed these amoeba are usually found in muddy sediments and thus can be stirred up into the water column when humans are playing in warm-water lakes. They can also survive in other environments, including soil.
In a couple of rare situations, amoeba are believed to have survived in household water lines. In both of these events, which occurred in Louisana in 2011, the amoeba were thought to have been introduced into the nasal passages of the victims thru the use of sinus-cleansing neti pots.
Given Minnesota children and adults probably spend millions of hours in our warm-water lakes each year, infection by one of these amoeba has to be considered rare, and hopefully does not discourage people from enjoying water activities. And likewise, given the hundreds of thousands of people who benefit from use of neti pots, it would seem to be a knee-jerk reaction to quit using them.
So, these deadly amoeba are just another reminder of the complex world we live in, with many perils that most of us amazingly survive for a long time. And, for me, it begs the question, "What role do these deadly protozoans serve?" To which I must answer, "I don't know, but they are undoubtedly an integral part of the bigger picture of life on Earth."