Latest News

Clues beginning to emerge on asymtomatic SARS-CoV-2 infection
Back in November of 2020, during the first wave of the COVID-19 pandemic, I was teaching an in-person microbiology laboratory. One of my students had just been home to see his parents, and they all c…
Read more
Could there maybe be better uses of genetics and probiotics?
Professor Meng Dong and his laboratory have created a probiotic that can metabolize alcohol quickly and maybe prevent some of the adverse effects of alcohol consumption. The scientists cloned a highl…
Read more
ChatGPT is not the end of essays in education
The takeover of AI is upon us! AI can now take all our jobs, is the click-bait premise you hear from the news. While I cannot predict the future, I am dubious that AI will play such a dubious role in…
Read more
Fighting infections with infections
Multi-drug-resistant bacterial infections are becoming more of an issue, with 1.2 million people dying of previously treatable bacterial infections. Scientists are frantically searching for new metho…
Read more
A tale of two colleges
COVID-19 at the University of Wisconsin this fall has been pretty much a non-issue. While we are wearing masks, full in-person teaching is happening on campus. Bars, restaurants, and all other busine…
Read more

News

To eat or to be eaten? The complex lives of Dictyostelium discoideum and Pseudomonas fluorescens


 

Dictyostelium discoideum is a eukaryotic microbe that lives a unique lifestyle that involves changing from a unicellular to multicellular organism. Recent studies have shown that not only is it unique in this aspect, but it is unique in that it actually cultivates its own food supply, being dubbed the world’s “smallest farmer” amongst microbiologists. This article is based on a recent study led by Debra Brock at the Washington Universty of St. Louis.

Dictyostelium discoideum is a heterotrophic, soil-living amoeba, and it’s unique in the fact that is starts out as a unicellular organism, but becomes a multicellular organism later in life. This occurs when its unicellular pieces come together to from a slug that can move around in the soil. But it’s not just unique in this aspect. It is also a rare species because it has been proven to carry its bacterial prey around with it and essentially “farm” it for a larger food supply

In 2011, these characteristics of D. discoideum were observed and recorded, but recent discoveries made by Debra Brock of Washington University in St. Louis show that this process is more complex than originally thought. It turns out that the bacterial prey of D. discoideum is actually found in two forms – an edible form and an inedible, toxic form. The bacterial prey is called Pseudomonas fluorescens.

The toxic form of P. fluorescens is a result of a mutation that affects the controls of two toxic chemicals, called chromene and pyrrolnitrin. These chemicals are believed to inhibit sporulation, which is an important step in the amoeba’s life cycle.

 Although the toxic form can kill D. dictyostelium, D. dictylostelium still carries both lineages in order to increase its food supply. This is actually statistically favorable because the toxic form of the bacterial prey only occurs about 10% of the time. It is believed that the original form of P. fluorescens is actually the inedible form, but it has evolved into the edible form in order to be picked up by the amoeba and to be transported to different areas in the environment with differing nutrient levels. This evolution is actually beneficial to the prey bacteria because it has a greater chance of survival if it can spread its population out. In turn, the amoeba allows its prey to grow in the new environment and can cultivate them for its own food supply.

This is a brand new discovery that allows a glimpse into mutualism, evolution, and altruism at the microbial level.