The Curious World of Bacteria by Ludger Wess

Author:Ludger Wess
Language: eng
Format: epub
Publisher: Greystone Books
Published: 2023-05-15T00:00:00+00:00

Chromulinavorax destructans

Destructive golden algae devourer

(in golden alga, nine hours after infection)

Shape: Spherical

Diameter: 350 to 400 nm (nanometers)

CHROMULINAVORAX DESTRUCTANS is a kind of zombie bacterium, bobbing around as an undead in the freshwater environments of our planet. It shows no signs of metabolic activity, so it neither grows, nor divides, nor multiplies. All this changes when it is swallowed by the golden alga Spumella elongata, one of the most common golden algae on Earth that swims in water and lives on bacteria, viruses, and protozoa. Once swallowed, C. destructans springs to life and begins eating its victim from the inside out. Microbiologists have aptly named it the destructive golden algae devourer.

It is the alga, not the parasite, that initially does the devouring. S. elongata surrounds the bacterium with a small protrusion and guides the bacterium inward to digest its contents. But C. destructans blocks this process and takes control of the alga’s metabolism. In just three hours, the alga’s mitochondria have gathered around the vesicle containing C. destructans, and they supply the energy for this zombie bacterium to use the alga’s cell components for its own growth and rapid cell division. After twelve hours, two-thirds of the alga is filled with new bacteria, and after another six hours, the alga bursts, releasing the new bacteria into the environment.

Analysis of the genome showed that the bacterium doesn’t have a single complete metabolic pathway, meaning that it can’t itself produce any of the building blocks necessary to make proteins, genes, carbohydrates, or fats. It can only destroy and remodel already available resources.

This bacterium has a lot in common with a virus—it can only multiply in particular cells and is completely inactive outside of its host. The important difference is that, unlike viruses, C. destructans is not dependent on the host’s cellular apparatus to replicate its genetic material.

When scientists first discovered this remarkable bacterium, which belongs to an equally strange phylum called Dependentiae (the plural of dependentia, Latin for “dependence”), they conducted a systematic search for unknown sequences in RNA libraries and soil samples. The researchers had some success, continued searching, and eventually found the same or highly similar gene sequences in sewage, in hot springs, and in biofilms coating shower heads, water pipes, and sinks. Rather like archaeologists reconstructing texts from fragments of papyrus, the researchers were able to use computers to assemble and evaluate genes and genomes from the sequences. These analyses showed that members of this new phylum had to be parasitic bacteria, that they had comparatively few genes for metabolic enzymes, but that they had many genes for transport proteins, so they apparently lived at the expense of other organisms. Other genes suggested that the host was most likely to be a single-celled eukaryotic organism. At this time, however, the researchers hadn’t even found any of these strange bacteria!

This happened once the researchers turned their attention to single-celled organisms that were present in the habitats where the genetic material was found. They determined that the host organisms had to be

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