Predatory bacteria
Microbes get sick, too: In deep sediments, they become the victims of
tiny bacteria
Date:
March 23, 2022
Source:
Max Planck Institute for Marine Microbiology
Summary:
Tiny predatory bacteria attack microorganisms. These
ultramicrobacteria are widely distributed, for example, in sewage
treatment plants and in the seafloor.
FULL STORY ==========================================================================
Most people think of microorganisms as a cause of disease rather than
as its victims. But in fact, they too can become victims of bacteria
that make them sick and even devour them. Such a predatory bacterium
has now been described by researcher Jens Harder and his team from the
Max Planck Institute for Marine Microbiology in Bremen, Germany.
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The assailant: Undercover for a long time For more than twenty years,
the predatory bacteria have been living largely unnoticed in Jens
Harder's laboratory at the Max Planck Institute in Bremen in a so-called enrichment culture that uses limonene for methane production. They
originally came from the digestion tower of the sewage treatment plant
in Osterholz-Scharmbeck, close to Bremen. "We have named the new microbe Velamenicoccus archaeovorus," says Harder. "It is an ultramicrobacterium
- a particularly tiny member of the microbial world, only 200 to 300
nanometres in size and thus invisible under a normal microscope." By comparison, a human is almost two billion nanometres tall. A few secrets
of these tiny bacteria have now been revealed.
The victim: Important for biogas production The second main character
of this story, the victim, is also found in sewage treatment plants: Methanosaeta, one of the most common microbes in the world, plays a
crucial role therein. This archaeon is mainly responsible for biogas
production in sewage treatment plants. Individual cells of Methanosaeta
live together in a protective tube, a filament. Using special dyes and
a special microscope, Harder and his team were now able to prove that
single cells in the Methanosaeta-filaments were sick or dead. They
were limp and contained neither ribosomal nucleic acids nor genetic
material -- typical components of living microbial cells. The cells
had presumably fallen victim to the ultramicrobacteria: "Most probably,
the cause of disease is attached bacteria, and these attached bacteria
are Velamenicoccus archaeovorus," Harder explains.
The weapon? A giant protein "Velamenicoccus archaeovorus is not
an unknown," Harder continues. "We have found parts of its genetic
material in deep sediments and other oxygen-free habitats. But what it
does there was not known." Now, researchers at the Max Planck Institute
for Marine Microbiology have been able to decode the genome of this ultramicrobacterium and identify its proteins, thereby unlocking some
of the tiny predator's secrets. One particularly remarkable gene is a strikingly large one. "While proteins on average consist of 333 amino
acids, this gene encodes a protein with 39678 amino acids," Harder
explains. Thereby, it would be one of the largest known proteins. It is integrated into the cell wall and its surface contains enzyme domains
that enable it to dissolve cells. Thus, this could well be the deadly
secret of Velamenicoccus.
Ecologically significant in deep sediments? Realising that we are
dealing with such a "dangerous" bacterium permits a new look at an
ecological question: Sediments are full of microorganisms, decreasing in
number with increasing depth. The deeper you go, the fewer cells you will
find. Until now, it was assumed that this was the result of the ongoing
die-off of cells. Now another possibility arises: Microorganisms use other microorganisms as a food source, and because this is not particularly efficient, the organic material is being increasingly lost as methane
and carbon dioxide. "Ultramicrobacteria can thus play a decisive role
in the conversion and recycling of biomass in sediments and cause an
overall reduction in biomass with depth," Harder concludes.
Fittingly: Velamenicoccus archaeovorus, the archaea-eating
microbe, belongs to the candidate phylum Omnitrophica, meaning the "all-eaters." The finding that they live as predators now shows for the
first time that this appellation is really accurate.
========================================================================== Story Source: Materials provided by Max_Planck_Institute_for_Marine_Microbiology. Note: Content may be edited
for style and length.
========================================================================== Related Multimedia:
* Methanosaeta ========================================================================== Journal Reference:
1. Jana Kizina, Sebastian F. A. Jordan, Gerrit Alexander Martens, Almud
Lonsing, Christina Probian, Androniki Kolovou, Rachel
Santarella-Mellwig, Erhard Rhiel, Sten Littmann, Stephanie
Markert, Kurt Stu"ber, Michael Richter, Thomas Schweder,
Jens Harder. Methanosaeta and " Candidatus Velamenicoccus
archaeovorus". Applied and Environmental Microbiology, 2022; DOI:
10.1128/aem.02407-21 ==========================================================================
Link to news story:
https://www.sciencedaily.com/releases/2022/03/220323101247.htm
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