Tracking down the origin of cholera pandemics
A new bacterial strain replaced older strains during the seventh cholera pandemic

Date:
January 6, 2022
Source:
Max-Planck-Gesellschaft
Summary:
The bacterium Vibrio cholerae is the causative agent of the
diarrheal disease cholera and is responsible for seven known
pandemics. The seventh cholera pandemic began in 1961 and is still
active. Unlike previous pandemics, it is caused by cholera strains
of a slightly different type.

How did the modified cholera strains develop and spread, and what
might have contributed to their success? Scientists have now gained
new insights into a molecular mechanism that provides insight into
the interactions between cholera bacteria and may have played a
role in the emergence of the seventh pandemic.



FULL STORY ==========================================================================
The bacterium Vibrio cholerae is the causative agent of the diarrheal
disease cholera and is responsible for seven known pandemics. The seventh cholera pandemic began in 1961 and is still active. Unlike previous
pandemics, it is caused by cholera strains of a slightly different
type. How did the modified cholera strains develop and spread, and what
might have contributed to their success? Scientists from the Max Planck Institute for Evolutionary Biology in Plo"n, Germany, and CAU Kiel,
in an international team with colleagues from City College New York and
the University of Texas Rio Grande Valley, have now gained new insights
into a molecular mechanism that provides insight into the interactions
between cholera bacteria and may have played a role in the emergence of
the seventh pandemic.


==========================================================================
In their natural environment, bacteria are subject to competition with
other bacteria for space and nutrients. In this process, molecular
mechanisms help them to hold their own. One such mechanism is the
so-called "type 6 secretion system" (T6SS), with which a bacterium
transports toxic proteins into a neighboring bacterium and thereby kills
it. Thus, cholera bacteria of the seventh pandemic use their T6SS to
keep other bacteria in check and presumably more easily cause infection.

Researchers now had the special opportunity to study the T6SS of cholera bacteria from previous pandemics. For this purpose, among other things,
the T6SS genome sequence of cholera bacteria from the 2nd pandemic was reconstructed from a museum specimen from the 19th century in a complex procedure and recreated in the laboratory.

In the process, the scientists were able to show that 2nd and 6th
pandemic cholera bacteria lack a functional T6SS. As a result, the
bacteria of earlier pandemics not only lack the ability to attack other bacteria, they are themselves killed by bacterial strains of the seventh pandemic. This may have been one of the reasons that older cholera strains
were displaced by modified cholera strains of the seventh pandemic and
are now hard to find.

Data from new lab Daniel Unterweger, one of the study's authors
and a group leader at the Max Planck Institute in Plo"n,
Germany, says: "With these findings, we support the theory that
microbial competition between bacteria is very important for
understanding pathogens and bacterial pandemics. Our research on
the cholera bacterium was made possible by an S2 laboratory newly
established at the institute. Here, we can conduct experiments with
bacterial pathogens under the necessary safety precautions. The
study contains some of the first data from the new laboratory." ========================================================================== Story Source: Materials provided by Max-Planck-Gesellschaft. Note:
Content may be edited for style and length.


========================================================================== Journal Reference:
1. Benjamin Kostiuk, Francis J. Santoriello, Laura Diaz-Satizabal,
Fabiana
Bisaro, Kyung-Jo Lee, Anna N. Dhody, Daniele Provenzano,
Daniel Unterweger, Stefan Pukatzki. Type VI secretion system
mutations reduced competitive fitness of classical Vibrio
cholerae biotype. Nature Communications, 2021; 12 (1) DOI:
10.1038/s41467-021-26847-y ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/01/220106110005.htm

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