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L form bacteria growth in low-osmolality medium.
Abstract
L form bacteria do not have a cell wall and are thought to require medium of high
osmolality for survival and growth. In this study we tested whether L forms can adapt
to growth in lower osmolality medium. We first tested the Escherichia coli L form
NC-7, generated in 1987 by Onoda following heavy mutagenesis. We started with growth
in osmoprotective medium (~ 764 mOsm kg-1) and diluted it stepwise into medium of lower osmolality. At each step the cells
were given up to 10 days to adapt and begin growing, during which they apparently
acquired multiple new mutations. We eventually obtained a strain that could grow in
LB containing only 34 mM NaCl, 137 mOsm kg-1 total. NC-7 showed a variety of morphologies including spherical, angular and cylindrical
cells. Some cells extruded a bud that appeared to be the outer membrane enclosing
an enlarged periplasm. Additional evidence for an outer membrane was sensitivity of
the cells to the compound CHIR-090, which blocks the LPS pathway, and to EDTA which
chelates Mg that may stabilize and rigidify the LPS in the outer membrane. We suggest
that the mechanical rigidity of the outer membrane enables the angular shapes and
provides some resistance to turgor in the low-osmolality media. Interestingly, cells
that had an elongated shape underwent division shortly after addition of EDTA, suggesting
that reducing the rigidity of the outer membrane under some turgor pressure induces
division before lysis occurs. We then tested a well-characterized L form from Bacillus
subtilis. L form strain LR-2L grew well with sucrose at 1246 and 791 mOsm kg-1. It survived when diluted directly into 440 mOsm kg-1 but grew poorly, achieving only 1/10 to 1/5 the density. The B. subtilis L form apparently
adapted to this direct dilution by rapidly reducing cytoplasmic osmolality.
Type
Journal articlePermalink
https://hdl.handle.net/10161/22299Published Version (Please cite this version)
10.1099/mic.0.000799Publication Info
Osawa, Masaki; & Erickson, Harold P (2019). L form bacteria growth in low-osmolality medium. Microbiology (Reading, England), 165(8). pp. 842-851. 10.1099/mic.0.000799. Retrieved from https://hdl.handle.net/10161/22299.This is constructed from limited available data and may be imprecise. To cite this
article, please review & use the official citation provided by the journal.
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Show full item recordScholars@Duke
Harold Paul Erickson
James B. Duke Distinguished Professor Emeritus
Recent research has been on cytoskeleton (eukaryotes and bacteria); a skirmish to
debunk the irisin story; a reinterpretation of proposed multivalent binders of the
coronavirus spike protein. I have also published an ebook on "Principles of Protein-Protein
Association" suitable for a course module or individual learning.
Masaki Osawa
Assistant Research Professor of Cell Biology
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