dictyNews
Electronic Edition
Volume 42, number
February 19, 2016
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Abstracts
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Amoeba-resisting bacteria found in multilamellar bodies secreted
by Dictyostelium discoideum: social amoebae can also package
bacteria
Valérie E. Paquet, Steve J. Charette
FEMS Microbiology Ecology, In press
Many bacteria can resist phagocytic digestion by various protozoa.
Some of these bacteria (all human pathogens) are known to be
packaged in multilamellar bodies produced in the phagocytic pathway
of the protozoa and that are secreted into the extracellular milieu.
Packaged bacteria are protected from harsh conditions, and the
packaging process is suspected to promote bacterial persistence
in the environment. To date, only a limited number of protozoa,
belonging to free-living amoebae and ciliates, have been shown to
perform bacteria packaging. It is still unknown if social amoebae
can do bacteria packaging. The link between the capacity of 136
bacterial isolates to resist the grazing of the social amoeba
Dictyostelium discoideum and to be packaged by this amoeba was
investigated in the present study. The 45 bacterial isolates
displaying a resisting phenotype were tested for their capacity
to be packaged. A total of seven isolates from Cupriavidus,
Micrococcus, Microbacterium, and Rathayibacter genera seemed to
be packaged and secreted by D. discoideum based on
immunofluorescence results. Electron microscopy confirmed that
the Cupriavidus and Rathayibacter isolates were formally packaged.
These results show that social amoebae can package some bacteria
from the environment revealing a new aspect of microbial ecology.
submitted by: Steve Charette [[log in to unmask]]
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Cellular Slime Mold Development as a Paradigm for the
Transition from Unicellular to Multicellular Life
Vidyanand Nanjundiah
Centre for Human Genetics, Bengaluru 560100, India
"Multicellularity: Origins and Evolution" (MIT Press,
2016, ed. K. J. Niklas and S. A. Newman, 2016, pp 105-130)
A number of studies have shown that what were believed to be
species-specific cellular slime mould (CSM) morphologies (a)
can overlap across species and (b) have originated more than
once in different clades. This article enlarges on what we know
about CSM development to make a case for the evolution of
multicellularity via aggregation and self-organization. A central
assumption is that (as has been shown in many cases) more
than one cellular or multicellular phenotype can be consistent
with a given genotype and environment. If so, significant
phenotypic variation could arise via the spontaneous generation
of distinct phenotypes in the same genetic background and the
same environmental condition. The variant phenotypes can be
thought of as different equilibria or steady states of a multistable
system. Their existence depends on the switch-like nature of
genetic circuits, which in turn rests on two facts: gene expression
is an inherently stochastic process, and interactions between
genes, proteins, and cells commonly involve feedbacks.
Cooperation between individuals of different genotype can be
sustained by the dynamics of their interaction. If natural selection
favours one phenotypic alternative over another, genetic changes
that take place later can cause a favoured phenotype to develop
constitutively.
submitted by: Vidya Nanjundiah [[log in to unmask]]
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[End dictyNews, volume 42, number 5]
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