dictyNews
Electronic Edition
Volume 42, number 5
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 [Steve.charette@bcm.ulaval.ca]
———————————————————————————————————————


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 [vidya@ces.iisc.ernet.in]
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[End dictyNews, volume 42, number 5]